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Cover

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DESIGN OF JOINTS INSTEEL STRUCTURES

UK EDITION

ECCS EUROCODE DESIGN MANUALSECCS EDITORIAL BOARDLuiacutes Simotildees da Silva (ECCS)Antoacutenio Lamas (Portugal)Jean-Pierre Jaspart (Belgium)Reidar Bjorhovde (USA)Ulrike Kuhlmann (Germany)

DESIGN OFSTEELSTRUCTURESndash 2ND EDITIONLuiacutes Simotildees da Silva Rui Simotildees and Helena Gervaacutesio

FIRE DESIGN OF STEEL STRUCTURES ndash 2ND EDITIONJean-Marc Franssen and Paulo Vila Real

DESIGN OF PLATED STRUCTURESDarko Beg Ulrike Kuhlmann Laurence Davaine and Benjamin Braun

FATIGUE DESIGN OF STEEL AND COMPOSITE STRUCTURESAlain Nussbaumer Luiacutes Borges and Laurence Davaine

DESIGN OF COLD-FORMED STEEL STRUCTURESDan Dubina Viorel Ungureanu and Raffaele Landolfo

DESIGN OF JOINTS IN STEEL AND COMPOSITE STRUCTURESJean-Pierre Jaspart and Klaus Weynand

DESIGN OF STEEL STRUCTURES FOR BUILDINGS IN SEISMIC AREASRaffaele Landolfo Federico Mazzolani Dan Dubina Luiacutes Simotildees da Silva andMario drsquoAniello

ECCS ndash SCI EUROCODE DESIGN MANUALS

DESIGN OF JOINTS IN STEEL STRUCTURES UK EDITIONJean-Pierre Jaspart and Klaus WeynandAdapted to UK by Graham Couchman and Ana M Giratildeo Coelho

DESIGN OF STEEL STRUCTURES UK EDITIONLuiacutes Simotildees da Silva Rui Simotildees Helena GervaacutesioAdapted to UK by Graham Couchman

ECCSEUROCODE DESIGN MANUALS ndashBRAZILIAN EDITIONS

DIMENSIONAMENTO DE ESTRUTURAS DE ACcedilOLuiacutes Simotildees da Silva Rui Simotildees Helena Gervaacutesio Pedro Vellasco Luciano Lima

INFORMATION AND ORDERING DETAILS

For price availability and ordering visit our website wwwsteelconstructcomFor more information about books and journals visit wwwernst-und-sohnde

DESIGN OF JOINTS IN STEELSTRUCTURES

Eurocode 3 Design of steel structuresPart 1-8 ndash Design of Joints

UK Edition

Jean-Pierre JaspartKlaus Weynand

Adapted for the UK byGraham CouchmanAna M Giratildeo Coelho

Design of Joints in Steel Structures

UK Edition2017

Published byECCS ndash European Convention for Constructional Steelworkpublicationssteelconstructcomwwwsteelconstructcom

SalesWilhelm Ernst amp Sohn Verlag fuumlr Architektur und technische WissenschaftenGmbH amp Co KG Berlin

All rights reserved No parts of this publication may be reproduced stored in aretrieval system or transmitted in any form or by any means electronic mechanicalphotocopying recording or otherwise without the prior permission of the copyrightowner

ECCS assumes no liability with respect to the use for any application of the materialand information contained in this publication

Copyright copy 2017 ECCS ndash European Convention for Constructional Steelwork

ISBN (ECCS) 978-92-9147-135-5ISBN (Ernst amp Sohn) 978-3-433-03216-9Legal dep Printed in Sersilito Empresa Graacutefica Lda Maia PortugalPhoto cover credits Image courtesy of Mark Lawson SCI

TABLE OF CONTENTS

_____

v

TABLE OF CONTENTS

FOREWORD xiii

PREFACE xv

UK FOREWORD xix

NOTATION xxix

Chapter 1

INTRODUCTION 1

11 General 1111 Aims of the book 1112 Brief description of the contents of the book 10113 Types of structural systems and joints covered 11114 Basis of design 12

12 Definitions 12121 Joint properties 14122 Sources of joint deformation 15123 Beam splices and column splices 19124 Beam-to-beam joints 20125 Column bases 21126 Hollow section joints 22

13 Material choice 22

14 Fabrication and erection 26

15 Costs 27

16 Application of the ldquostatic approachrdquo 27161 Component approach 29162 Hybrid joints aspects 35

17 Design tools 35171 Types of design tools 36

TABLE OF CONTENTS

_____

vi

172 Examples of design tools 37

18 Worked examples 40

Chapter 2

STRUCTURAL ANALYSIS AND DESIGN 43

21 Introduction 43211 Elastic or elastoplastic analysis and verification process 44212 First order or second order analysis 45213 Integration of joint response into the frame analysis anddesign process 46

22 Joint modelling 47221 General 47222 Modelling and sources of joint deformation 49223 Simplified modelling according to EN 1993 50224 Concentration of the joint deformation 51

23 Joint idealisation 56231 Elastic idealisation for an elastic analysis 57232 Rigid-plastic idealisation for a rigid-plastic analysis 58233 Non-linear idealisation for an elastic-plastic analysis 59

24 Joint classification 59241 General 59242 Classification based on mechanical joint properties 60

25 Ductility classes 62251 General concept 62252 Requirements for classes of joints 65

Chapter 3

CONNECTIONS WITH MECHANICAL FASTENERS 67

31 Mechanical fasteners 67

32 Categories of connections 69321 Shear connections 69322 Tension connections 71

TABLE OF CONTENTS

_____

vii

33 Positioning of bolt holes 72

34 Design of the basic components 74341 Bolts in shear 74342 Bolts in tension 75343 Bolts in shear and tension 76344 Preloaded bolts 77345 Plates in bearing 85346 Block tearing 86347 Injection bolts 87348 Pins 88349 Blind bolting 913410 Nails 943411 Eccentricity of angles 95

35 Design of connections 97351 Bolted lap joints 97352 Bolted T-stubs 101353 Gusset plates 113354 Long joints 117

Chapter 4

WELDED CONNECTIONS 119

41 Types of welds 119411 Butt welds 119412 Fillet welds 120413 Fillet welds all round 121414 Plug welds 122

42 Construction constraints 122421 Mechanical properties of materials 122422 Welding processes preparation of welds and weld quality 123423 Geometry and dimensions of welds 127

43 Design of welds 130431 Generalities 130432 Fillet welds 131433 Fillet welds all round 134

TABLE OF CONTENTS

_____

viii

434 Butt welds 135435 Plug welds 136436 Concept of full strength fillet weld 136

44 Distribution of forces in a welded joint 139441 Generalities 139442 Particular situations 141

Chapter 5

SIMPLE JOINTS 147

51 Introduction 147

52 Beam-to-column and beam-to-beam joints 149521 Introduction 149522 Scope and field of application 150523 Joint modelling for frame analysis and design requirements 153524 Design resistance 156525 Practical ways to satisfy the ductility and rotationrequirements 163

53 Column bases 174531 Introduction 174532 Basis for the evaluation of the design resistance 176533 Resistance to axial forces 177534 Resistance to shear forces 185

Chapter 6

MOMENT-RESISTING JOINTS 189

61 Introduction 189

62 Component characterisation 190621 Column web panel in shear in steel or composite joints 190622 Column web in transverse compression in steel or compositejoints 192623 Column web in transverse tension 196624 Column flange in transverse bending 197625 End plate in bending 203

TABLE OF CONTENTS

_____

ix

626 Flange cleat in bending 205627 Beam or column flange and web in compression 207628 Beam web in tension 209629 Plate in tension or compression 2106210 Bolts in tension 2116211 Bolts in shear 2126212 Bolts in bearing (on beam flange column flange end plateor cleat) 2136213 Concrete in compression including grout 2136214 Base plate in bending under compression 2146215 Base plate in bending under tension 2146216 Anchor bolts in tension 2156217 Anchor bolts in shear 2156218 Anchor bolts in bearing 2156219 Welds 2166220 Haunched beam 216

63 Assembly for resistance 217631 Joints under bending moments 217632 Joints under axial forces 225633 Joints under bending moments and axial forces 226634 M minus N minus V 233635 Design of welds 234

64 Assembly for rotational stiffness 238641 Joints under bending moments 238642 Joints under bending moments and axial forces 247

65 Assembly for ductility 249651 Steel bolted joints 250652 Steel welded joints 252

66 Application to steel beam-to-column joint configurations 253661 Extended scope 253662 Possible design simplifications for end plate connections 256663 Worked example 257

67 Application to steel column splices 281671 Common splice configurations 281

TABLE OF CONTENTS

_____

x

672 Design considerations 283

68 Application to column bases 284681 Common column basis configurations 284682 Design considerations 287

Chapter 7

LATTICE GIRDER JOINTS 295

71 General 295

72 Scope and field of application 296

73 Design models 298731 General 298732 Failure modes 299733 Models for CHS chords 300734 Model for RHS chords 301735 Punching shear failure 302736 Model for brace failure 303737 M-N interaction 304

Chapter 8

JOINTS UNDER VARIOUS LOADING SITUATIONS 305

81 Introduction 305

82 Joints in fire 306

83 Joints under cyclic loading 307

84 Joints under exceptional events 308

Chapter 9

DESIGN STRATEGIES 311

91 Introduction 311

92 Traditional design approach 314

93 Integrated design approach 317

94 Economic considerations 319

TABLE OF CONTENTS

_____

xi

941 Fabrication and erections costs 319942 Savings of material costs 322943 Summary and conclusions 323

BIBLIOGRAPHIC REFERENCES 325

Annex A Practical values for required rotation capacity 337

Annex B Values for lateral torsional buckling strength of a fin plate 339

FOREWORD

_____

xiii

FOREWORD

With the ECCS book ldquoJoints in Steel and Composite Structuresrdquo the authorssucceeded in placing the joints on the rightful place they deserve in thestructural behaviour of steel and composite steel-concrete structures Themany times used word ldquodetailsrdquo for the joints in structures by farunderestimates the importance of joints in the structural behaviour ofbuildings and civil engineering structures In their chapter ldquoAim of the bookrdquothe authors clearly explain how the design and safety verification ofstructures runs in an integral manner where all structural componentsincluding the joints play balanced roles leading to economic structures

This book can be seen as a background document for Eurocode 3 ldquoDesign ofSteel Structuresrdquo as far as it concerns structural joints The central theme indescribing the behaviour of joints is using the component method and this isleading all over in this book The book contain many aspects such as designfabrication erection and costs

In this book attention is paid on joint modelling and idealisation jointclassification for strength and stiffness and deformation capacity This all forconnections with mechanical fasteners and for welded connections for simplejoints and moment resistant joints Also lattice girder joints are described

The book provides the designer with design strategies to arrive at economicstructures

The authors based themselves on many bibliographic references covering atime span of about 65 years Many of these references present research of theauthors themselves and of the other members of the ECCS-TechnicalCommittee TC10 ldquoStructural Connectionsrdquo

It was really a privilege to have been the chairperson of this committee from1998 till the end of 2012 and I thank the authors Prof Dr Ir Jean-PierreJaspart and Dr-Ing Klaus Weynand for their large effort in writing this book

Prof ir Frans Bijlaard

PREFACE

_____

xv

PREFACE

Steel constructions and composite steel-concrete constructions are generallyerected on site by the assembly of prefabricated structural parts prepared inthe workshop These parts may themselves be the result of an assembly ofindividual elements An example is the assembly by bolting on site offabricated sections welded in the workshop

In these construction types joints and connections play a key role andrecommendations and guidelines are required for engineers and constructorsfaced with the conception and design the fabrication and the erection of suchstructures In the Structural Eurocodes these aspects are mainly covered in theexecution standard EN 1090-2 and in the design standard EN 1993-1-8(Eurocode 3 Design of steel structures Part 1-8 Design of Joints)

In the present book which is part of the series of ECCS Eurocode DesignManuals the main focus is given to design aspects but references are alsomade to EN 1090-2 when necessary

In comparison to other fields the design procedures for joints andconnections have significantly evolved in the last decades as a result of theprogressive awareness by practitioners of the significant contribution ofjoints and connections to the global cost of structures Design for lowfabrication and erection costs as well as high resistance is therefore thetargeted objective of modern design codes the achievement of which hasjustified the development of new calculation approaches now integrated intothe two afore-mentioned Eurocodes This situation justifies the writing of thepresent manual with the main goal to demystify the process by explainingthe new concepts for the design of joints and to integrate their mechanicalresponse into the structural frame analysis and design process by providingldquokeysrdquo for a proper application in practice and finally by providing welldocumented worked examples

To refer to ldquomodernrdquo or ldquonewrdquo design approaches and philosophies does notmean that traditional ways are out dated or no more valid It should beunderstood that the design methods recommended in the Eurocodes are a

PREFACE

_____

xvi

collection of European practices including the results of intensive researchefforts carried out in the last decades and so give many options andalternatives to engineers who are trying to develop safe and economicsolutions

Chapter 1 introduces generalities about joint properties aspects of materialsfabrication erection and costs design approach - and especially the so-calledcomponent method - and design tools available to practitioners for easiercode application The integration of the response of the joints into thestructural analysis and design process is addressed in chapter 2 In chapter 3attention is paid to the design of common connections with mechanicalfasteners Preloaded bolts and non-preloaded bolts are mainly considered butthe use of some less classical connectors is also briefly described Weldedconnections are covered in chapter 5

The next three chapters relate to three specific types of joints respectivelysimple joints moment resisting joints and lattice girder joints For thesesubstantial innovations are brought in the Eurocodes in comparison totraditional national codes particularly for simple and moment resistingjoints A significant number of pages is therefore devoted to these topics inthis manual

The design of joints under static loading as it is addressed in the seven firstchapters is essential in all cases but further checks or different conceptualdesign of the joints are often required in case of load reversal fireearthquake or even exceptional events like impact or explosion Chapter 8summarises present knowledge in this field

Traditionally joints were designed as rigid or pinned which enables the designof the frame and the design of the joints to be treated independently The cleareconomical advantage associated in many situations with the use of semi-rigidandor partial-strength joints leads however to ldquostructure-jointsrdquo interactionsthat have to be mastered by the engineer so as to fully profit from the potentialcost savings The Eurocodes do not cover this interaction From this point ofview chapter 9 may be considered as ldquoa premiegravererdquo even if the content hasalready been partly described years ago in an ECSC publication

Before letting the reader discover the contents of this book we would like toexpress acknowledgment We are very grateful to Prof Frans Bijlaard for all

PREFACE

_____

xvii

the comments suggestions and corrections he made through the reviewprocess of the present manual Warm thanks are also addressed to Joseacute Fuchsand Soumlnke Muumlller who helped us in preparing the drawings Last but notleast we would like to thank our wives for their patience when we workedldquoon our projectrdquo during innumerable evenings and weekends

Jean-Pierre JaspartKlaus Weynand

UK FOREWORD

_____

xix

UK FOREWORD

INTRODUCTION

This book is the second in a series of joint publications of the EuropeanConvention for Constructional Steelwork (ECCS) and The Steel ConstructionInstitute (SCI) It will help provide UK engineers and designers with a betterunderstanding of the design principles in the European Code of Practice for theDesign of Steel Structures (EN 1993 ndash Eurocode 3) and the individual Part 18(EN 1993-1-8) for the design of steel joints in particular Reference will alsobe made to the associated Eurocodes for concrete (EN 1992 ndash Eurocode 2) andearthquake engineering (EN 1998 ndash Eurocode 8) The book complements otherSCI design guides eg SCI (2011 and 2013a)

The current publication is a first UK edition based on the first edition of theECCS manual for the Design of Joints in Steel and Composite Structureswhich was published in 2016 The scope of this UK edition is narrower thanthe original publication in two specific areas that are felt to be of limitedinterest to current practice in the UK there is no content covering compositejoints and chapter 9 (covering frame design strategies) has been shortened tosimply give an overview of strategies In this edition the reader will findinformation that is either of a general nature or relevant to specific sectionsof the publication to facilitate its application in a UK context

The content includes useful background to the code rules and a reminder ofsome engineering principles Information is presented in the context of theEurocodes terminology and notation and with reference to clause numbersetc to help the readerrsquos familiarity with EN 1993-1-8 The document thatserves as the basis for content and numbering of clauses is the UKimplementation of EN 1993-1-82005 incorporating corrigenda December2005 and July 2009 At the time of writing (Autumn 2016) part 1-8 ofEN 1993 is being revised with publication anticipated after 2020

Finally it is noted and should be accepted that there will inevitably be somedifferences of interpretation between the ECCS recommendations and thosepreviously published by the SCI

UK FOREWORD

_____

xx

GENERAL COMMENTS

Design of joints (connections) in steel structures in the UK is covered byBS EN 1993-1-8 and its national Annex (NA) (BSI 2010) BS EN 1993-1-8has clear definitions for connections and joints The term joint refers to thezone where members are interconnected and a connection is the locationwhere elements meet The distinction in terminology is usually emphasised inContinental Europe but traditional practice in the UK is to use the generic termconnection

The following partial safety factors are defined in the UK NA

Partial factor Value Comment

γM2 125 Used for the resistance of bolts pins and welds

γM2 125Used for the resistance of plates in bearing(γM2=15 should be used if deformation control is important)

γM3 125 Used for slip resistance at Ultimate Limit States

γM3serv 110 Used for slip resistance at Serviceability Limit States (SLS)

γM4 100 Used for the resistance of injection bolts

γM5 100 Used for the resistance of joints in hollow section lattice girders

γM6serv 100 Used for the resistance of pins at SLS

γM7

110Used for the preload of high strength steel bolts conforming toBS EN 14399-4 and BS EN 14399-8 (BSI 2015 and 2007)

100 Used for the preload of (other) high strength steel bolts

Specific reference to the UK Building Regulations is also made in this UKedition The UK Building Regulations code has structural integrityrequirements in order to avoid disproportionate collapse and ensure robustnessof the complete structure Disproportionate collapse can be defined as a regionof structural collapse out of proportion to the initiating cause of failure Themost relevant to connectionjoint design is that the detailing for every beam

UK FOREWORD

_____

xxi

member must be adequate to resist a minimum horizontal force at ultimatefailure (or tying resistance) Guidance on the design values of tying forces canbe found in BS EN 1991-1-7 Annex A and its UK annex (BSI 2014)

SECTION SPECIFIC COMMENTS

Section 111

UK practice normally considers only two main forms of joint modellingsimple and continuous Ideally frames designed on the basis of simple jointmodelling should use joints between members that possess negligiblerotational stiffness and transmit the beam reactions in shear into thecolumns without developing significant moments These joints may betreated as perfect pins Members can then be designed in isolation either as(predominantly) axially loaded columns or as simply supported beamsJoints designed within the principles of continuous modelling are capable oftransmitting significant moments and are able to maintain the original anglebetween adjacent members virtually unchanged This form of construction ofsteel frames is particularly advantageous when beam deflections are criticalor if bracing systems are not possible

To comply with one or the other design assumption steelwork connectionsare detailed as simple or moment-resisting joints Because joints in framestructures are often treated by adopting a degree of standardisation thedesigner usually details the connections in accordance with the principlesin the series of SCI Green Books which present this material in the formof step-by-step design procedures and tables covering standardarrangements

Other approximate analysis methods continue to be used among Britishdesigners the most representative being the wind-moment method for thedesign of unbraced multi-storey steel frames The method assumes that(i) under gravity loads the beam-to-column joints act as pinnedconnections and (ii) under horizontal wind loads these joints are rigidalthough it lacks transparency This method can be seen as a manifestationof the semi-continuous principles Wind moment connection details can befound in SCI (1995a) With the now widespread use of software in designoffices for rigorous second-order analysis it is doubtful if the use of the

UK FOREWORD

_____

xxii

wind-moment method should be advocated any longer other than forinitial sizing

Section 13

Although S460 is attracting growing interest S355 is still the dominantgrade of steel used in the UK

Section 161

With reference to Figure 120 it is noted that (site) welded joints and angleflange cleats are rarely if ever used in the UK

Section 162

Hybrid connections are rarely used in the UK for the reasons noted

Section 172

There is not much use of CoPcopy in the UK There are a number of othersoftware tools on the market some more comprehensive than others

Section 22

Although in UK design practice most aspects related to joint modelling havedeveloped to a high degree of sophistication proper consideration of thestructural interaction between the joints and members is rarely fully takeninto account It is indeed very difficult to predict and model the complexbehaviour of a joint (strength stiffness and rotation capacity) TraditionalUK practice is to predict joint behaviour on the basis of past experience

BSI (2010) separates the modelling of the rotational behaviour of theconnection elements (that is the bolts the welds the plates etc) and thatof the column web panel in shear to characterise the overall jointbehaviour As a simplification the two sources of joint deformation arecombined by means of the so-called transformation parameter β Thiscoefficient is related to the web panel internal actions and can be calculatedfrom the moments at each side of the web panel The β parameter iscurrently only defined for same-depth beams which meet at the same levelIn many practical double-sided joints beams will not be of the same depthor at the same height BS EN 1993-1-8 is silent on such joints

UK FOREWORD

_____

xxiii

Section 23

As explained above typical UK design practice does not consider thissophisticated procedure for idealisation of joints

Section 24

The NA to BS EN 1993-1-8 gives practical guidance to classify joints Italso states the following

ldquoUntil experience is gained with the numerical method of calculatingrotational stiffness given in BS EN 1993-1-82005 63 and theclassification by stiffness method given in BS EN 1993-1-82005522 semi-continuous elastic design should only be used where eitherit is supported by test evidence according to BS EN 1993-1-820055221(2) or where it is based on satisfactorily performance in asimilar situationrdquo

Evidence on values of column base stiffness for practical global analysis isgiven in SCI (2006)

Section 25

The concept of ductility classes is not widely applied in the UK It isgenerally assumed that standard connection details to the SCI Green Booksprovide enough rotation capacity and so behave in a ductile manner asevidenced by physical testing and experience

Section 31

The NA to BS EN 1993-1-8 excludes bolts of classes 58 and 68 It alsostates that bolt class 48 may only be used if the manufacturing process (i) isin accordance with BS EN ISO 898-1 (BSI 2013) and (ii) includes suitableprocedures to avoid hydrogen embrittlement

Section 322

The NA to BS EN 1993-1-8 states that if the preload is not explicitly used inthe design calculations then no specific level of preload is required

Section 347

Injection bolts are rarely used in the UK

UK FOREWORD

_____

xxiv

Section 348

Reference is made to SCI (1995b) to calculate the bending moments in thepin of a pin bearing

Section 349

Flow drill blind bolting is not common practice in the UK SHS blind boltingis a common system but there are several manufactures other than thatsuggested in the book

Section 3410

Nails are rarely used in the UK

Section 352

T-stub configurations with four bolts in a row are rarely used in the UK

Section 353

Reference is made to the SCI method for the design of gusset plates seeSCI (2011)

Section 421

It is anticipated that specific rules given in the current BS EN 1993-1-12(BSI 2009) for high strength steels will be incorporated in the revisedBS EN 1993-1-8 to appear after 2020

Section 522

ldquoHeader platesrdquo are known as ldquopartial depth end platesrdquo in the UK Webcleat connections are no longer commonly used in the UK The full depthend plate connection shown on the left of Figure 59 is classified as a simplejoint in the UK (SCI 2011)

Section 523

The UK Building Regulations require that joints are designed for tyingforces in order to satisfy structural integrity requirements Guidance onthe design values of tying forces is given in BS EN 1991-1-7 Annex Aand its UK NA The requirements relate to the building class with a

UK FOREWORD

_____

xxv

design value of horizontal force generally not less than 75 kN andusually significantly higher Simple joints detailed to SCI (2011) satisfythese requirements

Section 525

It is generally safe to assume that the ductility (rotation requirements) aresatisfied provided that joints are detailed in accordance with SCI (2011)

Section 531

The column base detailing on the left of Figure 521 is not commonly used inthe UK We never recommend less than four bolts ndash they are needed toassure stability and facilitate location during erection The anchoringsystems shown in Figure 522 are not usually adopted in the UK Referenceis made to SCI (2013a) for common anchor systems

Section 62

Publication SCI (2013b) summarises the principal differences betweenBS 5950 and BS EN 1993-1-8 (BSI 2000 and 2010) in terms ofcomponent characterisation

With reference to Figure 66 it is anticipated that the revised BS EN1993-1-8will include analytical expressions for the definition of the so-called αcoefficient

Rules of thumb for the characterisation of the ductility of some individualcomponents are given in SCI (1995a)

Section 631

The UK NA to BS EN 1993-1-8 gives specific rules for the full plasticdistribution of effective design tension resistance The procedure is alsosummarised in SCI (2013a)

Section 633

Where a joint is subjected to combined bending moments and axial forcesthe concept of an applied moment modified by axial load can be used seeSCI (1995a)

UK FOREWORD

_____

xxvi

Section 64

Rotational stiffness is not normally evaluated in UK design practice whichusually relies on past experience

Section 65

Some rules of thumb for the characterisation of the ductility of moment-resisting joints are given in SCI (1995a)

Section 661

With reference to Figure 636 it is noted that this joint configuration ishardly (if ever) used in the UK

Section 663

It should be noted that European sections are not commonly used in the UKalthough there is growing interest in the market Steel grade S235 is not usedin the UK S355 being the current common grade Combinations of plates of15 mm thickness with M24 bolts are common This combination is assumedto provide enough rotation capacity thus satisfying ductility requirementsbecause ductile failure of the plates not brittle failure of the bolts governsthe behaviour

Section 672

Standard practice in the UK does not account for this 25 rule Columnsplices are usually detailed to SCI (2011) to ensure continuity of stiffnessthrough the splice so that the member design is not invalidated

Section 84

The UK Building Regulations require that joints are designed for tyingforces in order to satisfy structural integrity requirements Guidance on thedesign values of tying forces is given in BS EN 1991-1-7 Annex A and itsUK NA (BSI 2014)

Section 91

In the UK the ldquofabricatorsrdquo are known as ldquoSteelwork contractorsrdquo becausethey do more than just fabricate

UK FOREWORD

_____

xxvii

REFERENCES TO NATIONAL FOREWORD

BSI (2000) BS 5950-12000 ndash Structural use of steelwork in building ndash Part1 Code of Practice for Design rolled and welded sections British StandardsInstitution United Kingdom

BSI (2007) BS EN 14399-82007 ndash High-strength structural boltingassemblies for preloading System HV Hexagon fit bolt and nut assembliesBritish Standards Institution United Kingdom

BSI (2009) BS EN 1993-1-122007 ndash Eurocode 3 Design of steel structuresndash Part 112 Additional rules for the extension of EN 1993 up to steel gradesS 700 British Standards Institution United Kingdom

BSI (2010) BS EN 1993-1-82005 ndash Eurocode 3 Design of steel structuresndash Part 18 Design of joints British Standards Institution United Kingdom

BSI (2013) BS EN ISO 898-12013 ndash Mechanical properties of fastenersmade of carbon steel and alloy steel Bolts screws and studs with specifiedproperty classes Coarse thread and fine pitch thread British StandardsInstitution United Kingdom

BSI (2014) BS EN 1991-1-72006+A12014 ndash Eurocode 1 Actions on structuresndash Part 197 General actions British Standards Institution United Kingdom

BSI (2015) BS EN 14399-42015 ndash High-strength structural boltingassemblies for preloading System HV Hexagon bolt and nut assembliesBritish Standards Institution United Kingdom

SCI (1995a) Joints in steel construction Moment connections P207 TheSteel Construction Institute

SCI (1995b) Advisory Desk Notes Bending Moment in a pin AD 172 TheSteel Construction Institute

SCI (2006) Column base stiffness for global analysis NCCI-SN045a TheSteel Construction Institute

SCI (2011) Joints in steel construction Simple joints to Eurocode 3 P358The Steel Construction Institute

SCI (2013a) Joints in steel construction Moment-resisting joints toEurocode 3 P398 The Steel Construction Institute

UK FOREWORD

_____

xxviii

SCI (2013b) Interim Report Design of Portal Frames to Eurocode 3 Anoverview for UK designers P400 The Steel Construction Institute

DESIGN OF JOINTS INSTEEL STRUCTURES

UK EDITION

ECCS EUROCODE DESIGN MANUALSECCS EDITORIAL BOARDLuiacutes Simotildees da Silva (ECCS)Antoacutenio Lamas (Portugal)Jean-Pierre Jaspart (Belgium)Reidar Bjorhovde (USA)Ulrike Kuhlmann (Germany)

DESIGN OFSTEELSTRUCTURESndash 2ND EDITIONLuiacutes Simotildees da Silva Rui Simotildees and Helena Gervaacutesio

FIRE DESIGN OF STEEL STRUCTURES ndash 2ND EDITIONJean-Marc Franssen and Paulo Vila Real

DESIGN OF PLATED STRUCTURESDarko Beg Ulrike Kuhlmann Laurence Davaine and Benjamin Braun

FATIGUE DESIGN OF STEEL AND COMPOSITE STRUCTURESAlain Nussbaumer Luiacutes Borges and Laurence Davaine

DESIGN OF COLD-FORMED STEEL STRUCTURESDan Dubina Viorel Ungureanu and Raffaele Landolfo

DESIGN OF JOINTS IN STEEL AND COMPOSITE STRUCTURESJean-Pierre Jaspart and Klaus Weynand

DESIGN OF STEEL STRUCTURES FOR BUILDINGS IN SEISMIC AREASRaffaele Landolfo Federico Mazzolani Dan Dubina Luiacutes Simotildees da Silva andMario drsquoAniello

ECCS ndash SCI EUROCODE DESIGN MANUALS

DESIGN OF JOINTS IN STEEL STRUCTURES UK EDITIONJean-Pierre Jaspart and Klaus WeynandAdapted to UK by Graham Couchman and Ana M Giratildeo Coelho

DESIGN OF STEEL STRUCTURES UK EDITIONLuiacutes Simotildees da Silva Rui Simotildees Helena GervaacutesioAdapted to UK by Graham Couchman

ECCSEUROCODE DESIGN MANUALS ndashBRAZILIAN EDITIONS

DIMENSIONAMENTO DE ESTRUTURAS DE ACcedilOLuiacutes Simotildees da Silva Rui Simotildees Helena Gervaacutesio Pedro Vellasco Luciano Lima

INFORMATION AND ORDERING DETAILS

For price availability and ordering visit our website wwwsteelconstructcomFor more information about books and journals visit wwwernst-und-sohnde

DESIGN OF JOINTS IN STEELSTRUCTURES

Eurocode 3 Design of steel structuresPart 1-8 ndash Design of Joints

UK Edition

Jean-Pierre JaspartKlaus Weynand

Adapted for the UK byGraham CouchmanAna M Giratildeo Coelho

Design of Joints in Steel Structures

UK Edition2017

Published byECCS ndash European Convention for Constructional Steelworkpublicationssteelconstructcomwwwsteelconstructcom

SalesWilhelm Ernst amp Sohn Verlag fuumlr Architektur und technische WissenschaftenGmbH amp Co KG Berlin

All rights reserved No parts of this publication may be reproduced stored in aretrieval system or transmitted in any form or by any means electronic mechanicalphotocopying recording or otherwise without the prior permission of the copyrightowner

ECCS assumes no liability with respect to the use for any application of the materialand information contained in this publication

Copyright copy 2017 ECCS ndash European Convention for Constructional Steelwork

ISBN (ECCS) 978-92-9147-135-5ISBN (Ernst amp Sohn) 978-3-433-03216-9Legal dep Printed in Sersilito Empresa Graacutefica Lda Maia PortugalPhoto cover credits Image courtesy of Mark Lawson SCI

TABLE OF CONTENTS

_____

v

TABLE OF CONTENTS

FOREWORD xiii

PREFACE xv

UK FOREWORD xix

NOTATION xxix

Chapter 1

INTRODUCTION 1

11 General 1111 Aims of the book 1112 Brief description of the contents of the book 10113 Types of structural systems and joints covered 11114 Basis of design 12

12 Definitions 12121 Joint properties 14122 Sources of joint deformation 15123 Beam splices and column splices 19124 Beam-to-beam joints 20125 Column bases 21126 Hollow section joints 22

13 Material choice 22

14 Fabrication and erection 26

15 Costs 27

16 Application of the ldquostatic approachrdquo 27161 Component approach 29162 Hybrid joints aspects 35

17 Design tools 35171 Types of design tools 36

TABLE OF CONTENTS

_____

vi

172 Examples of design tools 37

18 Worked examples 40

Chapter 2

STRUCTURAL ANALYSIS AND DESIGN 43

21 Introduction 43211 Elastic or elastoplastic analysis and verification process 44212 First order or second order analysis 45213 Integration of joint response into the frame analysis anddesign process 46

22 Joint modelling 47221 General 47222 Modelling and sources of joint deformation 49223 Simplified modelling according to EN 1993 50224 Concentration of the joint deformation 51

23 Joint idealisation 56231 Elastic idealisation for an elastic analysis 57232 Rigid-plastic idealisation for a rigid-plastic analysis 58233 Non-linear idealisation for an elastic-plastic analysis 59

24 Joint classification 59241 General 59242 Classification based on mechanical joint properties 60

25 Ductility classes 62251 General concept 62252 Requirements for classes of joints 65

Chapter 3

CONNECTIONS WITH MECHANICAL FASTENERS 67

31 Mechanical fasteners 67

32 Categories of connections 69321 Shear connections 69322 Tension connections 71

TABLE OF CONTENTS

_____

vii

33 Positioning of bolt holes 72

34 Design of the basic components 74341 Bolts in shear 74342 Bolts in tension 75343 Bolts in shear and tension 76344 Preloaded bolts 77345 Plates in bearing 85346 Block tearing 86347 Injection bolts 87348 Pins 88349 Blind bolting 913410 Nails 943411 Eccentricity of angles 95

35 Design of connections 97351 Bolted lap joints 97352 Bolted T-stubs 101353 Gusset plates 113354 Long joints 117

Chapter 4

WELDED CONNECTIONS 119

41 Types of welds 119411 Butt welds 119412 Fillet welds 120413 Fillet welds all round 121414 Plug welds 122

42 Construction constraints 122421 Mechanical properties of materials 122422 Welding processes preparation of welds and weld quality 123423 Geometry and dimensions of welds 127

43 Design of welds 130431 Generalities 130432 Fillet welds 131433 Fillet welds all round 134

TABLE OF CONTENTS

_____

viii

434 Butt welds 135435 Plug welds 136436 Concept of full strength fillet weld 136

44 Distribution of forces in a welded joint 139441 Generalities 139442 Particular situations 141

Chapter 5

SIMPLE JOINTS 147

51 Introduction 147

52 Beam-to-column and beam-to-beam joints 149521 Introduction 149522 Scope and field of application 150523 Joint modelling for frame analysis and design requirements 153524 Design resistance 156525 Practical ways to satisfy the ductility and rotationrequirements 163

53 Column bases 174531 Introduction 174532 Basis for the evaluation of the design resistance 176533 Resistance to axial forces 177534 Resistance to shear forces 185

Chapter 6

MOMENT-RESISTING JOINTS 189

61 Introduction 189

62 Component characterisation 190621 Column web panel in shear in steel or composite joints 190622 Column web in transverse compression in steel or compositejoints 192623 Column web in transverse tension 196624 Column flange in transverse bending 197625 End plate in bending 203

TABLE OF CONTENTS

_____

ix

626 Flange cleat in bending 205627 Beam or column flange and web in compression 207628 Beam web in tension 209629 Plate in tension or compression 2106210 Bolts in tension 2116211 Bolts in shear 2126212 Bolts in bearing (on beam flange column flange end plateor cleat) 2136213 Concrete in compression including grout 2136214 Base plate in bending under compression 2146215 Base plate in bending under tension 2146216 Anchor bolts in tension 2156217 Anchor bolts in shear 2156218 Anchor bolts in bearing 2156219 Welds 2166220 Haunched beam 216

63 Assembly for resistance 217631 Joints under bending moments 217632 Joints under axial forces 225633 Joints under bending moments and axial forces 226634 M minus N minus V 233635 Design of welds 234

64 Assembly for rotational stiffness 238641 Joints under bending moments 238642 Joints under bending moments and axial forces 247

65 Assembly for ductility 249651 Steel bolted joints 250652 Steel welded joints 252

66 Application to steel beam-to-column joint configurations 253661 Extended scope 253662 Possible design simplifications for end plate connections 256663 Worked example 257

67 Application to steel column splices 281671 Common splice configurations 281

TABLE OF CONTENTS

_____

x

672 Design considerations 283

68 Application to column bases 284681 Common column basis configurations 284682 Design considerations 287

Chapter 7

LATTICE GIRDER JOINTS 295

71 General 295

72 Scope and field of application 296

73 Design models 298731 General 298732 Failure modes 299733 Models for CHS chords 300734 Model for RHS chords 301735 Punching shear failure 302736 Model for brace failure 303737 M-N interaction 304

Chapter 8

JOINTS UNDER VARIOUS LOADING SITUATIONS 305

81 Introduction 305

82 Joints in fire 306

83 Joints under cyclic loading 307

84 Joints under exceptional events 308

Chapter 9

DESIGN STRATEGIES 311

91 Introduction 311

92 Traditional design approach 314

93 Integrated design approach 317

94 Economic considerations 319

TABLE OF CONTENTS

_____

xi

941 Fabrication and erections costs 319942 Savings of material costs 322943 Summary and conclusions 323

BIBLIOGRAPHIC REFERENCES 325

Annex A Practical values for required rotation capacity 337

Annex B Values for lateral torsional buckling strength of a fin plate 339

FOREWORD

_____

xiii

FOREWORD

With the ECCS book ldquoJoints in Steel and Composite Structuresrdquo the authorssucceeded in placing the joints on the rightful place they deserve in thestructural behaviour of steel and composite steel-concrete structures Themany times used word ldquodetailsrdquo for the joints in structures by farunderestimates the importance of joints in the structural behaviour ofbuildings and civil engineering structures In their chapter ldquoAim of the bookrdquothe authors clearly explain how the design and safety verification ofstructures runs in an integral manner where all structural componentsincluding the joints play balanced roles leading to economic structures

This book can be seen as a background document for Eurocode 3 ldquoDesign ofSteel Structuresrdquo as far as it concerns structural joints The central theme indescribing the behaviour of joints is using the component method and this isleading all over in this book The book contain many aspects such as designfabrication erection and costs

In this book attention is paid on joint modelling and idealisation jointclassification for strength and stiffness and deformation capacity This all forconnections with mechanical fasteners and for welded connections for simplejoints and moment resistant joints Also lattice girder joints are described

The book provides the designer with design strategies to arrive at economicstructures

The authors based themselves on many bibliographic references covering atime span of about 65 years Many of these references present research of theauthors themselves and of the other members of the ECCS-TechnicalCommittee TC10 ldquoStructural Connectionsrdquo

It was really a privilege to have been the chairperson of this committee from1998 till the end of 2012 and I thank the authors Prof Dr Ir Jean-PierreJaspart and Dr-Ing Klaus Weynand for their large effort in writing this book

Prof ir Frans Bijlaard

PREFACE

_____

xv

PREFACE

Steel constructions and composite steel-concrete constructions are generallyerected on site by the assembly of prefabricated structural parts prepared inthe workshop These parts may themselves be the result of an assembly ofindividual elements An example is the assembly by bolting on site offabricated sections welded in the workshop

In these construction types joints and connections play a key role andrecommendations and guidelines are required for engineers and constructorsfaced with the conception and design the fabrication and the erection of suchstructures In the Structural Eurocodes these aspects are mainly covered in theexecution standard EN 1090-2 and in the design standard EN 1993-1-8(Eurocode 3 Design of steel structures Part 1-8 Design of Joints)

In the present book which is part of the series of ECCS Eurocode DesignManuals the main focus is given to design aspects but references are alsomade to EN 1090-2 when necessary

In comparison to other fields the design procedures for joints andconnections have significantly evolved in the last decades as a result of theprogressive awareness by practitioners of the significant contribution ofjoints and connections to the global cost of structures Design for lowfabrication and erection costs as well as high resistance is therefore thetargeted objective of modern design codes the achievement of which hasjustified the development of new calculation approaches now integrated intothe two afore-mentioned Eurocodes This situation justifies the writing of thepresent manual with the main goal to demystify the process by explainingthe new concepts for the design of joints and to integrate their mechanicalresponse into the structural frame analysis and design process by providingldquokeysrdquo for a proper application in practice and finally by providing welldocumented worked examples

To refer to ldquomodernrdquo or ldquonewrdquo design approaches and philosophies does notmean that traditional ways are out dated or no more valid It should beunderstood that the design methods recommended in the Eurocodes are a

PREFACE

_____

xvi

collection of European practices including the results of intensive researchefforts carried out in the last decades and so give many options andalternatives to engineers who are trying to develop safe and economicsolutions

Chapter 1 introduces generalities about joint properties aspects of materialsfabrication erection and costs design approach - and especially the so-calledcomponent method - and design tools available to practitioners for easiercode application The integration of the response of the joints into thestructural analysis and design process is addressed in chapter 2 In chapter 3attention is paid to the design of common connections with mechanicalfasteners Preloaded bolts and non-preloaded bolts are mainly considered butthe use of some less classical connectors is also briefly described Weldedconnections are covered in chapter 5

The next three chapters relate to three specific types of joints respectivelysimple joints moment resisting joints and lattice girder joints For thesesubstantial innovations are brought in the Eurocodes in comparison totraditional national codes particularly for simple and moment resistingjoints A significant number of pages is therefore devoted to these topics inthis manual

The design of joints under static loading as it is addressed in the seven firstchapters is essential in all cases but further checks or different conceptualdesign of the joints are often required in case of load reversal fireearthquake or even exceptional events like impact or explosion Chapter 8summarises present knowledge in this field

Traditionally joints were designed as rigid or pinned which enables the designof the frame and the design of the joints to be treated independently The cleareconomical advantage associated in many situations with the use of semi-rigidandor partial-strength joints leads however to ldquostructure-jointsrdquo interactionsthat have to be mastered by the engineer so as to fully profit from the potentialcost savings The Eurocodes do not cover this interaction From this point ofview chapter 9 may be considered as ldquoa premiegravererdquo even if the content hasalready been partly described years ago in an ECSC publication

Before letting the reader discover the contents of this book we would like toexpress acknowledgment We are very grateful to Prof Frans Bijlaard for all

PREFACE

_____

xvii

the comments suggestions and corrections he made through the reviewprocess of the present manual Warm thanks are also addressed to Joseacute Fuchsand Soumlnke Muumlller who helped us in preparing the drawings Last but notleast we would like to thank our wives for their patience when we workedldquoon our projectrdquo during innumerable evenings and weekends

Jean-Pierre JaspartKlaus Weynand

UK FOREWORD

_____

xix

UK FOREWORD

INTRODUCTION

This book is the second in a series of joint publications of the EuropeanConvention for Constructional Steelwork (ECCS) and The Steel ConstructionInstitute (SCI) It will help provide UK engineers and designers with a betterunderstanding of the design principles in the European Code of Practice for theDesign of Steel Structures (EN 1993 ndash Eurocode 3) and the individual Part 18(EN 1993-1-8) for the design of steel joints in particular Reference will alsobe made to the associated Eurocodes for concrete (EN 1992 ndash Eurocode 2) andearthquake engineering (EN 1998 ndash Eurocode 8) The book complements otherSCI design guides eg SCI (2011 and 2013a)

The current publication is a first UK edition based on the first edition of theECCS manual for the Design of Joints in Steel and Composite Structureswhich was published in 2016 The scope of this UK edition is narrower thanthe original publication in two specific areas that are felt to be of limitedinterest to current practice in the UK there is no content covering compositejoints and chapter 9 (covering frame design strategies) has been shortened tosimply give an overview of strategies In this edition the reader will findinformation that is either of a general nature or relevant to specific sectionsof the publication to facilitate its application in a UK context

The content includes useful background to the code rules and a reminder ofsome engineering principles Information is presented in the context of theEurocodes terminology and notation and with reference to clause numbersetc to help the readerrsquos familiarity with EN 1993-1-8 The document thatserves as the basis for content and numbering of clauses is the UKimplementation of EN 1993-1-82005 incorporating corrigenda December2005 and July 2009 At the time of writing (Autumn 2016) part 1-8 ofEN 1993 is being revised with publication anticipated after 2020

Finally it is noted and should be accepted that there will inevitably be somedifferences of interpretation between the ECCS recommendations and thosepreviously published by the SCI

UK FOREWORD

_____

xx

GENERAL COMMENTS

Design of joints (connections) in steel structures in the UK is covered byBS EN 1993-1-8 and its national Annex (NA) (BSI 2010) BS EN 1993-1-8has clear definitions for connections and joints The term joint refers to thezone where members are interconnected and a connection is the locationwhere elements meet The distinction in terminology is usually emphasised inContinental Europe but traditional practice in the UK is to use the generic termconnection

The following partial safety factors are defined in the UK NA

Partial factor Value Comment

γM2 125 Used for the resistance of bolts pins and welds

γM2 125Used for the resistance of plates in bearing(γM2=15 should be used if deformation control is important)

γM3 125 Used for slip resistance at Ultimate Limit States

γM3serv 110 Used for slip resistance at Serviceability Limit States (SLS)

γM4 100 Used for the resistance of injection bolts

γM5 100 Used for the resistance of joints in hollow section lattice girders

γM6serv 100 Used for the resistance of pins at SLS

γM7

110Used for the preload of high strength steel bolts conforming toBS EN 14399-4 and BS EN 14399-8 (BSI 2015 and 2007)

100 Used for the preload of (other) high strength steel bolts

Specific reference to the UK Building Regulations is also made in this UKedition The UK Building Regulations code has structural integrityrequirements in order to avoid disproportionate collapse and ensure robustnessof the complete structure Disproportionate collapse can be defined as a regionof structural collapse out of proportion to the initiating cause of failure Themost relevant to connectionjoint design is that the detailing for every beam

UK FOREWORD

_____

xxi

member must be adequate to resist a minimum horizontal force at ultimatefailure (or tying resistance) Guidance on the design values of tying forces canbe found in BS EN 1991-1-7 Annex A and its UK annex (BSI 2014)

SECTION SPECIFIC COMMENTS

Section 111

UK practice normally considers only two main forms of joint modellingsimple and continuous Ideally frames designed on the basis of simple jointmodelling should use joints between members that possess negligiblerotational stiffness and transmit the beam reactions in shear into thecolumns without developing significant moments These joints may betreated as perfect pins Members can then be designed in isolation either as(predominantly) axially loaded columns or as simply supported beamsJoints designed within the principles of continuous modelling are capable oftransmitting significant moments and are able to maintain the original anglebetween adjacent members virtually unchanged This form of construction ofsteel frames is particularly advantageous when beam deflections are criticalor if bracing systems are not possible

To comply with one or the other design assumption steelwork connectionsare detailed as simple or moment-resisting joints Because joints in framestructures are often treated by adopting a degree of standardisation thedesigner usually details the connections in accordance with the principlesin the series of SCI Green Books which present this material in the formof step-by-step design procedures and tables covering standardarrangements

Other approximate analysis methods continue to be used among Britishdesigners the most representative being the wind-moment method for thedesign of unbraced multi-storey steel frames The method assumes that(i) under gravity loads the beam-to-column joints act as pinnedconnections and (ii) under horizontal wind loads these joints are rigidalthough it lacks transparency This method can be seen as a manifestationof the semi-continuous principles Wind moment connection details can befound in SCI (1995a) With the now widespread use of software in designoffices for rigorous second-order analysis it is doubtful if the use of the

UK FOREWORD

_____

xxii

wind-moment method should be advocated any longer other than forinitial sizing

Section 13

Although S460 is attracting growing interest S355 is still the dominantgrade of steel used in the UK

Section 161

With reference to Figure 120 it is noted that (site) welded joints and angleflange cleats are rarely if ever used in the UK

Section 162

Hybrid connections are rarely used in the UK for the reasons noted

Section 172

There is not much use of CoPcopy in the UK There are a number of othersoftware tools on the market some more comprehensive than others

Section 22

Although in UK design practice most aspects related to joint modelling havedeveloped to a high degree of sophistication proper consideration of thestructural interaction between the joints and members is rarely fully takeninto account It is indeed very difficult to predict and model the complexbehaviour of a joint (strength stiffness and rotation capacity) TraditionalUK practice is to predict joint behaviour on the basis of past experience

BSI (2010) separates the modelling of the rotational behaviour of theconnection elements (that is the bolts the welds the plates etc) and thatof the column web panel in shear to characterise the overall jointbehaviour As a simplification the two sources of joint deformation arecombined by means of the so-called transformation parameter β Thiscoefficient is related to the web panel internal actions and can be calculatedfrom the moments at each side of the web panel The β parameter iscurrently only defined for same-depth beams which meet at the same levelIn many practical double-sided joints beams will not be of the same depthor at the same height BS EN 1993-1-8 is silent on such joints

UK FOREWORD

_____

xxiii

Section 23

As explained above typical UK design practice does not consider thissophisticated procedure for idealisation of joints

Section 24

The NA to BS EN 1993-1-8 gives practical guidance to classify joints Italso states the following

ldquoUntil experience is gained with the numerical method of calculatingrotational stiffness given in BS EN 1993-1-82005 63 and theclassification by stiffness method given in BS EN 1993-1-82005522 semi-continuous elastic design should only be used where eitherit is supported by test evidence according to BS EN 1993-1-820055221(2) or where it is based on satisfactorily performance in asimilar situationrdquo

Evidence on values of column base stiffness for practical global analysis isgiven in SCI (2006)

Section 25

The concept of ductility classes is not widely applied in the UK It isgenerally assumed that standard connection details to the SCI Green Booksprovide enough rotation capacity and so behave in a ductile manner asevidenced by physical testing and experience

Section 31

The NA to BS EN 1993-1-8 excludes bolts of classes 58 and 68 It alsostates that bolt class 48 may only be used if the manufacturing process (i) isin accordance with BS EN ISO 898-1 (BSI 2013) and (ii) includes suitableprocedures to avoid hydrogen embrittlement

Section 322

The NA to BS EN 1993-1-8 states that if the preload is not explicitly used inthe design calculations then no specific level of preload is required

Section 347

Injection bolts are rarely used in the UK

UK FOREWORD

_____

xxiv

Section 348

Reference is made to SCI (1995b) to calculate the bending moments in thepin of a pin bearing

Section 349

Flow drill blind bolting is not common practice in the UK SHS blind boltingis a common system but there are several manufactures other than thatsuggested in the book

Section 3410

Nails are rarely used in the UK

Section 352

T-stub configurations with four bolts in a row are rarely used in the UK

Section 353

Reference is made to the SCI method for the design of gusset plates seeSCI (2011)

Section 421

It is anticipated that specific rules given in the current BS EN 1993-1-12(BSI 2009) for high strength steels will be incorporated in the revisedBS EN 1993-1-8 to appear after 2020

Section 522

ldquoHeader platesrdquo are known as ldquopartial depth end platesrdquo in the UK Webcleat connections are no longer commonly used in the UK The full depthend plate connection shown on the left of Figure 59 is classified as a simplejoint in the UK (SCI 2011)

Section 523

The UK Building Regulations require that joints are designed for tyingforces in order to satisfy structural integrity requirements Guidance onthe design values of tying forces is given in BS EN 1991-1-7 Annex Aand its UK NA The requirements relate to the building class with a

UK FOREWORD

_____

xxv

design value of horizontal force generally not less than 75 kN andusually significantly higher Simple joints detailed to SCI (2011) satisfythese requirements

Section 525

It is generally safe to assume that the ductility (rotation requirements) aresatisfied provided that joints are detailed in accordance with SCI (2011)

Section 531

The column base detailing on the left of Figure 521 is not commonly used inthe UK We never recommend less than four bolts ndash they are needed toassure stability and facilitate location during erection The anchoringsystems shown in Figure 522 are not usually adopted in the UK Referenceis made to SCI (2013a) for common anchor systems

Section 62

Publication SCI (2013b) summarises the principal differences betweenBS 5950 and BS EN 1993-1-8 (BSI 2000 and 2010) in terms ofcomponent characterisation

With reference to Figure 66 it is anticipated that the revised BS EN1993-1-8will include analytical expressions for the definition of the so-called αcoefficient

Rules of thumb for the characterisation of the ductility of some individualcomponents are given in SCI (1995a)

Section 631

The UK NA to BS EN 1993-1-8 gives specific rules for the full plasticdistribution of effective design tension resistance The procedure is alsosummarised in SCI (2013a)

Section 633

Where a joint is subjected to combined bending moments and axial forcesthe concept of an applied moment modified by axial load can be used seeSCI (1995a)

UK FOREWORD

_____

xxvi

Section 64

Rotational stiffness is not normally evaluated in UK design practice whichusually relies on past experience

Section 65

Some rules of thumb for the characterisation of the ductility of moment-resisting joints are given in SCI (1995a)

Section 661

With reference to Figure 636 it is noted that this joint configuration ishardly (if ever) used in the UK

Section 663

It should be noted that European sections are not commonly used in the UKalthough there is growing interest in the market Steel grade S235 is not usedin the UK S355 being the current common grade Combinations of plates of15 mm thickness with M24 bolts are common This combination is assumedto provide enough rotation capacity thus satisfying ductility requirementsbecause ductile failure of the plates not brittle failure of the bolts governsthe behaviour

Section 672

Standard practice in the UK does not account for this 25 rule Columnsplices are usually detailed to SCI (2011) to ensure continuity of stiffnessthrough the splice so that the member design is not invalidated

Section 84

The UK Building Regulations require that joints are designed for tyingforces in order to satisfy structural integrity requirements Guidance on thedesign values of tying forces is given in BS EN 1991-1-7 Annex A and itsUK NA (BSI 2014)

Section 91

In the UK the ldquofabricatorsrdquo are known as ldquoSteelwork contractorsrdquo becausethey do more than just fabricate

UK FOREWORD

_____

xxvii

REFERENCES TO NATIONAL FOREWORD

BSI (2000) BS 5950-12000 ndash Structural use of steelwork in building ndash Part1 Code of Practice for Design rolled and welded sections British StandardsInstitution United Kingdom

BSI (2007) BS EN 14399-82007 ndash High-strength structural boltingassemblies for preloading System HV Hexagon fit bolt and nut assembliesBritish Standards Institution United Kingdom

BSI (2009) BS EN 1993-1-122007 ndash Eurocode 3 Design of steel structuresndash Part 112 Additional rules for the extension of EN 1993 up to steel gradesS 700 British Standards Institution United Kingdom

BSI (2010) BS EN 1993-1-82005 ndash Eurocode 3 Design of steel structuresndash Part 18 Design of joints British Standards Institution United Kingdom

BSI (2013) BS EN ISO 898-12013 ndash Mechanical properties of fastenersmade of carbon steel and alloy steel Bolts screws and studs with specifiedproperty classes Coarse thread and fine pitch thread British StandardsInstitution United Kingdom

BSI (2014) BS EN 1991-1-72006+A12014 ndash Eurocode 1 Actions on structuresndash Part 197 General actions British Standards Institution United Kingdom

BSI (2015) BS EN 14399-42015 ndash High-strength structural boltingassemblies for preloading System HV Hexagon bolt and nut assembliesBritish Standards Institution United Kingdom

SCI (1995a) Joints in steel construction Moment connections P207 TheSteel Construction Institute

SCI (1995b) Advisory Desk Notes Bending Moment in a pin AD 172 TheSteel Construction Institute

SCI (2006) Column base stiffness for global analysis NCCI-SN045a TheSteel Construction Institute

SCI (2011) Joints in steel construction Simple joints to Eurocode 3 P358The Steel Construction Institute

SCI (2013a) Joints in steel construction Moment-resisting joints toEurocode 3 P398 The Steel Construction Institute

UK FOREWORD

_____

xxviii

SCI (2013b) Interim Report Design of Portal Frames to Eurocode 3 Anoverview for UK designers P400 The Steel Construction Institute

ECCS EUROCODE DESIGN MANUALSECCS EDITORIAL BOARDLuiacutes Simotildees da Silva (ECCS)Antoacutenio Lamas (Portugal)Jean-Pierre Jaspart (Belgium)Reidar Bjorhovde (USA)Ulrike Kuhlmann (Germany)

DESIGN OFSTEELSTRUCTURESndash 2ND EDITIONLuiacutes Simotildees da Silva Rui Simotildees and Helena Gervaacutesio

FIRE DESIGN OF STEEL STRUCTURES ndash 2ND EDITIONJean-Marc Franssen and Paulo Vila Real

DESIGN OF PLATED STRUCTURESDarko Beg Ulrike Kuhlmann Laurence Davaine and Benjamin Braun

FATIGUE DESIGN OF STEEL AND COMPOSITE STRUCTURESAlain Nussbaumer Luiacutes Borges and Laurence Davaine

DESIGN OF COLD-FORMED STEEL STRUCTURESDan Dubina Viorel Ungureanu and Raffaele Landolfo

DESIGN OF JOINTS IN STEEL AND COMPOSITE STRUCTURESJean-Pierre Jaspart and Klaus Weynand

DESIGN OF STEEL STRUCTURES FOR BUILDINGS IN SEISMIC AREASRaffaele Landolfo Federico Mazzolani Dan Dubina Luiacutes Simotildees da Silva andMario drsquoAniello

ECCS ndash SCI EUROCODE DESIGN MANUALS

DESIGN OF JOINTS IN STEEL STRUCTURES UK EDITIONJean-Pierre Jaspart and Klaus WeynandAdapted to UK by Graham Couchman and Ana M Giratildeo Coelho

DESIGN OF STEEL STRUCTURES UK EDITIONLuiacutes Simotildees da Silva Rui Simotildees Helena GervaacutesioAdapted to UK by Graham Couchman

ECCSEUROCODE DESIGN MANUALS ndashBRAZILIAN EDITIONS

DIMENSIONAMENTO DE ESTRUTURAS DE ACcedilOLuiacutes Simotildees da Silva Rui Simotildees Helena Gervaacutesio Pedro Vellasco Luciano Lima

INFORMATION AND ORDERING DETAILS

For price availability and ordering visit our website wwwsteelconstructcomFor more information about books and journals visit wwwernst-und-sohnde

DESIGN OF JOINTS IN STEELSTRUCTURES

Eurocode 3 Design of steel structuresPart 1-8 ndash Design of Joints

UK Edition

Jean-Pierre JaspartKlaus Weynand

Adapted for the UK byGraham CouchmanAna M Giratildeo Coelho

Design of Joints in Steel Structures

UK Edition2017

Published byECCS ndash European Convention for Constructional Steelworkpublicationssteelconstructcomwwwsteelconstructcom

SalesWilhelm Ernst amp Sohn Verlag fuumlr Architektur und technische WissenschaftenGmbH amp Co KG Berlin

All rights reserved No parts of this publication may be reproduced stored in aretrieval system or transmitted in any form or by any means electronic mechanicalphotocopying recording or otherwise without the prior permission of the copyrightowner

ECCS assumes no liability with respect to the use for any application of the materialand information contained in this publication

Copyright copy 2017 ECCS ndash European Convention for Constructional Steelwork

ISBN (ECCS) 978-92-9147-135-5ISBN (Ernst amp Sohn) 978-3-433-03216-9Legal dep Printed in Sersilito Empresa Graacutefica Lda Maia PortugalPhoto cover credits Image courtesy of Mark Lawson SCI

TABLE OF CONTENTS

_____

v

TABLE OF CONTENTS

FOREWORD xiii

PREFACE xv

UK FOREWORD xix

NOTATION xxix

Chapter 1

INTRODUCTION 1

11 General 1111 Aims of the book 1112 Brief description of the contents of the book 10113 Types of structural systems and joints covered 11114 Basis of design 12

12 Definitions 12121 Joint properties 14122 Sources of joint deformation 15123 Beam splices and column splices 19124 Beam-to-beam joints 20125 Column bases 21126 Hollow section joints 22

13 Material choice 22

14 Fabrication and erection 26

15 Costs 27

16 Application of the ldquostatic approachrdquo 27161 Component approach 29162 Hybrid joints aspects 35

17 Design tools 35171 Types of design tools 36

TABLE OF CONTENTS

_____

vi

172 Examples of design tools 37

18 Worked examples 40

Chapter 2

STRUCTURAL ANALYSIS AND DESIGN 43

21 Introduction 43211 Elastic or elastoplastic analysis and verification process 44212 First order or second order analysis 45213 Integration of joint response into the frame analysis anddesign process 46

22 Joint modelling 47221 General 47222 Modelling and sources of joint deformation 49223 Simplified modelling according to EN 1993 50224 Concentration of the joint deformation 51

23 Joint idealisation 56231 Elastic idealisation for an elastic analysis 57232 Rigid-plastic idealisation for a rigid-plastic analysis 58233 Non-linear idealisation for an elastic-plastic analysis 59

24 Joint classification 59241 General 59242 Classification based on mechanical joint properties 60

25 Ductility classes 62251 General concept 62252 Requirements for classes of joints 65

Chapter 3

CONNECTIONS WITH MECHANICAL FASTENERS 67

31 Mechanical fasteners 67

32 Categories of connections 69321 Shear connections 69322 Tension connections 71

TABLE OF CONTENTS

_____

vii

33 Positioning of bolt holes 72

34 Design of the basic components 74341 Bolts in shear 74342 Bolts in tension 75343 Bolts in shear and tension 76344 Preloaded bolts 77345 Plates in bearing 85346 Block tearing 86347 Injection bolts 87348 Pins 88349 Blind bolting 913410 Nails 943411 Eccentricity of angles 95

35 Design of connections 97351 Bolted lap joints 97352 Bolted T-stubs 101353 Gusset plates 113354 Long joints 117

Chapter 4

WELDED CONNECTIONS 119

41 Types of welds 119411 Butt welds 119412 Fillet welds 120413 Fillet welds all round 121414 Plug welds 122

42 Construction constraints 122421 Mechanical properties of materials 122422 Welding processes preparation of welds and weld quality 123423 Geometry and dimensions of welds 127

43 Design of welds 130431 Generalities 130432 Fillet welds 131433 Fillet welds all round 134

TABLE OF CONTENTS

_____

viii

434 Butt welds 135435 Plug welds 136436 Concept of full strength fillet weld 136

44 Distribution of forces in a welded joint 139441 Generalities 139442 Particular situations 141

Chapter 5

SIMPLE JOINTS 147

51 Introduction 147

52 Beam-to-column and beam-to-beam joints 149521 Introduction 149522 Scope and field of application 150523 Joint modelling for frame analysis and design requirements 153524 Design resistance 156525 Practical ways to satisfy the ductility and rotationrequirements 163

53 Column bases 174531 Introduction 174532 Basis for the evaluation of the design resistance 176533 Resistance to axial forces 177534 Resistance to shear forces 185

Chapter 6

MOMENT-RESISTING JOINTS 189

61 Introduction 189

62 Component characterisation 190621 Column web panel in shear in steel or composite joints 190622 Column web in transverse compression in steel or compositejoints 192623 Column web in transverse tension 196624 Column flange in transverse bending 197625 End plate in bending 203

TABLE OF CONTENTS

_____

ix

626 Flange cleat in bending 205627 Beam or column flange and web in compression 207628 Beam web in tension 209629 Plate in tension or compression 2106210 Bolts in tension 2116211 Bolts in shear 2126212 Bolts in bearing (on beam flange column flange end plateor cleat) 2136213 Concrete in compression including grout 2136214 Base plate in bending under compression 2146215 Base plate in bending under tension 2146216 Anchor bolts in tension 2156217 Anchor bolts in shear 2156218 Anchor bolts in bearing 2156219 Welds 2166220 Haunched beam 216

63 Assembly for resistance 217631 Joints under bending moments 217632 Joints under axial forces 225633 Joints under bending moments and axial forces 226634 M minus N minus V 233635 Design of welds 234

64 Assembly for rotational stiffness 238641 Joints under bending moments 238642 Joints under bending moments and axial forces 247

65 Assembly for ductility 249651 Steel bolted joints 250652 Steel welded joints 252

66 Application to steel beam-to-column joint configurations 253661 Extended scope 253662 Possible design simplifications for end plate connections 256663 Worked example 257

67 Application to steel column splices 281671 Common splice configurations 281

TABLE OF CONTENTS

_____

x

672 Design considerations 283

68 Application to column bases 284681 Common column basis configurations 284682 Design considerations 287

Chapter 7

LATTICE GIRDER JOINTS 295

71 General 295

72 Scope and field of application 296

73 Design models 298731 General 298732 Failure modes 299733 Models for CHS chords 300734 Model for RHS chords 301735 Punching shear failure 302736 Model for brace failure 303737 M-N interaction 304

Chapter 8

JOINTS UNDER VARIOUS LOADING SITUATIONS 305

81 Introduction 305

82 Joints in fire 306

83 Joints under cyclic loading 307

84 Joints under exceptional events 308

Chapter 9

DESIGN STRATEGIES 311

91 Introduction 311

92 Traditional design approach 314

93 Integrated design approach 317

94 Economic considerations 319

TABLE OF CONTENTS

_____

xi

941 Fabrication and erections costs 319942 Savings of material costs 322943 Summary and conclusions 323

BIBLIOGRAPHIC REFERENCES 325

Annex A Practical values for required rotation capacity 337

Annex B Values for lateral torsional buckling strength of a fin plate 339

FOREWORD

_____

xiii

FOREWORD

With the ECCS book ldquoJoints in Steel and Composite Structuresrdquo the authorssucceeded in placing the joints on the rightful place they deserve in thestructural behaviour of steel and composite steel-concrete structures Themany times used word ldquodetailsrdquo for the joints in structures by farunderestimates the importance of joints in the structural behaviour ofbuildings and civil engineering structures In their chapter ldquoAim of the bookrdquothe authors clearly explain how the design and safety verification ofstructures runs in an integral manner where all structural componentsincluding the joints play balanced roles leading to economic structures

This book can be seen as a background document for Eurocode 3 ldquoDesign ofSteel Structuresrdquo as far as it concerns structural joints The central theme indescribing the behaviour of joints is using the component method and this isleading all over in this book The book contain many aspects such as designfabrication erection and costs

In this book attention is paid on joint modelling and idealisation jointclassification for strength and stiffness and deformation capacity This all forconnections with mechanical fasteners and for welded connections for simplejoints and moment resistant joints Also lattice girder joints are described

The book provides the designer with design strategies to arrive at economicstructures

The authors based themselves on many bibliographic references covering atime span of about 65 years Many of these references present research of theauthors themselves and of the other members of the ECCS-TechnicalCommittee TC10 ldquoStructural Connectionsrdquo

It was really a privilege to have been the chairperson of this committee from1998 till the end of 2012 and I thank the authors Prof Dr Ir Jean-PierreJaspart and Dr-Ing Klaus Weynand for their large effort in writing this book

Prof ir Frans Bijlaard

PREFACE

_____

xv

PREFACE

Steel constructions and composite steel-concrete constructions are generallyerected on site by the assembly of prefabricated structural parts prepared inthe workshop These parts may themselves be the result of an assembly ofindividual elements An example is the assembly by bolting on site offabricated sections welded in the workshop

In these construction types joints and connections play a key role andrecommendations and guidelines are required for engineers and constructorsfaced with the conception and design the fabrication and the erection of suchstructures In the Structural Eurocodes these aspects are mainly covered in theexecution standard EN 1090-2 and in the design standard EN 1993-1-8(Eurocode 3 Design of steel structures Part 1-8 Design of Joints)

In the present book which is part of the series of ECCS Eurocode DesignManuals the main focus is given to design aspects but references are alsomade to EN 1090-2 when necessary

In comparison to other fields the design procedures for joints andconnections have significantly evolved in the last decades as a result of theprogressive awareness by practitioners of the significant contribution ofjoints and connections to the global cost of structures Design for lowfabrication and erection costs as well as high resistance is therefore thetargeted objective of modern design codes the achievement of which hasjustified the development of new calculation approaches now integrated intothe two afore-mentioned Eurocodes This situation justifies the writing of thepresent manual with the main goal to demystify the process by explainingthe new concepts for the design of joints and to integrate their mechanicalresponse into the structural frame analysis and design process by providingldquokeysrdquo for a proper application in practice and finally by providing welldocumented worked examples

To refer to ldquomodernrdquo or ldquonewrdquo design approaches and philosophies does notmean that traditional ways are out dated or no more valid It should beunderstood that the design methods recommended in the Eurocodes are a

PREFACE

_____

xvi

collection of European practices including the results of intensive researchefforts carried out in the last decades and so give many options andalternatives to engineers who are trying to develop safe and economicsolutions

Chapter 1 introduces generalities about joint properties aspects of materialsfabrication erection and costs design approach - and especially the so-calledcomponent method - and design tools available to practitioners for easiercode application The integration of the response of the joints into thestructural analysis and design process is addressed in chapter 2 In chapter 3attention is paid to the design of common connections with mechanicalfasteners Preloaded bolts and non-preloaded bolts are mainly considered butthe use of some less classical connectors is also briefly described Weldedconnections are covered in chapter 5

The next three chapters relate to three specific types of joints respectivelysimple joints moment resisting joints and lattice girder joints For thesesubstantial innovations are brought in the Eurocodes in comparison totraditional national codes particularly for simple and moment resistingjoints A significant number of pages is therefore devoted to these topics inthis manual

The design of joints under static loading as it is addressed in the seven firstchapters is essential in all cases but further checks or different conceptualdesign of the joints are often required in case of load reversal fireearthquake or even exceptional events like impact or explosion Chapter 8summarises present knowledge in this field

Traditionally joints were designed as rigid or pinned which enables the designof the frame and the design of the joints to be treated independently The cleareconomical advantage associated in many situations with the use of semi-rigidandor partial-strength joints leads however to ldquostructure-jointsrdquo interactionsthat have to be mastered by the engineer so as to fully profit from the potentialcost savings The Eurocodes do not cover this interaction From this point ofview chapter 9 may be considered as ldquoa premiegravererdquo even if the content hasalready been partly described years ago in an ECSC publication

Before letting the reader discover the contents of this book we would like toexpress acknowledgment We are very grateful to Prof Frans Bijlaard for all

PREFACE

_____

xvii

the comments suggestions and corrections he made through the reviewprocess of the present manual Warm thanks are also addressed to Joseacute Fuchsand Soumlnke Muumlller who helped us in preparing the drawings Last but notleast we would like to thank our wives for their patience when we workedldquoon our projectrdquo during innumerable evenings and weekends

Jean-Pierre JaspartKlaus Weynand

UK FOREWORD

_____

xix

UK FOREWORD

INTRODUCTION

This book is the second in a series of joint publications of the EuropeanConvention for Constructional Steelwork (ECCS) and The Steel ConstructionInstitute (SCI) It will help provide UK engineers and designers with a betterunderstanding of the design principles in the European Code of Practice for theDesign of Steel Structures (EN 1993 ndash Eurocode 3) and the individual Part 18(EN 1993-1-8) for the design of steel joints in particular Reference will alsobe made to the associated Eurocodes for concrete (EN 1992 ndash Eurocode 2) andearthquake engineering (EN 1998 ndash Eurocode 8) The book complements otherSCI design guides eg SCI (2011 and 2013a)

The current publication is a first UK edition based on the first edition of theECCS manual for the Design of Joints in Steel and Composite Structureswhich was published in 2016 The scope of this UK edition is narrower thanthe original publication in two specific areas that are felt to be of limitedinterest to current practice in the UK there is no content covering compositejoints and chapter 9 (covering frame design strategies) has been shortened tosimply give an overview of strategies In this edition the reader will findinformation that is either of a general nature or relevant to specific sectionsof the publication to facilitate its application in a UK context

The content includes useful background to the code rules and a reminder ofsome engineering principles Information is presented in the context of theEurocodes terminology and notation and with reference to clause numbersetc to help the readerrsquos familiarity with EN 1993-1-8 The document thatserves as the basis for content and numbering of clauses is the UKimplementation of EN 1993-1-82005 incorporating corrigenda December2005 and July 2009 At the time of writing (Autumn 2016) part 1-8 ofEN 1993 is being revised with publication anticipated after 2020

Finally it is noted and should be accepted that there will inevitably be somedifferences of interpretation between the ECCS recommendations and thosepreviously published by the SCI

UK FOREWORD

_____

xx

GENERAL COMMENTS

Design of joints (connections) in steel structures in the UK is covered byBS EN 1993-1-8 and its national Annex (NA) (BSI 2010) BS EN 1993-1-8has clear definitions for connections and joints The term joint refers to thezone where members are interconnected and a connection is the locationwhere elements meet The distinction in terminology is usually emphasised inContinental Europe but traditional practice in the UK is to use the generic termconnection

The following partial safety factors are defined in the UK NA

Partial factor Value Comment

γM2 125 Used for the resistance of bolts pins and welds

γM2 125Used for the resistance of plates in bearing(γM2=15 should be used if deformation control is important)

γM3 125 Used for slip resistance at Ultimate Limit States

γM3serv 110 Used for slip resistance at Serviceability Limit States (SLS)

γM4 100 Used for the resistance of injection bolts

γM5 100 Used for the resistance of joints in hollow section lattice girders

γM6serv 100 Used for the resistance of pins at SLS

γM7

110Used for the preload of high strength steel bolts conforming toBS EN 14399-4 and BS EN 14399-8 (BSI 2015 and 2007)

100 Used for the preload of (other) high strength steel bolts

Specific reference to the UK Building Regulations is also made in this UKedition The UK Building Regulations code has structural integrityrequirements in order to avoid disproportionate collapse and ensure robustnessof the complete structure Disproportionate collapse can be defined as a regionof structural collapse out of proportion to the initiating cause of failure Themost relevant to connectionjoint design is that the detailing for every beam

UK FOREWORD

_____

xxi

member must be adequate to resist a minimum horizontal force at ultimatefailure (or tying resistance) Guidance on the design values of tying forces canbe found in BS EN 1991-1-7 Annex A and its UK annex (BSI 2014)

SECTION SPECIFIC COMMENTS

Section 111

UK practice normally considers only two main forms of joint modellingsimple and continuous Ideally frames designed on the basis of simple jointmodelling should use joints between members that possess negligiblerotational stiffness and transmit the beam reactions in shear into thecolumns without developing significant moments These joints may betreated as perfect pins Members can then be designed in isolation either as(predominantly) axially loaded columns or as simply supported beamsJoints designed within the principles of continuous modelling are capable oftransmitting significant moments and are able to maintain the original anglebetween adjacent members virtually unchanged This form of construction ofsteel frames is particularly advantageous when beam deflections are criticalor if bracing systems are not possible

To comply with one or the other design assumption steelwork connectionsare detailed as simple or moment-resisting joints Because joints in framestructures are often treated by adopting a degree of standardisation thedesigner usually details the connections in accordance with the principlesin the series of SCI Green Books which present this material in the formof step-by-step design procedures and tables covering standardarrangements

Other approximate analysis methods continue to be used among Britishdesigners the most representative being the wind-moment method for thedesign of unbraced multi-storey steel frames The method assumes that(i) under gravity loads the beam-to-column joints act as pinnedconnections and (ii) under horizontal wind loads these joints are rigidalthough it lacks transparency This method can be seen as a manifestationof the semi-continuous principles Wind moment connection details can befound in SCI (1995a) With the now widespread use of software in designoffices for rigorous second-order analysis it is doubtful if the use of the

UK FOREWORD

_____

xxii

wind-moment method should be advocated any longer other than forinitial sizing

Section 13

Although S460 is attracting growing interest S355 is still the dominantgrade of steel used in the UK

Section 161

With reference to Figure 120 it is noted that (site) welded joints and angleflange cleats are rarely if ever used in the UK

Section 162

Hybrid connections are rarely used in the UK for the reasons noted

Section 172

There is not much use of CoPcopy in the UK There are a number of othersoftware tools on the market some more comprehensive than others

Section 22

Although in UK design practice most aspects related to joint modelling havedeveloped to a high degree of sophistication proper consideration of thestructural interaction between the joints and members is rarely fully takeninto account It is indeed very difficult to predict and model the complexbehaviour of a joint (strength stiffness and rotation capacity) TraditionalUK practice is to predict joint behaviour on the basis of past experience

BSI (2010) separates the modelling of the rotational behaviour of theconnection elements (that is the bolts the welds the plates etc) and thatof the column web panel in shear to characterise the overall jointbehaviour As a simplification the two sources of joint deformation arecombined by means of the so-called transformation parameter β Thiscoefficient is related to the web panel internal actions and can be calculatedfrom the moments at each side of the web panel The β parameter iscurrently only defined for same-depth beams which meet at the same levelIn many practical double-sided joints beams will not be of the same depthor at the same height BS EN 1993-1-8 is silent on such joints

UK FOREWORD

_____

xxiii

Section 23

As explained above typical UK design practice does not consider thissophisticated procedure for idealisation of joints

Section 24

The NA to BS EN 1993-1-8 gives practical guidance to classify joints Italso states the following

ldquoUntil experience is gained with the numerical method of calculatingrotational stiffness given in BS EN 1993-1-82005 63 and theclassification by stiffness method given in BS EN 1993-1-82005522 semi-continuous elastic design should only be used where eitherit is supported by test evidence according to BS EN 1993-1-820055221(2) or where it is based on satisfactorily performance in asimilar situationrdquo

Evidence on values of column base stiffness for practical global analysis isgiven in SCI (2006)

Section 25

The concept of ductility classes is not widely applied in the UK It isgenerally assumed that standard connection details to the SCI Green Booksprovide enough rotation capacity and so behave in a ductile manner asevidenced by physical testing and experience

Section 31

The NA to BS EN 1993-1-8 excludes bolts of classes 58 and 68 It alsostates that bolt class 48 may only be used if the manufacturing process (i) isin accordance with BS EN ISO 898-1 (BSI 2013) and (ii) includes suitableprocedures to avoid hydrogen embrittlement

Section 322

The NA to BS EN 1993-1-8 states that if the preload is not explicitly used inthe design calculations then no specific level of preload is required

Section 347

Injection bolts are rarely used in the UK

UK FOREWORD

_____

xxiv

Section 348

Reference is made to SCI (1995b) to calculate the bending moments in thepin of a pin bearing

Section 349

Flow drill blind bolting is not common practice in the UK SHS blind boltingis a common system but there are several manufactures other than thatsuggested in the book

Section 3410

Nails are rarely used in the UK

Section 352

T-stub configurations with four bolts in a row are rarely used in the UK

Section 353

Reference is made to the SCI method for the design of gusset plates seeSCI (2011)

Section 421

It is anticipated that specific rules given in the current BS EN 1993-1-12(BSI 2009) for high strength steels will be incorporated in the revisedBS EN 1993-1-8 to appear after 2020

Section 522

ldquoHeader platesrdquo are known as ldquopartial depth end platesrdquo in the UK Webcleat connections are no longer commonly used in the UK The full depthend plate connection shown on the left of Figure 59 is classified as a simplejoint in the UK (SCI 2011)

Section 523

The UK Building Regulations require that joints are designed for tyingforces in order to satisfy structural integrity requirements Guidance onthe design values of tying forces is given in BS EN 1991-1-7 Annex Aand its UK NA The requirements relate to the building class with a

UK FOREWORD

_____

xxv

design value of horizontal force generally not less than 75 kN andusually significantly higher Simple joints detailed to SCI (2011) satisfythese requirements

Section 525

It is generally safe to assume that the ductility (rotation requirements) aresatisfied provided that joints are detailed in accordance with SCI (2011)

Section 531

The column base detailing on the left of Figure 521 is not commonly used inthe UK We never recommend less than four bolts ndash they are needed toassure stability and facilitate location during erection The anchoringsystems shown in Figure 522 are not usually adopted in the UK Referenceis made to SCI (2013a) for common anchor systems

Section 62

Publication SCI (2013b) summarises the principal differences betweenBS 5950 and BS EN 1993-1-8 (BSI 2000 and 2010) in terms ofcomponent characterisation

With reference to Figure 66 it is anticipated that the revised BS EN1993-1-8will include analytical expressions for the definition of the so-called αcoefficient

Rules of thumb for the characterisation of the ductility of some individualcomponents are given in SCI (1995a)

Section 631

The UK NA to BS EN 1993-1-8 gives specific rules for the full plasticdistribution of effective design tension resistance The procedure is alsosummarised in SCI (2013a)

Section 633

Where a joint is subjected to combined bending moments and axial forcesthe concept of an applied moment modified by axial load can be used seeSCI (1995a)

UK FOREWORD

_____

xxvi

Section 64

Rotational stiffness is not normally evaluated in UK design practice whichusually relies on past experience

Section 65

Some rules of thumb for the characterisation of the ductility of moment-resisting joints are given in SCI (1995a)

Section 661

With reference to Figure 636 it is noted that this joint configuration ishardly (if ever) used in the UK

Section 663

It should be noted that European sections are not commonly used in the UKalthough there is growing interest in the market Steel grade S235 is not usedin the UK S355 being the current common grade Combinations of plates of15 mm thickness with M24 bolts are common This combination is assumedto provide enough rotation capacity thus satisfying ductility requirementsbecause ductile failure of the plates not brittle failure of the bolts governsthe behaviour

Section 672

Standard practice in the UK does not account for this 25 rule Columnsplices are usually detailed to SCI (2011) to ensure continuity of stiffnessthrough the splice so that the member design is not invalidated

Section 84

The UK Building Regulations require that joints are designed for tyingforces in order to satisfy structural integrity requirements Guidance on thedesign values of tying forces is given in BS EN 1991-1-7 Annex A and itsUK NA (BSI 2014)

Section 91

In the UK the ldquofabricatorsrdquo are known as ldquoSteelwork contractorsrdquo becausethey do more than just fabricate

UK FOREWORD

_____

xxvii

REFERENCES TO NATIONAL FOREWORD

BSI (2000) BS 5950-12000 ndash Structural use of steelwork in building ndash Part1 Code of Practice for Design rolled and welded sections British StandardsInstitution United Kingdom

BSI (2007) BS EN 14399-82007 ndash High-strength structural boltingassemblies for preloading System HV Hexagon fit bolt and nut assembliesBritish Standards Institution United Kingdom

BSI (2009) BS EN 1993-1-122007 ndash Eurocode 3 Design of steel structuresndash Part 112 Additional rules for the extension of EN 1993 up to steel gradesS 700 British Standards Institution United Kingdom

BSI (2010) BS EN 1993-1-82005 ndash Eurocode 3 Design of steel structuresndash Part 18 Design of joints British Standards Institution United Kingdom

BSI (2013) BS EN ISO 898-12013 ndash Mechanical properties of fastenersmade of carbon steel and alloy steel Bolts screws and studs with specifiedproperty classes Coarse thread and fine pitch thread British StandardsInstitution United Kingdom

BSI (2014) BS EN 1991-1-72006+A12014 ndash Eurocode 1 Actions on structuresndash Part 197 General actions British Standards Institution United Kingdom

BSI (2015) BS EN 14399-42015 ndash High-strength structural boltingassemblies for preloading System HV Hexagon bolt and nut assembliesBritish Standards Institution United Kingdom

SCI (1995a) Joints in steel construction Moment connections P207 TheSteel Construction Institute

SCI (1995b) Advisory Desk Notes Bending Moment in a pin AD 172 TheSteel Construction Institute

SCI (2006) Column base stiffness for global analysis NCCI-SN045a TheSteel Construction Institute

SCI (2011) Joints in steel construction Simple joints to Eurocode 3 P358The Steel Construction Institute

SCI (2013a) Joints in steel construction Moment-resisting joints toEurocode 3 P398 The Steel Construction Institute

UK FOREWORD

_____

xxviii

SCI (2013b) Interim Report Design of Portal Frames to Eurocode 3 Anoverview for UK designers P400 The Steel Construction Institute

DESIGN OF JOINTS IN STEELSTRUCTURES

Eurocode 3 Design of steel structuresPart 1-8 ndash Design of Joints

UK Edition

Jean-Pierre JaspartKlaus Weynand

Adapted for the UK byGraham CouchmanAna M Giratildeo Coelho

Design of Joints in Steel Structures

UK Edition2017

Published byECCS ndash European Convention for Constructional Steelworkpublicationssteelconstructcomwwwsteelconstructcom

SalesWilhelm Ernst amp Sohn Verlag fuumlr Architektur und technische WissenschaftenGmbH amp Co KG Berlin

All rights reserved No parts of this publication may be reproduced stored in aretrieval system or transmitted in any form or by any means electronic mechanicalphotocopying recording or otherwise without the prior permission of the copyrightowner

ECCS assumes no liability with respect to the use for any application of the materialand information contained in this publication

Copyright copy 2017 ECCS ndash European Convention for Constructional Steelwork

ISBN (ECCS) 978-92-9147-135-5ISBN (Ernst amp Sohn) 978-3-433-03216-9Legal dep Printed in Sersilito Empresa Graacutefica Lda Maia PortugalPhoto cover credits Image courtesy of Mark Lawson SCI

TABLE OF CONTENTS

_____

v

TABLE OF CONTENTS

FOREWORD xiii

PREFACE xv

UK FOREWORD xix

NOTATION xxix

Chapter 1

INTRODUCTION 1

11 General 1111 Aims of the book 1112 Brief description of the contents of the book 10113 Types of structural systems and joints covered 11114 Basis of design 12

12 Definitions 12121 Joint properties 14122 Sources of joint deformation 15123 Beam splices and column splices 19124 Beam-to-beam joints 20125 Column bases 21126 Hollow section joints 22

13 Material choice 22

14 Fabrication and erection 26

15 Costs 27

16 Application of the ldquostatic approachrdquo 27161 Component approach 29162 Hybrid joints aspects 35

17 Design tools 35171 Types of design tools 36

TABLE OF CONTENTS

_____

vi

172 Examples of design tools 37

18 Worked examples 40

Chapter 2

STRUCTURAL ANALYSIS AND DESIGN 43

21 Introduction 43211 Elastic or elastoplastic analysis and verification process 44212 First order or second order analysis 45213 Integration of joint response into the frame analysis anddesign process 46

22 Joint modelling 47221 General 47222 Modelling and sources of joint deformation 49223 Simplified modelling according to EN 1993 50224 Concentration of the joint deformation 51

23 Joint idealisation 56231 Elastic idealisation for an elastic analysis 57232 Rigid-plastic idealisation for a rigid-plastic analysis 58233 Non-linear idealisation for an elastic-plastic analysis 59

24 Joint classification 59241 General 59242 Classification based on mechanical joint properties 60

25 Ductility classes 62251 General concept 62252 Requirements for classes of joints 65

Chapter 3

CONNECTIONS WITH MECHANICAL FASTENERS 67

31 Mechanical fasteners 67

32 Categories of connections 69321 Shear connections 69322 Tension connections 71

TABLE OF CONTENTS

_____

vii

33 Positioning of bolt holes 72

34 Design of the basic components 74341 Bolts in shear 74342 Bolts in tension 75343 Bolts in shear and tension 76344 Preloaded bolts 77345 Plates in bearing 85346 Block tearing 86347 Injection bolts 87348 Pins 88349 Blind bolting 913410 Nails 943411 Eccentricity of angles 95

35 Design of connections 97351 Bolted lap joints 97352 Bolted T-stubs 101353 Gusset plates 113354 Long joints 117

Chapter 4

WELDED CONNECTIONS 119

41 Types of welds 119411 Butt welds 119412 Fillet welds 120413 Fillet welds all round 121414 Plug welds 122

42 Construction constraints 122421 Mechanical properties of materials 122422 Welding processes preparation of welds and weld quality 123423 Geometry and dimensions of welds 127

43 Design of welds 130431 Generalities 130432 Fillet welds 131433 Fillet welds all round 134

TABLE OF CONTENTS

_____

viii

434 Butt welds 135435 Plug welds 136436 Concept of full strength fillet weld 136

44 Distribution of forces in a welded joint 139441 Generalities 139442 Particular situations 141

Chapter 5

SIMPLE JOINTS 147

51 Introduction 147

52 Beam-to-column and beam-to-beam joints 149521 Introduction 149522 Scope and field of application 150523 Joint modelling for frame analysis and design requirements 153524 Design resistance 156525 Practical ways to satisfy the ductility and rotationrequirements 163

53 Column bases 174531 Introduction 174532 Basis for the evaluation of the design resistance 176533 Resistance to axial forces 177534 Resistance to shear forces 185

Chapter 6

MOMENT-RESISTING JOINTS 189

61 Introduction 189

62 Component characterisation 190621 Column web panel in shear in steel or composite joints 190622 Column web in transverse compression in steel or compositejoints 192623 Column web in transverse tension 196624 Column flange in transverse bending 197625 End plate in bending 203

TABLE OF CONTENTS

_____

ix

626 Flange cleat in bending 205627 Beam or column flange and web in compression 207628 Beam web in tension 209629 Plate in tension or compression 2106210 Bolts in tension 2116211 Bolts in shear 2126212 Bolts in bearing (on beam flange column flange end plateor cleat) 2136213 Concrete in compression including grout 2136214 Base plate in bending under compression 2146215 Base plate in bending under tension 2146216 Anchor bolts in tension 2156217 Anchor bolts in shear 2156218 Anchor bolts in bearing 2156219 Welds 2166220 Haunched beam 216

63 Assembly for resistance 217631 Joints under bending moments 217632 Joints under axial forces 225633 Joints under bending moments and axial forces 226634 M minus N minus V 233635 Design of welds 234

64 Assembly for rotational stiffness 238641 Joints under bending moments 238642 Joints under bending moments and axial forces 247

65 Assembly for ductility 249651 Steel bolted joints 250652 Steel welded joints 252

66 Application to steel beam-to-column joint configurations 253661 Extended scope 253662 Possible design simplifications for end plate connections 256663 Worked example 257

67 Application to steel column splices 281671 Common splice configurations 281

TABLE OF CONTENTS

_____

x

672 Design considerations 283

68 Application to column bases 284681 Common column basis configurations 284682 Design considerations 287

Chapter 7

LATTICE GIRDER JOINTS 295

71 General 295

72 Scope and field of application 296

73 Design models 298731 General 298732 Failure modes 299733 Models for CHS chords 300734 Model for RHS chords 301735 Punching shear failure 302736 Model for brace failure 303737 M-N interaction 304

Chapter 8

JOINTS UNDER VARIOUS LOADING SITUATIONS 305

81 Introduction 305

82 Joints in fire 306

83 Joints under cyclic loading 307

84 Joints under exceptional events 308

Chapter 9

DESIGN STRATEGIES 311

91 Introduction 311

92 Traditional design approach 314

93 Integrated design approach 317

94 Economic considerations 319

TABLE OF CONTENTS

_____

xi

941 Fabrication and erections costs 319942 Savings of material costs 322943 Summary and conclusions 323

BIBLIOGRAPHIC REFERENCES 325

Annex A Practical values for required rotation capacity 337

Annex B Values for lateral torsional buckling strength of a fin plate 339

FOREWORD

_____

xiii

FOREWORD

With the ECCS book ldquoJoints in Steel and Composite Structuresrdquo the authorssucceeded in placing the joints on the rightful place they deserve in thestructural behaviour of steel and composite steel-concrete structures Themany times used word ldquodetailsrdquo for the joints in structures by farunderestimates the importance of joints in the structural behaviour ofbuildings and civil engineering structures In their chapter ldquoAim of the bookrdquothe authors clearly explain how the design and safety verification ofstructures runs in an integral manner where all structural componentsincluding the joints play balanced roles leading to economic structures

This book can be seen as a background document for Eurocode 3 ldquoDesign ofSteel Structuresrdquo as far as it concerns structural joints The central theme indescribing the behaviour of joints is using the component method and this isleading all over in this book The book contain many aspects such as designfabrication erection and costs

In this book attention is paid on joint modelling and idealisation jointclassification for strength and stiffness and deformation capacity This all forconnections with mechanical fasteners and for welded connections for simplejoints and moment resistant joints Also lattice girder joints are described

The book provides the designer with design strategies to arrive at economicstructures

The authors based themselves on many bibliographic references covering atime span of about 65 years Many of these references present research of theauthors themselves and of the other members of the ECCS-TechnicalCommittee TC10 ldquoStructural Connectionsrdquo

It was really a privilege to have been the chairperson of this committee from1998 till the end of 2012 and I thank the authors Prof Dr Ir Jean-PierreJaspart and Dr-Ing Klaus Weynand for their large effort in writing this book

Prof ir Frans Bijlaard

PREFACE

_____

xv

PREFACE

Steel constructions and composite steel-concrete constructions are generallyerected on site by the assembly of prefabricated structural parts prepared inthe workshop These parts may themselves be the result of an assembly ofindividual elements An example is the assembly by bolting on site offabricated sections welded in the workshop

In these construction types joints and connections play a key role andrecommendations and guidelines are required for engineers and constructorsfaced with the conception and design the fabrication and the erection of suchstructures In the Structural Eurocodes these aspects are mainly covered in theexecution standard EN 1090-2 and in the design standard EN 1993-1-8(Eurocode 3 Design of steel structures Part 1-8 Design of Joints)

In the present book which is part of the series of ECCS Eurocode DesignManuals the main focus is given to design aspects but references are alsomade to EN 1090-2 when necessary

In comparison to other fields the design procedures for joints andconnections have significantly evolved in the last decades as a result of theprogressive awareness by practitioners of the significant contribution ofjoints and connections to the global cost of structures Design for lowfabrication and erection costs as well as high resistance is therefore thetargeted objective of modern design codes the achievement of which hasjustified the development of new calculation approaches now integrated intothe two afore-mentioned Eurocodes This situation justifies the writing of thepresent manual with the main goal to demystify the process by explainingthe new concepts for the design of joints and to integrate their mechanicalresponse into the structural frame analysis and design process by providingldquokeysrdquo for a proper application in practice and finally by providing welldocumented worked examples

To refer to ldquomodernrdquo or ldquonewrdquo design approaches and philosophies does notmean that traditional ways are out dated or no more valid It should beunderstood that the design methods recommended in the Eurocodes are a

PREFACE

_____

xvi

collection of European practices including the results of intensive researchefforts carried out in the last decades and so give many options andalternatives to engineers who are trying to develop safe and economicsolutions

Chapter 1 introduces generalities about joint properties aspects of materialsfabrication erection and costs design approach - and especially the so-calledcomponent method - and design tools available to practitioners for easiercode application The integration of the response of the joints into thestructural analysis and design process is addressed in chapter 2 In chapter 3attention is paid to the design of common connections with mechanicalfasteners Preloaded bolts and non-preloaded bolts are mainly considered butthe use of some less classical connectors is also briefly described Weldedconnections are covered in chapter 5

The next three chapters relate to three specific types of joints respectivelysimple joints moment resisting joints and lattice girder joints For thesesubstantial innovations are brought in the Eurocodes in comparison totraditional national codes particularly for simple and moment resistingjoints A significant number of pages is therefore devoted to these topics inthis manual

The design of joints under static loading as it is addressed in the seven firstchapters is essential in all cases but further checks or different conceptualdesign of the joints are often required in case of load reversal fireearthquake or even exceptional events like impact or explosion Chapter 8summarises present knowledge in this field

Traditionally joints were designed as rigid or pinned which enables the designof the frame and the design of the joints to be treated independently The cleareconomical advantage associated in many situations with the use of semi-rigidandor partial-strength joints leads however to ldquostructure-jointsrdquo interactionsthat have to be mastered by the engineer so as to fully profit from the potentialcost savings The Eurocodes do not cover this interaction From this point ofview chapter 9 may be considered as ldquoa premiegravererdquo even if the content hasalready been partly described years ago in an ECSC publication

Before letting the reader discover the contents of this book we would like toexpress acknowledgment We are very grateful to Prof Frans Bijlaard for all

PREFACE

_____

xvii

the comments suggestions and corrections he made through the reviewprocess of the present manual Warm thanks are also addressed to Joseacute Fuchsand Soumlnke Muumlller who helped us in preparing the drawings Last but notleast we would like to thank our wives for their patience when we workedldquoon our projectrdquo during innumerable evenings and weekends

Jean-Pierre JaspartKlaus Weynand

UK FOREWORD

_____

xix

UK FOREWORD

INTRODUCTION

This book is the second in a series of joint publications of the EuropeanConvention for Constructional Steelwork (ECCS) and The Steel ConstructionInstitute (SCI) It will help provide UK engineers and designers with a betterunderstanding of the design principles in the European Code of Practice for theDesign of Steel Structures (EN 1993 ndash Eurocode 3) and the individual Part 18(EN 1993-1-8) for the design of steel joints in particular Reference will alsobe made to the associated Eurocodes for concrete (EN 1992 ndash Eurocode 2) andearthquake engineering (EN 1998 ndash Eurocode 8) The book complements otherSCI design guides eg SCI (2011 and 2013a)

The current publication is a first UK edition based on the first edition of theECCS manual for the Design of Joints in Steel and Composite Structureswhich was published in 2016 The scope of this UK edition is narrower thanthe original publication in two specific areas that are felt to be of limitedinterest to current practice in the UK there is no content covering compositejoints and chapter 9 (covering frame design strategies) has been shortened tosimply give an overview of strategies In this edition the reader will findinformation that is either of a general nature or relevant to specific sectionsof the publication to facilitate its application in a UK context

The content includes useful background to the code rules and a reminder ofsome engineering principles Information is presented in the context of theEurocodes terminology and notation and with reference to clause numbersetc to help the readerrsquos familiarity with EN 1993-1-8 The document thatserves as the basis for content and numbering of clauses is the UKimplementation of EN 1993-1-82005 incorporating corrigenda December2005 and July 2009 At the time of writing (Autumn 2016) part 1-8 ofEN 1993 is being revised with publication anticipated after 2020

Finally it is noted and should be accepted that there will inevitably be somedifferences of interpretation between the ECCS recommendations and thosepreviously published by the SCI

UK FOREWORD

_____

xx

GENERAL COMMENTS

Design of joints (connections) in steel structures in the UK is covered byBS EN 1993-1-8 and its national Annex (NA) (BSI 2010) BS EN 1993-1-8has clear definitions for connections and joints The term joint refers to thezone where members are interconnected and a connection is the locationwhere elements meet The distinction in terminology is usually emphasised inContinental Europe but traditional practice in the UK is to use the generic termconnection

The following partial safety factors are defined in the UK NA

Partial factor Value Comment

γM2 125 Used for the resistance of bolts pins and welds

γM2 125Used for the resistance of plates in bearing(γM2=15 should be used if deformation control is important)

γM3 125 Used for slip resistance at Ultimate Limit States

γM3serv 110 Used for slip resistance at Serviceability Limit States (SLS)

γM4 100 Used for the resistance of injection bolts

γM5 100 Used for the resistance of joints in hollow section lattice girders

γM6serv 100 Used for the resistance of pins at SLS

γM7

110Used for the preload of high strength steel bolts conforming toBS EN 14399-4 and BS EN 14399-8 (BSI 2015 and 2007)

100 Used for the preload of (other) high strength steel bolts

Specific reference to the UK Building Regulations is also made in this UKedition The UK Building Regulations code has structural integrityrequirements in order to avoid disproportionate collapse and ensure robustnessof the complete structure Disproportionate collapse can be defined as a regionof structural collapse out of proportion to the initiating cause of failure Themost relevant to connectionjoint design is that the detailing for every beam

UK FOREWORD

_____

xxi

member must be adequate to resist a minimum horizontal force at ultimatefailure (or tying resistance) Guidance on the design values of tying forces canbe found in BS EN 1991-1-7 Annex A and its UK annex (BSI 2014)

SECTION SPECIFIC COMMENTS

Section 111

UK practice normally considers only two main forms of joint modellingsimple and continuous Ideally frames designed on the basis of simple jointmodelling should use joints between members that possess negligiblerotational stiffness and transmit the beam reactions in shear into thecolumns without developing significant moments These joints may betreated as perfect pins Members can then be designed in isolation either as(predominantly) axially loaded columns or as simply supported beamsJoints designed within the principles of continuous modelling are capable oftransmitting significant moments and are able to maintain the original anglebetween adjacent members virtually unchanged This form of construction ofsteel frames is particularly advantageous when beam deflections are criticalor if bracing systems are not possible

To comply with one or the other design assumption steelwork connectionsare detailed as simple or moment-resisting joints Because joints in framestructures are often treated by adopting a degree of standardisation thedesigner usually details the connections in accordance with the principlesin the series of SCI Green Books which present this material in the formof step-by-step design procedures and tables covering standardarrangements

Other approximate analysis methods continue to be used among Britishdesigners the most representative being the wind-moment method for thedesign of unbraced multi-storey steel frames The method assumes that(i) under gravity loads the beam-to-column joints act as pinnedconnections and (ii) under horizontal wind loads these joints are rigidalthough it lacks transparency This method can be seen as a manifestationof the semi-continuous principles Wind moment connection details can befound in SCI (1995a) With the now widespread use of software in designoffices for rigorous second-order analysis it is doubtful if the use of the

UK FOREWORD

_____

xxii

wind-moment method should be advocated any longer other than forinitial sizing

Section 13

Although S460 is attracting growing interest S355 is still the dominantgrade of steel used in the UK

Section 161

With reference to Figure 120 it is noted that (site) welded joints and angleflange cleats are rarely if ever used in the UK

Section 162

Hybrid connections are rarely used in the UK for the reasons noted

Section 172

There is not much use of CoPcopy in the UK There are a number of othersoftware tools on the market some more comprehensive than others

Section 22

Although in UK design practice most aspects related to joint modelling havedeveloped to a high degree of sophistication proper consideration of thestructural interaction between the joints and members is rarely fully takeninto account It is indeed very difficult to predict and model the complexbehaviour of a joint (strength stiffness and rotation capacity) TraditionalUK practice is to predict joint behaviour on the basis of past experience

BSI (2010) separates the modelling of the rotational behaviour of theconnection elements (that is the bolts the welds the plates etc) and thatof the column web panel in shear to characterise the overall jointbehaviour As a simplification the two sources of joint deformation arecombined by means of the so-called transformation parameter β Thiscoefficient is related to the web panel internal actions and can be calculatedfrom the moments at each side of the web panel The β parameter iscurrently only defined for same-depth beams which meet at the same levelIn many practical double-sided joints beams will not be of the same depthor at the same height BS EN 1993-1-8 is silent on such joints

UK FOREWORD

_____

xxiii

Section 23

As explained above typical UK design practice does not consider thissophisticated procedure for idealisation of joints

Section 24

The NA to BS EN 1993-1-8 gives practical guidance to classify joints Italso states the following

ldquoUntil experience is gained with the numerical method of calculatingrotational stiffness given in BS EN 1993-1-82005 63 and theclassification by stiffness method given in BS EN 1993-1-82005522 semi-continuous elastic design should only be used where eitherit is supported by test evidence according to BS EN 1993-1-820055221(2) or where it is based on satisfactorily performance in asimilar situationrdquo

Evidence on values of column base stiffness for practical global analysis isgiven in SCI (2006)

Section 25

The concept of ductility classes is not widely applied in the UK It isgenerally assumed that standard connection details to the SCI Green Booksprovide enough rotation capacity and so behave in a ductile manner asevidenced by physical testing and experience

Section 31

The NA to BS EN 1993-1-8 excludes bolts of classes 58 and 68 It alsostates that bolt class 48 may only be used if the manufacturing process (i) isin accordance with BS EN ISO 898-1 (BSI 2013) and (ii) includes suitableprocedures to avoid hydrogen embrittlement

Section 322

The NA to BS EN 1993-1-8 states that if the preload is not explicitly used inthe design calculations then no specific level of preload is required

Section 347

Injection bolts are rarely used in the UK

UK FOREWORD

_____

xxiv

Section 348

Reference is made to SCI (1995b) to calculate the bending moments in thepin of a pin bearing

Section 349

Flow drill blind bolting is not common practice in the UK SHS blind boltingis a common system but there are several manufactures other than thatsuggested in the book

Section 3410

Nails are rarely used in the UK

Section 352

T-stub configurations with four bolts in a row are rarely used in the UK

Section 353

Reference is made to the SCI method for the design of gusset plates seeSCI (2011)

Section 421

It is anticipated that specific rules given in the current BS EN 1993-1-12(BSI 2009) for high strength steels will be incorporated in the revisedBS EN 1993-1-8 to appear after 2020

Section 522

ldquoHeader platesrdquo are known as ldquopartial depth end platesrdquo in the UK Webcleat connections are no longer commonly used in the UK The full depthend plate connection shown on the left of Figure 59 is classified as a simplejoint in the UK (SCI 2011)

Section 523

The UK Building Regulations require that joints are designed for tyingforces in order to satisfy structural integrity requirements Guidance onthe design values of tying forces is given in BS EN 1991-1-7 Annex Aand its UK NA The requirements relate to the building class with a

UK FOREWORD

_____

xxv

design value of horizontal force generally not less than 75 kN andusually significantly higher Simple joints detailed to SCI (2011) satisfythese requirements

Section 525

It is generally safe to assume that the ductility (rotation requirements) aresatisfied provided that joints are detailed in accordance with SCI (2011)

Section 531

The column base detailing on the left of Figure 521 is not commonly used inthe UK We never recommend less than four bolts ndash they are needed toassure stability and facilitate location during erection The anchoringsystems shown in Figure 522 are not usually adopted in the UK Referenceis made to SCI (2013a) for common anchor systems

Section 62

Publication SCI (2013b) summarises the principal differences betweenBS 5950 and BS EN 1993-1-8 (BSI 2000 and 2010) in terms ofcomponent characterisation

With reference to Figure 66 it is anticipated that the revised BS EN1993-1-8will include analytical expressions for the definition of the so-called αcoefficient

Rules of thumb for the characterisation of the ductility of some individualcomponents are given in SCI (1995a)

Section 631

The UK NA to BS EN 1993-1-8 gives specific rules for the full plasticdistribution of effective design tension resistance The procedure is alsosummarised in SCI (2013a)

Section 633

Where a joint is subjected to combined bending moments and axial forcesthe concept of an applied moment modified by axial load can be used seeSCI (1995a)

UK FOREWORD

_____

xxvi

Section 64

Rotational stiffness is not normally evaluated in UK design practice whichusually relies on past experience

Section 65

Some rules of thumb for the characterisation of the ductility of moment-resisting joints are given in SCI (1995a)

Section 661

With reference to Figure 636 it is noted that this joint configuration ishardly (if ever) used in the UK

Section 663

It should be noted that European sections are not commonly used in the UKalthough there is growing interest in the market Steel grade S235 is not usedin the UK S355 being the current common grade Combinations of plates of15 mm thickness with M24 bolts are common This combination is assumedto provide enough rotation capacity thus satisfying ductility requirementsbecause ductile failure of the plates not brittle failure of the bolts governsthe behaviour

Section 672

Standard practice in the UK does not account for this 25 rule Columnsplices are usually detailed to SCI (2011) to ensure continuity of stiffnessthrough the splice so that the member design is not invalidated

Section 84

The UK Building Regulations require that joints are designed for tyingforces in order to satisfy structural integrity requirements Guidance on thedesign values of tying forces is given in BS EN 1991-1-7 Annex A and itsUK NA (BSI 2014)

Section 91

In the UK the ldquofabricatorsrdquo are known as ldquoSteelwork contractorsrdquo becausethey do more than just fabricate

UK FOREWORD

_____

xxvii

REFERENCES TO NATIONAL FOREWORD

BSI (2000) BS 5950-12000 ndash Structural use of steelwork in building ndash Part1 Code of Practice for Design rolled and welded sections British StandardsInstitution United Kingdom

BSI (2007) BS EN 14399-82007 ndash High-strength structural boltingassemblies for preloading System HV Hexagon fit bolt and nut assembliesBritish Standards Institution United Kingdom

BSI (2009) BS EN 1993-1-122007 ndash Eurocode 3 Design of steel structuresndash Part 112 Additional rules for the extension of EN 1993 up to steel gradesS 700 British Standards Institution United Kingdom

BSI (2010) BS EN 1993-1-82005 ndash Eurocode 3 Design of steel structuresndash Part 18 Design of joints British Standards Institution United Kingdom

BSI (2013) BS EN ISO 898-12013 ndash Mechanical properties of fastenersmade of carbon steel and alloy steel Bolts screws and studs with specifiedproperty classes Coarse thread and fine pitch thread British StandardsInstitution United Kingdom

BSI (2014) BS EN 1991-1-72006+A12014 ndash Eurocode 1 Actions on structuresndash Part 197 General actions British Standards Institution United Kingdom

BSI (2015) BS EN 14399-42015 ndash High-strength structural boltingassemblies for preloading System HV Hexagon bolt and nut assembliesBritish Standards Institution United Kingdom

SCI (1995a) Joints in steel construction Moment connections P207 TheSteel Construction Institute

SCI (1995b) Advisory Desk Notes Bending Moment in a pin AD 172 TheSteel Construction Institute

SCI (2006) Column base stiffness for global analysis NCCI-SN045a TheSteel Construction Institute

SCI (2011) Joints in steel construction Simple joints to Eurocode 3 P358The Steel Construction Institute

SCI (2013a) Joints in steel construction Moment-resisting joints toEurocode 3 P398 The Steel Construction Institute

UK FOREWORD

_____

xxviii

SCI (2013b) Interim Report Design of Portal Frames to Eurocode 3 Anoverview for UK designers P400 The Steel Construction Institute

Design of Joints in Steel Structures

UK Edition2017

Published byECCS ndash European Convention for Constructional Steelworkpublicationssteelconstructcomwwwsteelconstructcom

SalesWilhelm Ernst amp Sohn Verlag fuumlr Architektur und technische WissenschaftenGmbH amp Co KG Berlin

All rights reserved No parts of this publication may be reproduced stored in aretrieval system or transmitted in any form or by any means electronic mechanicalphotocopying recording or otherwise without the prior permission of the copyrightowner

ECCS assumes no liability with respect to the use for any application of the materialand information contained in this publication

Copyright copy 2017 ECCS ndash European Convention for Constructional Steelwork

ISBN (ECCS) 978-92-9147-135-5ISBN (Ernst amp Sohn) 978-3-433-03216-9Legal dep Printed in Sersilito Empresa Graacutefica Lda Maia PortugalPhoto cover credits Image courtesy of Mark Lawson SCI

TABLE OF CONTENTS

_____

v

TABLE OF CONTENTS

FOREWORD xiii

PREFACE xv

UK FOREWORD xix

NOTATION xxix

Chapter 1

INTRODUCTION 1

11 General 1111 Aims of the book 1112 Brief description of the contents of the book 10113 Types of structural systems and joints covered 11114 Basis of design 12

12 Definitions 12121 Joint properties 14122 Sources of joint deformation 15123 Beam splices and column splices 19124 Beam-to-beam joints 20125 Column bases 21126 Hollow section joints 22

13 Material choice 22

14 Fabrication and erection 26

15 Costs 27

16 Application of the ldquostatic approachrdquo 27161 Component approach 29162 Hybrid joints aspects 35

17 Design tools 35171 Types of design tools 36

TABLE OF CONTENTS

_____

vi

172 Examples of design tools 37

18 Worked examples 40

Chapter 2

STRUCTURAL ANALYSIS AND DESIGN 43

21 Introduction 43211 Elastic or elastoplastic analysis and verification process 44212 First order or second order analysis 45213 Integration of joint response into the frame analysis anddesign process 46

22 Joint modelling 47221 General 47222 Modelling and sources of joint deformation 49223 Simplified modelling according to EN 1993 50224 Concentration of the joint deformation 51

23 Joint idealisation 56231 Elastic idealisation for an elastic analysis 57232 Rigid-plastic idealisation for a rigid-plastic analysis 58233 Non-linear idealisation for an elastic-plastic analysis 59

24 Joint classification 59241 General 59242 Classification based on mechanical joint properties 60

25 Ductility classes 62251 General concept 62252 Requirements for classes of joints 65

Chapter 3

CONNECTIONS WITH MECHANICAL FASTENERS 67

31 Mechanical fasteners 67

32 Categories of connections 69321 Shear connections 69322 Tension connections 71

TABLE OF CONTENTS

_____

vii

33 Positioning of bolt holes 72

34 Design of the basic components 74341 Bolts in shear 74342 Bolts in tension 75343 Bolts in shear and tension 76344 Preloaded bolts 77345 Plates in bearing 85346 Block tearing 86347 Injection bolts 87348 Pins 88349 Blind bolting 913410 Nails 943411 Eccentricity of angles 95

35 Design of connections 97351 Bolted lap joints 97352 Bolted T-stubs 101353 Gusset plates 113354 Long joints 117

Chapter 4

WELDED CONNECTIONS 119

41 Types of welds 119411 Butt welds 119412 Fillet welds 120413 Fillet welds all round 121414 Plug welds 122

42 Construction constraints 122421 Mechanical properties of materials 122422 Welding processes preparation of welds and weld quality 123423 Geometry and dimensions of welds 127

43 Design of welds 130431 Generalities 130432 Fillet welds 131433 Fillet welds all round 134

TABLE OF CONTENTS

_____

viii

434 Butt welds 135435 Plug welds 136436 Concept of full strength fillet weld 136

44 Distribution of forces in a welded joint 139441 Generalities 139442 Particular situations 141

Chapter 5

SIMPLE JOINTS 147

51 Introduction 147

52 Beam-to-column and beam-to-beam joints 149521 Introduction 149522 Scope and field of application 150523 Joint modelling for frame analysis and design requirements 153524 Design resistance 156525 Practical ways to satisfy the ductility and rotationrequirements 163

53 Column bases 174531 Introduction 174532 Basis for the evaluation of the design resistance 176533 Resistance to axial forces 177534 Resistance to shear forces 185

Chapter 6

MOMENT-RESISTING JOINTS 189

61 Introduction 189

62 Component characterisation 190621 Column web panel in shear in steel or composite joints 190622 Column web in transverse compression in steel or compositejoints 192623 Column web in transverse tension 196624 Column flange in transverse bending 197625 End plate in bending 203

TABLE OF CONTENTS

_____

ix

626 Flange cleat in bending 205627 Beam or column flange and web in compression 207628 Beam web in tension 209629 Plate in tension or compression 2106210 Bolts in tension 2116211 Bolts in shear 2126212 Bolts in bearing (on beam flange column flange end plateor cleat) 2136213 Concrete in compression including grout 2136214 Base plate in bending under compression 2146215 Base plate in bending under tension 2146216 Anchor bolts in tension 2156217 Anchor bolts in shear 2156218 Anchor bolts in bearing 2156219 Welds 2166220 Haunched beam 216

63 Assembly for resistance 217631 Joints under bending moments 217632 Joints under axial forces 225633 Joints under bending moments and axial forces 226634 M minus N minus V 233635 Design of welds 234

64 Assembly for rotational stiffness 238641 Joints under bending moments 238642 Joints under bending moments and axial forces 247

65 Assembly for ductility 249651 Steel bolted joints 250652 Steel welded joints 252

66 Application to steel beam-to-column joint configurations 253661 Extended scope 253662 Possible design simplifications for end plate connections 256663 Worked example 257

67 Application to steel column splices 281671 Common splice configurations 281

TABLE OF CONTENTS

_____

x

672 Design considerations 283

68 Application to column bases 284681 Common column basis configurations 284682 Design considerations 287

Chapter 7

LATTICE GIRDER JOINTS 295

71 General 295

72 Scope and field of application 296

73 Design models 298731 General 298732 Failure modes 299733 Models for CHS chords 300734 Model for RHS chords 301735 Punching shear failure 302736 Model for brace failure 303737 M-N interaction 304

Chapter 8

JOINTS UNDER VARIOUS LOADING SITUATIONS 305

81 Introduction 305

82 Joints in fire 306

83 Joints under cyclic loading 307

84 Joints under exceptional events 308

Chapter 9

DESIGN STRATEGIES 311

91 Introduction 311

92 Traditional design approach 314

93 Integrated design approach 317

94 Economic considerations 319

TABLE OF CONTENTS

_____

xi

941 Fabrication and erections costs 319942 Savings of material costs 322943 Summary and conclusions 323

BIBLIOGRAPHIC REFERENCES 325

Annex A Practical values for required rotation capacity 337

Annex B Values for lateral torsional buckling strength of a fin plate 339

FOREWORD

_____

xiii

FOREWORD

With the ECCS book ldquoJoints in Steel and Composite Structuresrdquo the authorssucceeded in placing the joints on the rightful place they deserve in thestructural behaviour of steel and composite steel-concrete structures Themany times used word ldquodetailsrdquo for the joints in structures by farunderestimates the importance of joints in the structural behaviour ofbuildings and civil engineering structures In their chapter ldquoAim of the bookrdquothe authors clearly explain how the design and safety verification ofstructures runs in an integral manner where all structural componentsincluding the joints play balanced roles leading to economic structures

This book can be seen as a background document for Eurocode 3 ldquoDesign ofSteel Structuresrdquo as far as it concerns structural joints The central theme indescribing the behaviour of joints is using the component method and this isleading all over in this book The book contain many aspects such as designfabrication erection and costs

In this book attention is paid on joint modelling and idealisation jointclassification for strength and stiffness and deformation capacity This all forconnections with mechanical fasteners and for welded connections for simplejoints and moment resistant joints Also lattice girder joints are described

The book provides the designer with design strategies to arrive at economicstructures

The authors based themselves on many bibliographic references covering atime span of about 65 years Many of these references present research of theauthors themselves and of the other members of the ECCS-TechnicalCommittee TC10 ldquoStructural Connectionsrdquo

It was really a privilege to have been the chairperson of this committee from1998 till the end of 2012 and I thank the authors Prof Dr Ir Jean-PierreJaspart and Dr-Ing Klaus Weynand for their large effort in writing this book

Prof ir Frans Bijlaard

PREFACE

_____

xv

PREFACE

Steel constructions and composite steel-concrete constructions are generallyerected on site by the assembly of prefabricated structural parts prepared inthe workshop These parts may themselves be the result of an assembly ofindividual elements An example is the assembly by bolting on site offabricated sections welded in the workshop

In these construction types joints and connections play a key role andrecommendations and guidelines are required for engineers and constructorsfaced with the conception and design the fabrication and the erection of suchstructures In the Structural Eurocodes these aspects are mainly covered in theexecution standard EN 1090-2 and in the design standard EN 1993-1-8(Eurocode 3 Design of steel structures Part 1-8 Design of Joints)

In the present book which is part of the series of ECCS Eurocode DesignManuals the main focus is given to design aspects but references are alsomade to EN 1090-2 when necessary

In comparison to other fields the design procedures for joints andconnections have significantly evolved in the last decades as a result of theprogressive awareness by practitioners of the significant contribution ofjoints and connections to the global cost of structures Design for lowfabrication and erection costs as well as high resistance is therefore thetargeted objective of modern design codes the achievement of which hasjustified the development of new calculation approaches now integrated intothe two afore-mentioned Eurocodes This situation justifies the writing of thepresent manual with the main goal to demystify the process by explainingthe new concepts for the design of joints and to integrate their mechanicalresponse into the structural frame analysis and design process by providingldquokeysrdquo for a proper application in practice and finally by providing welldocumented worked examples

To refer to ldquomodernrdquo or ldquonewrdquo design approaches and philosophies does notmean that traditional ways are out dated or no more valid It should beunderstood that the design methods recommended in the Eurocodes are a

PREFACE

_____

xvi

collection of European practices including the results of intensive researchefforts carried out in the last decades and so give many options andalternatives to engineers who are trying to develop safe and economicsolutions

Chapter 1 introduces generalities about joint properties aspects of materialsfabrication erection and costs design approach - and especially the so-calledcomponent method - and design tools available to practitioners for easiercode application The integration of the response of the joints into thestructural analysis and design process is addressed in chapter 2 In chapter 3attention is paid to the design of common connections with mechanicalfasteners Preloaded bolts and non-preloaded bolts are mainly considered butthe use of some less classical connectors is also briefly described Weldedconnections are covered in chapter 5

The next three chapters relate to three specific types of joints respectivelysimple joints moment resisting joints and lattice girder joints For thesesubstantial innovations are brought in the Eurocodes in comparison totraditional national codes particularly for simple and moment resistingjoints A significant number of pages is therefore devoted to these topics inthis manual

The design of joints under static loading as it is addressed in the seven firstchapters is essential in all cases but further checks or different conceptualdesign of the joints are often required in case of load reversal fireearthquake or even exceptional events like impact or explosion Chapter 8summarises present knowledge in this field

Traditionally joints were designed as rigid or pinned which enables the designof the frame and the design of the joints to be treated independently The cleareconomical advantage associated in many situations with the use of semi-rigidandor partial-strength joints leads however to ldquostructure-jointsrdquo interactionsthat have to be mastered by the engineer so as to fully profit from the potentialcost savings The Eurocodes do not cover this interaction From this point ofview chapter 9 may be considered as ldquoa premiegravererdquo even if the content hasalready been partly described years ago in an ECSC publication

Before letting the reader discover the contents of this book we would like toexpress acknowledgment We are very grateful to Prof Frans Bijlaard for all

PREFACE

_____

xvii

the comments suggestions and corrections he made through the reviewprocess of the present manual Warm thanks are also addressed to Joseacute Fuchsand Soumlnke Muumlller who helped us in preparing the drawings Last but notleast we would like to thank our wives for their patience when we workedldquoon our projectrdquo during innumerable evenings and weekends

Jean-Pierre JaspartKlaus Weynand

UK FOREWORD

_____

xix

UK FOREWORD

INTRODUCTION

This book is the second in a series of joint publications of the EuropeanConvention for Constructional Steelwork (ECCS) and The Steel ConstructionInstitute (SCI) It will help provide UK engineers and designers with a betterunderstanding of the design principles in the European Code of Practice for theDesign of Steel Structures (EN 1993 ndash Eurocode 3) and the individual Part 18(EN 1993-1-8) for the design of steel joints in particular Reference will alsobe made to the associated Eurocodes for concrete (EN 1992 ndash Eurocode 2) andearthquake engineering (EN 1998 ndash Eurocode 8) The book complements otherSCI design guides eg SCI (2011 and 2013a)

The current publication is a first UK edition based on the first edition of theECCS manual for the Design of Joints in Steel and Composite Structureswhich was published in 2016 The scope of this UK edition is narrower thanthe original publication in two specific areas that are felt to be of limitedinterest to current practice in the UK there is no content covering compositejoints and chapter 9 (covering frame design strategies) has been shortened tosimply give an overview of strategies In this edition the reader will findinformation that is either of a general nature or relevant to specific sectionsof the publication to facilitate its application in a UK context

The content includes useful background to the code rules and a reminder ofsome engineering principles Information is presented in the context of theEurocodes terminology and notation and with reference to clause numbersetc to help the readerrsquos familiarity with EN 1993-1-8 The document thatserves as the basis for content and numbering of clauses is the UKimplementation of EN 1993-1-82005 incorporating corrigenda December2005 and July 2009 At the time of writing (Autumn 2016) part 1-8 ofEN 1993 is being revised with publication anticipated after 2020

Finally it is noted and should be accepted that there will inevitably be somedifferences of interpretation between the ECCS recommendations and thosepreviously published by the SCI

UK FOREWORD

_____

xx

GENERAL COMMENTS

Design of joints (connections) in steel structures in the UK is covered byBS EN 1993-1-8 and its national Annex (NA) (BSI 2010) BS EN 1993-1-8has clear definitions for connections and joints The term joint refers to thezone where members are interconnected and a connection is the locationwhere elements meet The distinction in terminology is usually emphasised inContinental Europe but traditional practice in the UK is to use the generic termconnection

The following partial safety factors are defined in the UK NA

Partial factor Value Comment

γM2 125 Used for the resistance of bolts pins and welds

γM2 125Used for the resistance of plates in bearing(γM2=15 should be used if deformation control is important)

γM3 125 Used for slip resistance at Ultimate Limit States

γM3serv 110 Used for slip resistance at Serviceability Limit States (SLS)

γM4 100 Used for the resistance of injection bolts

γM5 100 Used for the resistance of joints in hollow section lattice girders

γM6serv 100 Used for the resistance of pins at SLS

γM7

110Used for the preload of high strength steel bolts conforming toBS EN 14399-4 and BS EN 14399-8 (BSI 2015 and 2007)

100 Used for the preload of (other) high strength steel bolts

Specific reference to the UK Building Regulations is also made in this UKedition The UK Building Regulations code has structural integrityrequirements in order to avoid disproportionate collapse and ensure robustnessof the complete structure Disproportionate collapse can be defined as a regionof structural collapse out of proportion to the initiating cause of failure Themost relevant to connectionjoint design is that the detailing for every beam

UK FOREWORD

_____

xxi

member must be adequate to resist a minimum horizontal force at ultimatefailure (or tying resistance) Guidance on the design values of tying forces canbe found in BS EN 1991-1-7 Annex A and its UK annex (BSI 2014)

SECTION SPECIFIC COMMENTS

Section 111

UK practice normally considers only two main forms of joint modellingsimple and continuous Ideally frames designed on the basis of simple jointmodelling should use joints between members that possess negligiblerotational stiffness and transmit the beam reactions in shear into thecolumns without developing significant moments These joints may betreated as perfect pins Members can then be designed in isolation either as(predominantly) axially loaded columns or as simply supported beamsJoints designed within the principles of continuous modelling are capable oftransmitting significant moments and are able to maintain the original anglebetween adjacent members virtually unchanged This form of construction ofsteel frames is particularly advantageous when beam deflections are criticalor if bracing systems are not possible

To comply with one or the other design assumption steelwork connectionsare detailed as simple or moment-resisting joints Because joints in framestructures are often treated by adopting a degree of standardisation thedesigner usually details the connections in accordance with the principlesin the series of SCI Green Books which present this material in the formof step-by-step design procedures and tables covering standardarrangements

Other approximate analysis methods continue to be used among Britishdesigners the most representative being the wind-moment method for thedesign of unbraced multi-storey steel frames The method assumes that(i) under gravity loads the beam-to-column joints act as pinnedconnections and (ii) under horizontal wind loads these joints are rigidalthough it lacks transparency This method can be seen as a manifestationof the semi-continuous principles Wind moment connection details can befound in SCI (1995a) With the now widespread use of software in designoffices for rigorous second-order analysis it is doubtful if the use of the

UK FOREWORD

_____

xxii

wind-moment method should be advocated any longer other than forinitial sizing

Section 13

Although S460 is attracting growing interest S355 is still the dominantgrade of steel used in the UK

Section 161

With reference to Figure 120 it is noted that (site) welded joints and angleflange cleats are rarely if ever used in the UK

Section 162

Hybrid connections are rarely used in the UK for the reasons noted

Section 172

There is not much use of CoPcopy in the UK There are a number of othersoftware tools on the market some more comprehensive than others

Section 22

Although in UK design practice most aspects related to joint modelling havedeveloped to a high degree of sophistication proper consideration of thestructural interaction between the joints and members is rarely fully takeninto account It is indeed very difficult to predict and model the complexbehaviour of a joint (strength stiffness and rotation capacity) TraditionalUK practice is to predict joint behaviour on the basis of past experience

BSI (2010) separates the modelling of the rotational behaviour of theconnection elements (that is the bolts the welds the plates etc) and thatof the column web panel in shear to characterise the overall jointbehaviour As a simplification the two sources of joint deformation arecombined by means of the so-called transformation parameter β Thiscoefficient is related to the web panel internal actions and can be calculatedfrom the moments at each side of the web panel The β parameter iscurrently only defined for same-depth beams which meet at the same levelIn many practical double-sided joints beams will not be of the same depthor at the same height BS EN 1993-1-8 is silent on such joints

UK FOREWORD

_____

xxiii

Section 23

As explained above typical UK design practice does not consider thissophisticated procedure for idealisation of joints

Section 24

The NA to BS EN 1993-1-8 gives practical guidance to classify joints Italso states the following

ldquoUntil experience is gained with the numerical method of calculatingrotational stiffness given in BS EN 1993-1-82005 63 and theclassification by stiffness method given in BS EN 1993-1-82005522 semi-continuous elastic design should only be used where eitherit is supported by test evidence according to BS EN 1993-1-820055221(2) or where it is based on satisfactorily performance in asimilar situationrdquo

Evidence on values of column base stiffness for practical global analysis isgiven in SCI (2006)

Section 25

The concept of ductility classes is not widely applied in the UK It isgenerally assumed that standard connection details to the SCI Green Booksprovide enough rotation capacity and so behave in a ductile manner asevidenced by physical testing and experience

Section 31

The NA to BS EN 1993-1-8 excludes bolts of classes 58 and 68 It alsostates that bolt class 48 may only be used if the manufacturing process (i) isin accordance with BS EN ISO 898-1 (BSI 2013) and (ii) includes suitableprocedures to avoid hydrogen embrittlement

Section 322

The NA to BS EN 1993-1-8 states that if the preload is not explicitly used inthe design calculations then no specific level of preload is required

Section 347

Injection bolts are rarely used in the UK

UK FOREWORD

_____

xxiv

Section 348

Reference is made to SCI (1995b) to calculate the bending moments in thepin of a pin bearing

Section 349

Flow drill blind bolting is not common practice in the UK SHS blind boltingis a common system but there are several manufactures other than thatsuggested in the book

Section 3410

Nails are rarely used in the UK

Section 352

T-stub configurations with four bolts in a row are rarely used in the UK

Section 353

Reference is made to the SCI method for the design of gusset plates seeSCI (2011)

Section 421

It is anticipated that specific rules given in the current BS EN 1993-1-12(BSI 2009) for high strength steels will be incorporated in the revisedBS EN 1993-1-8 to appear after 2020

Section 522

ldquoHeader platesrdquo are known as ldquopartial depth end platesrdquo in the UK Webcleat connections are no longer commonly used in the UK The full depthend plate connection shown on the left of Figure 59 is classified as a simplejoint in the UK (SCI 2011)

Section 523

The UK Building Regulations require that joints are designed for tyingforces in order to satisfy structural integrity requirements Guidance onthe design values of tying forces is given in BS EN 1991-1-7 Annex Aand its UK NA The requirements relate to the building class with a

UK FOREWORD

_____

xxv

design value of horizontal force generally not less than 75 kN andusually significantly higher Simple joints detailed to SCI (2011) satisfythese requirements

Section 525

It is generally safe to assume that the ductility (rotation requirements) aresatisfied provided that joints are detailed in accordance with SCI (2011)

Section 531

The column base detailing on the left of Figure 521 is not commonly used inthe UK We never recommend less than four bolts ndash they are needed toassure stability and facilitate location during erection The anchoringsystems shown in Figure 522 are not usually adopted in the UK Referenceis made to SCI (2013a) for common anchor systems

Section 62

Publication SCI (2013b) summarises the principal differences betweenBS 5950 and BS EN 1993-1-8 (BSI 2000 and 2010) in terms ofcomponent characterisation

With reference to Figure 66 it is anticipated that the revised BS EN1993-1-8will include analytical expressions for the definition of the so-called αcoefficient

Rules of thumb for the characterisation of the ductility of some individualcomponents are given in SCI (1995a)

Section 631

The UK NA to BS EN 1993-1-8 gives specific rules for the full plasticdistribution of effective design tension resistance The procedure is alsosummarised in SCI (2013a)

Section 633

Where a joint is subjected to combined bending moments and axial forcesthe concept of an applied moment modified by axial load can be used seeSCI (1995a)

UK FOREWORD

_____

xxvi

Section 64

Rotational stiffness is not normally evaluated in UK design practice whichusually relies on past experience

Section 65

Some rules of thumb for the characterisation of the ductility of moment-resisting joints are given in SCI (1995a)

Section 661

With reference to Figure 636 it is noted that this joint configuration ishardly (if ever) used in the UK

Section 663

It should be noted that European sections are not commonly used in the UKalthough there is growing interest in the market Steel grade S235 is not usedin the UK S355 being the current common grade Combinations of plates of15 mm thickness with M24 bolts are common This combination is assumedto provide enough rotation capacity thus satisfying ductility requirementsbecause ductile failure of the plates not brittle failure of the bolts governsthe behaviour

Section 672

Standard practice in the UK does not account for this 25 rule Columnsplices are usually detailed to SCI (2011) to ensure continuity of stiffnessthrough the splice so that the member design is not invalidated

Section 84

The UK Building Regulations require that joints are designed for tyingforces in order to satisfy structural integrity requirements Guidance on thedesign values of tying forces is given in BS EN 1991-1-7 Annex A and itsUK NA (BSI 2014)

Section 91

In the UK the ldquofabricatorsrdquo are known as ldquoSteelwork contractorsrdquo becausethey do more than just fabricate

UK FOREWORD

_____

xxvii

REFERENCES TO NATIONAL FOREWORD

BSI (2000) BS 5950-12000 ndash Structural use of steelwork in building ndash Part1 Code of Practice for Design rolled and welded sections British StandardsInstitution United Kingdom

BSI (2007) BS EN 14399-82007 ndash High-strength structural boltingassemblies for preloading System HV Hexagon fit bolt and nut assembliesBritish Standards Institution United Kingdom

BSI (2009) BS EN 1993-1-122007 ndash Eurocode 3 Design of steel structuresndash Part 112 Additional rules for the extension of EN 1993 up to steel gradesS 700 British Standards Institution United Kingdom

BSI (2010) BS EN 1993-1-82005 ndash Eurocode 3 Design of steel structuresndash Part 18 Design of joints British Standards Institution United Kingdom

BSI (2013) BS EN ISO 898-12013 ndash Mechanical properties of fastenersmade of carbon steel and alloy steel Bolts screws and studs with specifiedproperty classes Coarse thread and fine pitch thread British StandardsInstitution United Kingdom

BSI (2014) BS EN 1991-1-72006+A12014 ndash Eurocode 1 Actions on structuresndash Part 197 General actions British Standards Institution United Kingdom

BSI (2015) BS EN 14399-42015 ndash High-strength structural boltingassemblies for preloading System HV Hexagon bolt and nut assembliesBritish Standards Institution United Kingdom

SCI (1995a) Joints in steel construction Moment connections P207 TheSteel Construction Institute

SCI (1995b) Advisory Desk Notes Bending Moment in a pin AD 172 TheSteel Construction Institute

SCI (2006) Column base stiffness for global analysis NCCI-SN045a TheSteel Construction Institute

SCI (2011) Joints in steel construction Simple joints to Eurocode 3 P358The Steel Construction Institute

SCI (2013a) Joints in steel construction Moment-resisting joints toEurocode 3 P398 The Steel Construction Institute

UK FOREWORD

_____

xxviii

SCI (2013b) Interim Report Design of Portal Frames to Eurocode 3 Anoverview for UK designers P400 The Steel Construction Institute

TABLE OF CONTENTS

_____

v

TABLE OF CONTENTS

FOREWORD xiii

PREFACE xv

UK FOREWORD xix

NOTATION xxix

Chapter 1

INTRODUCTION 1

11 General 1111 Aims of the book 1112 Brief description of the contents of the book 10113 Types of structural systems and joints covered 11114 Basis of design 12

12 Definitions 12121 Joint properties 14122 Sources of joint deformation 15123 Beam splices and column splices 19124 Beam-to-beam joints 20125 Column bases 21126 Hollow section joints 22

13 Material choice 22

14 Fabrication and erection 26

15 Costs 27

16 Application of the ldquostatic approachrdquo 27161 Component approach 29162 Hybrid joints aspects 35

17 Design tools 35171 Types of design tools 36

TABLE OF CONTENTS

_____

vi

172 Examples of design tools 37

18 Worked examples 40

Chapter 2

STRUCTURAL ANALYSIS AND DESIGN 43

21 Introduction 43211 Elastic or elastoplastic analysis and verification process 44212 First order or second order analysis 45213 Integration of joint response into the frame analysis anddesign process 46

22 Joint modelling 47221 General 47222 Modelling and sources of joint deformation 49223 Simplified modelling according to EN 1993 50224 Concentration of the joint deformation 51

23 Joint idealisation 56231 Elastic idealisation for an elastic analysis 57232 Rigid-plastic idealisation for a rigid-plastic analysis 58233 Non-linear idealisation for an elastic-plastic analysis 59

24 Joint classification 59241 General 59242 Classification based on mechanical joint properties 60

25 Ductility classes 62251 General concept 62252 Requirements for classes of joints 65

Chapter 3

CONNECTIONS WITH MECHANICAL FASTENERS 67

31 Mechanical fasteners 67

32 Categories of connections 69321 Shear connections 69322 Tension connections 71

TABLE OF CONTENTS

_____

vii

33 Positioning of bolt holes 72

34 Design of the basic components 74341 Bolts in shear 74342 Bolts in tension 75343 Bolts in shear and tension 76344 Preloaded bolts 77345 Plates in bearing 85346 Block tearing 86347 Injection bolts 87348 Pins 88349 Blind bolting 913410 Nails 943411 Eccentricity of angles 95

35 Design of connections 97351 Bolted lap joints 97352 Bolted T-stubs 101353 Gusset plates 113354 Long joints 117

Chapter 4

WELDED CONNECTIONS 119

41 Types of welds 119411 Butt welds 119412 Fillet welds 120413 Fillet welds all round 121414 Plug welds 122

42 Construction constraints 122421 Mechanical properties of materials 122422 Welding processes preparation of welds and weld quality 123423 Geometry and dimensions of welds 127

43 Design of welds 130431 Generalities 130432 Fillet welds 131433 Fillet welds all round 134

TABLE OF CONTENTS

_____

viii

434 Butt welds 135435 Plug welds 136436 Concept of full strength fillet weld 136

44 Distribution of forces in a welded joint 139441 Generalities 139442 Particular situations 141

Chapter 5

SIMPLE JOINTS 147

51 Introduction 147

52 Beam-to-column and beam-to-beam joints 149521 Introduction 149522 Scope and field of application 150523 Joint modelling for frame analysis and design requirements 153524 Design resistance 156525 Practical ways to satisfy the ductility and rotationrequirements 163

53 Column bases 174531 Introduction 174532 Basis for the evaluation of the design resistance 176533 Resistance to axial forces 177534 Resistance to shear forces 185

Chapter 6

MOMENT-RESISTING JOINTS 189

61 Introduction 189

62 Component characterisation 190621 Column web panel in shear in steel or composite joints 190622 Column web in transverse compression in steel or compositejoints 192623 Column web in transverse tension 196624 Column flange in transverse bending 197625 End plate in bending 203

TABLE OF CONTENTS

_____

ix

626 Flange cleat in bending 205627 Beam or column flange and web in compression 207628 Beam web in tension 209629 Plate in tension or compression 2106210 Bolts in tension 2116211 Bolts in shear 2126212 Bolts in bearing (on beam flange column flange end plateor cleat) 2136213 Concrete in compression including grout 2136214 Base plate in bending under compression 2146215 Base plate in bending under tension 2146216 Anchor bolts in tension 2156217 Anchor bolts in shear 2156218 Anchor bolts in bearing 2156219 Welds 2166220 Haunched beam 216

63 Assembly for resistance 217631 Joints under bending moments 217632 Joints under axial forces 225633 Joints under bending moments and axial forces 226634 M minus N minus V 233635 Design of welds 234

64 Assembly for rotational stiffness 238641 Joints under bending moments 238642 Joints under bending moments and axial forces 247

65 Assembly for ductility 249651 Steel bolted joints 250652 Steel welded joints 252

66 Application to steel beam-to-column joint configurations 253661 Extended scope 253662 Possible design simplifications for end plate connections 256663 Worked example 257

67 Application to steel column splices 281671 Common splice configurations 281

TABLE OF CONTENTS

_____

x

672 Design considerations 283

68 Application to column bases 284681 Common column basis configurations 284682 Design considerations 287

Chapter 7

LATTICE GIRDER JOINTS 295

71 General 295

72 Scope and field of application 296

73 Design models 298731 General 298732 Failure modes 299733 Models for CHS chords 300734 Model for RHS chords 301735 Punching shear failure 302736 Model for brace failure 303737 M-N interaction 304

Chapter 8

JOINTS UNDER VARIOUS LOADING SITUATIONS 305

81 Introduction 305

82 Joints in fire 306

83 Joints under cyclic loading 307

84 Joints under exceptional events 308

Chapter 9

DESIGN STRATEGIES 311

91 Introduction 311

92 Traditional design approach 314

93 Integrated design approach 317

94 Economic considerations 319

TABLE OF CONTENTS

_____

xi

941 Fabrication and erections costs 319942 Savings of material costs 322943 Summary and conclusions 323

BIBLIOGRAPHIC REFERENCES 325

Annex A Practical values for required rotation capacity 337

Annex B Values for lateral torsional buckling strength of a fin plate 339

FOREWORD

_____

xiii

FOREWORD

With the ECCS book ldquoJoints in Steel and Composite Structuresrdquo the authorssucceeded in placing the joints on the rightful place they deserve in thestructural behaviour of steel and composite steel-concrete structures Themany times used word ldquodetailsrdquo for the joints in structures by farunderestimates the importance of joints in the structural behaviour ofbuildings and civil engineering structures In their chapter ldquoAim of the bookrdquothe authors clearly explain how the design and safety verification ofstructures runs in an integral manner where all structural componentsincluding the joints play balanced roles leading to economic structures

This book can be seen as a background document for Eurocode 3 ldquoDesign ofSteel Structuresrdquo as far as it concerns structural joints The central theme indescribing the behaviour of joints is using the component method and this isleading all over in this book The book contain many aspects such as designfabrication erection and costs

In this book attention is paid on joint modelling and idealisation jointclassification for strength and stiffness and deformation capacity This all forconnections with mechanical fasteners and for welded connections for simplejoints and moment resistant joints Also lattice girder joints are described

The book provides the designer with design strategies to arrive at economicstructures

The authors based themselves on many bibliographic references covering atime span of about 65 years Many of these references present research of theauthors themselves and of the other members of the ECCS-TechnicalCommittee TC10 ldquoStructural Connectionsrdquo

It was really a privilege to have been the chairperson of this committee from1998 till the end of 2012 and I thank the authors Prof Dr Ir Jean-PierreJaspart and Dr-Ing Klaus Weynand for their large effort in writing this book

Prof ir Frans Bijlaard

PREFACE

_____

xv

PREFACE

Steel constructions and composite steel-concrete constructions are generallyerected on site by the assembly of prefabricated structural parts prepared inthe workshop These parts may themselves be the result of an assembly ofindividual elements An example is the assembly by bolting on site offabricated sections welded in the workshop

In these construction types joints and connections play a key role andrecommendations and guidelines are required for engineers and constructorsfaced with the conception and design the fabrication and the erection of suchstructures In the Structural Eurocodes these aspects are mainly covered in theexecution standard EN 1090-2 and in the design standard EN 1993-1-8(Eurocode 3 Design of steel structures Part 1-8 Design of Joints)

In the present book which is part of the series of ECCS Eurocode DesignManuals the main focus is given to design aspects but references are alsomade to EN 1090-2 when necessary

In comparison to other fields the design procedures for joints andconnections have significantly evolved in the last decades as a result of theprogressive awareness by practitioners of the significant contribution ofjoints and connections to the global cost of structures Design for lowfabrication and erection costs as well as high resistance is therefore thetargeted objective of modern design codes the achievement of which hasjustified the development of new calculation approaches now integrated intothe two afore-mentioned Eurocodes This situation justifies the writing of thepresent manual with the main goal to demystify the process by explainingthe new concepts for the design of joints and to integrate their mechanicalresponse into the structural frame analysis and design process by providingldquokeysrdquo for a proper application in practice and finally by providing welldocumented worked examples

To refer to ldquomodernrdquo or ldquonewrdquo design approaches and philosophies does notmean that traditional ways are out dated or no more valid It should beunderstood that the design methods recommended in the Eurocodes are a

PREFACE

_____

xvi

collection of European practices including the results of intensive researchefforts carried out in the last decades and so give many options andalternatives to engineers who are trying to develop safe and economicsolutions

Chapter 1 introduces generalities about joint properties aspects of materialsfabrication erection and costs design approach - and especially the so-calledcomponent method - and design tools available to practitioners for easiercode application The integration of the response of the joints into thestructural analysis and design process is addressed in chapter 2 In chapter 3attention is paid to the design of common connections with mechanicalfasteners Preloaded bolts and non-preloaded bolts are mainly considered butthe use of some less classical connectors is also briefly described Weldedconnections are covered in chapter 5

The next three chapters relate to three specific types of joints respectivelysimple joints moment resisting joints and lattice girder joints For thesesubstantial innovations are brought in the Eurocodes in comparison totraditional national codes particularly for simple and moment resistingjoints A significant number of pages is therefore devoted to these topics inthis manual

The design of joints under static loading as it is addressed in the seven firstchapters is essential in all cases but further checks or different conceptualdesign of the joints are often required in case of load reversal fireearthquake or even exceptional events like impact or explosion Chapter 8summarises present knowledge in this field

Traditionally joints were designed as rigid or pinned which enables the designof the frame and the design of the joints to be treated independently The cleareconomical advantage associated in many situations with the use of semi-rigidandor partial-strength joints leads however to ldquostructure-jointsrdquo interactionsthat have to be mastered by the engineer so as to fully profit from the potentialcost savings The Eurocodes do not cover this interaction From this point ofview chapter 9 may be considered as ldquoa premiegravererdquo even if the content hasalready been partly described years ago in an ECSC publication

Before letting the reader discover the contents of this book we would like toexpress acknowledgment We are very grateful to Prof Frans Bijlaard for all

PREFACE

_____

xvii

the comments suggestions and corrections he made through the reviewprocess of the present manual Warm thanks are also addressed to Joseacute Fuchsand Soumlnke Muumlller who helped us in preparing the drawings Last but notleast we would like to thank our wives for their patience when we workedldquoon our projectrdquo during innumerable evenings and weekends

Jean-Pierre JaspartKlaus Weynand

UK FOREWORD

_____

xix

UK FOREWORD

INTRODUCTION

This book is the second in a series of joint publications of the EuropeanConvention for Constructional Steelwork (ECCS) and The Steel ConstructionInstitute (SCI) It will help provide UK engineers and designers with a betterunderstanding of the design principles in the European Code of Practice for theDesign of Steel Structures (EN 1993 ndash Eurocode 3) and the individual Part 18(EN 1993-1-8) for the design of steel joints in particular Reference will alsobe made to the associated Eurocodes for concrete (EN 1992 ndash Eurocode 2) andearthquake engineering (EN 1998 ndash Eurocode 8) The book complements otherSCI design guides eg SCI (2011 and 2013a)

The current publication is a first UK edition based on the first edition of theECCS manual for the Design of Joints in Steel and Composite Structureswhich was published in 2016 The scope of this UK edition is narrower thanthe original publication in two specific areas that are felt to be of limitedinterest to current practice in the UK there is no content covering compositejoints and chapter 9 (covering frame design strategies) has been shortened tosimply give an overview of strategies In this edition the reader will findinformation that is either of a general nature or relevant to specific sectionsof the publication to facilitate its application in a UK context

The content includes useful background to the code rules and a reminder ofsome engineering principles Information is presented in the context of theEurocodes terminology and notation and with reference to clause numbersetc to help the readerrsquos familiarity with EN 1993-1-8 The document thatserves as the basis for content and numbering of clauses is the UKimplementation of EN 1993-1-82005 incorporating corrigenda December2005 and July 2009 At the time of writing (Autumn 2016) part 1-8 ofEN 1993 is being revised with publication anticipated after 2020

Finally it is noted and should be accepted that there will inevitably be somedifferences of interpretation between the ECCS recommendations and thosepreviously published by the SCI

UK FOREWORD

_____

xx

GENERAL COMMENTS

Design of joints (connections) in steel structures in the UK is covered byBS EN 1993-1-8 and its national Annex (NA) (BSI 2010) BS EN 1993-1-8has clear definitions for connections and joints The term joint refers to thezone where members are interconnected and a connection is the locationwhere elements meet The distinction in terminology is usually emphasised inContinental Europe but traditional practice in the UK is to use the generic termconnection

The following partial safety factors are defined in the UK NA

Partial factor Value Comment

γM2 125 Used for the resistance of bolts pins and welds

γM2 125Used for the resistance of plates in bearing(γM2=15 should be used if deformation control is important)

γM3 125 Used for slip resistance at Ultimate Limit States

γM3serv 110 Used for slip resistance at Serviceability Limit States (SLS)

γM4 100 Used for the resistance of injection bolts

γM5 100 Used for the resistance of joints in hollow section lattice girders

γM6serv 100 Used for the resistance of pins at SLS

γM7

110Used for the preload of high strength steel bolts conforming toBS EN 14399-4 and BS EN 14399-8 (BSI 2015 and 2007)

100 Used for the preload of (other) high strength steel bolts

Specific reference to the UK Building Regulations is also made in this UKedition The UK Building Regulations code has structural integrityrequirements in order to avoid disproportionate collapse and ensure robustnessof the complete structure Disproportionate collapse can be defined as a regionof structural collapse out of proportion to the initiating cause of failure Themost relevant to connectionjoint design is that the detailing for every beam

UK FOREWORD

_____

xxi

member must be adequate to resist a minimum horizontal force at ultimatefailure (or tying resistance) Guidance on the design values of tying forces canbe found in BS EN 1991-1-7 Annex A and its UK annex (BSI 2014)

SECTION SPECIFIC COMMENTS

Section 111

UK practice normally considers only two main forms of joint modellingsimple and continuous Ideally frames designed on the basis of simple jointmodelling should use joints between members that possess negligiblerotational stiffness and transmit the beam reactions in shear into thecolumns without developing significant moments These joints may betreated as perfect pins Members can then be designed in isolation either as(predominantly) axially loaded columns or as simply supported beamsJoints designed within the principles of continuous modelling are capable oftransmitting significant moments and are able to maintain the original anglebetween adjacent members virtually unchanged This form of construction ofsteel frames is particularly advantageous when beam deflections are criticalor if bracing systems are not possible

To comply with one or the other design assumption steelwork connectionsare detailed as simple or moment-resisting joints Because joints in framestructures are often treated by adopting a degree of standardisation thedesigner usually details the connections in accordance with the principlesin the series of SCI Green Books which present this material in the formof step-by-step design procedures and tables covering standardarrangements

Other approximate analysis methods continue to be used among Britishdesigners the most representative being the wind-moment method for thedesign of unbraced multi-storey steel frames The method assumes that(i) under gravity loads the beam-to-column joints act as pinnedconnections and (ii) under horizontal wind loads these joints are rigidalthough it lacks transparency This method can be seen as a manifestationof the semi-continuous principles Wind moment connection details can befound in SCI (1995a) With the now widespread use of software in designoffices for rigorous second-order analysis it is doubtful if the use of the

UK FOREWORD

_____

xxii

wind-moment method should be advocated any longer other than forinitial sizing

Section 13

Although S460 is attracting growing interest S355 is still the dominantgrade of steel used in the UK

Section 161

With reference to Figure 120 it is noted that (site) welded joints and angleflange cleats are rarely if ever used in the UK

Section 162

Hybrid connections are rarely used in the UK for the reasons noted

Section 172

There is not much use of CoPcopy in the UK There are a number of othersoftware tools on the market some more comprehensive than others

Section 22

Although in UK design practice most aspects related to joint modelling havedeveloped to a high degree of sophistication proper consideration of thestructural interaction between the joints and members is rarely fully takeninto account It is indeed very difficult to predict and model the complexbehaviour of a joint (strength stiffness and rotation capacity) TraditionalUK practice is to predict joint behaviour on the basis of past experience

BSI (2010) separates the modelling of the rotational behaviour of theconnection elements (that is the bolts the welds the plates etc) and thatof the column web panel in shear to characterise the overall jointbehaviour As a simplification the two sources of joint deformation arecombined by means of the so-called transformation parameter β Thiscoefficient is related to the web panel internal actions and can be calculatedfrom the moments at each side of the web panel The β parameter iscurrently only defined for same-depth beams which meet at the same levelIn many practical double-sided joints beams will not be of the same depthor at the same height BS EN 1993-1-8 is silent on such joints

UK FOREWORD

_____

xxiii

Section 23

As explained above typical UK design practice does not consider thissophisticated procedure for idealisation of joints

Section 24

The NA to BS EN 1993-1-8 gives practical guidance to classify joints Italso states the following

ldquoUntil experience is gained with the numerical method of calculatingrotational stiffness given in BS EN 1993-1-82005 63 and theclassification by stiffness method given in BS EN 1993-1-82005522 semi-continuous elastic design should only be used where eitherit is supported by test evidence according to BS EN 1993-1-820055221(2) or where it is based on satisfactorily performance in asimilar situationrdquo

Evidence on values of column base stiffness for practical global analysis isgiven in SCI (2006)

Section 25

The concept of ductility classes is not widely applied in the UK It isgenerally assumed that standard connection details to the SCI Green Booksprovide enough rotation capacity and so behave in a ductile manner asevidenced by physical testing and experience

Section 31

The NA to BS EN 1993-1-8 excludes bolts of classes 58 and 68 It alsostates that bolt class 48 may only be used if the manufacturing process (i) isin accordance with BS EN ISO 898-1 (BSI 2013) and (ii) includes suitableprocedures to avoid hydrogen embrittlement

Section 322

The NA to BS EN 1993-1-8 states that if the preload is not explicitly used inthe design calculations then no specific level of preload is required

Section 347

Injection bolts are rarely used in the UK

UK FOREWORD

_____

xxiv

Section 348

Reference is made to SCI (1995b) to calculate the bending moments in thepin of a pin bearing

Section 349

Flow drill blind bolting is not common practice in the UK SHS blind boltingis a common system but there are several manufactures other than thatsuggested in the book

Section 3410

Nails are rarely used in the UK

Section 352

T-stub configurations with four bolts in a row are rarely used in the UK

Section 353

Reference is made to the SCI method for the design of gusset plates seeSCI (2011)

Section 421

It is anticipated that specific rules given in the current BS EN 1993-1-12(BSI 2009) for high strength steels will be incorporated in the revisedBS EN 1993-1-8 to appear after 2020

Section 522

ldquoHeader platesrdquo are known as ldquopartial depth end platesrdquo in the UK Webcleat connections are no longer commonly used in the UK The full depthend plate connection shown on the left of Figure 59 is classified as a simplejoint in the UK (SCI 2011)

Section 523

The UK Building Regulations require that joints are designed for tyingforces in order to satisfy structural integrity requirements Guidance onthe design values of tying forces is given in BS EN 1991-1-7 Annex Aand its UK NA The requirements relate to the building class with a

UK FOREWORD

_____

xxv

design value of horizontal force generally not less than 75 kN andusually significantly higher Simple joints detailed to SCI (2011) satisfythese requirements

Section 525

It is generally safe to assume that the ductility (rotation requirements) aresatisfied provided that joints are detailed in accordance with SCI (2011)

Section 531

The column base detailing on the left of Figure 521 is not commonly used inthe UK We never recommend less than four bolts ndash they are needed toassure stability and facilitate location during erection The anchoringsystems shown in Figure 522 are not usually adopted in the UK Referenceis made to SCI (2013a) for common anchor systems

Section 62

Publication SCI (2013b) summarises the principal differences betweenBS 5950 and BS EN 1993-1-8 (BSI 2000 and 2010) in terms ofcomponent characterisation

With reference to Figure 66 it is anticipated that the revised BS EN1993-1-8will include analytical expressions for the definition of the so-called αcoefficient

Rules of thumb for the characterisation of the ductility of some individualcomponents are given in SCI (1995a)

Section 631

The UK NA to BS EN 1993-1-8 gives specific rules for the full plasticdistribution of effective design tension resistance The procedure is alsosummarised in SCI (2013a)

Section 633

Where a joint is subjected to combined bending moments and axial forcesthe concept of an applied moment modified by axial load can be used seeSCI (1995a)

UK FOREWORD

_____

xxvi

Section 64

Rotational stiffness is not normally evaluated in UK design practice whichusually relies on past experience

Section 65

Some rules of thumb for the characterisation of the ductility of moment-resisting joints are given in SCI (1995a)

Section 661

With reference to Figure 636 it is noted that this joint configuration ishardly (if ever) used in the UK

Section 663

It should be noted that European sections are not commonly used in the UKalthough there is growing interest in the market Steel grade S235 is not usedin the UK S355 being the current common grade Combinations of plates of15 mm thickness with M24 bolts are common This combination is assumedto provide enough rotation capacity thus satisfying ductility requirementsbecause ductile failure of the plates not brittle failure of the bolts governsthe behaviour

Section 672

Standard practice in the UK does not account for this 25 rule Columnsplices are usually detailed to SCI (2011) to ensure continuity of stiffnessthrough the splice so that the member design is not invalidated

Section 84

The UK Building Regulations require that joints are designed for tyingforces in order to satisfy structural integrity requirements Guidance on thedesign values of tying forces is given in BS EN 1991-1-7 Annex A and itsUK NA (BSI 2014)

Section 91

In the UK the ldquofabricatorsrdquo are known as ldquoSteelwork contractorsrdquo becausethey do more than just fabricate

UK FOREWORD

_____

xxvii

REFERENCES TO NATIONAL FOREWORD

BSI (2000) BS 5950-12000 ndash Structural use of steelwork in building ndash Part1 Code of Practice for Design rolled and welded sections British StandardsInstitution United Kingdom

BSI (2007) BS EN 14399-82007 ndash High-strength structural boltingassemblies for preloading System HV Hexagon fit bolt and nut assembliesBritish Standards Institution United Kingdom

BSI (2009) BS EN 1993-1-122007 ndash Eurocode 3 Design of steel structuresndash Part 112 Additional rules for the extension of EN 1993 up to steel gradesS 700 British Standards Institution United Kingdom

BSI (2010) BS EN 1993-1-82005 ndash Eurocode 3 Design of steel structuresndash Part 18 Design of joints British Standards Institution United Kingdom

BSI (2013) BS EN ISO 898-12013 ndash Mechanical properties of fastenersmade of carbon steel and alloy steel Bolts screws and studs with specifiedproperty classes Coarse thread and fine pitch thread British StandardsInstitution United Kingdom

BSI (2014) BS EN 1991-1-72006+A12014 ndash Eurocode 1 Actions on structuresndash Part 197 General actions British Standards Institution United Kingdom

BSI (2015) BS EN 14399-42015 ndash High-strength structural boltingassemblies for preloading System HV Hexagon bolt and nut assembliesBritish Standards Institution United Kingdom

SCI (1995a) Joints in steel construction Moment connections P207 TheSteel Construction Institute

SCI (1995b) Advisory Desk Notes Bending Moment in a pin AD 172 TheSteel Construction Institute

SCI (2006) Column base stiffness for global analysis NCCI-SN045a TheSteel Construction Institute

SCI (2011) Joints in steel construction Simple joints to Eurocode 3 P358The Steel Construction Institute

SCI (2013a) Joints in steel construction Moment-resisting joints toEurocode 3 P398 The Steel Construction Institute

UK FOREWORD

_____

xxviii

SCI (2013b) Interim Report Design of Portal Frames to Eurocode 3 Anoverview for UK designers P400 The Steel Construction Institute

TABLE OF CONTENTS

_____

vi

172 Examples of design tools 37

18 Worked examples 40

Chapter 2

STRUCTURAL ANALYSIS AND DESIGN 43

21 Introduction 43211 Elastic or elastoplastic analysis and verification process 44212 First order or second order analysis 45213 Integration of joint response into the frame analysis anddesign process 46

22 Joint modelling 47221 General 47222 Modelling and sources of joint deformation 49223 Simplified modelling according to EN 1993 50224 Concentration of the joint deformation 51

23 Joint idealisation 56231 Elastic idealisation for an elastic analysis 57232 Rigid-plastic idealisation for a rigid-plastic analysis 58233 Non-linear idealisation for an elastic-plastic analysis 59

24 Joint classification 59241 General 59242 Classification based on mechanical joint properties 60

25 Ductility classes 62251 General concept 62252 Requirements for classes of joints 65

Chapter 3

CONNECTIONS WITH MECHANICAL FASTENERS 67

31 Mechanical fasteners 67

32 Categories of connections 69321 Shear connections 69322 Tension connections 71

TABLE OF CONTENTS

_____

vii

33 Positioning of bolt holes 72

34 Design of the basic components 74341 Bolts in shear 74342 Bolts in tension 75343 Bolts in shear and tension 76344 Preloaded bolts 77345 Plates in bearing 85346 Block tearing 86347 Injection bolts 87348 Pins 88349 Blind bolting 913410 Nails 943411 Eccentricity of angles 95

35 Design of connections 97351 Bolted lap joints 97352 Bolted T-stubs 101353 Gusset plates 113354 Long joints 117

Chapter 4

WELDED CONNECTIONS 119

41 Types of welds 119411 Butt welds 119412 Fillet welds 120413 Fillet welds all round 121414 Plug welds 122

42 Construction constraints 122421 Mechanical properties of materials 122422 Welding processes preparation of welds and weld quality 123423 Geometry and dimensions of welds 127

43 Design of welds 130431 Generalities 130432 Fillet welds 131433 Fillet welds all round 134

TABLE OF CONTENTS

_____

viii

434 Butt welds 135435 Plug welds 136436 Concept of full strength fillet weld 136

44 Distribution of forces in a welded joint 139441 Generalities 139442 Particular situations 141

Chapter 5

SIMPLE JOINTS 147

51 Introduction 147

52 Beam-to-column and beam-to-beam joints 149521 Introduction 149522 Scope and field of application 150523 Joint modelling for frame analysis and design requirements 153524 Design resistance 156525 Practical ways to satisfy the ductility and rotationrequirements 163

53 Column bases 174531 Introduction 174532 Basis for the evaluation of the design resistance 176533 Resistance to axial forces 177534 Resistance to shear forces 185

Chapter 6

MOMENT-RESISTING JOINTS 189

61 Introduction 189

62 Component characterisation 190621 Column web panel in shear in steel or composite joints 190622 Column web in transverse compression in steel or compositejoints 192623 Column web in transverse tension 196624 Column flange in transverse bending 197625 End plate in bending 203

TABLE OF CONTENTS

_____

ix

626 Flange cleat in bending 205627 Beam or column flange and web in compression 207628 Beam web in tension 209629 Plate in tension or compression 2106210 Bolts in tension 2116211 Bolts in shear 2126212 Bolts in bearing (on beam flange column flange end plateor cleat) 2136213 Concrete in compression including grout 2136214 Base plate in bending under compression 2146215 Base plate in bending under tension 2146216 Anchor bolts in tension 2156217 Anchor bolts in shear 2156218 Anchor bolts in bearing 2156219 Welds 2166220 Haunched beam 216

63 Assembly for resistance 217631 Joints under bending moments 217632 Joints under axial forces 225633 Joints under bending moments and axial forces 226634 M minus N minus V 233635 Design of welds 234

64 Assembly for rotational stiffness 238641 Joints under bending moments 238642 Joints under bending moments and axial forces 247

65 Assembly for ductility 249651 Steel bolted joints 250652 Steel welded joints 252

66 Application to steel beam-to-column joint configurations 253661 Extended scope 253662 Possible design simplifications for end plate connections 256663 Worked example 257

67 Application to steel column splices 281671 Common splice configurations 281

TABLE OF CONTENTS

_____

x

672 Design considerations 283

68 Application to column bases 284681 Common column basis configurations 284682 Design considerations 287

Chapter 7

LATTICE GIRDER JOINTS 295

71 General 295

72 Scope and field of application 296

73 Design models 298731 General 298732 Failure modes 299733 Models for CHS chords 300734 Model for RHS chords 301735 Punching shear failure 302736 Model for brace failure 303737 M-N interaction 304

Chapter 8

JOINTS UNDER VARIOUS LOADING SITUATIONS 305

81 Introduction 305

82 Joints in fire 306

83 Joints under cyclic loading 307

84 Joints under exceptional events 308

Chapter 9

DESIGN STRATEGIES 311

91 Introduction 311

92 Traditional design approach 314

93 Integrated design approach 317

94 Economic considerations 319

TABLE OF CONTENTS

_____

xi

941 Fabrication and erections costs 319942 Savings of material costs 322943 Summary and conclusions 323

BIBLIOGRAPHIC REFERENCES 325

Annex A Practical values for required rotation capacity 337

Annex B Values for lateral torsional buckling strength of a fin plate 339

FOREWORD

_____

xiii

FOREWORD

With the ECCS book ldquoJoints in Steel and Composite Structuresrdquo the authorssucceeded in placing the joints on the rightful place they deserve in thestructural behaviour of steel and composite steel-concrete structures Themany times used word ldquodetailsrdquo for the joints in structures by farunderestimates the importance of joints in the structural behaviour ofbuildings and civil engineering structures In their chapter ldquoAim of the bookrdquothe authors clearly explain how the design and safety verification ofstructures runs in an integral manner where all structural componentsincluding the joints play balanced roles leading to economic structures

This book can be seen as a background document for Eurocode 3 ldquoDesign ofSteel Structuresrdquo as far as it concerns structural joints The central theme indescribing the behaviour of joints is using the component method and this isleading all over in this book The book contain many aspects such as designfabrication erection and costs

In this book attention is paid on joint modelling and idealisation jointclassification for strength and stiffness and deformation capacity This all forconnections with mechanical fasteners and for welded connections for simplejoints and moment resistant joints Also lattice girder joints are described

The book provides the designer with design strategies to arrive at economicstructures

The authors based themselves on many bibliographic references covering atime span of about 65 years Many of these references present research of theauthors themselves and of the other members of the ECCS-TechnicalCommittee TC10 ldquoStructural Connectionsrdquo

It was really a privilege to have been the chairperson of this committee from1998 till the end of 2012 and I thank the authors Prof Dr Ir Jean-PierreJaspart and Dr-Ing Klaus Weynand for their large effort in writing this book

Prof ir Frans Bijlaard

PREFACE

_____

xv

PREFACE

Steel constructions and composite steel-concrete constructions are generallyerected on site by the assembly of prefabricated structural parts prepared inthe workshop These parts may themselves be the result of an assembly ofindividual elements An example is the assembly by bolting on site offabricated sections welded in the workshop

In these construction types joints and connections play a key role andrecommendations and guidelines are required for engineers and constructorsfaced with the conception and design the fabrication and the erection of suchstructures In the Structural Eurocodes these aspects are mainly covered in theexecution standard EN 1090-2 and in the design standard EN 1993-1-8(Eurocode 3 Design of steel structures Part 1-8 Design of Joints)

In the present book which is part of the series of ECCS Eurocode DesignManuals the main focus is given to design aspects but references are alsomade to EN 1090-2 when necessary

In comparison to other fields the design procedures for joints andconnections have significantly evolved in the last decades as a result of theprogressive awareness by practitioners of the significant contribution ofjoints and connections to the global cost of structures Design for lowfabrication and erection costs as well as high resistance is therefore thetargeted objective of modern design codes the achievement of which hasjustified the development of new calculation approaches now integrated intothe two afore-mentioned Eurocodes This situation justifies the writing of thepresent manual with the main goal to demystify the process by explainingthe new concepts for the design of joints and to integrate their mechanicalresponse into the structural frame analysis and design process by providingldquokeysrdquo for a proper application in practice and finally by providing welldocumented worked examples

To refer to ldquomodernrdquo or ldquonewrdquo design approaches and philosophies does notmean that traditional ways are out dated or no more valid It should beunderstood that the design methods recommended in the Eurocodes are a

PREFACE

_____

xvi

collection of European practices including the results of intensive researchefforts carried out in the last decades and so give many options andalternatives to engineers who are trying to develop safe and economicsolutions

Chapter 1 introduces generalities about joint properties aspects of materialsfabrication erection and costs design approach - and especially the so-calledcomponent method - and design tools available to practitioners for easiercode application The integration of the response of the joints into thestructural analysis and design process is addressed in chapter 2 In chapter 3attention is paid to the design of common connections with mechanicalfasteners Preloaded bolts and non-preloaded bolts are mainly considered butthe use of some less classical connectors is also briefly described Weldedconnections are covered in chapter 5

The next three chapters relate to three specific types of joints respectivelysimple joints moment resisting joints and lattice girder joints For thesesubstantial innovations are brought in the Eurocodes in comparison totraditional national codes particularly for simple and moment resistingjoints A significant number of pages is therefore devoted to these topics inthis manual

The design of joints under static loading as it is addressed in the seven firstchapters is essential in all cases but further checks or different conceptualdesign of the joints are often required in case of load reversal fireearthquake or even exceptional events like impact or explosion Chapter 8summarises present knowledge in this field

Traditionally joints were designed as rigid or pinned which enables the designof the frame and the design of the joints to be treated independently The cleareconomical advantage associated in many situations with the use of semi-rigidandor partial-strength joints leads however to ldquostructure-jointsrdquo interactionsthat have to be mastered by the engineer so as to fully profit from the potentialcost savings The Eurocodes do not cover this interaction From this point ofview chapter 9 may be considered as ldquoa premiegravererdquo even if the content hasalready been partly described years ago in an ECSC publication

Before letting the reader discover the contents of this book we would like toexpress acknowledgment We are very grateful to Prof Frans Bijlaard for all

PREFACE

_____

xvii

the comments suggestions and corrections he made through the reviewprocess of the present manual Warm thanks are also addressed to Joseacute Fuchsand Soumlnke Muumlller who helped us in preparing the drawings Last but notleast we would like to thank our wives for their patience when we workedldquoon our projectrdquo during innumerable evenings and weekends

Jean-Pierre JaspartKlaus Weynand

UK FOREWORD

_____

xix

UK FOREWORD

INTRODUCTION

This book is the second in a series of joint publications of the EuropeanConvention for Constructional Steelwork (ECCS) and The Steel ConstructionInstitute (SCI) It will help provide UK engineers and designers with a betterunderstanding of the design principles in the European Code of Practice for theDesign of Steel Structures (EN 1993 ndash Eurocode 3) and the individual Part 18(EN 1993-1-8) for the design of steel joints in particular Reference will alsobe made to the associated Eurocodes for concrete (EN 1992 ndash Eurocode 2) andearthquake engineering (EN 1998 ndash Eurocode 8) The book complements otherSCI design guides eg SCI (2011 and 2013a)

The current publication is a first UK edition based on the first edition of theECCS manual for the Design of Joints in Steel and Composite Structureswhich was published in 2016 The scope of this UK edition is narrower thanthe original publication in two specific areas that are felt to be of limitedinterest to current practice in the UK there is no content covering compositejoints and chapter 9 (covering frame design strategies) has been shortened tosimply give an overview of strategies In this edition the reader will findinformation that is either of a general nature or relevant to specific sectionsof the publication to facilitate its application in a UK context

The content includes useful background to the code rules and a reminder ofsome engineering principles Information is presented in the context of theEurocodes terminology and notation and with reference to clause numbersetc to help the readerrsquos familiarity with EN 1993-1-8 The document thatserves as the basis for content and numbering of clauses is the UKimplementation of EN 1993-1-82005 incorporating corrigenda December2005 and July 2009 At the time of writing (Autumn 2016) part 1-8 ofEN 1993 is being revised with publication anticipated after 2020

Finally it is noted and should be accepted that there will inevitably be somedifferences of interpretation between the ECCS recommendations and thosepreviously published by the SCI

UK FOREWORD

_____

xx

GENERAL COMMENTS

Design of joints (connections) in steel structures in the UK is covered byBS EN 1993-1-8 and its national Annex (NA) (BSI 2010) BS EN 1993-1-8has clear definitions for connections and joints The term joint refers to thezone where members are interconnected and a connection is the locationwhere elements meet The distinction in terminology is usually emphasised inContinental Europe but traditional practice in the UK is to use the generic termconnection

The following partial safety factors are defined in the UK NA

Partial factor Value Comment

γM2 125 Used for the resistance of bolts pins and welds

γM2 125Used for the resistance of plates in bearing(γM2=15 should be used if deformation control is important)

γM3 125 Used for slip resistance at Ultimate Limit States

γM3serv 110 Used for slip resistance at Serviceability Limit States (SLS)

γM4 100 Used for the resistance of injection bolts

γM5 100 Used for the resistance of joints in hollow section lattice girders

γM6serv 100 Used for the resistance of pins at SLS

γM7

110Used for the preload of high strength steel bolts conforming toBS EN 14399-4 and BS EN 14399-8 (BSI 2015 and 2007)

100 Used for the preload of (other) high strength steel bolts

Specific reference to the UK Building Regulations is also made in this UKedition The UK Building Regulations code has structural integrityrequirements in order to avoid disproportionate collapse and ensure robustnessof the complete structure Disproportionate collapse can be defined as a regionof structural collapse out of proportion to the initiating cause of failure Themost relevant to connectionjoint design is that the detailing for every beam

UK FOREWORD

_____

xxi

member must be adequate to resist a minimum horizontal force at ultimatefailure (or tying resistance) Guidance on the design values of tying forces canbe found in BS EN 1991-1-7 Annex A and its UK annex (BSI 2014)

SECTION SPECIFIC COMMENTS

Section 111

UK practice normally considers only two main forms of joint modellingsimple and continuous Ideally frames designed on the basis of simple jointmodelling should use joints between members that possess negligiblerotational stiffness and transmit the beam reactions in shear into thecolumns without developing significant moments These joints may betreated as perfect pins Members can then be designed in isolation either as(predominantly) axially loaded columns or as simply supported beamsJoints designed within the principles of continuous modelling are capable oftransmitting significant moments and are able to maintain the original anglebetween adjacent members virtually unchanged This form of construction ofsteel frames is particularly advantageous when beam deflections are criticalor if bracing systems are not possible

To comply with one or the other design assumption steelwork connectionsare detailed as simple or moment-resisting joints Because joints in framestructures are often treated by adopting a degree of standardisation thedesigner usually details the connections in accordance with the principlesin the series of SCI Green Books which present this material in the formof step-by-step design procedures and tables covering standardarrangements

Other approximate analysis methods continue to be used among Britishdesigners the most representative being the wind-moment method for thedesign of unbraced multi-storey steel frames The method assumes that(i) under gravity loads the beam-to-column joints act as pinnedconnections and (ii) under horizontal wind loads these joints are rigidalthough it lacks transparency This method can be seen as a manifestationof the semi-continuous principles Wind moment connection details can befound in SCI (1995a) With the now widespread use of software in designoffices for rigorous second-order analysis it is doubtful if the use of the

UK FOREWORD

_____

xxii

wind-moment method should be advocated any longer other than forinitial sizing

Section 13

Although S460 is attracting growing interest S355 is still the dominantgrade of steel used in the UK

Section 161

With reference to Figure 120 it is noted that (site) welded joints and angleflange cleats are rarely if ever used in the UK

Section 162

Hybrid connections are rarely used in the UK for the reasons noted

Section 172

There is not much use of CoPcopy in the UK There are a number of othersoftware tools on the market some more comprehensive than others

Section 22

Although in UK design practice most aspects related to joint modelling havedeveloped to a high degree of sophistication proper consideration of thestructural interaction between the joints and members is rarely fully takeninto account It is indeed very difficult to predict and model the complexbehaviour of a joint (strength stiffness and rotation capacity) TraditionalUK practice is to predict joint behaviour on the basis of past experience

BSI (2010) separates the modelling of the rotational behaviour of theconnection elements (that is the bolts the welds the plates etc) and thatof the column web panel in shear to characterise the overall jointbehaviour As a simplification the two sources of joint deformation arecombined by means of the so-called transformation parameter β Thiscoefficient is related to the web panel internal actions and can be calculatedfrom the moments at each side of the web panel The β parameter iscurrently only defined for same-depth beams which meet at the same levelIn many practical double-sided joints beams will not be of the same depthor at the same height BS EN 1993-1-8 is silent on such joints

UK FOREWORD

_____

xxiii

Section 23

As explained above typical UK design practice does not consider thissophisticated procedure for idealisation of joints

Section 24

The NA to BS EN 1993-1-8 gives practical guidance to classify joints Italso states the following

ldquoUntil experience is gained with the numerical method of calculatingrotational stiffness given in BS EN 1993-1-82005 63 and theclassification by stiffness method given in BS EN 1993-1-82005522 semi-continuous elastic design should only be used where eitherit is supported by test evidence according to BS EN 1993-1-820055221(2) or where it is based on satisfactorily performance in asimilar situationrdquo

Evidence on values of column base stiffness for practical global analysis isgiven in SCI (2006)

Section 25

The concept of ductility classes is not widely applied in the UK It isgenerally assumed that standard connection details to the SCI Green Booksprovide enough rotation capacity and so behave in a ductile manner asevidenced by physical testing and experience

Section 31

The NA to BS EN 1993-1-8 excludes bolts of classes 58 and 68 It alsostates that bolt class 48 may only be used if the manufacturing process (i) isin accordance with BS EN ISO 898-1 (BSI 2013) and (ii) includes suitableprocedures to avoid hydrogen embrittlement

Section 322

The NA to BS EN 1993-1-8 states that if the preload is not explicitly used inthe design calculations then no specific level of preload is required

Section 347

Injection bolts are rarely used in the UK

UK FOREWORD

_____

xxiv

Section 348

Reference is made to SCI (1995b) to calculate the bending moments in thepin of a pin bearing

Section 349

Flow drill blind bolting is not common practice in the UK SHS blind boltingis a common system but there are several manufactures other than thatsuggested in the book

Section 3410

Nails are rarely used in the UK

Section 352

T-stub configurations with four bolts in a row are rarely used in the UK

Section 353

Reference is made to the SCI method for the design of gusset plates seeSCI (2011)

Section 421

It is anticipated that specific rules given in the current BS EN 1993-1-12(BSI 2009) for high strength steels will be incorporated in the revisedBS EN 1993-1-8 to appear after 2020

Section 522

ldquoHeader platesrdquo are known as ldquopartial depth end platesrdquo in the UK Webcleat connections are no longer commonly used in the UK The full depthend plate connection shown on the left of Figure 59 is classified as a simplejoint in the UK (SCI 2011)

Section 523

The UK Building Regulations require that joints are designed for tyingforces in order to satisfy structural integrity requirements Guidance onthe design values of tying forces is given in BS EN 1991-1-7 Annex Aand its UK NA The requirements relate to the building class with a

UK FOREWORD

_____

xxv

design value of horizontal force generally not less than 75 kN andusually significantly higher Simple joints detailed to SCI (2011) satisfythese requirements

Section 525

It is generally safe to assume that the ductility (rotation requirements) aresatisfied provided that joints are detailed in accordance with SCI (2011)

Section 531

The column base detailing on the left of Figure 521 is not commonly used inthe UK We never recommend less than four bolts ndash they are needed toassure stability and facilitate location during erection The anchoringsystems shown in Figure 522 are not usually adopted in the UK Referenceis made to SCI (2013a) for common anchor systems

Section 62

Publication SCI (2013b) summarises the principal differences betweenBS 5950 and BS EN 1993-1-8 (BSI 2000 and 2010) in terms ofcomponent characterisation

With reference to Figure 66 it is anticipated that the revised BS EN1993-1-8will include analytical expressions for the definition of the so-called αcoefficient

Rules of thumb for the characterisation of the ductility of some individualcomponents are given in SCI (1995a)

Section 631

The UK NA to BS EN 1993-1-8 gives specific rules for the full plasticdistribution of effective design tension resistance The procedure is alsosummarised in SCI (2013a)

Section 633

Where a joint is subjected to combined bending moments and axial forcesthe concept of an applied moment modified by axial load can be used seeSCI (1995a)

UK FOREWORD

_____

xxvi

Section 64

Rotational stiffness is not normally evaluated in UK design practice whichusually relies on past experience

Section 65

Some rules of thumb for the characterisation of the ductility of moment-resisting joints are given in SCI (1995a)

Section 661

With reference to Figure 636 it is noted that this joint configuration ishardly (if ever) used in the UK

Section 663

It should be noted that European sections are not commonly used in the UKalthough there is growing interest in the market Steel grade S235 is not usedin the UK S355 being the current common grade Combinations of plates of15 mm thickness with M24 bolts are common This combination is assumedto provide enough rotation capacity thus satisfying ductility requirementsbecause ductile failure of the plates not brittle failure of the bolts governsthe behaviour

Section 672

Standard practice in the UK does not account for this 25 rule Columnsplices are usually detailed to SCI (2011) to ensure continuity of stiffnessthrough the splice so that the member design is not invalidated

Section 84

The UK Building Regulations require that joints are designed for tyingforces in order to satisfy structural integrity requirements Guidance on thedesign values of tying forces is given in BS EN 1991-1-7 Annex A and itsUK NA (BSI 2014)

Section 91

In the UK the ldquofabricatorsrdquo are known as ldquoSteelwork contractorsrdquo becausethey do more than just fabricate

UK FOREWORD

_____

xxvii

REFERENCES TO NATIONAL FOREWORD

BSI (2000) BS 5950-12000 ndash Structural use of steelwork in building ndash Part1 Code of Practice for Design rolled and welded sections British StandardsInstitution United Kingdom

BSI (2007) BS EN 14399-82007 ndash High-strength structural boltingassemblies for preloading System HV Hexagon fit bolt and nut assembliesBritish Standards Institution United Kingdom

BSI (2009) BS EN 1993-1-122007 ndash Eurocode 3 Design of steel structuresndash Part 112 Additional rules for the extension of EN 1993 up to steel gradesS 700 British Standards Institution United Kingdom

BSI (2010) BS EN 1993-1-82005 ndash Eurocode 3 Design of steel structuresndash Part 18 Design of joints British Standards Institution United Kingdom

BSI (2013) BS EN ISO 898-12013 ndash Mechanical properties of fastenersmade of carbon steel and alloy steel Bolts screws and studs with specifiedproperty classes Coarse thread and fine pitch thread British StandardsInstitution United Kingdom

BSI (2014) BS EN 1991-1-72006+A12014 ndash Eurocode 1 Actions on structuresndash Part 197 General actions British Standards Institution United Kingdom

BSI (2015) BS EN 14399-42015 ndash High-strength structural boltingassemblies for preloading System HV Hexagon bolt and nut assembliesBritish Standards Institution United Kingdom

SCI (1995a) Joints in steel construction Moment connections P207 TheSteel Construction Institute

SCI (1995b) Advisory Desk Notes Bending Moment in a pin AD 172 TheSteel Construction Institute

SCI (2006) Column base stiffness for global analysis NCCI-SN045a TheSteel Construction Institute

SCI (2011) Joints in steel construction Simple joints to Eurocode 3 P358The Steel Construction Institute

SCI (2013a) Joints in steel construction Moment-resisting joints toEurocode 3 P398 The Steel Construction Institute

UK FOREWORD

_____

xxviii

SCI (2013b) Interim Report Design of Portal Frames to Eurocode 3 Anoverview for UK designers P400 The Steel Construction Institute

TABLE OF CONTENTS

_____

vii

33 Positioning of bolt holes 72

34 Design of the basic components 74341 Bolts in shear 74342 Bolts in tension 75343 Bolts in shear and tension 76344 Preloaded bolts 77345 Plates in bearing 85346 Block tearing 86347 Injection bolts 87348 Pins 88349 Blind bolting 913410 Nails 943411 Eccentricity of angles 95

35 Design of connections 97351 Bolted lap joints 97352 Bolted T-stubs 101353 Gusset plates 113354 Long joints 117

Chapter 4

WELDED CONNECTIONS 119

41 Types of welds 119411 Butt welds 119412 Fillet welds 120413 Fillet welds all round 121414 Plug welds 122

42 Construction constraints 122421 Mechanical properties of materials 122422 Welding processes preparation of welds and weld quality 123423 Geometry and dimensions of welds 127

43 Design of welds 130431 Generalities 130432 Fillet welds 131433 Fillet welds all round 134

TABLE OF CONTENTS

_____

viii

434 Butt welds 135435 Plug welds 136436 Concept of full strength fillet weld 136

44 Distribution of forces in a welded joint 139441 Generalities 139442 Particular situations 141

Chapter 5

SIMPLE JOINTS 147

51 Introduction 147

52 Beam-to-column and beam-to-beam joints 149521 Introduction 149522 Scope and field of application 150523 Joint modelling for frame analysis and design requirements 153524 Design resistance 156525 Practical ways to satisfy the ductility and rotationrequirements 163

53 Column bases 174531 Introduction 174532 Basis for the evaluation of the design resistance 176533 Resistance to axial forces 177534 Resistance to shear forces 185

Chapter 6

MOMENT-RESISTING JOINTS 189

61 Introduction 189

62 Component characterisation 190621 Column web panel in shear in steel or composite joints 190622 Column web in transverse compression in steel or compositejoints 192623 Column web in transverse tension 196624 Column flange in transverse bending 197625 End plate in bending 203

TABLE OF CONTENTS

_____

ix

626 Flange cleat in bending 205627 Beam or column flange and web in compression 207628 Beam web in tension 209629 Plate in tension or compression 2106210 Bolts in tension 2116211 Bolts in shear 2126212 Bolts in bearing (on beam flange column flange end plateor cleat) 2136213 Concrete in compression including grout 2136214 Base plate in bending under compression 2146215 Base plate in bending under tension 2146216 Anchor bolts in tension 2156217 Anchor bolts in shear 2156218 Anchor bolts in bearing 2156219 Welds 2166220 Haunched beam 216

63 Assembly for resistance 217631 Joints under bending moments 217632 Joints under axial forces 225633 Joints under bending moments and axial forces 226634 M minus N minus V 233635 Design of welds 234

64 Assembly for rotational stiffness 238641 Joints under bending moments 238642 Joints under bending moments and axial forces 247

65 Assembly for ductility 249651 Steel bolted joints 250652 Steel welded joints 252

66 Application to steel beam-to-column joint configurations 253661 Extended scope 253662 Possible design simplifications for end plate connections 256663 Worked example 257

67 Application to steel column splices 281671 Common splice configurations 281

TABLE OF CONTENTS

_____

x

672 Design considerations 283

68 Application to column bases 284681 Common column basis configurations 284682 Design considerations 287

Chapter 7

LATTICE GIRDER JOINTS 295

71 General 295

72 Scope and field of application 296

73 Design models 298731 General 298732 Failure modes 299733 Models for CHS chords 300734 Model for RHS chords 301735 Punching shear failure 302736 Model for brace failure 303737 M-N interaction 304

Chapter 8

JOINTS UNDER VARIOUS LOADING SITUATIONS 305

81 Introduction 305

82 Joints in fire 306

83 Joints under cyclic loading 307

84 Joints under exceptional events 308

Chapter 9

DESIGN STRATEGIES 311

91 Introduction 311

92 Traditional design approach 314

93 Integrated design approach 317

94 Economic considerations 319

TABLE OF CONTENTS

_____

xi

941 Fabrication and erections costs 319942 Savings of material costs 322943 Summary and conclusions 323

BIBLIOGRAPHIC REFERENCES 325

Annex A Practical values for required rotation capacity 337

Annex B Values for lateral torsional buckling strength of a fin plate 339

FOREWORD

_____

xiii

FOREWORD

With the ECCS book ldquoJoints in Steel and Composite Structuresrdquo the authorssucceeded in placing the joints on the rightful place they deserve in thestructural behaviour of steel and composite steel-concrete structures Themany times used word ldquodetailsrdquo for the joints in structures by farunderestimates the importance of joints in the structural behaviour ofbuildings and civil engineering structures In their chapter ldquoAim of the bookrdquothe authors clearly explain how the design and safety verification ofstructures runs in an integral manner where all structural componentsincluding the joints play balanced roles leading to economic structures

This book can be seen as a background document for Eurocode 3 ldquoDesign ofSteel Structuresrdquo as far as it concerns structural joints The central theme indescribing the behaviour of joints is using the component method and this isleading all over in this book The book contain many aspects such as designfabrication erection and costs

In this book attention is paid on joint modelling and idealisation jointclassification for strength and stiffness and deformation capacity This all forconnections with mechanical fasteners and for welded connections for simplejoints and moment resistant joints Also lattice girder joints are described

The book provides the designer with design strategies to arrive at economicstructures

The authors based themselves on many bibliographic references covering atime span of about 65 years Many of these references present research of theauthors themselves and of the other members of the ECCS-TechnicalCommittee TC10 ldquoStructural Connectionsrdquo

It was really a privilege to have been the chairperson of this committee from1998 till the end of 2012 and I thank the authors Prof Dr Ir Jean-PierreJaspart and Dr-Ing Klaus Weynand for their large effort in writing this book

Prof ir Frans Bijlaard

PREFACE

_____

xv

PREFACE

Steel constructions and composite steel-concrete constructions are generallyerected on site by the assembly of prefabricated structural parts prepared inthe workshop These parts may themselves be the result of an assembly ofindividual elements An example is the assembly by bolting on site offabricated sections welded in the workshop

In these construction types joints and connections play a key role andrecommendations and guidelines are required for engineers and constructorsfaced with the conception and design the fabrication and the erection of suchstructures In the Structural Eurocodes these aspects are mainly covered in theexecution standard EN 1090-2 and in the design standard EN 1993-1-8(Eurocode 3 Design of steel structures Part 1-8 Design of Joints)

In the present book which is part of the series of ECCS Eurocode DesignManuals the main focus is given to design aspects but references are alsomade to EN 1090-2 when necessary

In comparison to other fields the design procedures for joints andconnections have significantly evolved in the last decades as a result of theprogressive awareness by practitioners of the significant contribution ofjoints and connections to the global cost of structures Design for lowfabrication and erection costs as well as high resistance is therefore thetargeted objective of modern design codes the achievement of which hasjustified the development of new calculation approaches now integrated intothe two afore-mentioned Eurocodes This situation justifies the writing of thepresent manual with the main goal to demystify the process by explainingthe new concepts for the design of joints and to integrate their mechanicalresponse into the structural frame analysis and design process by providingldquokeysrdquo for a proper application in practice and finally by providing welldocumented worked examples

To refer to ldquomodernrdquo or ldquonewrdquo design approaches and philosophies does notmean that traditional ways are out dated or no more valid It should beunderstood that the design methods recommended in the Eurocodes are a

PREFACE

_____

xvi

collection of European practices including the results of intensive researchefforts carried out in the last decades and so give many options andalternatives to engineers who are trying to develop safe and economicsolutions

Chapter 1 introduces generalities about joint properties aspects of materialsfabrication erection and costs design approach - and especially the so-calledcomponent method - and design tools available to practitioners for easiercode application The integration of the response of the joints into thestructural analysis and design process is addressed in chapter 2 In chapter 3attention is paid to the design of common connections with mechanicalfasteners Preloaded bolts and non-preloaded bolts are mainly considered butthe use of some less classical connectors is also briefly described Weldedconnections are covered in chapter 5

The next three chapters relate to three specific types of joints respectivelysimple joints moment resisting joints and lattice girder joints For thesesubstantial innovations are brought in the Eurocodes in comparison totraditional national codes particularly for simple and moment resistingjoints A significant number of pages is therefore devoted to these topics inthis manual

The design of joints under static loading as it is addressed in the seven firstchapters is essential in all cases but further checks or different conceptualdesign of the joints are often required in case of load reversal fireearthquake or even exceptional events like impact or explosion Chapter 8summarises present knowledge in this field

Traditionally joints were designed as rigid or pinned which enables the designof the frame and the design of the joints to be treated independently The cleareconomical advantage associated in many situations with the use of semi-rigidandor partial-strength joints leads however to ldquostructure-jointsrdquo interactionsthat have to be mastered by the engineer so as to fully profit from the potentialcost savings The Eurocodes do not cover this interaction From this point ofview chapter 9 may be considered as ldquoa premiegravererdquo even if the content hasalready been partly described years ago in an ECSC publication

Before letting the reader discover the contents of this book we would like toexpress acknowledgment We are very grateful to Prof Frans Bijlaard for all

PREFACE

_____

xvii

the comments suggestions and corrections he made through the reviewprocess of the present manual Warm thanks are also addressed to Joseacute Fuchsand Soumlnke Muumlller who helped us in preparing the drawings Last but notleast we would like to thank our wives for their patience when we workedldquoon our projectrdquo during innumerable evenings and weekends

Jean-Pierre JaspartKlaus Weynand

UK FOREWORD

_____

xix

UK FOREWORD

INTRODUCTION

This book is the second in a series of joint publications of the EuropeanConvention for Constructional Steelwork (ECCS) and The Steel ConstructionInstitute (SCI) It will help provide UK engineers and designers with a betterunderstanding of the design principles in the European Code of Practice for theDesign of Steel Structures (EN 1993 ndash Eurocode 3) and the individual Part 18(EN 1993-1-8) for the design of steel joints in particular Reference will alsobe made to the associated Eurocodes for concrete (EN 1992 ndash Eurocode 2) andearthquake engineering (EN 1998 ndash Eurocode 8) The book complements otherSCI design guides eg SCI (2011 and 2013a)

The current publication is a first UK edition based on the first edition of theECCS manual for the Design of Joints in Steel and Composite Structureswhich was published in 2016 The scope of this UK edition is narrower thanthe original publication in two specific areas that are felt to be of limitedinterest to current practice in the UK there is no content covering compositejoints and chapter 9 (covering frame design strategies) has been shortened tosimply give an overview of strategies In this edition the reader will findinformation that is either of a general nature or relevant to specific sectionsof the publication to facilitate its application in a UK context

The content includes useful background to the code rules and a reminder ofsome engineering principles Information is presented in the context of theEurocodes terminology and notation and with reference to clause numbersetc to help the readerrsquos familiarity with EN 1993-1-8 The document thatserves as the basis for content and numbering of clauses is the UKimplementation of EN 1993-1-82005 incorporating corrigenda December2005 and July 2009 At the time of writing (Autumn 2016) part 1-8 ofEN 1993 is being revised with publication anticipated after 2020

Finally it is noted and should be accepted that there will inevitably be somedifferences of interpretation between the ECCS recommendations and thosepreviously published by the SCI

UK FOREWORD

_____

xx

GENERAL COMMENTS

Design of joints (connections) in steel structures in the UK is covered byBS EN 1993-1-8 and its national Annex (NA) (BSI 2010) BS EN 1993-1-8has clear definitions for connections and joints The term joint refers to thezone where members are interconnected and a connection is the locationwhere elements meet The distinction in terminology is usually emphasised inContinental Europe but traditional practice in the UK is to use the generic termconnection

The following partial safety factors are defined in the UK NA

Partial factor Value Comment

γM2 125 Used for the resistance of bolts pins and welds

γM2 125Used for the resistance of plates in bearing(γM2=15 should be used if deformation control is important)

γM3 125 Used for slip resistance at Ultimate Limit States

γM3serv 110 Used for slip resistance at Serviceability Limit States (SLS)

γM4 100 Used for the resistance of injection bolts

γM5 100 Used for the resistance of joints in hollow section lattice girders

γM6serv 100 Used for the resistance of pins at SLS

γM7

110Used for the preload of high strength steel bolts conforming toBS EN 14399-4 and BS EN 14399-8 (BSI 2015 and 2007)

100 Used for the preload of (other) high strength steel bolts

Specific reference to the UK Building Regulations is also made in this UKedition The UK Building Regulations code has structural integrityrequirements in order to avoid disproportionate collapse and ensure robustnessof the complete structure Disproportionate collapse can be defined as a regionof structural collapse out of proportion to the initiating cause of failure Themost relevant to connectionjoint design is that the detailing for every beam

UK FOREWORD

_____

xxi

member must be adequate to resist a minimum horizontal force at ultimatefailure (or tying resistance) Guidance on the design values of tying forces canbe found in BS EN 1991-1-7 Annex A and its UK annex (BSI 2014)

SECTION SPECIFIC COMMENTS

Section 111

UK practice normally considers only two main forms of joint modellingsimple and continuous Ideally frames designed on the basis of simple jointmodelling should use joints between members that possess negligiblerotational stiffness and transmit the beam reactions in shear into thecolumns without developing significant moments These joints may betreated as perfect pins Members can then be designed in isolation either as(predominantly) axially loaded columns or as simply supported beamsJoints designed within the principles of continuous modelling are capable oftransmitting significant moments and are able to maintain the original anglebetween adjacent members virtually unchanged This form of construction ofsteel frames is particularly advantageous when beam deflections are criticalor if bracing systems are not possible

To comply with one or the other design assumption steelwork connectionsare detailed as simple or moment-resisting joints Because joints in framestructures are often treated by adopting a degree of standardisation thedesigner usually details the connections in accordance with the principlesin the series of SCI Green Books which present this material in the formof step-by-step design procedures and tables covering standardarrangements

Other approximate analysis methods continue to be used among Britishdesigners the most representative being the wind-moment method for thedesign of unbraced multi-storey steel frames The method assumes that(i) under gravity loads the beam-to-column joints act as pinnedconnections and (ii) under horizontal wind loads these joints are rigidalthough it lacks transparency This method can be seen as a manifestationof the semi-continuous principles Wind moment connection details can befound in SCI (1995a) With the now widespread use of software in designoffices for rigorous second-order analysis it is doubtful if the use of the

UK FOREWORD

_____

xxii

wind-moment method should be advocated any longer other than forinitial sizing

Section 13

Although S460 is attracting growing interest S355 is still the dominantgrade of steel used in the UK

Section 161

With reference to Figure 120 it is noted that (site) welded joints and angleflange cleats are rarely if ever used in the UK

Section 162

Hybrid connections are rarely used in the UK for the reasons noted

Section 172

There is not much use of CoPcopy in the UK There are a number of othersoftware tools on the market some more comprehensive than others

Section 22

Although in UK design practice most aspects related to joint modelling havedeveloped to a high degree of sophistication proper consideration of thestructural interaction between the joints and members is rarely fully takeninto account It is indeed very difficult to predict and model the complexbehaviour of a joint (strength stiffness and rotation capacity) TraditionalUK practice is to predict joint behaviour on the basis of past experience

BSI (2010) separates the modelling of the rotational behaviour of theconnection elements (that is the bolts the welds the plates etc) and thatof the column web panel in shear to characterise the overall jointbehaviour As a simplification the two sources of joint deformation arecombined by means of the so-called transformation parameter β Thiscoefficient is related to the web panel internal actions and can be calculatedfrom the moments at each side of the web panel The β parameter iscurrently only defined for same-depth beams which meet at the same levelIn many practical double-sided joints beams will not be of the same depthor at the same height BS EN 1993-1-8 is silent on such joints

UK FOREWORD

_____

xxiii

Section 23

As explained above typical UK design practice does not consider thissophisticated procedure for idealisation of joints

Section 24

The NA to BS EN 1993-1-8 gives practical guidance to classify joints Italso states the following

ldquoUntil experience is gained with the numerical method of calculatingrotational stiffness given in BS EN 1993-1-82005 63 and theclassification by stiffness method given in BS EN 1993-1-82005522 semi-continuous elastic design should only be used where eitherit is supported by test evidence according to BS EN 1993-1-820055221(2) or where it is based on satisfactorily performance in asimilar situationrdquo

Evidence on values of column base stiffness for practical global analysis isgiven in SCI (2006)

Section 25

The concept of ductility classes is not widely applied in the UK It isgenerally assumed that standard connection details to the SCI Green Booksprovide enough rotation capacity and so behave in a ductile manner asevidenced by physical testing and experience

Section 31

The NA to BS EN 1993-1-8 excludes bolts of classes 58 and 68 It alsostates that bolt class 48 may only be used if the manufacturing process (i) isin accordance with BS EN ISO 898-1 (BSI 2013) and (ii) includes suitableprocedures to avoid hydrogen embrittlement

Section 322

The NA to BS EN 1993-1-8 states that if the preload is not explicitly used inthe design calculations then no specific level of preload is required

Section 347

Injection bolts are rarely used in the UK

UK FOREWORD

_____

xxiv

Section 348

Reference is made to SCI (1995b) to calculate the bending moments in thepin of a pin bearing

Section 349

Flow drill blind bolting is not common practice in the UK SHS blind boltingis a common system but there are several manufactures other than thatsuggested in the book

Section 3410

Nails are rarely used in the UK

Section 352

T-stub configurations with four bolts in a row are rarely used in the UK

Section 353

Reference is made to the SCI method for the design of gusset plates seeSCI (2011)

Section 421

It is anticipated that specific rules given in the current BS EN 1993-1-12(BSI 2009) for high strength steels will be incorporated in the revisedBS EN 1993-1-8 to appear after 2020

Section 522

ldquoHeader platesrdquo are known as ldquopartial depth end platesrdquo in the UK Webcleat connections are no longer commonly used in the UK The full depthend plate connection shown on the left of Figure 59 is classified as a simplejoint in the UK (SCI 2011)

Section 523

The UK Building Regulations require that joints are designed for tyingforces in order to satisfy structural integrity requirements Guidance onthe design values of tying forces is given in BS EN 1991-1-7 Annex Aand its UK NA The requirements relate to the building class with a

UK FOREWORD

_____

xxv

design value of horizontal force generally not less than 75 kN andusually significantly higher Simple joints detailed to SCI (2011) satisfythese requirements

Section 525

It is generally safe to assume that the ductility (rotation requirements) aresatisfied provided that joints are detailed in accordance with SCI (2011)

Section 531

The column base detailing on the left of Figure 521 is not commonly used inthe UK We never recommend less than four bolts ndash they are needed toassure stability and facilitate location during erection The anchoringsystems shown in Figure 522 are not usually adopted in the UK Referenceis made to SCI (2013a) for common anchor systems

Section 62

Publication SCI (2013b) summarises the principal differences betweenBS 5950 and BS EN 1993-1-8 (BSI 2000 and 2010) in terms ofcomponent characterisation

With reference to Figure 66 it is anticipated that the revised BS EN1993-1-8will include analytical expressions for the definition of the so-called αcoefficient

Rules of thumb for the characterisation of the ductility of some individualcomponents are given in SCI (1995a)

Section 631

The UK NA to BS EN 1993-1-8 gives specific rules for the full plasticdistribution of effective design tension resistance The procedure is alsosummarised in SCI (2013a)

Section 633

Where a joint is subjected to combined bending moments and axial forcesthe concept of an applied moment modified by axial load can be used seeSCI (1995a)

UK FOREWORD

_____

xxvi

Section 64

Rotational stiffness is not normally evaluated in UK design practice whichusually relies on past experience

Section 65

Some rules of thumb for the characterisation of the ductility of moment-resisting joints are given in SCI (1995a)

Section 661

With reference to Figure 636 it is noted that this joint configuration ishardly (if ever) used in the UK

Section 663

It should be noted that European sections are not commonly used in the UKalthough there is growing interest in the market Steel grade S235 is not usedin the UK S355 being the current common grade Combinations of plates of15 mm thickness with M24 bolts are common This combination is assumedto provide enough rotation capacity thus satisfying ductility requirementsbecause ductile failure of the plates not brittle failure of the bolts governsthe behaviour

Section 672

Standard practice in the UK does not account for this 25 rule Columnsplices are usually detailed to SCI (2011) to ensure continuity of stiffnessthrough the splice so that the member design is not invalidated

Section 84

The UK Building Regulations require that joints are designed for tyingforces in order to satisfy structural integrity requirements Guidance on thedesign values of tying forces is given in BS EN 1991-1-7 Annex A and itsUK NA (BSI 2014)

Section 91

In the UK the ldquofabricatorsrdquo are known as ldquoSteelwork contractorsrdquo becausethey do more than just fabricate

UK FOREWORD

_____

xxvii

REFERENCES TO NATIONAL FOREWORD

BSI (2000) BS 5950-12000 ndash Structural use of steelwork in building ndash Part1 Code of Practice for Design rolled and welded sections British StandardsInstitution United Kingdom

BSI (2007) BS EN 14399-82007 ndash High-strength structural boltingassemblies for preloading System HV Hexagon fit bolt and nut assembliesBritish Standards Institution United Kingdom

BSI (2009) BS EN 1993-1-122007 ndash Eurocode 3 Design of steel structuresndash Part 112 Additional rules for the extension of EN 1993 up to steel gradesS 700 British Standards Institution United Kingdom

BSI (2010) BS EN 1993-1-82005 ndash Eurocode 3 Design of steel structuresndash Part 18 Design of joints British Standards Institution United Kingdom

BSI (2013) BS EN ISO 898-12013 ndash Mechanical properties of fastenersmade of carbon steel and alloy steel Bolts screws and studs with specifiedproperty classes Coarse thread and fine pitch thread British StandardsInstitution United Kingdom

BSI (2014) BS EN 1991-1-72006+A12014 ndash Eurocode 1 Actions on structuresndash Part 197 General actions British Standards Institution United Kingdom

BSI (2015) BS EN 14399-42015 ndash High-strength structural boltingassemblies for preloading System HV Hexagon bolt and nut assembliesBritish Standards Institution United Kingdom

SCI (1995a) Joints in steel construction Moment connections P207 TheSteel Construction Institute

SCI (1995b) Advisory Desk Notes Bending Moment in a pin AD 172 TheSteel Construction Institute

SCI (2006) Column base stiffness for global analysis NCCI-SN045a TheSteel Construction Institute

SCI (2011) Joints in steel construction Simple joints to Eurocode 3 P358The Steel Construction Institute

SCI (2013a) Joints in steel construction Moment-resisting joints toEurocode 3 P398 The Steel Construction Institute

UK FOREWORD

_____

xxviii

SCI (2013b) Interim Report Design of Portal Frames to Eurocode 3 Anoverview for UK designers P400 The Steel Construction Institute

TABLE OF CONTENTS

_____

viii

434 Butt welds 135435 Plug welds 136436 Concept of full strength fillet weld 136

44 Distribution of forces in a welded joint 139441 Generalities 139442 Particular situations 141

Chapter 5

SIMPLE JOINTS 147

51 Introduction 147

52 Beam-to-column and beam-to-beam joints 149521 Introduction 149522 Scope and field of application 150523 Joint modelling for frame analysis and design requirements 153524 Design resistance 156525 Practical ways to satisfy the ductility and rotationrequirements 163

53 Column bases 174531 Introduction 174532 Basis for the evaluation of the design resistance 176533 Resistance to axial forces 177534 Resistance to shear forces 185

Chapter 6

MOMENT-RESISTING JOINTS 189

61 Introduction 189

62 Component characterisation 190621 Column web panel in shear in steel or composite joints 190622 Column web in transverse compression in steel or compositejoints 192623 Column web in transverse tension 196624 Column flange in transverse bending 197625 End plate in bending 203

TABLE OF CONTENTS

_____

ix

626 Flange cleat in bending 205627 Beam or column flange and web in compression 207628 Beam web in tension 209629 Plate in tension or compression 2106210 Bolts in tension 2116211 Bolts in shear 2126212 Bolts in bearing (on beam flange column flange end plateor cleat) 2136213 Concrete in compression including grout 2136214 Base plate in bending under compression 2146215 Base plate in bending under tension 2146216 Anchor bolts in tension 2156217 Anchor bolts in shear 2156218 Anchor bolts in bearing 2156219 Welds 2166220 Haunched beam 216

63 Assembly for resistance 217631 Joints under bending moments 217632 Joints under axial forces 225633 Joints under bending moments and axial forces 226634 M minus N minus V 233635 Design of welds 234

64 Assembly for rotational stiffness 238641 Joints under bending moments 238642 Joints under bending moments and axial forces 247

65 Assembly for ductility 249651 Steel bolted joints 250652 Steel welded joints 252

66 Application to steel beam-to-column joint configurations 253661 Extended scope 253662 Possible design simplifications for end plate connections 256663 Worked example 257

67 Application to steel column splices 281671 Common splice configurations 281

TABLE OF CONTENTS

_____

x

672 Design considerations 283

68 Application to column bases 284681 Common column basis configurations 284682 Design considerations 287

Chapter 7

LATTICE GIRDER JOINTS 295

71 General 295

72 Scope and field of application 296

73 Design models 298731 General 298732 Failure modes 299733 Models for CHS chords 300734 Model for RHS chords 301735 Punching shear failure 302736 Model for brace failure 303737 M-N interaction 304

Chapter 8

JOINTS UNDER VARIOUS LOADING SITUATIONS 305

81 Introduction 305

82 Joints in fire 306

83 Joints under cyclic loading 307

84 Joints under exceptional events 308

Chapter 9

DESIGN STRATEGIES 311

91 Introduction 311

92 Traditional design approach 314

93 Integrated design approach 317

94 Economic considerations 319

TABLE OF CONTENTS

_____

xi

941 Fabrication and erections costs 319942 Savings of material costs 322943 Summary and conclusions 323

BIBLIOGRAPHIC REFERENCES 325

Annex A Practical values for required rotation capacity 337

Annex B Values for lateral torsional buckling strength of a fin plate 339

FOREWORD

_____

xiii

FOREWORD

With the ECCS book ldquoJoints in Steel and Composite Structuresrdquo the authorssucceeded in placing the joints on the rightful place they deserve in thestructural behaviour of steel and composite steel-concrete structures Themany times used word ldquodetailsrdquo for the joints in structures by farunderestimates the importance of joints in the structural behaviour ofbuildings and civil engineering structures In their chapter ldquoAim of the bookrdquothe authors clearly explain how the design and safety verification ofstructures runs in an integral manner where all structural componentsincluding the joints play balanced roles leading to economic structures

This book can be seen as a background document for Eurocode 3 ldquoDesign ofSteel Structuresrdquo as far as it concerns structural joints The central theme indescribing the behaviour of joints is using the component method and this isleading all over in this book The book contain many aspects such as designfabrication erection and costs

In this book attention is paid on joint modelling and idealisation jointclassification for strength and stiffness and deformation capacity This all forconnections with mechanical fasteners and for welded connections for simplejoints and moment resistant joints Also lattice girder joints are described

The book provides the designer with design strategies to arrive at economicstructures

The authors based themselves on many bibliographic references covering atime span of about 65 years Many of these references present research of theauthors themselves and of the other members of the ECCS-TechnicalCommittee TC10 ldquoStructural Connectionsrdquo

It was really a privilege to have been the chairperson of this committee from1998 till the end of 2012 and I thank the authors Prof Dr Ir Jean-PierreJaspart and Dr-Ing Klaus Weynand for their large effort in writing this book

Prof ir Frans Bijlaard

PREFACE

_____

xv

PREFACE

Steel constructions and composite steel-concrete constructions are generallyerected on site by the assembly of prefabricated structural parts prepared inthe workshop These parts may themselves be the result of an assembly ofindividual elements An example is the assembly by bolting on site offabricated sections welded in the workshop

In these construction types joints and connections play a key role andrecommendations and guidelines are required for engineers and constructorsfaced with the conception and design the fabrication and the erection of suchstructures In the Structural Eurocodes these aspects are mainly covered in theexecution standard EN 1090-2 and in the design standard EN 1993-1-8(Eurocode 3 Design of steel structures Part 1-8 Design of Joints)

In the present book which is part of the series of ECCS Eurocode DesignManuals the main focus is given to design aspects but references are alsomade to EN 1090-2 when necessary

In comparison to other fields the design procedures for joints andconnections have significantly evolved in the last decades as a result of theprogressive awareness by practitioners of the significant contribution ofjoints and connections to the global cost of structures Design for lowfabrication and erection costs as well as high resistance is therefore thetargeted objective of modern design codes the achievement of which hasjustified the development of new calculation approaches now integrated intothe two afore-mentioned Eurocodes This situation justifies the writing of thepresent manual with the main goal to demystify the process by explainingthe new concepts for the design of joints and to integrate their mechanicalresponse into the structural frame analysis and design process by providingldquokeysrdquo for a proper application in practice and finally by providing welldocumented worked examples

To refer to ldquomodernrdquo or ldquonewrdquo design approaches and philosophies does notmean that traditional ways are out dated or no more valid It should beunderstood that the design methods recommended in the Eurocodes are a

PREFACE

_____

xvi

collection of European practices including the results of intensive researchefforts carried out in the last decades and so give many options andalternatives to engineers who are trying to develop safe and economicsolutions

Chapter 1 introduces generalities about joint properties aspects of materialsfabrication erection and costs design approach - and especially the so-calledcomponent method - and design tools available to practitioners for easiercode application The integration of the response of the joints into thestructural analysis and design process is addressed in chapter 2 In chapter 3attention is paid to the design of common connections with mechanicalfasteners Preloaded bolts and non-preloaded bolts are mainly considered butthe use of some less classical connectors is also briefly described Weldedconnections are covered in chapter 5

The next three chapters relate to three specific types of joints respectivelysimple joints moment resisting joints and lattice girder joints For thesesubstantial innovations are brought in the Eurocodes in comparison totraditional national codes particularly for simple and moment resistingjoints A significant number of pages is therefore devoted to these topics inthis manual

The design of joints under static loading as it is addressed in the seven firstchapters is essential in all cases but further checks or different conceptualdesign of the joints are often required in case of load reversal fireearthquake or even exceptional events like impact or explosion Chapter 8summarises present knowledge in this field

Traditionally joints were designed as rigid or pinned which enables the designof the frame and the design of the joints to be treated independently The cleareconomical advantage associated in many situations with the use of semi-rigidandor partial-strength joints leads however to ldquostructure-jointsrdquo interactionsthat have to be mastered by the engineer so as to fully profit from the potentialcost savings The Eurocodes do not cover this interaction From this point ofview chapter 9 may be considered as ldquoa premiegravererdquo even if the content hasalready been partly described years ago in an ECSC publication

Before letting the reader discover the contents of this book we would like toexpress acknowledgment We are very grateful to Prof Frans Bijlaard for all

PREFACE

_____

xvii

the comments suggestions and corrections he made through the reviewprocess of the present manual Warm thanks are also addressed to Joseacute Fuchsand Soumlnke Muumlller who helped us in preparing the drawings Last but notleast we would like to thank our wives for their patience when we workedldquoon our projectrdquo during innumerable evenings and weekends

Jean-Pierre JaspartKlaus Weynand

UK FOREWORD

_____

xix

UK FOREWORD

INTRODUCTION

This book is the second in a series of joint publications of the EuropeanConvention for Constructional Steelwork (ECCS) and The Steel ConstructionInstitute (SCI) It will help provide UK engineers and designers with a betterunderstanding of the design principles in the European Code of Practice for theDesign of Steel Structures (EN 1993 ndash Eurocode 3) and the individual Part 18(EN 1993-1-8) for the design of steel joints in particular Reference will alsobe made to the associated Eurocodes for concrete (EN 1992 ndash Eurocode 2) andearthquake engineering (EN 1998 ndash Eurocode 8) The book complements otherSCI design guides eg SCI (2011 and 2013a)

The current publication is a first UK edition based on the first edition of theECCS manual for the Design of Joints in Steel and Composite Structureswhich was published in 2016 The scope of this UK edition is narrower thanthe original publication in two specific areas that are felt to be of limitedinterest to current practice in the UK there is no content covering compositejoints and chapter 9 (covering frame design strategies) has been shortened tosimply give an overview of strategies In this edition the reader will findinformation that is either of a general nature or relevant to specific sectionsof the publication to facilitate its application in a UK context

The content includes useful background to the code rules and a reminder ofsome engineering principles Information is presented in the context of theEurocodes terminology and notation and with reference to clause numbersetc to help the readerrsquos familiarity with EN 1993-1-8 The document thatserves as the basis for content and numbering of clauses is the UKimplementation of EN 1993-1-82005 incorporating corrigenda December2005 and July 2009 At the time of writing (Autumn 2016) part 1-8 ofEN 1993 is being revised with publication anticipated after 2020

Finally it is noted and should be accepted that there will inevitably be somedifferences of interpretation between the ECCS recommendations and thosepreviously published by the SCI

UK FOREWORD

_____

xx

GENERAL COMMENTS

Design of joints (connections) in steel structures in the UK is covered byBS EN 1993-1-8 and its national Annex (NA) (BSI 2010) BS EN 1993-1-8has clear definitions for connections and joints The term joint refers to thezone where members are interconnected and a connection is the locationwhere elements meet The distinction in terminology is usually emphasised inContinental Europe but traditional practice in the UK is to use the generic termconnection

The following partial safety factors are defined in the UK NA

Partial factor Value Comment

γM2 125 Used for the resistance of bolts pins and welds

γM2 125Used for the resistance of plates in bearing(γM2=15 should be used if deformation control is important)

γM3 125 Used for slip resistance at Ultimate Limit States

γM3serv 110 Used for slip resistance at Serviceability Limit States (SLS)

γM4 100 Used for the resistance of injection bolts

γM5 100 Used for the resistance of joints in hollow section lattice girders

γM6serv 100 Used for the resistance of pins at SLS

γM7

110Used for the preload of high strength steel bolts conforming toBS EN 14399-4 and BS EN 14399-8 (BSI 2015 and 2007)

100 Used for the preload of (other) high strength steel bolts

Specific reference to the UK Building Regulations is also made in this UKedition The UK Building Regulations code has structural integrityrequirements in order to avoid disproportionate collapse and ensure robustnessof the complete structure Disproportionate collapse can be defined as a regionof structural collapse out of proportion to the initiating cause of failure Themost relevant to connectionjoint design is that the detailing for every beam

UK FOREWORD

_____

xxi

member must be adequate to resist a minimum horizontal force at ultimatefailure (or tying resistance) Guidance on the design values of tying forces canbe found in BS EN 1991-1-7 Annex A and its UK annex (BSI 2014)

SECTION SPECIFIC COMMENTS

Section 111

UK practice normally considers only two main forms of joint modellingsimple and continuous Ideally frames designed on the basis of simple jointmodelling should use joints between members that possess negligiblerotational stiffness and transmit the beam reactions in shear into thecolumns without developing significant moments These joints may betreated as perfect pins Members can then be designed in isolation either as(predominantly) axially loaded columns or as simply supported beamsJoints designed within the principles of continuous modelling are capable oftransmitting significant moments and are able to maintain the original anglebetween adjacent members virtually unchanged This form of construction ofsteel frames is particularly advantageous when beam deflections are criticalor if bracing systems are not possible

To comply with one or the other design assumption steelwork connectionsare detailed as simple or moment-resisting joints Because joints in framestructures are often treated by adopting a degree of standardisation thedesigner usually details the connections in accordance with the principlesin the series of SCI Green Books which present this material in the formof step-by-step design procedures and tables covering standardarrangements

Other approximate analysis methods continue to be used among Britishdesigners the most representative being the wind-moment method for thedesign of unbraced multi-storey steel frames The method assumes that(i) under gravity loads the beam-to-column joints act as pinnedconnections and (ii) under horizontal wind loads these joints are rigidalthough it lacks transparency This method can be seen as a manifestationof the semi-continuous principles Wind moment connection details can befound in SCI (1995a) With the now widespread use of software in designoffices for rigorous second-order analysis it is doubtful if the use of the

UK FOREWORD

_____

xxii

wind-moment method should be advocated any longer other than forinitial sizing

Section 13

Although S460 is attracting growing interest S355 is still the dominantgrade of steel used in the UK

Section 161

With reference to Figure 120 it is noted that (site) welded joints and angleflange cleats are rarely if ever used in the UK

Section 162

Hybrid connections are rarely used in the UK for the reasons noted

Section 172

There is not much use of CoPcopy in the UK There are a number of othersoftware tools on the market some more comprehensive than others

Section 22

Although in UK design practice most aspects related to joint modelling havedeveloped to a high degree of sophistication proper consideration of thestructural interaction between the joints and members is rarely fully takeninto account It is indeed very difficult to predict and model the complexbehaviour of a joint (strength stiffness and rotation capacity) TraditionalUK practice is to predict joint behaviour on the basis of past experience

BSI (2010) separates the modelling of the rotational behaviour of theconnection elements (that is the bolts the welds the plates etc) and thatof the column web panel in shear to characterise the overall jointbehaviour As a simplification the two sources of joint deformation arecombined by means of the so-called transformation parameter β Thiscoefficient is related to the web panel internal actions and can be calculatedfrom the moments at each side of the web panel The β parameter iscurrently only defined for same-depth beams which meet at the same levelIn many practical double-sided joints beams will not be of the same depthor at the same height BS EN 1993-1-8 is silent on such joints

UK FOREWORD

_____

xxiii

Section 23

As explained above typical UK design practice does not consider thissophisticated procedure for idealisation of joints

Section 24

The NA to BS EN 1993-1-8 gives practical guidance to classify joints Italso states the following

ldquoUntil experience is gained with the numerical method of calculatingrotational stiffness given in BS EN 1993-1-82005 63 and theclassification by stiffness method given in BS EN 1993-1-82005522 semi-continuous elastic design should only be used where eitherit is supported by test evidence according to BS EN 1993-1-820055221(2) or where it is based on satisfactorily performance in asimilar situationrdquo

Evidence on values of column base stiffness for practical global analysis isgiven in SCI (2006)

Section 25

The concept of ductility classes is not widely applied in the UK It isgenerally assumed that standard connection details to the SCI Green Booksprovide enough rotation capacity and so behave in a ductile manner asevidenced by physical testing and experience

Section 31

The NA to BS EN 1993-1-8 excludes bolts of classes 58 and 68 It alsostates that bolt class 48 may only be used if the manufacturing process (i) isin accordance with BS EN ISO 898-1 (BSI 2013) and (ii) includes suitableprocedures to avoid hydrogen embrittlement

Section 322

The NA to BS EN 1993-1-8 states that if the preload is not explicitly used inthe design calculations then no specific level of preload is required

Section 347

Injection bolts are rarely used in the UK

UK FOREWORD

_____

xxiv

Section 348

Reference is made to SCI (1995b) to calculate the bending moments in thepin of a pin bearing

Section 349

Flow drill blind bolting is not common practice in the UK SHS blind boltingis a common system but there are several manufactures other than thatsuggested in the book

Section 3410

Nails are rarely used in the UK

Section 352

T-stub configurations with four bolts in a row are rarely used in the UK

Section 353

Reference is made to the SCI method for the design of gusset plates seeSCI (2011)

Section 421

It is anticipated that specific rules given in the current BS EN 1993-1-12(BSI 2009) for high strength steels will be incorporated in the revisedBS EN 1993-1-8 to appear after 2020

Section 522

ldquoHeader platesrdquo are known as ldquopartial depth end platesrdquo in the UK Webcleat connections are no longer commonly used in the UK The full depthend plate connection shown on the left of Figure 59 is classified as a simplejoint in the UK (SCI 2011)

Section 523

The UK Building Regulations require that joints are designed for tyingforces in order to satisfy structural integrity requirements Guidance onthe design values of tying forces is given in BS EN 1991-1-7 Annex Aand its UK NA The requirements relate to the building class with a

UK FOREWORD

_____

xxv

design value of horizontal force generally not less than 75 kN andusually significantly higher Simple joints detailed to SCI (2011) satisfythese requirements

Section 525

It is generally safe to assume that the ductility (rotation requirements) aresatisfied provided that joints are detailed in accordance with SCI (2011)

Section 531

The column base detailing on the left of Figure 521 is not commonly used inthe UK We never recommend less than four bolts ndash they are needed toassure stability and facilitate location during erection The anchoringsystems shown in Figure 522 are not usually adopted in the UK Referenceis made to SCI (2013a) for common anchor systems

Section 62

Publication SCI (2013b) summarises the principal differences betweenBS 5950 and BS EN 1993-1-8 (BSI 2000 and 2010) in terms ofcomponent characterisation

With reference to Figure 66 it is anticipated that the revised BS EN1993-1-8will include analytical expressions for the definition of the so-called αcoefficient

Rules of thumb for the characterisation of the ductility of some individualcomponents are given in SCI (1995a)

Section 631

The UK NA to BS EN 1993-1-8 gives specific rules for the full plasticdistribution of effective design tension resistance The procedure is alsosummarised in SCI (2013a)

Section 633

Where a joint is subjected to combined bending moments and axial forcesthe concept of an applied moment modified by axial load can be used seeSCI (1995a)

UK FOREWORD

_____

xxvi

Section 64

Rotational stiffness is not normally evaluated in UK design practice whichusually relies on past experience

Section 65

Some rules of thumb for the characterisation of the ductility of moment-resisting joints are given in SCI (1995a)

Section 661

With reference to Figure 636 it is noted that this joint configuration ishardly (if ever) used in the UK

Section 663

It should be noted that European sections are not commonly used in the UKalthough there is growing interest in the market Steel grade S235 is not usedin the UK S355 being the current common grade Combinations of plates of15 mm thickness with M24 bolts are common This combination is assumedto provide enough rotation capacity thus satisfying ductility requirementsbecause ductile failure of the plates not brittle failure of the bolts governsthe behaviour

Section 672

Standard practice in the UK does not account for this 25 rule Columnsplices are usually detailed to SCI (2011) to ensure continuity of stiffnessthrough the splice so that the member design is not invalidated

Section 84

The UK Building Regulations require that joints are designed for tyingforces in order to satisfy structural integrity requirements Guidance on thedesign values of tying forces is given in BS EN 1991-1-7 Annex A and itsUK NA (BSI 2014)

Section 91

In the UK the ldquofabricatorsrdquo are known as ldquoSteelwork contractorsrdquo becausethey do more than just fabricate

UK FOREWORD

_____

xxvii

REFERENCES TO NATIONAL FOREWORD

BSI (2000) BS 5950-12000 ndash Structural use of steelwork in building ndash Part1 Code of Practice for Design rolled and welded sections British StandardsInstitution United Kingdom

BSI (2007) BS EN 14399-82007 ndash High-strength structural boltingassemblies for preloading System HV Hexagon fit bolt and nut assembliesBritish Standards Institution United Kingdom

BSI (2009) BS EN 1993-1-122007 ndash Eurocode 3 Design of steel structuresndash Part 112 Additional rules for the extension of EN 1993 up to steel gradesS 700 British Standards Institution United Kingdom

BSI (2010) BS EN 1993-1-82005 ndash Eurocode 3 Design of steel structuresndash Part 18 Design of joints British Standards Institution United Kingdom

BSI (2013) BS EN ISO 898-12013 ndash Mechanical properties of fastenersmade of carbon steel and alloy steel Bolts screws and studs with specifiedproperty classes Coarse thread and fine pitch thread British StandardsInstitution United Kingdom

BSI (2014) BS EN 1991-1-72006+A12014 ndash Eurocode 1 Actions on structuresndash Part 197 General actions British Standards Institution United Kingdom

BSI (2015) BS EN 14399-42015 ndash High-strength structural boltingassemblies for preloading System HV Hexagon bolt and nut assembliesBritish Standards Institution United Kingdom

SCI (1995a) Joints in steel construction Moment connections P207 TheSteel Construction Institute

SCI (1995b) Advisory Desk Notes Bending Moment in a pin AD 172 TheSteel Construction Institute

SCI (2006) Column base stiffness for global analysis NCCI-SN045a TheSteel Construction Institute

SCI (2011) Joints in steel construction Simple joints to Eurocode 3 P358The Steel Construction Institute

SCI (2013a) Joints in steel construction Moment-resisting joints toEurocode 3 P398 The Steel Construction Institute

UK FOREWORD

_____

xxviii

SCI (2013b) Interim Report Design of Portal Frames to Eurocode 3 Anoverview for UK designers P400 The Steel Construction Institute

TABLE OF CONTENTS

_____

ix

626 Flange cleat in bending 205627 Beam or column flange and web in compression 207628 Beam web in tension 209629 Plate in tension or compression 2106210 Bolts in tension 2116211 Bolts in shear 2126212 Bolts in bearing (on beam flange column flange end plateor cleat) 2136213 Concrete in compression including grout 2136214 Base plate in bending under compression 2146215 Base plate in bending under tension 2146216 Anchor bolts in tension 2156217 Anchor bolts in shear 2156218 Anchor bolts in bearing 2156219 Welds 2166220 Haunched beam 216

63 Assembly for resistance 217631 Joints under bending moments 217632 Joints under axial forces 225633 Joints under bending moments and axial forces 226634 M minus N minus V 233635 Design of welds 234

64 Assembly for rotational stiffness 238641 Joints under bending moments 238642 Joints under bending moments and axial forces 247

65 Assembly for ductility 249651 Steel bolted joints 250652 Steel welded joints 252

66 Application to steel beam-to-column joint configurations 253661 Extended scope 253662 Possible design simplifications for end plate connections 256663 Worked example 257

67 Application to steel column splices 281671 Common splice configurations 281

TABLE OF CONTENTS

_____

x

672 Design considerations 283

68 Application to column bases 284681 Common column basis configurations 284682 Design considerations 287

Chapter 7

LATTICE GIRDER JOINTS 295

71 General 295

72 Scope and field of application 296

73 Design models 298731 General 298732 Failure modes 299733 Models for CHS chords 300734 Model for RHS chords 301735 Punching shear failure 302736 Model for brace failure 303737 M-N interaction 304

Chapter 8

JOINTS UNDER VARIOUS LOADING SITUATIONS 305

81 Introduction 305

82 Joints in fire 306

83 Joints under cyclic loading 307

84 Joints under exceptional events 308

Chapter 9

DESIGN STRATEGIES 311

91 Introduction 311

92 Traditional design approach 314

93 Integrated design approach 317

94 Economic considerations 319

TABLE OF CONTENTS

_____

xi

941 Fabrication and erections costs 319942 Savings of material costs 322943 Summary and conclusions 323

BIBLIOGRAPHIC REFERENCES 325

Annex A Practical values for required rotation capacity 337

Annex B Values for lateral torsional buckling strength of a fin plate 339

FOREWORD

_____

xiii

FOREWORD

With the ECCS book ldquoJoints in Steel and Composite Structuresrdquo the authorssucceeded in placing the joints on the rightful place they deserve in thestructural behaviour of steel and composite steel-concrete structures Themany times used word ldquodetailsrdquo for the joints in structures by farunderestimates the importance of joints in the structural behaviour ofbuildings and civil engineering structures In their chapter ldquoAim of the bookrdquothe authors clearly explain how the design and safety verification ofstructures runs in an integral manner where all structural componentsincluding the joints play balanced roles leading to economic structures

This book can be seen as a background document for Eurocode 3 ldquoDesign ofSteel Structuresrdquo as far as it concerns structural joints The central theme indescribing the behaviour of joints is using the component method and this isleading all over in this book The book contain many aspects such as designfabrication erection and costs

In this book attention is paid on joint modelling and idealisation jointclassification for strength and stiffness and deformation capacity This all forconnections with mechanical fasteners and for welded connections for simplejoints and moment resistant joints Also lattice girder joints are described

The book provides the designer with design strategies to arrive at economicstructures

The authors based themselves on many bibliographic references covering atime span of about 65 years Many of these references present research of theauthors themselves and of the other members of the ECCS-TechnicalCommittee TC10 ldquoStructural Connectionsrdquo

It was really a privilege to have been the chairperson of this committee from1998 till the end of 2012 and I thank the authors Prof Dr Ir Jean-PierreJaspart and Dr-Ing Klaus Weynand for their large effort in writing this book

Prof ir Frans Bijlaard

PREFACE

_____

xv

PREFACE

Steel constructions and composite steel-concrete constructions are generallyerected on site by the assembly of prefabricated structural parts prepared inthe workshop These parts may themselves be the result of an assembly ofindividual elements An example is the assembly by bolting on site offabricated sections welded in the workshop

In these construction types joints and connections play a key role andrecommendations and guidelines are required for engineers and constructorsfaced with the conception and design the fabrication and the erection of suchstructures In the Structural Eurocodes these aspects are mainly covered in theexecution standard EN 1090-2 and in the design standard EN 1993-1-8(Eurocode 3 Design of steel structures Part 1-8 Design of Joints)

In the present book which is part of the series of ECCS Eurocode DesignManuals the main focus is given to design aspects but references are alsomade to EN 1090-2 when necessary

In comparison to other fields the design procedures for joints andconnections have significantly evolved in the last decades as a result of theprogressive awareness by practitioners of the significant contribution ofjoints and connections to the global cost of structures Design for lowfabrication and erection costs as well as high resistance is therefore thetargeted objective of modern design codes the achievement of which hasjustified the development of new calculation approaches now integrated intothe two afore-mentioned Eurocodes This situation justifies the writing of thepresent manual with the main goal to demystify the process by explainingthe new concepts for the design of joints and to integrate their mechanicalresponse into the structural frame analysis and design process by providingldquokeysrdquo for a proper application in practice and finally by providing welldocumented worked examples

To refer to ldquomodernrdquo or ldquonewrdquo design approaches and philosophies does notmean that traditional ways are out dated or no more valid It should beunderstood that the design methods recommended in the Eurocodes are a

PREFACE

_____

xvi

collection of European practices including the results of intensive researchefforts carried out in the last decades and so give many options andalternatives to engineers who are trying to develop safe and economicsolutions

Chapter 1 introduces generalities about joint properties aspects of materialsfabrication erection and costs design approach - and especially the so-calledcomponent method - and design tools available to practitioners for easiercode application The integration of the response of the joints into thestructural analysis and design process is addressed in chapter 2 In chapter 3attention is paid to the design of common connections with mechanicalfasteners Preloaded bolts and non-preloaded bolts are mainly considered butthe use of some less classical connectors is also briefly described Weldedconnections are covered in chapter 5

The next three chapters relate to three specific types of joints respectivelysimple joints moment resisting joints and lattice girder joints For thesesubstantial innovations are brought in the Eurocodes in comparison totraditional national codes particularly for simple and moment resistingjoints A significant number of pages is therefore devoted to these topics inthis manual

The design of joints under static loading as it is addressed in the seven firstchapters is essential in all cases but further checks or different conceptualdesign of the joints are often required in case of load reversal fireearthquake or even exceptional events like impact or explosion Chapter 8summarises present knowledge in this field

Traditionally joints were designed as rigid or pinned which enables the designof the frame and the design of the joints to be treated independently The cleareconomical advantage associated in many situations with the use of semi-rigidandor partial-strength joints leads however to ldquostructure-jointsrdquo interactionsthat have to be mastered by the engineer so as to fully profit from the potentialcost savings The Eurocodes do not cover this interaction From this point ofview chapter 9 may be considered as ldquoa premiegravererdquo even if the content hasalready been partly described years ago in an ECSC publication

Before letting the reader discover the contents of this book we would like toexpress acknowledgment We are very grateful to Prof Frans Bijlaard for all

PREFACE

_____

xvii

the comments suggestions and corrections he made through the reviewprocess of the present manual Warm thanks are also addressed to Joseacute Fuchsand Soumlnke Muumlller who helped us in preparing the drawings Last but notleast we would like to thank our wives for their patience when we workedldquoon our projectrdquo during innumerable evenings and weekends

Jean-Pierre JaspartKlaus Weynand

UK FOREWORD

_____

xix

UK FOREWORD

INTRODUCTION

This book is the second in a series of joint publications of the EuropeanConvention for Constructional Steelwork (ECCS) and The Steel ConstructionInstitute (SCI) It will help provide UK engineers and designers with a betterunderstanding of the design principles in the European Code of Practice for theDesign of Steel Structures (EN 1993 ndash Eurocode 3) and the individual Part 18(EN 1993-1-8) for the design of steel joints in particular Reference will alsobe made to the associated Eurocodes for concrete (EN 1992 ndash Eurocode 2) andearthquake engineering (EN 1998 ndash Eurocode 8) The book complements otherSCI design guides eg SCI (2011 and 2013a)

The current publication is a first UK edition based on the first edition of theECCS manual for the Design of Joints in Steel and Composite Structureswhich was published in 2016 The scope of this UK edition is narrower thanthe original publication in two specific areas that are felt to be of limitedinterest to current practice in the UK there is no content covering compositejoints and chapter 9 (covering frame design strategies) has been shortened tosimply give an overview of strategies In this edition the reader will findinformation that is either of a general nature or relevant to specific sectionsof the publication to facilitate its application in a UK context

The content includes useful background to the code rules and a reminder ofsome engineering principles Information is presented in the context of theEurocodes terminology and notation and with reference to clause numbersetc to help the readerrsquos familiarity with EN 1993-1-8 The document thatserves as the basis for content and numbering of clauses is the UKimplementation of EN 1993-1-82005 incorporating corrigenda December2005 and July 2009 At the time of writing (Autumn 2016) part 1-8 ofEN 1993 is being revised with publication anticipated after 2020

Finally it is noted and should be accepted that there will inevitably be somedifferences of interpretation between the ECCS recommendations and thosepreviously published by the SCI

UK FOREWORD

_____

xx

GENERAL COMMENTS

Design of joints (connections) in steel structures in the UK is covered byBS EN 1993-1-8 and its national Annex (NA) (BSI 2010) BS EN 1993-1-8has clear definitions for connections and joints The term joint refers to thezone where members are interconnected and a connection is the locationwhere elements meet The distinction in terminology is usually emphasised inContinental Europe but traditional practice in the UK is to use the generic termconnection

The following partial safety factors are defined in the UK NA

Partial factor Value Comment

γM2 125 Used for the resistance of bolts pins and welds

γM2 125Used for the resistance of plates in bearing(γM2=15 should be used if deformation control is important)

γM3 125 Used for slip resistance at Ultimate Limit States

γM3serv 110 Used for slip resistance at Serviceability Limit States (SLS)

γM4 100 Used for the resistance of injection bolts

γM5 100 Used for the resistance of joints in hollow section lattice girders

γM6serv 100 Used for the resistance of pins at SLS

γM7

110Used for the preload of high strength steel bolts conforming toBS EN 14399-4 and BS EN 14399-8 (BSI 2015 and 2007)

100 Used for the preload of (other) high strength steel bolts

Specific reference to the UK Building Regulations is also made in this UKedition The UK Building Regulations code has structural integrityrequirements in order to avoid disproportionate collapse and ensure robustnessof the complete structure Disproportionate collapse can be defined as a regionof structural collapse out of proportion to the initiating cause of failure Themost relevant to connectionjoint design is that the detailing for every beam

UK FOREWORD

_____

xxi

member must be adequate to resist a minimum horizontal force at ultimatefailure (or tying resistance) Guidance on the design values of tying forces canbe found in BS EN 1991-1-7 Annex A and its UK annex (BSI 2014)

SECTION SPECIFIC COMMENTS

Section 111

UK practice normally considers only two main forms of joint modellingsimple and continuous Ideally frames designed on the basis of simple jointmodelling should use joints between members that possess negligiblerotational stiffness and transmit the beam reactions in shear into thecolumns without developing significant moments These joints may betreated as perfect pins Members can then be designed in isolation either as(predominantly) axially loaded columns or as simply supported beamsJoints designed within the principles of continuous modelling are capable oftransmitting significant moments and are able to maintain the original anglebetween adjacent members virtually unchanged This form of construction ofsteel frames is particularly advantageous when beam deflections are criticalor if bracing systems are not possible

To comply with one or the other design assumption steelwork connectionsare detailed as simple or moment-resisting joints Because joints in framestructures are often treated by adopting a degree of standardisation thedesigner usually details the connections in accordance with the principlesin the series of SCI Green Books which present this material in the formof step-by-step design procedures and tables covering standardarrangements

Other approximate analysis methods continue to be used among Britishdesigners the most representative being the wind-moment method for thedesign of unbraced multi-storey steel frames The method assumes that(i) under gravity loads the beam-to-column joints act as pinnedconnections and (ii) under horizontal wind loads these joints are rigidalthough it lacks transparency This method can be seen as a manifestationof the semi-continuous principles Wind moment connection details can befound in SCI (1995a) With the now widespread use of software in designoffices for rigorous second-order analysis it is doubtful if the use of the

UK FOREWORD

_____

xxii

wind-moment method should be advocated any longer other than forinitial sizing

Section 13

Although S460 is attracting growing interest S355 is still the dominantgrade of steel used in the UK

Section 161

With reference to Figure 120 it is noted that (site) welded joints and angleflange cleats are rarely if ever used in the UK

Section 162

Hybrid connections are rarely used in the UK for the reasons noted

Section 172

There is not much use of CoPcopy in the UK There are a number of othersoftware tools on the market some more comprehensive than others

Section 22

Although in UK design practice most aspects related to joint modelling havedeveloped to a high degree of sophistication proper consideration of thestructural interaction between the joints and members is rarely fully takeninto account It is indeed very difficult to predict and model the complexbehaviour of a joint (strength stiffness and rotation capacity) TraditionalUK practice is to predict joint behaviour on the basis of past experience

BSI (2010) separates the modelling of the rotational behaviour of theconnection elements (that is the bolts the welds the plates etc) and thatof the column web panel in shear to characterise the overall jointbehaviour As a simplification the two sources of joint deformation arecombined by means of the so-called transformation parameter β Thiscoefficient is related to the web panel internal actions and can be calculatedfrom the moments at each side of the web panel The β parameter iscurrently only defined for same-depth beams which meet at the same levelIn many practical double-sided joints beams will not be of the same depthor at the same height BS EN 1993-1-8 is silent on such joints

UK FOREWORD

_____

xxiii

Section 23

As explained above typical UK design practice does not consider thissophisticated procedure for idealisation of joints

Section 24

The NA to BS EN 1993-1-8 gives practical guidance to classify joints Italso states the following

ldquoUntil experience is gained with the numerical method of calculatingrotational stiffness given in BS EN 1993-1-82005 63 and theclassification by stiffness method given in BS EN 1993-1-82005522 semi-continuous elastic design should only be used where eitherit is supported by test evidence according to BS EN 1993-1-820055221(2) or where it is based on satisfactorily performance in asimilar situationrdquo

Evidence on values of column base stiffness for practical global analysis isgiven in SCI (2006)

Section 25

The concept of ductility classes is not widely applied in the UK It isgenerally assumed that standard connection details to the SCI Green Booksprovide enough rotation capacity and so behave in a ductile manner asevidenced by physical testing and experience

Section 31

The NA to BS EN 1993-1-8 excludes bolts of classes 58 and 68 It alsostates that bolt class 48 may only be used if the manufacturing process (i) isin accordance with BS EN ISO 898-1 (BSI 2013) and (ii) includes suitableprocedures to avoid hydrogen embrittlement

Section 322

The NA to BS EN 1993-1-8 states that if the preload is not explicitly used inthe design calculations then no specific level of preload is required

Section 347

Injection bolts are rarely used in the UK

UK FOREWORD

_____

xxiv

Section 348

Reference is made to SCI (1995b) to calculate the bending moments in thepin of a pin bearing

Section 349

Flow drill blind bolting is not common practice in the UK SHS blind boltingis a common system but there are several manufactures other than thatsuggested in the book

Section 3410

Nails are rarely used in the UK

Section 352

T-stub configurations with four bolts in a row are rarely used in the UK

Section 353

Reference is made to the SCI method for the design of gusset plates seeSCI (2011)

Section 421

It is anticipated that specific rules given in the current BS EN 1993-1-12(BSI 2009) for high strength steels will be incorporated in the revisedBS EN 1993-1-8 to appear after 2020

Section 522

ldquoHeader platesrdquo are known as ldquopartial depth end platesrdquo in the UK Webcleat connections are no longer commonly used in the UK The full depthend plate connection shown on the left of Figure 59 is classified as a simplejoint in the UK (SCI 2011)

Section 523

The UK Building Regulations require that joints are designed for tyingforces in order to satisfy structural integrity requirements Guidance onthe design values of tying forces is given in BS EN 1991-1-7 Annex Aand its UK NA The requirements relate to the building class with a

UK FOREWORD

_____

xxv

design value of horizontal force generally not less than 75 kN andusually significantly higher Simple joints detailed to SCI (2011) satisfythese requirements

Section 525

It is generally safe to assume that the ductility (rotation requirements) aresatisfied provided that joints are detailed in accordance with SCI (2011)

Section 531

The column base detailing on the left of Figure 521 is not commonly used inthe UK We never recommend less than four bolts ndash they are needed toassure stability and facilitate location during erection The anchoringsystems shown in Figure 522 are not usually adopted in the UK Referenceis made to SCI (2013a) for common anchor systems

Section 62

Publication SCI (2013b) summarises the principal differences betweenBS 5950 and BS EN 1993-1-8 (BSI 2000 and 2010) in terms ofcomponent characterisation

With reference to Figure 66 it is anticipated that the revised BS EN1993-1-8will include analytical expressions for the definition of the so-called αcoefficient

Rules of thumb for the characterisation of the ductility of some individualcomponents are given in SCI (1995a)

Section 631

The UK NA to BS EN 1993-1-8 gives specific rules for the full plasticdistribution of effective design tension resistance The procedure is alsosummarised in SCI (2013a)

Section 633

Where a joint is subjected to combined bending moments and axial forcesthe concept of an applied moment modified by axial load can be used seeSCI (1995a)

UK FOREWORD

_____

xxvi

Section 64

Rotational stiffness is not normally evaluated in UK design practice whichusually relies on past experience

Section 65

Some rules of thumb for the characterisation of the ductility of moment-resisting joints are given in SCI (1995a)

Section 661

With reference to Figure 636 it is noted that this joint configuration ishardly (if ever) used in the UK

Section 663

It should be noted that European sections are not commonly used in the UKalthough there is growing interest in the market Steel grade S235 is not usedin the UK S355 being the current common grade Combinations of plates of15 mm thickness with M24 bolts are common This combination is assumedto provide enough rotation capacity thus satisfying ductility requirementsbecause ductile failure of the plates not brittle failure of the bolts governsthe behaviour

Section 672

Standard practice in the UK does not account for this 25 rule Columnsplices are usually detailed to SCI (2011) to ensure continuity of stiffnessthrough the splice so that the member design is not invalidated

Section 84

The UK Building Regulations require that joints are designed for tyingforces in order to satisfy structural integrity requirements Guidance on thedesign values of tying forces is given in BS EN 1991-1-7 Annex A and itsUK NA (BSI 2014)

Section 91

In the UK the ldquofabricatorsrdquo are known as ldquoSteelwork contractorsrdquo becausethey do more than just fabricate

UK FOREWORD

_____

xxvii

REFERENCES TO NATIONAL FOREWORD

BSI (2000) BS 5950-12000 ndash Structural use of steelwork in building ndash Part1 Code of Practice for Design rolled and welded sections British StandardsInstitution United Kingdom

BSI (2007) BS EN 14399-82007 ndash High-strength structural boltingassemblies for preloading System HV Hexagon fit bolt and nut assembliesBritish Standards Institution United Kingdom

BSI (2009) BS EN 1993-1-122007 ndash Eurocode 3 Design of steel structuresndash Part 112 Additional rules for the extension of EN 1993 up to steel gradesS 700 British Standards Institution United Kingdom

BSI (2010) BS EN 1993-1-82005 ndash Eurocode 3 Design of steel structuresndash Part 18 Design of joints British Standards Institution United Kingdom

BSI (2013) BS EN ISO 898-12013 ndash Mechanical properties of fastenersmade of carbon steel and alloy steel Bolts screws and studs with specifiedproperty classes Coarse thread and fine pitch thread British StandardsInstitution United Kingdom

BSI (2014) BS EN 1991-1-72006+A12014 ndash Eurocode 1 Actions on structuresndash Part 197 General actions British Standards Institution United Kingdom

BSI (2015) BS EN 14399-42015 ndash High-strength structural boltingassemblies for preloading System HV Hexagon bolt and nut assembliesBritish Standards Institution United Kingdom

SCI (1995a) Joints in steel construction Moment connections P207 TheSteel Construction Institute

SCI (1995b) Advisory Desk Notes Bending Moment in a pin AD 172 TheSteel Construction Institute

SCI (2006) Column base stiffness for global analysis NCCI-SN045a TheSteel Construction Institute

SCI (2011) Joints in steel construction Simple joints to Eurocode 3 P358The Steel Construction Institute

SCI (2013a) Joints in steel construction Moment-resisting joints toEurocode 3 P398 The Steel Construction Institute

UK FOREWORD

_____

xxviii

SCI (2013b) Interim Report Design of Portal Frames to Eurocode 3 Anoverview for UK designers P400 The Steel Construction Institute

TABLE OF CONTENTS

_____

x

672 Design considerations 283

68 Application to column bases 284681 Common column basis configurations 284682 Design considerations 287

Chapter 7

LATTICE GIRDER JOINTS 295

71 General 295

72 Scope and field of application 296

73 Design models 298731 General 298732 Failure modes 299733 Models for CHS chords 300734 Model for RHS chords 301735 Punching shear failure 302736 Model for brace failure 303737 M-N interaction 304

Chapter 8

JOINTS UNDER VARIOUS LOADING SITUATIONS 305

81 Introduction 305

82 Joints in fire 306

83 Joints under cyclic loading 307

84 Joints under exceptional events 308

Chapter 9

DESIGN STRATEGIES 311

91 Introduction 311

92 Traditional design approach 314

93 Integrated design approach 317

94 Economic considerations 319

TABLE OF CONTENTS

_____

xi

941 Fabrication and erections costs 319942 Savings of material costs 322943 Summary and conclusions 323

BIBLIOGRAPHIC REFERENCES 325

Annex A Practical values for required rotation capacity 337

Annex B Values for lateral torsional buckling strength of a fin plate 339

FOREWORD

_____

xiii

FOREWORD

With the ECCS book ldquoJoints in Steel and Composite Structuresrdquo the authorssucceeded in placing the joints on the rightful place they deserve in thestructural behaviour of steel and composite steel-concrete structures Themany times used word ldquodetailsrdquo for the joints in structures by farunderestimates the importance of joints in the structural behaviour ofbuildings and civil engineering structures In their chapter ldquoAim of the bookrdquothe authors clearly explain how the design and safety verification ofstructures runs in an integral manner where all structural componentsincluding the joints play balanced roles leading to economic structures

This book can be seen as a background document for Eurocode 3 ldquoDesign ofSteel Structuresrdquo as far as it concerns structural joints The central theme indescribing the behaviour of joints is using the component method and this isleading all over in this book The book contain many aspects such as designfabrication erection and costs

In this book attention is paid on joint modelling and idealisation jointclassification for strength and stiffness and deformation capacity This all forconnections with mechanical fasteners and for welded connections for simplejoints and moment resistant joints Also lattice girder joints are described

The book provides the designer with design strategies to arrive at economicstructures

The authors based themselves on many bibliographic references covering atime span of about 65 years Many of these references present research of theauthors themselves and of the other members of the ECCS-TechnicalCommittee TC10 ldquoStructural Connectionsrdquo

It was really a privilege to have been the chairperson of this committee from1998 till the end of 2012 and I thank the authors Prof Dr Ir Jean-PierreJaspart and Dr-Ing Klaus Weynand for their large effort in writing this book

Prof ir Frans Bijlaard

PREFACE

_____

xv

PREFACE

Steel constructions and composite steel-concrete constructions are generallyerected on site by the assembly of prefabricated structural parts prepared inthe workshop These parts may themselves be the result of an assembly ofindividual elements An example is the assembly by bolting on site offabricated sections welded in the workshop

In these construction types joints and connections play a key role andrecommendations and guidelines are required for engineers and constructorsfaced with the conception and design the fabrication and the erection of suchstructures In the Structural Eurocodes these aspects are mainly covered in theexecution standard EN 1090-2 and in the design standard EN 1993-1-8(Eurocode 3 Design of steel structures Part 1-8 Design of Joints)

In the present book which is part of the series of ECCS Eurocode DesignManuals the main focus is given to design aspects but references are alsomade to EN 1090-2 when necessary

In comparison to other fields the design procedures for joints andconnections have significantly evolved in the last decades as a result of theprogressive awareness by practitioners of the significant contribution ofjoints and connections to the global cost of structures Design for lowfabrication and erection costs as well as high resistance is therefore thetargeted objective of modern design codes the achievement of which hasjustified the development of new calculation approaches now integrated intothe two afore-mentioned Eurocodes This situation justifies the writing of thepresent manual with the main goal to demystify the process by explainingthe new concepts for the design of joints and to integrate their mechanicalresponse into the structural frame analysis and design process by providingldquokeysrdquo for a proper application in practice and finally by providing welldocumented worked examples

To refer to ldquomodernrdquo or ldquonewrdquo design approaches and philosophies does notmean that traditional ways are out dated or no more valid It should beunderstood that the design methods recommended in the Eurocodes are a

PREFACE

_____

xvi

collection of European practices including the results of intensive researchefforts carried out in the last decades and so give many options andalternatives to engineers who are trying to develop safe and economicsolutions

Chapter 1 introduces generalities about joint properties aspects of materialsfabrication erection and costs design approach - and especially the so-calledcomponent method - and design tools available to practitioners for easiercode application The integration of the response of the joints into thestructural analysis and design process is addressed in chapter 2 In chapter 3attention is paid to the design of common connections with mechanicalfasteners Preloaded bolts and non-preloaded bolts are mainly considered butthe use of some less classical connectors is also briefly described Weldedconnections are covered in chapter 5

The next three chapters relate to three specific types of joints respectivelysimple joints moment resisting joints and lattice girder joints For thesesubstantial innovations are brought in the Eurocodes in comparison totraditional national codes particularly for simple and moment resistingjoints A significant number of pages is therefore devoted to these topics inthis manual

The design of joints under static loading as it is addressed in the seven firstchapters is essential in all cases but further checks or different conceptualdesign of the joints are often required in case of load reversal fireearthquake or even exceptional events like impact or explosion Chapter 8summarises present knowledge in this field

Traditionally joints were designed as rigid or pinned which enables the designof the frame and the design of the joints to be treated independently The cleareconomical advantage associated in many situations with the use of semi-rigidandor partial-strength joints leads however to ldquostructure-jointsrdquo interactionsthat have to be mastered by the engineer so as to fully profit from the potentialcost savings The Eurocodes do not cover this interaction From this point ofview chapter 9 may be considered as ldquoa premiegravererdquo even if the content hasalready been partly described years ago in an ECSC publication

Before letting the reader discover the contents of this book we would like toexpress acknowledgment We are very grateful to Prof Frans Bijlaard for all

PREFACE

_____

xvii

the comments suggestions and corrections he made through the reviewprocess of the present manual Warm thanks are also addressed to Joseacute Fuchsand Soumlnke Muumlller who helped us in preparing the drawings Last but notleast we would like to thank our wives for their patience when we workedldquoon our projectrdquo during innumerable evenings and weekends

Jean-Pierre JaspartKlaus Weynand

UK FOREWORD

_____

xix

UK FOREWORD

INTRODUCTION

This book is the second in a series of joint publications of the EuropeanConvention for Constructional Steelwork (ECCS) and The Steel ConstructionInstitute (SCI) It will help provide UK engineers and designers with a betterunderstanding of the design principles in the European Code of Practice for theDesign of Steel Structures (EN 1993 ndash Eurocode 3) and the individual Part 18(EN 1993-1-8) for the design of steel joints in particular Reference will alsobe made to the associated Eurocodes for concrete (EN 1992 ndash Eurocode 2) andearthquake engineering (EN 1998 ndash Eurocode 8) The book complements otherSCI design guides eg SCI (2011 and 2013a)

The current publication is a first UK edition based on the first edition of theECCS manual for the Design of Joints in Steel and Composite Structureswhich was published in 2016 The scope of this UK edition is narrower thanthe original publication in two specific areas that are felt to be of limitedinterest to current practice in the UK there is no content covering compositejoints and chapter 9 (covering frame design strategies) has been shortened tosimply give an overview of strategies In this edition the reader will findinformation that is either of a general nature or relevant to specific sectionsof the publication to facilitate its application in a UK context

The content includes useful background to the code rules and a reminder ofsome engineering principles Information is presented in the context of theEurocodes terminology and notation and with reference to clause numbersetc to help the readerrsquos familiarity with EN 1993-1-8 The document thatserves as the basis for content and numbering of clauses is the UKimplementation of EN 1993-1-82005 incorporating corrigenda December2005 and July 2009 At the time of writing (Autumn 2016) part 1-8 ofEN 1993 is being revised with publication anticipated after 2020

Finally it is noted and should be accepted that there will inevitably be somedifferences of interpretation between the ECCS recommendations and thosepreviously published by the SCI

UK FOREWORD

_____

xx

GENERAL COMMENTS

Design of joints (connections) in steel structures in the UK is covered byBS EN 1993-1-8 and its national Annex (NA) (BSI 2010) BS EN 1993-1-8has clear definitions for connections and joints The term joint refers to thezone where members are interconnected and a connection is the locationwhere elements meet The distinction in terminology is usually emphasised inContinental Europe but traditional practice in the UK is to use the generic termconnection

The following partial safety factors are defined in the UK NA

Partial factor Value Comment

γM2 125 Used for the resistance of bolts pins and welds

γM2 125Used for the resistance of plates in bearing(γM2=15 should be used if deformation control is important)

γM3 125 Used for slip resistance at Ultimate Limit States

γM3serv 110 Used for slip resistance at Serviceability Limit States (SLS)

γM4 100 Used for the resistance of injection bolts

γM5 100 Used for the resistance of joints in hollow section lattice girders

γM6serv 100 Used for the resistance of pins at SLS

γM7

110Used for the preload of high strength steel bolts conforming toBS EN 14399-4 and BS EN 14399-8 (BSI 2015 and 2007)

100 Used for the preload of (other) high strength steel bolts

Specific reference to the UK Building Regulations is also made in this UKedition The UK Building Regulations code has structural integrityrequirements in order to avoid disproportionate collapse and ensure robustnessof the complete structure Disproportionate collapse can be defined as a regionof structural collapse out of proportion to the initiating cause of failure Themost relevant to connectionjoint design is that the detailing for every beam

UK FOREWORD

_____

xxi

member must be adequate to resist a minimum horizontal force at ultimatefailure (or tying resistance) Guidance on the design values of tying forces canbe found in BS EN 1991-1-7 Annex A and its UK annex (BSI 2014)

SECTION SPECIFIC COMMENTS

Section 111

UK practice normally considers only two main forms of joint modellingsimple and continuous Ideally frames designed on the basis of simple jointmodelling should use joints between members that possess negligiblerotational stiffness and transmit the beam reactions in shear into thecolumns without developing significant moments These joints may betreated as perfect pins Members can then be designed in isolation either as(predominantly) axially loaded columns or as simply supported beamsJoints designed within the principles of continuous modelling are capable oftransmitting significant moments and are able to maintain the original anglebetween adjacent members virtually unchanged This form of construction ofsteel frames is particularly advantageous when beam deflections are criticalor if bracing systems are not possible

To comply with one or the other design assumption steelwork connectionsare detailed as simple or moment-resisting joints Because joints in framestructures are often treated by adopting a degree of standardisation thedesigner usually details the connections in accordance with the principlesin the series of SCI Green Books which present this material in the formof step-by-step design procedures and tables covering standardarrangements

Other approximate analysis methods continue to be used among Britishdesigners the most representative being the wind-moment method for thedesign of unbraced multi-storey steel frames The method assumes that(i) under gravity loads the beam-to-column joints act as pinnedconnections and (ii) under horizontal wind loads these joints are rigidalthough it lacks transparency This method can be seen as a manifestationof the semi-continuous principles Wind moment connection details can befound in SCI (1995a) With the now widespread use of software in designoffices for rigorous second-order analysis it is doubtful if the use of the

UK FOREWORD

_____

xxii

wind-moment method should be advocated any longer other than forinitial sizing

Section 13

Although S460 is attracting growing interest S355 is still the dominantgrade of steel used in the UK

Section 161

With reference to Figure 120 it is noted that (site) welded joints and angleflange cleats are rarely if ever used in the UK

Section 162

Hybrid connections are rarely used in the UK for the reasons noted

Section 172

There is not much use of CoPcopy in the UK There are a number of othersoftware tools on the market some more comprehensive than others

Section 22

Although in UK design practice most aspects related to joint modelling havedeveloped to a high degree of sophistication proper consideration of thestructural interaction between the joints and members is rarely fully takeninto account It is indeed very difficult to predict and model the complexbehaviour of a joint (strength stiffness and rotation capacity) TraditionalUK practice is to predict joint behaviour on the basis of past experience

BSI (2010) separates the modelling of the rotational behaviour of theconnection elements (that is the bolts the welds the plates etc) and thatof the column web panel in shear to characterise the overall jointbehaviour As a simplification the two sources of joint deformation arecombined by means of the so-called transformation parameter β Thiscoefficient is related to the web panel internal actions and can be calculatedfrom the moments at each side of the web panel The β parameter iscurrently only defined for same-depth beams which meet at the same levelIn many practical double-sided joints beams will not be of the same depthor at the same height BS EN 1993-1-8 is silent on such joints

UK FOREWORD

_____

xxiii

Section 23

As explained above typical UK design practice does not consider thissophisticated procedure for idealisation of joints

Section 24

The NA to BS EN 1993-1-8 gives practical guidance to classify joints Italso states the following

ldquoUntil experience is gained with the numerical method of calculatingrotational stiffness given in BS EN 1993-1-82005 63 and theclassification by stiffness method given in BS EN 1993-1-82005522 semi-continuous elastic design should only be used where eitherit is supported by test evidence according to BS EN 1993-1-820055221(2) or where it is based on satisfactorily performance in asimilar situationrdquo

Evidence on values of column base stiffness for practical global analysis isgiven in SCI (2006)

Section 25

The concept of ductility classes is not widely applied in the UK It isgenerally assumed that standard connection details to the SCI Green Booksprovide enough rotation capacity and so behave in a ductile manner asevidenced by physical testing and experience

Section 31

The NA to BS EN 1993-1-8 excludes bolts of classes 58 and 68 It alsostates that bolt class 48 may only be used if the manufacturing process (i) isin accordance with BS EN ISO 898-1 (BSI 2013) and (ii) includes suitableprocedures to avoid hydrogen embrittlement

Section 322

The NA to BS EN 1993-1-8 states that if the preload is not explicitly used inthe design calculations then no specific level of preload is required

Section 347

Injection bolts are rarely used in the UK

UK FOREWORD

_____

xxiv

Section 348

Reference is made to SCI (1995b) to calculate the bending moments in thepin of a pin bearing

Section 349

Flow drill blind bolting is not common practice in the UK SHS blind boltingis a common system but there are several manufactures other than thatsuggested in the book

Section 3410

Nails are rarely used in the UK

Section 352

T-stub configurations with four bolts in a row are rarely used in the UK

Section 353

Reference is made to the SCI method for the design of gusset plates seeSCI (2011)

Section 421

It is anticipated that specific rules given in the current BS EN 1993-1-12(BSI 2009) for high strength steels will be incorporated in the revisedBS EN 1993-1-8 to appear after 2020

Section 522

ldquoHeader platesrdquo are known as ldquopartial depth end platesrdquo in the UK Webcleat connections are no longer commonly used in the UK The full depthend plate connection shown on the left of Figure 59 is classified as a simplejoint in the UK (SCI 2011)

Section 523

The UK Building Regulations require that joints are designed for tyingforces in order to satisfy structural integrity requirements Guidance onthe design values of tying forces is given in BS EN 1991-1-7 Annex Aand its UK NA The requirements relate to the building class with a

UK FOREWORD

_____

xxv

design value of horizontal force generally not less than 75 kN andusually significantly higher Simple joints detailed to SCI (2011) satisfythese requirements

Section 525

It is generally safe to assume that the ductility (rotation requirements) aresatisfied provided that joints are detailed in accordance with SCI (2011)

Section 531

The column base detailing on the left of Figure 521 is not commonly used inthe UK We never recommend less than four bolts ndash they are needed toassure stability and facilitate location during erection The anchoringsystems shown in Figure 522 are not usually adopted in the UK Referenceis made to SCI (2013a) for common anchor systems

Section 62

Publication SCI (2013b) summarises the principal differences betweenBS 5950 and BS EN 1993-1-8 (BSI 2000 and 2010) in terms ofcomponent characterisation

With reference to Figure 66 it is anticipated that the revised BS EN1993-1-8will include analytical expressions for the definition of the so-called αcoefficient

Rules of thumb for the characterisation of the ductility of some individualcomponents are given in SCI (1995a)

Section 631

The UK NA to BS EN 1993-1-8 gives specific rules for the full plasticdistribution of effective design tension resistance The procedure is alsosummarised in SCI (2013a)

Section 633

Where a joint is subjected to combined bending moments and axial forcesthe concept of an applied moment modified by axial load can be used seeSCI (1995a)

UK FOREWORD

_____

xxvi

Section 64

Rotational stiffness is not normally evaluated in UK design practice whichusually relies on past experience

Section 65

Some rules of thumb for the characterisation of the ductility of moment-resisting joints are given in SCI (1995a)

Section 661

With reference to Figure 636 it is noted that this joint configuration ishardly (if ever) used in the UK

Section 663

It should be noted that European sections are not commonly used in the UKalthough there is growing interest in the market Steel grade S235 is not usedin the UK S355 being the current common grade Combinations of plates of15 mm thickness with M24 bolts are common This combination is assumedto provide enough rotation capacity thus satisfying ductility requirementsbecause ductile failure of the plates not brittle failure of the bolts governsthe behaviour

Section 672

Standard practice in the UK does not account for this 25 rule Columnsplices are usually detailed to SCI (2011) to ensure continuity of stiffnessthrough the splice so that the member design is not invalidated

Section 84

The UK Building Regulations require that joints are designed for tyingforces in order to satisfy structural integrity requirements Guidance on thedesign values of tying forces is given in BS EN 1991-1-7 Annex A and itsUK NA (BSI 2014)

Section 91

In the UK the ldquofabricatorsrdquo are known as ldquoSteelwork contractorsrdquo becausethey do more than just fabricate

UK FOREWORD

_____

xxvii

REFERENCES TO NATIONAL FOREWORD

BSI (2000) BS 5950-12000 ndash Structural use of steelwork in building ndash Part1 Code of Practice for Design rolled and welded sections British StandardsInstitution United Kingdom

BSI (2007) BS EN 14399-82007 ndash High-strength structural boltingassemblies for preloading System HV Hexagon fit bolt and nut assembliesBritish Standards Institution United Kingdom

BSI (2009) BS EN 1993-1-122007 ndash Eurocode 3 Design of steel structuresndash Part 112 Additional rules for the extension of EN 1993 up to steel gradesS 700 British Standards Institution United Kingdom

BSI (2010) BS EN 1993-1-82005 ndash Eurocode 3 Design of steel structuresndash Part 18 Design of joints British Standards Institution United Kingdom

BSI (2013) BS EN ISO 898-12013 ndash Mechanical properties of fastenersmade of carbon steel and alloy steel Bolts screws and studs with specifiedproperty classes Coarse thread and fine pitch thread British StandardsInstitution United Kingdom

BSI (2014) BS EN 1991-1-72006+A12014 ndash Eurocode 1 Actions on structuresndash Part 197 General actions British Standards Institution United Kingdom

BSI (2015) BS EN 14399-42015 ndash High-strength structural boltingassemblies for preloading System HV Hexagon bolt and nut assembliesBritish Standards Institution United Kingdom

SCI (1995a) Joints in steel construction Moment connections P207 TheSteel Construction Institute

SCI (1995b) Advisory Desk Notes Bending Moment in a pin AD 172 TheSteel Construction Institute

SCI (2006) Column base stiffness for global analysis NCCI-SN045a TheSteel Construction Institute

SCI (2011) Joints in steel construction Simple joints to Eurocode 3 P358The Steel Construction Institute

SCI (2013a) Joints in steel construction Moment-resisting joints toEurocode 3 P398 The Steel Construction Institute

UK FOREWORD

_____

xxviii

SCI (2013b) Interim Report Design of Portal Frames to Eurocode 3 Anoverview for UK designers P400 The Steel Construction Institute

TABLE OF CONTENTS

_____

xi

941 Fabrication and erections costs 319942 Savings of material costs 322943 Summary and conclusions 323

BIBLIOGRAPHIC REFERENCES 325

Annex A Practical values for required rotation capacity 337

Annex B Values for lateral torsional buckling strength of a fin plate 339

FOREWORD

_____

xiii

FOREWORD

With the ECCS book ldquoJoints in Steel and Composite Structuresrdquo the authorssucceeded in placing the joints on the rightful place they deserve in thestructural behaviour of steel and composite steel-concrete structures Themany times used word ldquodetailsrdquo for the joints in structures by farunderestimates the importance of joints in the structural behaviour ofbuildings and civil engineering structures In their chapter ldquoAim of the bookrdquothe authors clearly explain how the design and safety verification ofstructures runs in an integral manner where all structural componentsincluding the joints play balanced roles leading to economic structures

This book can be seen as a background document for Eurocode 3 ldquoDesign ofSteel Structuresrdquo as far as it concerns structural joints The central theme indescribing the behaviour of joints is using the component method and this isleading all over in this book The book contain many aspects such as designfabrication erection and costs

In this book attention is paid on joint modelling and idealisation jointclassification for strength and stiffness and deformation capacity This all forconnections with mechanical fasteners and for welded connections for simplejoints and moment resistant joints Also lattice girder joints are described

The book provides the designer with design strategies to arrive at economicstructures

The authors based themselves on many bibliographic references covering atime span of about 65 years Many of these references present research of theauthors themselves and of the other members of the ECCS-TechnicalCommittee TC10 ldquoStructural Connectionsrdquo

It was really a privilege to have been the chairperson of this committee from1998 till the end of 2012 and I thank the authors Prof Dr Ir Jean-PierreJaspart and Dr-Ing Klaus Weynand for their large effort in writing this book

Prof ir Frans Bijlaard

PREFACE

_____

xv

PREFACE

Steel constructions and composite steel-concrete constructions are generallyerected on site by the assembly of prefabricated structural parts prepared inthe workshop These parts may themselves be the result of an assembly ofindividual elements An example is the assembly by bolting on site offabricated sections welded in the workshop

In these construction types joints and connections play a key role andrecommendations and guidelines are required for engineers and constructorsfaced with the conception and design the fabrication and the erection of suchstructures In the Structural Eurocodes these aspects are mainly covered in theexecution standard EN 1090-2 and in the design standard EN 1993-1-8(Eurocode 3 Design of steel structures Part 1-8 Design of Joints)

In the present book which is part of the series of ECCS Eurocode DesignManuals the main focus is given to design aspects but references are alsomade to EN 1090-2 when necessary

In comparison to other fields the design procedures for joints andconnections have significantly evolved in the last decades as a result of theprogressive awareness by practitioners of the significant contribution ofjoints and connections to the global cost of structures Design for lowfabrication and erection costs as well as high resistance is therefore thetargeted objective of modern design codes the achievement of which hasjustified the development of new calculation approaches now integrated intothe two afore-mentioned Eurocodes This situation justifies the writing of thepresent manual with the main goal to demystify the process by explainingthe new concepts for the design of joints and to integrate their mechanicalresponse into the structural frame analysis and design process by providingldquokeysrdquo for a proper application in practice and finally by providing welldocumented worked examples

To refer to ldquomodernrdquo or ldquonewrdquo design approaches and philosophies does notmean that traditional ways are out dated or no more valid It should beunderstood that the design methods recommended in the Eurocodes are a

PREFACE

_____

xvi

collection of European practices including the results of intensive researchefforts carried out in the last decades and so give many options andalternatives to engineers who are trying to develop safe and economicsolutions

Chapter 1 introduces generalities about joint properties aspects of materialsfabrication erection and costs design approach - and especially the so-calledcomponent method - and design tools available to practitioners for easiercode application The integration of the response of the joints into thestructural analysis and design process is addressed in chapter 2 In chapter 3attention is paid to the design of common connections with mechanicalfasteners Preloaded bolts and non-preloaded bolts are mainly considered butthe use of some less classical connectors is also briefly described Weldedconnections are covered in chapter 5

The next three chapters relate to three specific types of joints respectivelysimple joints moment resisting joints and lattice girder joints For thesesubstantial innovations are brought in the Eurocodes in comparison totraditional national codes particularly for simple and moment resistingjoints A significant number of pages is therefore devoted to these topics inthis manual

The design of joints under static loading as it is addressed in the seven firstchapters is essential in all cases but further checks or different conceptualdesign of the joints are often required in case of load reversal fireearthquake or even exceptional events like impact or explosion Chapter 8summarises present knowledge in this field

Traditionally joints were designed as rigid or pinned which enables the designof the frame and the design of the joints to be treated independently The cleareconomical advantage associated in many situations with the use of semi-rigidandor partial-strength joints leads however to ldquostructure-jointsrdquo interactionsthat have to be mastered by the engineer so as to fully profit from the potentialcost savings The Eurocodes do not cover this interaction From this point ofview chapter 9 may be considered as ldquoa premiegravererdquo even if the content hasalready been partly described years ago in an ECSC publication

Before letting the reader discover the contents of this book we would like toexpress acknowledgment We are very grateful to Prof Frans Bijlaard for all

PREFACE

_____

xvii

the comments suggestions and corrections he made through the reviewprocess of the present manual Warm thanks are also addressed to Joseacute Fuchsand Soumlnke Muumlller who helped us in preparing the drawings Last but notleast we would like to thank our wives for their patience when we workedldquoon our projectrdquo during innumerable evenings and weekends

Jean-Pierre JaspartKlaus Weynand

UK FOREWORD

_____

xix

UK FOREWORD

INTRODUCTION

This book is the second in a series of joint publications of the EuropeanConvention for Constructional Steelwork (ECCS) and The Steel ConstructionInstitute (SCI) It will help provide UK engineers and designers with a betterunderstanding of the design principles in the European Code of Practice for theDesign of Steel Structures (EN 1993 ndash Eurocode 3) and the individual Part 18(EN 1993-1-8) for the design of steel joints in particular Reference will alsobe made to the associated Eurocodes for concrete (EN 1992 ndash Eurocode 2) andearthquake engineering (EN 1998 ndash Eurocode 8) The book complements otherSCI design guides eg SCI (2011 and 2013a)

The current publication is a first UK edition based on the first edition of theECCS manual for the Design of Joints in Steel and Composite Structureswhich was published in 2016 The scope of this UK edition is narrower thanthe original publication in two specific areas that are felt to be of limitedinterest to current practice in the UK there is no content covering compositejoints and chapter 9 (covering frame design strategies) has been shortened tosimply give an overview of strategies In this edition the reader will findinformation that is either of a general nature or relevant to specific sectionsof the publication to facilitate its application in a UK context

The content includes useful background to the code rules and a reminder ofsome engineering principles Information is presented in the context of theEurocodes terminology and notation and with reference to clause numbersetc to help the readerrsquos familiarity with EN 1993-1-8 The document thatserves as the basis for content and numbering of clauses is the UKimplementation of EN 1993-1-82005 incorporating corrigenda December2005 and July 2009 At the time of writing (Autumn 2016) part 1-8 ofEN 1993 is being revised with publication anticipated after 2020

Finally it is noted and should be accepted that there will inevitably be somedifferences of interpretation between the ECCS recommendations and thosepreviously published by the SCI

UK FOREWORD

_____

xx

GENERAL COMMENTS

Design of joints (connections) in steel structures in the UK is covered byBS EN 1993-1-8 and its national Annex (NA) (BSI 2010) BS EN 1993-1-8has clear definitions for connections and joints The term joint refers to thezone where members are interconnected and a connection is the locationwhere elements meet The distinction in terminology is usually emphasised inContinental Europe but traditional practice in the UK is to use the generic termconnection

The following partial safety factors are defined in the UK NA

Partial factor Value Comment

γM2 125 Used for the resistance of bolts pins and welds

γM2 125Used for the resistance of plates in bearing(γM2=15 should be used if deformation control is important)

γM3 125 Used for slip resistance at Ultimate Limit States

γM3serv 110 Used for slip resistance at Serviceability Limit States (SLS)

γM4 100 Used for the resistance of injection bolts

γM5 100 Used for the resistance of joints in hollow section lattice girders

γM6serv 100 Used for the resistance of pins at SLS

γM7

110Used for the preload of high strength steel bolts conforming toBS EN 14399-4 and BS EN 14399-8 (BSI 2015 and 2007)

100 Used for the preload of (other) high strength steel bolts

Specific reference to the UK Building Regulations is also made in this UKedition The UK Building Regulations code has structural integrityrequirements in order to avoid disproportionate collapse and ensure robustnessof the complete structure Disproportionate collapse can be defined as a regionof structural collapse out of proportion to the initiating cause of failure Themost relevant to connectionjoint design is that the detailing for every beam

UK FOREWORD

_____

xxi

member must be adequate to resist a minimum horizontal force at ultimatefailure (or tying resistance) Guidance on the design values of tying forces canbe found in BS EN 1991-1-7 Annex A and its UK annex (BSI 2014)

SECTION SPECIFIC COMMENTS

Section 111

UK practice normally considers only two main forms of joint modellingsimple and continuous Ideally frames designed on the basis of simple jointmodelling should use joints between members that possess negligiblerotational stiffness and transmit the beam reactions in shear into thecolumns without developing significant moments These joints may betreated as perfect pins Members can then be designed in isolation either as(predominantly) axially loaded columns or as simply supported beamsJoints designed within the principles of continuous modelling are capable oftransmitting significant moments and are able to maintain the original anglebetween adjacent members virtually unchanged This form of construction ofsteel frames is particularly advantageous when beam deflections are criticalor if bracing systems are not possible

To comply with one or the other design assumption steelwork connectionsare detailed as simple or moment-resisting joints Because joints in framestructures are often treated by adopting a degree of standardisation thedesigner usually details the connections in accordance with the principlesin the series of SCI Green Books which present this material in the formof step-by-step design procedures and tables covering standardarrangements

Other approximate analysis methods continue to be used among Britishdesigners the most representative being the wind-moment method for thedesign of unbraced multi-storey steel frames The method assumes that(i) under gravity loads the beam-to-column joints act as pinnedconnections and (ii) under horizontal wind loads these joints are rigidalthough it lacks transparency This method can be seen as a manifestationof the semi-continuous principles Wind moment connection details can befound in SCI (1995a) With the now widespread use of software in designoffices for rigorous second-order analysis it is doubtful if the use of the

UK FOREWORD

_____

xxii

wind-moment method should be advocated any longer other than forinitial sizing

Section 13

Although S460 is attracting growing interest S355 is still the dominantgrade of steel used in the UK

Section 161

With reference to Figure 120 it is noted that (site) welded joints and angleflange cleats are rarely if ever used in the UK

Section 162

Hybrid connections are rarely used in the UK for the reasons noted

Section 172

There is not much use of CoPcopy in the UK There are a number of othersoftware tools on the market some more comprehensive than others

Section 22

Although in UK design practice most aspects related to joint modelling havedeveloped to a high degree of sophistication proper consideration of thestructural interaction between the joints and members is rarely fully takeninto account It is indeed very difficult to predict and model the complexbehaviour of a joint (strength stiffness and rotation capacity) TraditionalUK practice is to predict joint behaviour on the basis of past experience

BSI (2010) separates the modelling of the rotational behaviour of theconnection elements (that is the bolts the welds the plates etc) and thatof the column web panel in shear to characterise the overall jointbehaviour As a simplification the two sources of joint deformation arecombined by means of the so-called transformation parameter β Thiscoefficient is related to the web panel internal actions and can be calculatedfrom the moments at each side of the web panel The β parameter iscurrently only defined for same-depth beams which meet at the same levelIn many practical double-sided joints beams will not be of the same depthor at the same height BS EN 1993-1-8 is silent on such joints

UK FOREWORD

_____

xxiii

Section 23

As explained above typical UK design practice does not consider thissophisticated procedure for idealisation of joints

Section 24

The NA to BS EN 1993-1-8 gives practical guidance to classify joints Italso states the following

ldquoUntil experience is gained with the numerical method of calculatingrotational stiffness given in BS EN 1993-1-82005 63 and theclassification by stiffness method given in BS EN 1993-1-82005522 semi-continuous elastic design should only be used where eitherit is supported by test evidence according to BS EN 1993-1-820055221(2) or where it is based on satisfactorily performance in asimilar situationrdquo

Evidence on values of column base stiffness for practical global analysis isgiven in SCI (2006)

Section 25

The concept of ductility classes is not widely applied in the UK It isgenerally assumed that standard connection details to the SCI Green Booksprovide enough rotation capacity and so behave in a ductile manner asevidenced by physical testing and experience

Section 31

The NA to BS EN 1993-1-8 excludes bolts of classes 58 and 68 It alsostates that bolt class 48 may only be used if the manufacturing process (i) isin accordance with BS EN ISO 898-1 (BSI 2013) and (ii) includes suitableprocedures to avoid hydrogen embrittlement

Section 322

The NA to BS EN 1993-1-8 states that if the preload is not explicitly used inthe design calculations then no specific level of preload is required

Section 347

Injection bolts are rarely used in the UK

UK FOREWORD

_____

xxiv

Section 348

Reference is made to SCI (1995b) to calculate the bending moments in thepin of a pin bearing

Section 349

Flow drill blind bolting is not common practice in the UK SHS blind boltingis a common system but there are several manufactures other than thatsuggested in the book

Section 3410

Nails are rarely used in the UK

Section 352

T-stub configurations with four bolts in a row are rarely used in the UK

Section 353

Reference is made to the SCI method for the design of gusset plates seeSCI (2011)

Section 421

It is anticipated that specific rules given in the current BS EN 1993-1-12(BSI 2009) for high strength steels will be incorporated in the revisedBS EN 1993-1-8 to appear after 2020

Section 522

ldquoHeader platesrdquo are known as ldquopartial depth end platesrdquo in the UK Webcleat connections are no longer commonly used in the UK The full depthend plate connection shown on the left of Figure 59 is classified as a simplejoint in the UK (SCI 2011)

Section 523

The UK Building Regulations require that joints are designed for tyingforces in order to satisfy structural integrity requirements Guidance onthe design values of tying forces is given in BS EN 1991-1-7 Annex Aand its UK NA The requirements relate to the building class with a

UK FOREWORD

_____

xxv

design value of horizontal force generally not less than 75 kN andusually significantly higher Simple joints detailed to SCI (2011) satisfythese requirements

Section 525

It is generally safe to assume that the ductility (rotation requirements) aresatisfied provided that joints are detailed in accordance with SCI (2011)

Section 531

The column base detailing on the left of Figure 521 is not commonly used inthe UK We never recommend less than four bolts ndash they are needed toassure stability and facilitate location during erection The anchoringsystems shown in Figure 522 are not usually adopted in the UK Referenceis made to SCI (2013a) for common anchor systems

Section 62

Publication SCI (2013b) summarises the principal differences betweenBS 5950 and BS EN 1993-1-8 (BSI 2000 and 2010) in terms ofcomponent characterisation

With reference to Figure 66 it is anticipated that the revised BS EN1993-1-8will include analytical expressions for the definition of the so-called αcoefficient

Rules of thumb for the characterisation of the ductility of some individualcomponents are given in SCI (1995a)

Section 631

The UK NA to BS EN 1993-1-8 gives specific rules for the full plasticdistribution of effective design tension resistance The procedure is alsosummarised in SCI (2013a)

Section 633

Where a joint is subjected to combined bending moments and axial forcesthe concept of an applied moment modified by axial load can be used seeSCI (1995a)

UK FOREWORD

_____

xxvi

Section 64

Rotational stiffness is not normally evaluated in UK design practice whichusually relies on past experience

Section 65

Some rules of thumb for the characterisation of the ductility of moment-resisting joints are given in SCI (1995a)

Section 661

With reference to Figure 636 it is noted that this joint configuration ishardly (if ever) used in the UK

Section 663

It should be noted that European sections are not commonly used in the UKalthough there is growing interest in the market Steel grade S235 is not usedin the UK S355 being the current common grade Combinations of plates of15 mm thickness with M24 bolts are common This combination is assumedto provide enough rotation capacity thus satisfying ductility requirementsbecause ductile failure of the plates not brittle failure of the bolts governsthe behaviour

Section 672

Standard practice in the UK does not account for this 25 rule Columnsplices are usually detailed to SCI (2011) to ensure continuity of stiffnessthrough the splice so that the member design is not invalidated

Section 84

The UK Building Regulations require that joints are designed for tyingforces in order to satisfy structural integrity requirements Guidance on thedesign values of tying forces is given in BS EN 1991-1-7 Annex A and itsUK NA (BSI 2014)

Section 91

In the UK the ldquofabricatorsrdquo are known as ldquoSteelwork contractorsrdquo becausethey do more than just fabricate

UK FOREWORD

_____

xxvii

REFERENCES TO NATIONAL FOREWORD

BSI (2000) BS 5950-12000 ndash Structural use of steelwork in building ndash Part1 Code of Practice for Design rolled and welded sections British StandardsInstitution United Kingdom

BSI (2007) BS EN 14399-82007 ndash High-strength structural boltingassemblies for preloading System HV Hexagon fit bolt and nut assembliesBritish Standards Institution United Kingdom

BSI (2009) BS EN 1993-1-122007 ndash Eurocode 3 Design of steel structuresndash Part 112 Additional rules for the extension of EN 1993 up to steel gradesS 700 British Standards Institution United Kingdom

BSI (2010) BS EN 1993-1-82005 ndash Eurocode 3 Design of steel structuresndash Part 18 Design of joints British Standards Institution United Kingdom

BSI (2013) BS EN ISO 898-12013 ndash Mechanical properties of fastenersmade of carbon steel and alloy steel Bolts screws and studs with specifiedproperty classes Coarse thread and fine pitch thread British StandardsInstitution United Kingdom

BSI (2014) BS EN 1991-1-72006+A12014 ndash Eurocode 1 Actions on structuresndash Part 197 General actions British Standards Institution United Kingdom

BSI (2015) BS EN 14399-42015 ndash High-strength structural boltingassemblies for preloading System HV Hexagon bolt and nut assembliesBritish Standards Institution United Kingdom

SCI (1995a) Joints in steel construction Moment connections P207 TheSteel Construction Institute

SCI (1995b) Advisory Desk Notes Bending Moment in a pin AD 172 TheSteel Construction Institute

SCI (2006) Column base stiffness for global analysis NCCI-SN045a TheSteel Construction Institute

SCI (2011) Joints in steel construction Simple joints to Eurocode 3 P358The Steel Construction Institute

SCI (2013a) Joints in steel construction Moment-resisting joints toEurocode 3 P398 The Steel Construction Institute

UK FOREWORD

_____

xxviii

SCI (2013b) Interim Report Design of Portal Frames to Eurocode 3 Anoverview for UK designers P400 The Steel Construction Institute

FOREWORD

_____

xiii

FOREWORD

With the ECCS book ldquoJoints in Steel and Composite Structuresrdquo the authorssucceeded in placing the joints on the rightful place they deserve in thestructural behaviour of steel and composite steel-concrete structures Themany times used word ldquodetailsrdquo for the joints in structures by farunderestimates the importance of joints in the structural behaviour ofbuildings and civil engineering structures In their chapter ldquoAim of the bookrdquothe authors clearly explain how the design and safety verification ofstructures runs in an integral manner where all structural componentsincluding the joints play balanced roles leading to economic structures

This book can be seen as a background document for Eurocode 3 ldquoDesign ofSteel Structuresrdquo as far as it concerns structural joints The central theme indescribing the behaviour of joints is using the component method and this isleading all over in this book The book contain many aspects such as designfabrication erection and costs

In this book attention is paid on joint modelling and idealisation jointclassification for strength and stiffness and deformation capacity This all forconnections with mechanical fasteners and for welded connections for simplejoints and moment resistant joints Also lattice girder joints are described

The book provides the designer with design strategies to arrive at economicstructures

The authors based themselves on many bibliographic references covering atime span of about 65 years Many of these references present research of theauthors themselves and of the other members of the ECCS-TechnicalCommittee TC10 ldquoStructural Connectionsrdquo

It was really a privilege to have been the chairperson of this committee from1998 till the end of 2012 and I thank the authors Prof Dr Ir Jean-PierreJaspart and Dr-Ing Klaus Weynand for their large effort in writing this book

Prof ir Frans Bijlaard

PREFACE

_____

xv

PREFACE

Steel constructions and composite steel-concrete constructions are generallyerected on site by the assembly of prefabricated structural parts prepared inthe workshop These parts may themselves be the result of an assembly ofindividual elements An example is the assembly by bolting on site offabricated sections welded in the workshop

In these construction types joints and connections play a key role andrecommendations and guidelines are required for engineers and constructorsfaced with the conception and design the fabrication and the erection of suchstructures In the Structural Eurocodes these aspects are mainly covered in theexecution standard EN 1090-2 and in the design standard EN 1993-1-8(Eurocode 3 Design of steel structures Part 1-8 Design of Joints)

In the present book which is part of the series of ECCS Eurocode DesignManuals the main focus is given to design aspects but references are alsomade to EN 1090-2 when necessary

In comparison to other fields the design procedures for joints andconnections have significantly evolved in the last decades as a result of theprogressive awareness by practitioners of the significant contribution ofjoints and connections to the global cost of structures Design for lowfabrication and erection costs as well as high resistance is therefore thetargeted objective of modern design codes the achievement of which hasjustified the development of new calculation approaches now integrated intothe two afore-mentioned Eurocodes This situation justifies the writing of thepresent manual with the main goal to demystify the process by explainingthe new concepts for the design of joints and to integrate their mechanicalresponse into the structural frame analysis and design process by providingldquokeysrdquo for a proper application in practice and finally by providing welldocumented worked examples

To refer to ldquomodernrdquo or ldquonewrdquo design approaches and philosophies does notmean that traditional ways are out dated or no more valid It should beunderstood that the design methods recommended in the Eurocodes are a

PREFACE

_____

xvi

collection of European practices including the results of intensive researchefforts carried out in the last decades and so give many options andalternatives to engineers who are trying to develop safe and economicsolutions

Chapter 1 introduces generalities about joint properties aspects of materialsfabrication erection and costs design approach - and especially the so-calledcomponent method - and design tools available to practitioners for easiercode application The integration of the response of the joints into thestructural analysis and design process is addressed in chapter 2 In chapter 3attention is paid to the design of common connections with mechanicalfasteners Preloaded bolts and non-preloaded bolts are mainly considered butthe use of some less classical connectors is also briefly described Weldedconnections are covered in chapter 5

The next three chapters relate to three specific types of joints respectivelysimple joints moment resisting joints and lattice girder joints For thesesubstantial innovations are brought in the Eurocodes in comparison totraditional national codes particularly for simple and moment resistingjoints A significant number of pages is therefore devoted to these topics inthis manual

The design of joints under static loading as it is addressed in the seven firstchapters is essential in all cases but further checks or different conceptualdesign of the joints are often required in case of load reversal fireearthquake or even exceptional events like impact or explosion Chapter 8summarises present knowledge in this field

Traditionally joints were designed as rigid or pinned which enables the designof the frame and the design of the joints to be treated independently The cleareconomical advantage associated in many situations with the use of semi-rigidandor partial-strength joints leads however to ldquostructure-jointsrdquo interactionsthat have to be mastered by the engineer so as to fully profit from the potentialcost savings The Eurocodes do not cover this interaction From this point ofview chapter 9 may be considered as ldquoa premiegravererdquo even if the content hasalready been partly described years ago in an ECSC publication

Before letting the reader discover the contents of this book we would like toexpress acknowledgment We are very grateful to Prof Frans Bijlaard for all

PREFACE

_____

xvii

the comments suggestions and corrections he made through the reviewprocess of the present manual Warm thanks are also addressed to Joseacute Fuchsand Soumlnke Muumlller who helped us in preparing the drawings Last but notleast we would like to thank our wives for their patience when we workedldquoon our projectrdquo during innumerable evenings and weekends

Jean-Pierre JaspartKlaus Weynand

UK FOREWORD

_____

xix

UK FOREWORD

INTRODUCTION

This book is the second in a series of joint publications of the EuropeanConvention for Constructional Steelwork (ECCS) and The Steel ConstructionInstitute (SCI) It will help provide UK engineers and designers with a betterunderstanding of the design principles in the European Code of Practice for theDesign of Steel Structures (EN 1993 ndash Eurocode 3) and the individual Part 18(EN 1993-1-8) for the design of steel joints in particular Reference will alsobe made to the associated Eurocodes for concrete (EN 1992 ndash Eurocode 2) andearthquake engineering (EN 1998 ndash Eurocode 8) The book complements otherSCI design guides eg SCI (2011 and 2013a)

The current publication is a first UK edition based on the first edition of theECCS manual for the Design of Joints in Steel and Composite Structureswhich was published in 2016 The scope of this UK edition is narrower thanthe original publication in two specific areas that are felt to be of limitedinterest to current practice in the UK there is no content covering compositejoints and chapter 9 (covering frame design strategies) has been shortened tosimply give an overview of strategies In this edition the reader will findinformation that is either of a general nature or relevant to specific sectionsof the publication to facilitate its application in a UK context

The content includes useful background to the code rules and a reminder ofsome engineering principles Information is presented in the context of theEurocodes terminology and notation and with reference to clause numbersetc to help the readerrsquos familiarity with EN 1993-1-8 The document thatserves as the basis for content and numbering of clauses is the UKimplementation of EN 1993-1-82005 incorporating corrigenda December2005 and July 2009 At the time of writing (Autumn 2016) part 1-8 ofEN 1993 is being revised with publication anticipated after 2020

Finally it is noted and should be accepted that there will inevitably be somedifferences of interpretation between the ECCS recommendations and thosepreviously published by the SCI

UK FOREWORD

_____

xx

GENERAL COMMENTS

Design of joints (connections) in steel structures in the UK is covered byBS EN 1993-1-8 and its national Annex (NA) (BSI 2010) BS EN 1993-1-8has clear definitions for connections and joints The term joint refers to thezone where members are interconnected and a connection is the locationwhere elements meet The distinction in terminology is usually emphasised inContinental Europe but traditional practice in the UK is to use the generic termconnection

The following partial safety factors are defined in the UK NA

Partial factor Value Comment

γM2 125 Used for the resistance of bolts pins and welds

γM2 125Used for the resistance of plates in bearing(γM2=15 should be used if deformation control is important)

γM3 125 Used for slip resistance at Ultimate Limit States

γM3serv 110 Used for slip resistance at Serviceability Limit States (SLS)

γM4 100 Used for the resistance of injection bolts

γM5 100 Used for the resistance of joints in hollow section lattice girders

γM6serv 100 Used for the resistance of pins at SLS

γM7

110Used for the preload of high strength steel bolts conforming toBS EN 14399-4 and BS EN 14399-8 (BSI 2015 and 2007)

100 Used for the preload of (other) high strength steel bolts

Specific reference to the UK Building Regulations is also made in this UKedition The UK Building Regulations code has structural integrityrequirements in order to avoid disproportionate collapse and ensure robustnessof the complete structure Disproportionate collapse can be defined as a regionof structural collapse out of proportion to the initiating cause of failure Themost relevant to connectionjoint design is that the detailing for every beam

UK FOREWORD

_____

xxi

member must be adequate to resist a minimum horizontal force at ultimatefailure (or tying resistance) Guidance on the design values of tying forces canbe found in BS EN 1991-1-7 Annex A and its UK annex (BSI 2014)

SECTION SPECIFIC COMMENTS

Section 111

UK practice normally considers only two main forms of joint modellingsimple and continuous Ideally frames designed on the basis of simple jointmodelling should use joints between members that possess negligiblerotational stiffness and transmit the beam reactions in shear into thecolumns without developing significant moments These joints may betreated as perfect pins Members can then be designed in isolation either as(predominantly) axially loaded columns or as simply supported beamsJoints designed within the principles of continuous modelling are capable oftransmitting significant moments and are able to maintain the original anglebetween adjacent members virtually unchanged This form of construction ofsteel frames is particularly advantageous when beam deflections are criticalor if bracing systems are not possible

To comply with one or the other design assumption steelwork connectionsare detailed as simple or moment-resisting joints Because joints in framestructures are often treated by adopting a degree of standardisation thedesigner usually details the connections in accordance with the principlesin the series of SCI Green Books which present this material in the formof step-by-step design procedures and tables covering standardarrangements

Other approximate analysis methods continue to be used among Britishdesigners the most representative being the wind-moment method for thedesign of unbraced multi-storey steel frames The method assumes that(i) under gravity loads the beam-to-column joints act as pinnedconnections and (ii) under horizontal wind loads these joints are rigidalthough it lacks transparency This method can be seen as a manifestationof the semi-continuous principles Wind moment connection details can befound in SCI (1995a) With the now widespread use of software in designoffices for rigorous second-order analysis it is doubtful if the use of the

UK FOREWORD

_____

xxii

wind-moment method should be advocated any longer other than forinitial sizing

Section 13

Although S460 is attracting growing interest S355 is still the dominantgrade of steel used in the UK

Section 161

With reference to Figure 120 it is noted that (site) welded joints and angleflange cleats are rarely if ever used in the UK

Section 162

Hybrid connections are rarely used in the UK for the reasons noted

Section 172

There is not much use of CoPcopy in the UK There are a number of othersoftware tools on the market some more comprehensive than others

Section 22

Although in UK design practice most aspects related to joint modelling havedeveloped to a high degree of sophistication proper consideration of thestructural interaction between the joints and members is rarely fully takeninto account It is indeed very difficult to predict and model the complexbehaviour of a joint (strength stiffness and rotation capacity) TraditionalUK practice is to predict joint behaviour on the basis of past experience

BSI (2010) separates the modelling of the rotational behaviour of theconnection elements (that is the bolts the welds the plates etc) and thatof the column web panel in shear to characterise the overall jointbehaviour As a simplification the two sources of joint deformation arecombined by means of the so-called transformation parameter β Thiscoefficient is related to the web panel internal actions and can be calculatedfrom the moments at each side of the web panel The β parameter iscurrently only defined for same-depth beams which meet at the same levelIn many practical double-sided joints beams will not be of the same depthor at the same height BS EN 1993-1-8 is silent on such joints

UK FOREWORD

_____

xxiii

Section 23

As explained above typical UK design practice does not consider thissophisticated procedure for idealisation of joints

Section 24

The NA to BS EN 1993-1-8 gives practical guidance to classify joints Italso states the following

ldquoUntil experience is gained with the numerical method of calculatingrotational stiffness given in BS EN 1993-1-82005 63 and theclassification by stiffness method given in BS EN 1993-1-82005522 semi-continuous elastic design should only be used where eitherit is supported by test evidence according to BS EN 1993-1-820055221(2) or where it is based on satisfactorily performance in asimilar situationrdquo

Evidence on values of column base stiffness for practical global analysis isgiven in SCI (2006)

Section 25

The concept of ductility classes is not widely applied in the UK It isgenerally assumed that standard connection details to the SCI Green Booksprovide enough rotation capacity and so behave in a ductile manner asevidenced by physical testing and experience

Section 31

The NA to BS EN 1993-1-8 excludes bolts of classes 58 and 68 It alsostates that bolt class 48 may only be used if the manufacturing process (i) isin accordance with BS EN ISO 898-1 (BSI 2013) and (ii) includes suitableprocedures to avoid hydrogen embrittlement

Section 322

The NA to BS EN 1993-1-8 states that if the preload is not explicitly used inthe design calculations then no specific level of preload is required

Section 347

Injection bolts are rarely used in the UK

UK FOREWORD

_____

xxiv

Section 348

Reference is made to SCI (1995b) to calculate the bending moments in thepin of a pin bearing

Section 349

Flow drill blind bolting is not common practice in the UK SHS blind boltingis a common system but there are several manufactures other than thatsuggested in the book

Section 3410

Nails are rarely used in the UK

Section 352

T-stub configurations with four bolts in a row are rarely used in the UK

Section 353

Reference is made to the SCI method for the design of gusset plates seeSCI (2011)

Section 421

It is anticipated that specific rules given in the current BS EN 1993-1-12(BSI 2009) for high strength steels will be incorporated in the revisedBS EN 1993-1-8 to appear after 2020

Section 522

ldquoHeader platesrdquo are known as ldquopartial depth end platesrdquo in the UK Webcleat connections are no longer commonly used in the UK The full depthend plate connection shown on the left of Figure 59 is classified as a simplejoint in the UK (SCI 2011)

Section 523

The UK Building Regulations require that joints are designed for tyingforces in order to satisfy structural integrity requirements Guidance onthe design values of tying forces is given in BS EN 1991-1-7 Annex Aand its UK NA The requirements relate to the building class with a

UK FOREWORD

_____

xxv

design value of horizontal force generally not less than 75 kN andusually significantly higher Simple joints detailed to SCI (2011) satisfythese requirements

Section 525

It is generally safe to assume that the ductility (rotation requirements) aresatisfied provided that joints are detailed in accordance with SCI (2011)

Section 531

The column base detailing on the left of Figure 521 is not commonly used inthe UK We never recommend less than four bolts ndash they are needed toassure stability and facilitate location during erection The anchoringsystems shown in Figure 522 are not usually adopted in the UK Referenceis made to SCI (2013a) for common anchor systems

Section 62

Publication SCI (2013b) summarises the principal differences betweenBS 5950 and BS EN 1993-1-8 (BSI 2000 and 2010) in terms ofcomponent characterisation

With reference to Figure 66 it is anticipated that the revised BS EN1993-1-8will include analytical expressions for the definition of the so-called αcoefficient

Rules of thumb for the characterisation of the ductility of some individualcomponents are given in SCI (1995a)

Section 631

The UK NA to BS EN 1993-1-8 gives specific rules for the full plasticdistribution of effective design tension resistance The procedure is alsosummarised in SCI (2013a)

Section 633

Where a joint is subjected to combined bending moments and axial forcesthe concept of an applied moment modified by axial load can be used seeSCI (1995a)

UK FOREWORD

_____

xxvi

Section 64

Rotational stiffness is not normally evaluated in UK design practice whichusually relies on past experience

Section 65

Some rules of thumb for the characterisation of the ductility of moment-resisting joints are given in SCI (1995a)

Section 661

With reference to Figure 636 it is noted that this joint configuration ishardly (if ever) used in the UK

Section 663

It should be noted that European sections are not commonly used in the UKalthough there is growing interest in the market Steel grade S235 is not usedin the UK S355 being the current common grade Combinations of plates of15 mm thickness with M24 bolts are common This combination is assumedto provide enough rotation capacity thus satisfying ductility requirementsbecause ductile failure of the plates not brittle failure of the bolts governsthe behaviour

Section 672

Standard practice in the UK does not account for this 25 rule Columnsplices are usually detailed to SCI (2011) to ensure continuity of stiffnessthrough the splice so that the member design is not invalidated

Section 84

The UK Building Regulations require that joints are designed for tyingforces in order to satisfy structural integrity requirements Guidance on thedesign values of tying forces is given in BS EN 1991-1-7 Annex A and itsUK NA (BSI 2014)

Section 91

In the UK the ldquofabricatorsrdquo are known as ldquoSteelwork contractorsrdquo becausethey do more than just fabricate

UK FOREWORD

_____

xxvii

REFERENCES TO NATIONAL FOREWORD

BSI (2000) BS 5950-12000 ndash Structural use of steelwork in building ndash Part1 Code of Practice for Design rolled and welded sections British StandardsInstitution United Kingdom

BSI (2007) BS EN 14399-82007 ndash High-strength structural boltingassemblies for preloading System HV Hexagon fit bolt and nut assembliesBritish Standards Institution United Kingdom

BSI (2009) BS EN 1993-1-122007 ndash Eurocode 3 Design of steel structuresndash Part 112 Additional rules for the extension of EN 1993 up to steel gradesS 700 British Standards Institution United Kingdom

BSI (2010) BS EN 1993-1-82005 ndash Eurocode 3 Design of steel structuresndash Part 18 Design of joints British Standards Institution United Kingdom

BSI (2013) BS EN ISO 898-12013 ndash Mechanical properties of fastenersmade of carbon steel and alloy steel Bolts screws and studs with specifiedproperty classes Coarse thread and fine pitch thread British StandardsInstitution United Kingdom

BSI (2014) BS EN 1991-1-72006+A12014 ndash Eurocode 1 Actions on structuresndash Part 197 General actions British Standards Institution United Kingdom

BSI (2015) BS EN 14399-42015 ndash High-strength structural boltingassemblies for preloading System HV Hexagon bolt and nut assembliesBritish Standards Institution United Kingdom

SCI (1995a) Joints in steel construction Moment connections P207 TheSteel Construction Institute

SCI (1995b) Advisory Desk Notes Bending Moment in a pin AD 172 TheSteel Construction Institute

SCI (2006) Column base stiffness for global analysis NCCI-SN045a TheSteel Construction Institute

SCI (2011) Joints in steel construction Simple joints to Eurocode 3 P358The Steel Construction Institute

SCI (2013a) Joints in steel construction Moment-resisting joints toEurocode 3 P398 The Steel Construction Institute

UK FOREWORD

_____

xxviii

SCI (2013b) Interim Report Design of Portal Frames to Eurocode 3 Anoverview for UK designers P400 The Steel Construction Institute

PREFACE

_____

xv

PREFACE

Steel constructions and composite steel-concrete constructions are generallyerected on site by the assembly of prefabricated structural parts prepared inthe workshop These parts may themselves be the result of an assembly ofindividual elements An example is the assembly by bolting on site offabricated sections welded in the workshop

In these construction types joints and connections play a key role andrecommendations and guidelines are required for engineers and constructorsfaced with the conception and design the fabrication and the erection of suchstructures In the Structural Eurocodes these aspects are mainly covered in theexecution standard EN 1090-2 and in the design standard EN 1993-1-8(Eurocode 3 Design of steel structures Part 1-8 Design of Joints)

In the present book which is part of the series of ECCS Eurocode DesignManuals the main focus is given to design aspects but references are alsomade to EN 1090-2 when necessary

In comparison to other fields the design procedures for joints andconnections have significantly evolved in the last decades as a result of theprogressive awareness by practitioners of the significant contribution ofjoints and connections to the global cost of structures Design for lowfabrication and erection costs as well as high resistance is therefore thetargeted objective of modern design codes the achievement of which hasjustified the development of new calculation approaches now integrated intothe two afore-mentioned Eurocodes This situation justifies the writing of thepresent manual with the main goal to demystify the process by explainingthe new concepts for the design of joints and to integrate their mechanicalresponse into the structural frame analysis and design process by providingldquokeysrdquo for a proper application in practice and finally by providing welldocumented worked examples

To refer to ldquomodernrdquo or ldquonewrdquo design approaches and philosophies does notmean that traditional ways are out dated or no more valid It should beunderstood that the design methods recommended in the Eurocodes are a

PREFACE

_____

xvi

collection of European practices including the results of intensive researchefforts carried out in the last decades and so give many options andalternatives to engineers who are trying to develop safe and economicsolutions

Chapter 1 introduces generalities about joint properties aspects of materialsfabrication erection and costs design approach - and especially the so-calledcomponent method - and design tools available to practitioners for easiercode application The integration of the response of the joints into thestructural analysis and design process is addressed in chapter 2 In chapter 3attention is paid to the design of common connections with mechanicalfasteners Preloaded bolts and non-preloaded bolts are mainly considered butthe use of some less classical connectors is also briefly described Weldedconnections are covered in chapter 5

The next three chapters relate to three specific types of joints respectivelysimple joints moment resisting joints and lattice girder joints For thesesubstantial innovations are brought in the Eurocodes in comparison totraditional national codes particularly for simple and moment resistingjoints A significant number of pages is therefore devoted to these topics inthis manual

The design of joints under static loading as it is addressed in the seven firstchapters is essential in all cases but further checks or different conceptualdesign of the joints are often required in case of load reversal fireearthquake or even exceptional events like impact or explosion Chapter 8summarises present knowledge in this field

Traditionally joints were designed as rigid or pinned which enables the designof the frame and the design of the joints to be treated independently The cleareconomical advantage associated in many situations with the use of semi-rigidandor partial-strength joints leads however to ldquostructure-jointsrdquo interactionsthat have to be mastered by the engineer so as to fully profit from the potentialcost savings The Eurocodes do not cover this interaction From this point ofview chapter 9 may be considered as ldquoa premiegravererdquo even if the content hasalready been partly described years ago in an ECSC publication

Before letting the reader discover the contents of this book we would like toexpress acknowledgment We are very grateful to Prof Frans Bijlaard for all

PREFACE

_____

xvii

the comments suggestions and corrections he made through the reviewprocess of the present manual Warm thanks are also addressed to Joseacute Fuchsand Soumlnke Muumlller who helped us in preparing the drawings Last but notleast we would like to thank our wives for their patience when we workedldquoon our projectrdquo during innumerable evenings and weekends

Jean-Pierre JaspartKlaus Weynand

UK FOREWORD

_____

xix

UK FOREWORD

INTRODUCTION

This book is the second in a series of joint publications of the EuropeanConvention for Constructional Steelwork (ECCS) and The Steel ConstructionInstitute (SCI) It will help provide UK engineers and designers with a betterunderstanding of the design principles in the European Code of Practice for theDesign of Steel Structures (EN 1993 ndash Eurocode 3) and the individual Part 18(EN 1993-1-8) for the design of steel joints in particular Reference will alsobe made to the associated Eurocodes for concrete (EN 1992 ndash Eurocode 2) andearthquake engineering (EN 1998 ndash Eurocode 8) The book complements otherSCI design guides eg SCI (2011 and 2013a)

The current publication is a first UK edition based on the first edition of theECCS manual for the Design of Joints in Steel and Composite Structureswhich was published in 2016 The scope of this UK edition is narrower thanthe original publication in two specific areas that are felt to be of limitedinterest to current practice in the UK there is no content covering compositejoints and chapter 9 (covering frame design strategies) has been shortened tosimply give an overview of strategies In this edition the reader will findinformation that is either of a general nature or relevant to specific sectionsof the publication to facilitate its application in a UK context

The content includes useful background to the code rules and a reminder ofsome engineering principles Information is presented in the context of theEurocodes terminology and notation and with reference to clause numbersetc to help the readerrsquos familiarity with EN 1993-1-8 The document thatserves as the basis for content and numbering of clauses is the UKimplementation of EN 1993-1-82005 incorporating corrigenda December2005 and July 2009 At the time of writing (Autumn 2016) part 1-8 ofEN 1993 is being revised with publication anticipated after 2020

Finally it is noted and should be accepted that there will inevitably be somedifferences of interpretation between the ECCS recommendations and thosepreviously published by the SCI

UK FOREWORD

_____

xx

GENERAL COMMENTS

Design of joints (connections) in steel structures in the UK is covered byBS EN 1993-1-8 and its national Annex (NA) (BSI 2010) BS EN 1993-1-8has clear definitions for connections and joints The term joint refers to thezone where members are interconnected and a connection is the locationwhere elements meet The distinction in terminology is usually emphasised inContinental Europe but traditional practice in the UK is to use the generic termconnection

The following partial safety factors are defined in the UK NA

Partial factor Value Comment

γM2 125 Used for the resistance of bolts pins and welds

γM2 125Used for the resistance of plates in bearing(γM2=15 should be used if deformation control is important)

γM3 125 Used for slip resistance at Ultimate Limit States

γM3serv 110 Used for slip resistance at Serviceability Limit States (SLS)

γM4 100 Used for the resistance of injection bolts

γM5 100 Used for the resistance of joints in hollow section lattice girders

γM6serv 100 Used for the resistance of pins at SLS

γM7

110Used for the preload of high strength steel bolts conforming toBS EN 14399-4 and BS EN 14399-8 (BSI 2015 and 2007)

100 Used for the preload of (other) high strength steel bolts

Specific reference to the UK Building Regulations is also made in this UKedition The UK Building Regulations code has structural integrityrequirements in order to avoid disproportionate collapse and ensure robustnessof the complete structure Disproportionate collapse can be defined as a regionof structural collapse out of proportion to the initiating cause of failure Themost relevant to connectionjoint design is that the detailing for every beam

UK FOREWORD

_____

xxi

member must be adequate to resist a minimum horizontal force at ultimatefailure (or tying resistance) Guidance on the design values of tying forces canbe found in BS EN 1991-1-7 Annex A and its UK annex (BSI 2014)

SECTION SPECIFIC COMMENTS

Section 111

UK practice normally considers only two main forms of joint modellingsimple and continuous Ideally frames designed on the basis of simple jointmodelling should use joints between members that possess negligiblerotational stiffness and transmit the beam reactions in shear into thecolumns without developing significant moments These joints may betreated as perfect pins Members can then be designed in isolation either as(predominantly) axially loaded columns or as simply supported beamsJoints designed within the principles of continuous modelling are capable oftransmitting significant moments and are able to maintain the original anglebetween adjacent members virtually unchanged This form of construction ofsteel frames is particularly advantageous when beam deflections are criticalor if bracing systems are not possible

To comply with one or the other design assumption steelwork connectionsare detailed as simple or moment-resisting joints Because joints in framestructures are often treated by adopting a degree of standardisation thedesigner usually details the connections in accordance with the principlesin the series of SCI Green Books which present this material in the formof step-by-step design procedures and tables covering standardarrangements

Other approximate analysis methods continue to be used among Britishdesigners the most representative being the wind-moment method for thedesign of unbraced multi-storey steel frames The method assumes that(i) under gravity loads the beam-to-column joints act as pinnedconnections and (ii) under horizontal wind loads these joints are rigidalthough it lacks transparency This method can be seen as a manifestationof the semi-continuous principles Wind moment connection details can befound in SCI (1995a) With the now widespread use of software in designoffices for rigorous second-order analysis it is doubtful if the use of the

UK FOREWORD

_____

xxii

wind-moment method should be advocated any longer other than forinitial sizing

Section 13

Although S460 is attracting growing interest S355 is still the dominantgrade of steel used in the UK

Section 161

With reference to Figure 120 it is noted that (site) welded joints and angleflange cleats are rarely if ever used in the UK

Section 162

Hybrid connections are rarely used in the UK for the reasons noted

Section 172

There is not much use of CoPcopy in the UK There are a number of othersoftware tools on the market some more comprehensive than others

Section 22

Although in UK design practice most aspects related to joint modelling havedeveloped to a high degree of sophistication proper consideration of thestructural interaction between the joints and members is rarely fully takeninto account It is indeed very difficult to predict and model the complexbehaviour of a joint (strength stiffness and rotation capacity) TraditionalUK practice is to predict joint behaviour on the basis of past experience

BSI (2010) separates the modelling of the rotational behaviour of theconnection elements (that is the bolts the welds the plates etc) and thatof the column web panel in shear to characterise the overall jointbehaviour As a simplification the two sources of joint deformation arecombined by means of the so-called transformation parameter β Thiscoefficient is related to the web panel internal actions and can be calculatedfrom the moments at each side of the web panel The β parameter iscurrently only defined for same-depth beams which meet at the same levelIn many practical double-sided joints beams will not be of the same depthor at the same height BS EN 1993-1-8 is silent on such joints

UK FOREWORD

_____

xxiii

Section 23

As explained above typical UK design practice does not consider thissophisticated procedure for idealisation of joints

Section 24

The NA to BS EN 1993-1-8 gives practical guidance to classify joints Italso states the following

ldquoUntil experience is gained with the numerical method of calculatingrotational stiffness given in BS EN 1993-1-82005 63 and theclassification by stiffness method given in BS EN 1993-1-82005522 semi-continuous elastic design should only be used where eitherit is supported by test evidence according to BS EN 1993-1-820055221(2) or where it is based on satisfactorily performance in asimilar situationrdquo

Evidence on values of column base stiffness for practical global analysis isgiven in SCI (2006)

Section 25

The concept of ductility classes is not widely applied in the UK It isgenerally assumed that standard connection details to the SCI Green Booksprovide enough rotation capacity and so behave in a ductile manner asevidenced by physical testing and experience

Section 31

The NA to BS EN 1993-1-8 excludes bolts of classes 58 and 68 It alsostates that bolt class 48 may only be used if the manufacturing process (i) isin accordance with BS EN ISO 898-1 (BSI 2013) and (ii) includes suitableprocedures to avoid hydrogen embrittlement

Section 322

The NA to BS EN 1993-1-8 states that if the preload is not explicitly used inthe design calculations then no specific level of preload is required

Section 347

Injection bolts are rarely used in the UK

UK FOREWORD

_____

xxiv

Section 348

Reference is made to SCI (1995b) to calculate the bending moments in thepin of a pin bearing

Section 349

Flow drill blind bolting is not common practice in the UK SHS blind boltingis a common system but there are several manufactures other than thatsuggested in the book

Section 3410

Nails are rarely used in the UK

Section 352

T-stub configurations with four bolts in a row are rarely used in the UK

Section 353

Reference is made to the SCI method for the design of gusset plates seeSCI (2011)

Section 421

It is anticipated that specific rules given in the current BS EN 1993-1-12(BSI 2009) for high strength steels will be incorporated in the revisedBS EN 1993-1-8 to appear after 2020

Section 522

ldquoHeader platesrdquo are known as ldquopartial depth end platesrdquo in the UK Webcleat connections are no longer commonly used in the UK The full depthend plate connection shown on the left of Figure 59 is classified as a simplejoint in the UK (SCI 2011)

Section 523

The UK Building Regulations require that joints are designed for tyingforces in order to satisfy structural integrity requirements Guidance onthe design values of tying forces is given in BS EN 1991-1-7 Annex Aand its UK NA The requirements relate to the building class with a

UK FOREWORD

_____

xxv

design value of horizontal force generally not less than 75 kN andusually significantly higher Simple joints detailed to SCI (2011) satisfythese requirements

Section 525

It is generally safe to assume that the ductility (rotation requirements) aresatisfied provided that joints are detailed in accordance with SCI (2011)

Section 531

The column base detailing on the left of Figure 521 is not commonly used inthe UK We never recommend less than four bolts ndash they are needed toassure stability and facilitate location during erection The anchoringsystems shown in Figure 522 are not usually adopted in the UK Referenceis made to SCI (2013a) for common anchor systems

Section 62

Publication SCI (2013b) summarises the principal differences betweenBS 5950 and BS EN 1993-1-8 (BSI 2000 and 2010) in terms ofcomponent characterisation

With reference to Figure 66 it is anticipated that the revised BS EN1993-1-8will include analytical expressions for the definition of the so-called αcoefficient

Rules of thumb for the characterisation of the ductility of some individualcomponents are given in SCI (1995a)

Section 631

The UK NA to BS EN 1993-1-8 gives specific rules for the full plasticdistribution of effective design tension resistance The procedure is alsosummarised in SCI (2013a)

Section 633

Where a joint is subjected to combined bending moments and axial forcesthe concept of an applied moment modified by axial load can be used seeSCI (1995a)

UK FOREWORD

_____

xxvi

Section 64

Rotational stiffness is not normally evaluated in UK design practice whichusually relies on past experience

Section 65

Some rules of thumb for the characterisation of the ductility of moment-resisting joints are given in SCI (1995a)

Section 661

With reference to Figure 636 it is noted that this joint configuration ishardly (if ever) used in the UK

Section 663

It should be noted that European sections are not commonly used in the UKalthough there is growing interest in the market Steel grade S235 is not usedin the UK S355 being the current common grade Combinations of plates of15 mm thickness with M24 bolts are common This combination is assumedto provide enough rotation capacity thus satisfying ductility requirementsbecause ductile failure of the plates not brittle failure of the bolts governsthe behaviour

Section 672

Standard practice in the UK does not account for this 25 rule Columnsplices are usually detailed to SCI (2011) to ensure continuity of stiffnessthrough the splice so that the member design is not invalidated

Section 84

The UK Building Regulations require that joints are designed for tyingforces in order to satisfy structural integrity requirements Guidance on thedesign values of tying forces is given in BS EN 1991-1-7 Annex A and itsUK NA (BSI 2014)

Section 91

In the UK the ldquofabricatorsrdquo are known as ldquoSteelwork contractorsrdquo becausethey do more than just fabricate

UK FOREWORD

_____

xxvii

REFERENCES TO NATIONAL FOREWORD

BSI (2000) BS 5950-12000 ndash Structural use of steelwork in building ndash Part1 Code of Practice for Design rolled and welded sections British StandardsInstitution United Kingdom

BSI (2007) BS EN 14399-82007 ndash High-strength structural boltingassemblies for preloading System HV Hexagon fit bolt and nut assembliesBritish Standards Institution United Kingdom

BSI (2009) BS EN 1993-1-122007 ndash Eurocode 3 Design of steel structuresndash Part 112 Additional rules for the extension of EN 1993 up to steel gradesS 700 British Standards Institution United Kingdom

BSI (2010) BS EN 1993-1-82005 ndash Eurocode 3 Design of steel structuresndash Part 18 Design of joints British Standards Institution United Kingdom

BSI (2013) BS EN ISO 898-12013 ndash Mechanical properties of fastenersmade of carbon steel and alloy steel Bolts screws and studs with specifiedproperty classes Coarse thread and fine pitch thread British StandardsInstitution United Kingdom

BSI (2014) BS EN 1991-1-72006+A12014 ndash Eurocode 1 Actions on structuresndash Part 197 General actions British Standards Institution United Kingdom

BSI (2015) BS EN 14399-42015 ndash High-strength structural boltingassemblies for preloading System HV Hexagon bolt and nut assembliesBritish Standards Institution United Kingdom

SCI (1995a) Joints in steel construction Moment connections P207 TheSteel Construction Institute

SCI (1995b) Advisory Desk Notes Bending Moment in a pin AD 172 TheSteel Construction Institute

SCI (2006) Column base stiffness for global analysis NCCI-SN045a TheSteel Construction Institute

SCI (2011) Joints in steel construction Simple joints to Eurocode 3 P358The Steel Construction Institute

SCI (2013a) Joints in steel construction Moment-resisting joints toEurocode 3 P398 The Steel Construction Institute

UK FOREWORD

_____

xxviii

SCI (2013b) Interim Report Design of Portal Frames to Eurocode 3 Anoverview for UK designers P400 The Steel Construction Institute

PREFACE

_____

xvi

collection of European practices including the results of intensive researchefforts carried out in the last decades and so give many options andalternatives to engineers who are trying to develop safe and economicsolutions

Chapter 1 introduces generalities about joint properties aspects of materialsfabrication erection and costs design approach - and especially the so-calledcomponent method - and design tools available to practitioners for easiercode application The integration of the response of the joints into thestructural analysis and design process is addressed in chapter 2 In chapter 3attention is paid to the design of common connections with mechanicalfasteners Preloaded bolts and non-preloaded bolts are mainly considered butthe use of some less classical connectors is also briefly described Weldedconnections are covered in chapter 5

The next three chapters relate to three specific types of joints respectivelysimple joints moment resisting joints and lattice girder joints For thesesubstantial innovations are brought in the Eurocodes in comparison totraditional national codes particularly for simple and moment resistingjoints A significant number of pages is therefore devoted to these topics inthis manual

The design of joints under static loading as it is addressed in the seven firstchapters is essential in all cases but further checks or different conceptualdesign of the joints are often required in case of load reversal fireearthquake or even exceptional events like impact or explosion Chapter 8summarises present knowledge in this field

Traditionally joints were designed as rigid or pinned which enables the designof the frame and the design of the joints to be treated independently The cleareconomical advantage associated in many situations with the use of semi-rigidandor partial-strength joints leads however to ldquostructure-jointsrdquo interactionsthat have to be mastered by the engineer so as to fully profit from the potentialcost savings The Eurocodes do not cover this interaction From this point ofview chapter 9 may be considered as ldquoa premiegravererdquo even if the content hasalready been partly described years ago in an ECSC publication

Before letting the reader discover the contents of this book we would like toexpress acknowledgment We are very grateful to Prof Frans Bijlaard for all

PREFACE

_____

xvii

the comments suggestions and corrections he made through the reviewprocess of the present manual Warm thanks are also addressed to Joseacute Fuchsand Soumlnke Muumlller who helped us in preparing the drawings Last but notleast we would like to thank our wives for their patience when we workedldquoon our projectrdquo during innumerable evenings and weekends

Jean-Pierre JaspartKlaus Weynand

UK FOREWORD

_____

xix

UK FOREWORD

INTRODUCTION

This book is the second in a series of joint publications of the EuropeanConvention for Constructional Steelwork (ECCS) and The Steel ConstructionInstitute (SCI) It will help provide UK engineers and designers with a betterunderstanding of the design principles in the European Code of Practice for theDesign of Steel Structures (EN 1993 ndash Eurocode 3) and the individual Part 18(EN 1993-1-8) for the design of steel joints in particular Reference will alsobe made to the associated Eurocodes for concrete (EN 1992 ndash Eurocode 2) andearthquake engineering (EN 1998 ndash Eurocode 8) The book complements otherSCI design guides eg SCI (2011 and 2013a)

The current publication is a first UK edition based on the first edition of theECCS manual for the Design of Joints in Steel and Composite Structureswhich was published in 2016 The scope of this UK edition is narrower thanthe original publication in two specific areas that are felt to be of limitedinterest to current practice in the UK there is no content covering compositejoints and chapter 9 (covering frame design strategies) has been shortened tosimply give an overview of strategies In this edition the reader will findinformation that is either of a general nature or relevant to specific sectionsof the publication to facilitate its application in a UK context

The content includes useful background to the code rules and a reminder ofsome engineering principles Information is presented in the context of theEurocodes terminology and notation and with reference to clause numbersetc to help the readerrsquos familiarity with EN 1993-1-8 The document thatserves as the basis for content and numbering of clauses is the UKimplementation of EN 1993-1-82005 incorporating corrigenda December2005 and July 2009 At the time of writing (Autumn 2016) part 1-8 ofEN 1993 is being revised with publication anticipated after 2020

Finally it is noted and should be accepted that there will inevitably be somedifferences of interpretation between the ECCS recommendations and thosepreviously published by the SCI

UK FOREWORD

_____

xx

GENERAL COMMENTS

Design of joints (connections) in steel structures in the UK is covered byBS EN 1993-1-8 and its national Annex (NA) (BSI 2010) BS EN 1993-1-8has clear definitions for connections and joints The term joint refers to thezone where members are interconnected and a connection is the locationwhere elements meet The distinction in terminology is usually emphasised inContinental Europe but traditional practice in the UK is to use the generic termconnection

The following partial safety factors are defined in the UK NA

Partial factor Value Comment

γM2 125 Used for the resistance of bolts pins and welds

γM2 125Used for the resistance of plates in bearing(γM2=15 should be used if deformation control is important)

γM3 125 Used for slip resistance at Ultimate Limit States

γM3serv 110 Used for slip resistance at Serviceability Limit States (SLS)

γM4 100 Used for the resistance of injection bolts

γM5 100 Used for the resistance of joints in hollow section lattice girders

γM6serv 100 Used for the resistance of pins at SLS

γM7

110Used for the preload of high strength steel bolts conforming toBS EN 14399-4 and BS EN 14399-8 (BSI 2015 and 2007)

100 Used for the preload of (other) high strength steel bolts

Specific reference to the UK Building Regulations is also made in this UKedition The UK Building Regulations code has structural integrityrequirements in order to avoid disproportionate collapse and ensure robustnessof the complete structure Disproportionate collapse can be defined as a regionof structural collapse out of proportion to the initiating cause of failure Themost relevant to connectionjoint design is that the detailing for every beam

UK FOREWORD

_____

xxi

member must be adequate to resist a minimum horizontal force at ultimatefailure (or tying resistance) Guidance on the design values of tying forces canbe found in BS EN 1991-1-7 Annex A and its UK annex (BSI 2014)

SECTION SPECIFIC COMMENTS

Section 111

UK practice normally considers only two main forms of joint modellingsimple and continuous Ideally frames designed on the basis of simple jointmodelling should use joints between members that possess negligiblerotational stiffness and transmit the beam reactions in shear into thecolumns without developing significant moments These joints may betreated as perfect pins Members can then be designed in isolation either as(predominantly) axially loaded columns or as simply supported beamsJoints designed within the principles of continuous modelling are capable oftransmitting significant moments and are able to maintain the original anglebetween adjacent members virtually unchanged This form of construction ofsteel frames is particularly advantageous when beam deflections are criticalor if bracing systems are not possible

To comply with one or the other design assumption steelwork connectionsare detailed as simple or moment-resisting joints Because joints in framestructures are often treated by adopting a degree of standardisation thedesigner usually details the connections in accordance with the principlesin the series of SCI Green Books which present this material in the formof step-by-step design procedures and tables covering standardarrangements

Other approximate analysis methods continue to be used among Britishdesigners the most representative being the wind-moment method for thedesign of unbraced multi-storey steel frames The method assumes that(i) under gravity loads the beam-to-column joints act as pinnedconnections and (ii) under horizontal wind loads these joints are rigidalthough it lacks transparency This method can be seen as a manifestationof the semi-continuous principles Wind moment connection details can befound in SCI (1995a) With the now widespread use of software in designoffices for rigorous second-order analysis it is doubtful if the use of the

UK FOREWORD

_____

xxii

wind-moment method should be advocated any longer other than forinitial sizing

Section 13

Although S460 is attracting growing interest S355 is still the dominantgrade of steel used in the UK

Section 161

With reference to Figure 120 it is noted that (site) welded joints and angleflange cleats are rarely if ever used in the UK

Section 162

Hybrid connections are rarely used in the UK for the reasons noted

Section 172

There is not much use of CoPcopy in the UK There are a number of othersoftware tools on the market some more comprehensive than others

Section 22

Although in UK design practice most aspects related to joint modelling havedeveloped to a high degree of sophistication proper consideration of thestructural interaction between the joints and members is rarely fully takeninto account It is indeed very difficult to predict and model the complexbehaviour of a joint (strength stiffness and rotation capacity) TraditionalUK practice is to predict joint behaviour on the basis of past experience

BSI (2010) separates the modelling of the rotational behaviour of theconnection elements (that is the bolts the welds the plates etc) and thatof the column web panel in shear to characterise the overall jointbehaviour As a simplification the two sources of joint deformation arecombined by means of the so-called transformation parameter β Thiscoefficient is related to the web panel internal actions and can be calculatedfrom the moments at each side of the web panel The β parameter iscurrently only defined for same-depth beams which meet at the same levelIn many practical double-sided joints beams will not be of the same depthor at the same height BS EN 1993-1-8 is silent on such joints

UK FOREWORD

_____

xxiii

Section 23

As explained above typical UK design practice does not consider thissophisticated procedure for idealisation of joints

Section 24

The NA to BS EN 1993-1-8 gives practical guidance to classify joints Italso states the following

ldquoUntil experience is gained with the numerical method of calculatingrotational stiffness given in BS EN 1993-1-82005 63 and theclassification by stiffness method given in BS EN 1993-1-82005522 semi-continuous elastic design should only be used where eitherit is supported by test evidence according to BS EN 1993-1-820055221(2) or where it is based on satisfactorily performance in asimilar situationrdquo

Evidence on values of column base stiffness for practical global analysis isgiven in SCI (2006)

Section 25

The concept of ductility classes is not widely applied in the UK It isgenerally assumed that standard connection details to the SCI Green Booksprovide enough rotation capacity and so behave in a ductile manner asevidenced by physical testing and experience

Section 31

The NA to BS EN 1993-1-8 excludes bolts of classes 58 and 68 It alsostates that bolt class 48 may only be used if the manufacturing process (i) isin accordance with BS EN ISO 898-1 (BSI 2013) and (ii) includes suitableprocedures to avoid hydrogen embrittlement

Section 322

The NA to BS EN 1993-1-8 states that if the preload is not explicitly used inthe design calculations then no specific level of preload is required

Section 347

Injection bolts are rarely used in the UK

UK FOREWORD

_____

xxiv

Section 348

Reference is made to SCI (1995b) to calculate the bending moments in thepin of a pin bearing

Section 349

Flow drill blind bolting is not common practice in the UK SHS blind boltingis a common system but there are several manufactures other than thatsuggested in the book

Section 3410

Nails are rarely used in the UK

Section 352

T-stub configurations with four bolts in a row are rarely used in the UK

Section 353

Reference is made to the SCI method for the design of gusset plates seeSCI (2011)

Section 421

It is anticipated that specific rules given in the current BS EN 1993-1-12(BSI 2009) for high strength steels will be incorporated in the revisedBS EN 1993-1-8 to appear after 2020

Section 522

ldquoHeader platesrdquo are known as ldquopartial depth end platesrdquo in the UK Webcleat connections are no longer commonly used in the UK The full depthend plate connection shown on the left of Figure 59 is classified as a simplejoint in the UK (SCI 2011)

Section 523

The UK Building Regulations require that joints are designed for tyingforces in order to satisfy structural integrity requirements Guidance onthe design values of tying forces is given in BS EN 1991-1-7 Annex Aand its UK NA The requirements relate to the building class with a

UK FOREWORD

_____

xxv

design value of horizontal force generally not less than 75 kN andusually significantly higher Simple joints detailed to SCI (2011) satisfythese requirements

Section 525

It is generally safe to assume that the ductility (rotation requirements) aresatisfied provided that joints are detailed in accordance with SCI (2011)

Section 531

The column base detailing on the left of Figure 521 is not commonly used inthe UK We never recommend less than four bolts ndash they are needed toassure stability and facilitate location during erection The anchoringsystems shown in Figure 522 are not usually adopted in the UK Referenceis made to SCI (2013a) for common anchor systems

Section 62

Publication SCI (2013b) summarises the principal differences betweenBS 5950 and BS EN 1993-1-8 (BSI 2000 and 2010) in terms ofcomponent characterisation

With reference to Figure 66 it is anticipated that the revised BS EN1993-1-8will include analytical expressions for the definition of the so-called αcoefficient

Rules of thumb for the characterisation of the ductility of some individualcomponents are given in SCI (1995a)

Section 631

The UK NA to BS EN 1993-1-8 gives specific rules for the full plasticdistribution of effective design tension resistance The procedure is alsosummarised in SCI (2013a)

Section 633

Where a joint is subjected to combined bending moments and axial forcesthe concept of an applied moment modified by axial load can be used seeSCI (1995a)

UK FOREWORD

_____

xxvi

Section 64

Rotational stiffness is not normally evaluated in UK design practice whichusually relies on past experience

Section 65

Some rules of thumb for the characterisation of the ductility of moment-resisting joints are given in SCI (1995a)

Section 661

With reference to Figure 636 it is noted that this joint configuration ishardly (if ever) used in the UK

Section 663

It should be noted that European sections are not commonly used in the UKalthough there is growing interest in the market Steel grade S235 is not usedin the UK S355 being the current common grade Combinations of plates of15 mm thickness with M24 bolts are common This combination is assumedto provide enough rotation capacity thus satisfying ductility requirementsbecause ductile failure of the plates not brittle failure of the bolts governsthe behaviour

Section 672

Standard practice in the UK does not account for this 25 rule Columnsplices are usually detailed to SCI (2011) to ensure continuity of stiffnessthrough the splice so that the member design is not invalidated

Section 84

The UK Building Regulations require that joints are designed for tyingforces in order to satisfy structural integrity requirements Guidance on thedesign values of tying forces is given in BS EN 1991-1-7 Annex A and itsUK NA (BSI 2014)

Section 91

In the UK the ldquofabricatorsrdquo are known as ldquoSteelwork contractorsrdquo becausethey do more than just fabricate

UK FOREWORD

_____

xxvii

REFERENCES TO NATIONAL FOREWORD

BSI (2000) BS 5950-12000 ndash Structural use of steelwork in building ndash Part1 Code of Practice for Design rolled and welded sections British StandardsInstitution United Kingdom

BSI (2007) BS EN 14399-82007 ndash High-strength structural boltingassemblies for preloading System HV Hexagon fit bolt and nut assembliesBritish Standards Institution United Kingdom

BSI (2009) BS EN 1993-1-122007 ndash Eurocode 3 Design of steel structuresndash Part 112 Additional rules for the extension of EN 1993 up to steel gradesS 700 British Standards Institution United Kingdom

BSI (2010) BS EN 1993-1-82005 ndash Eurocode 3 Design of steel structuresndash Part 18 Design of joints British Standards Institution United Kingdom

BSI (2013) BS EN ISO 898-12013 ndash Mechanical properties of fastenersmade of carbon steel and alloy steel Bolts screws and studs with specifiedproperty classes Coarse thread and fine pitch thread British StandardsInstitution United Kingdom

BSI (2014) BS EN 1991-1-72006+A12014 ndash Eurocode 1 Actions on structuresndash Part 197 General actions British Standards Institution United Kingdom

BSI (2015) BS EN 14399-42015 ndash High-strength structural boltingassemblies for preloading System HV Hexagon bolt and nut assembliesBritish Standards Institution United Kingdom

SCI (1995a) Joints in steel construction Moment connections P207 TheSteel Construction Institute

SCI (1995b) Advisory Desk Notes Bending Moment in a pin AD 172 TheSteel Construction Institute

SCI (2006) Column base stiffness for global analysis NCCI-SN045a TheSteel Construction Institute

SCI (2011) Joints in steel construction Simple joints to Eurocode 3 P358The Steel Construction Institute

SCI (2013a) Joints in steel construction Moment-resisting joints toEurocode 3 P398 The Steel Construction Institute

UK FOREWORD

_____

xxviii

SCI (2013b) Interim Report Design of Portal Frames to Eurocode 3 Anoverview for UK designers P400 The Steel Construction Institute

PREFACE

_____

xvii

the comments suggestions and corrections he made through the reviewprocess of the present manual Warm thanks are also addressed to Joseacute Fuchsand Soumlnke Muumlller who helped us in preparing the drawings Last but notleast we would like to thank our wives for their patience when we workedldquoon our projectrdquo during innumerable evenings and weekends

Jean-Pierre JaspartKlaus Weynand

UK FOREWORD

_____

xix

UK FOREWORD

INTRODUCTION

This book is the second in a series of joint publications of the EuropeanConvention for Constructional Steelwork (ECCS) and The Steel ConstructionInstitute (SCI) It will help provide UK engineers and designers with a betterunderstanding of the design principles in the European Code of Practice for theDesign of Steel Structures (EN 1993 ndash Eurocode 3) and the individual Part 18(EN 1993-1-8) for the design of steel joints in particular Reference will alsobe made to the associated Eurocodes for concrete (EN 1992 ndash Eurocode 2) andearthquake engineering (EN 1998 ndash Eurocode 8) The book complements otherSCI design guides eg SCI (2011 and 2013a)

The current publication is a first UK edition based on the first edition of theECCS manual for the Design of Joints in Steel and Composite Structureswhich was published in 2016 The scope of this UK edition is narrower thanthe original publication in two specific areas that are felt to be of limitedinterest to current practice in the UK there is no content covering compositejoints and chapter 9 (covering frame design strategies) has been shortened tosimply give an overview of strategies In this edition the reader will findinformation that is either of a general nature or relevant to specific sectionsof the publication to facilitate its application in a UK context

The content includes useful background to the code rules and a reminder ofsome engineering principles Information is presented in the context of theEurocodes terminology and notation and with reference to clause numbersetc to help the readerrsquos familiarity with EN 1993-1-8 The document thatserves as the basis for content and numbering of clauses is the UKimplementation of EN 1993-1-82005 incorporating corrigenda December2005 and July 2009 At the time of writing (Autumn 2016) part 1-8 ofEN 1993 is being revised with publication anticipated after 2020

Finally it is noted and should be accepted that there will inevitably be somedifferences of interpretation between the ECCS recommendations and thosepreviously published by the SCI

UK FOREWORD

_____

xx

GENERAL COMMENTS

Design of joints (connections) in steel structures in the UK is covered byBS EN 1993-1-8 and its national Annex (NA) (BSI 2010) BS EN 1993-1-8has clear definitions for connections and joints The term joint refers to thezone where members are interconnected and a connection is the locationwhere elements meet The distinction in terminology is usually emphasised inContinental Europe but traditional practice in the UK is to use the generic termconnection

The following partial safety factors are defined in the UK NA

Partial factor Value Comment

γM2 125 Used for the resistance of bolts pins and welds

γM2 125Used for the resistance of plates in bearing(γM2=15 should be used if deformation control is important)

γM3 125 Used for slip resistance at Ultimate Limit States

γM3serv 110 Used for slip resistance at Serviceability Limit States (SLS)

γM4 100 Used for the resistance of injection bolts

γM5 100 Used for the resistance of joints in hollow section lattice girders

γM6serv 100 Used for the resistance of pins at SLS

γM7

110Used for the preload of high strength steel bolts conforming toBS EN 14399-4 and BS EN 14399-8 (BSI 2015 and 2007)

100 Used for the preload of (other) high strength steel bolts

Specific reference to the UK Building Regulations is also made in this UKedition The UK Building Regulations code has structural integrityrequirements in order to avoid disproportionate collapse and ensure robustnessof the complete structure Disproportionate collapse can be defined as a regionof structural collapse out of proportion to the initiating cause of failure Themost relevant to connectionjoint design is that the detailing for every beam

UK FOREWORD

_____

xxi

member must be adequate to resist a minimum horizontal force at ultimatefailure (or tying resistance) Guidance on the design values of tying forces canbe found in BS EN 1991-1-7 Annex A and its UK annex (BSI 2014)

SECTION SPECIFIC COMMENTS

Section 111

UK practice normally considers only two main forms of joint modellingsimple and continuous Ideally frames designed on the basis of simple jointmodelling should use joints between members that possess negligiblerotational stiffness and transmit the beam reactions in shear into thecolumns without developing significant moments These joints may betreated as perfect pins Members can then be designed in isolation either as(predominantly) axially loaded columns or as simply supported beamsJoints designed within the principles of continuous modelling are capable oftransmitting significant moments and are able to maintain the original anglebetween adjacent members virtually unchanged This form of construction ofsteel frames is particularly advantageous when beam deflections are criticalor if bracing systems are not possible

To comply with one or the other design assumption steelwork connectionsare detailed as simple or moment-resisting joints Because joints in framestructures are often treated by adopting a degree of standardisation thedesigner usually details the connections in accordance with the principlesin the series of SCI Green Books which present this material in the formof step-by-step design procedures and tables covering standardarrangements

Other approximate analysis methods continue to be used among Britishdesigners the most representative being the wind-moment method for thedesign of unbraced multi-storey steel frames The method assumes that(i) under gravity loads the beam-to-column joints act as pinnedconnections and (ii) under horizontal wind loads these joints are rigidalthough it lacks transparency This method can be seen as a manifestationof the semi-continuous principles Wind moment connection details can befound in SCI (1995a) With the now widespread use of software in designoffices for rigorous second-order analysis it is doubtful if the use of the

UK FOREWORD

_____

xxii

wind-moment method should be advocated any longer other than forinitial sizing

Section 13

Although S460 is attracting growing interest S355 is still the dominantgrade of steel used in the UK

Section 161

With reference to Figure 120 it is noted that (site) welded joints and angleflange cleats are rarely if ever used in the UK

Section 162

Hybrid connections are rarely used in the UK for the reasons noted

Section 172

There is not much use of CoPcopy in the UK There are a number of othersoftware tools on the market some more comprehensive than others

Section 22

Although in UK design practice most aspects related to joint modelling havedeveloped to a high degree of sophistication proper consideration of thestructural interaction between the joints and members is rarely fully takeninto account It is indeed very difficult to predict and model the complexbehaviour of a joint (strength stiffness and rotation capacity) TraditionalUK practice is to predict joint behaviour on the basis of past experience

BSI (2010) separates the modelling of the rotational behaviour of theconnection elements (that is the bolts the welds the plates etc) and thatof the column web panel in shear to characterise the overall jointbehaviour As a simplification the two sources of joint deformation arecombined by means of the so-called transformation parameter β Thiscoefficient is related to the web panel internal actions and can be calculatedfrom the moments at each side of the web panel The β parameter iscurrently only defined for same-depth beams which meet at the same levelIn many practical double-sided joints beams will not be of the same depthor at the same height BS EN 1993-1-8 is silent on such joints

UK FOREWORD

_____

xxiii

Section 23

As explained above typical UK design practice does not consider thissophisticated procedure for idealisation of joints

Section 24

The NA to BS EN 1993-1-8 gives practical guidance to classify joints Italso states the following

ldquoUntil experience is gained with the numerical method of calculatingrotational stiffness given in BS EN 1993-1-82005 63 and theclassification by stiffness method given in BS EN 1993-1-82005522 semi-continuous elastic design should only be used where eitherit is supported by test evidence according to BS EN 1993-1-820055221(2) or where it is based on satisfactorily performance in asimilar situationrdquo

Evidence on values of column base stiffness for practical global analysis isgiven in SCI (2006)

Section 25

The concept of ductility classes is not widely applied in the UK It isgenerally assumed that standard connection details to the SCI Green Booksprovide enough rotation capacity and so behave in a ductile manner asevidenced by physical testing and experience

Section 31

The NA to BS EN 1993-1-8 excludes bolts of classes 58 and 68 It alsostates that bolt class 48 may only be used if the manufacturing process (i) isin accordance with BS EN ISO 898-1 (BSI 2013) and (ii) includes suitableprocedures to avoid hydrogen embrittlement

Section 322

The NA to BS EN 1993-1-8 states that if the preload is not explicitly used inthe design calculations then no specific level of preload is required

Section 347

Injection bolts are rarely used in the UK

UK FOREWORD

_____

xxiv

Section 348

Reference is made to SCI (1995b) to calculate the bending moments in thepin of a pin bearing

Section 349

Flow drill blind bolting is not common practice in the UK SHS blind boltingis a common system but there are several manufactures other than thatsuggested in the book

Section 3410

Nails are rarely used in the UK

Section 352

T-stub configurations with four bolts in a row are rarely used in the UK

Section 353

Reference is made to the SCI method for the design of gusset plates seeSCI (2011)

Section 421

It is anticipated that specific rules given in the current BS EN 1993-1-12(BSI 2009) for high strength steels will be incorporated in the revisedBS EN 1993-1-8 to appear after 2020

Section 522

ldquoHeader platesrdquo are known as ldquopartial depth end platesrdquo in the UK Webcleat connections are no longer commonly used in the UK The full depthend plate connection shown on the left of Figure 59 is classified as a simplejoint in the UK (SCI 2011)

Section 523

The UK Building Regulations require that joints are designed for tyingforces in order to satisfy structural integrity requirements Guidance onthe design values of tying forces is given in BS EN 1991-1-7 Annex Aand its UK NA The requirements relate to the building class with a

UK FOREWORD

_____

xxv

design value of horizontal force generally not less than 75 kN andusually significantly higher Simple joints detailed to SCI (2011) satisfythese requirements

Section 525

It is generally safe to assume that the ductility (rotation requirements) aresatisfied provided that joints are detailed in accordance with SCI (2011)

Section 531

The column base detailing on the left of Figure 521 is not commonly used inthe UK We never recommend less than four bolts ndash they are needed toassure stability and facilitate location during erection The anchoringsystems shown in Figure 522 are not usually adopted in the UK Referenceis made to SCI (2013a) for common anchor systems

Section 62

Publication SCI (2013b) summarises the principal differences betweenBS 5950 and BS EN 1993-1-8 (BSI 2000 and 2010) in terms ofcomponent characterisation

With reference to Figure 66 it is anticipated that the revised BS EN1993-1-8will include analytical expressions for the definition of the so-called αcoefficient

Rules of thumb for the characterisation of the ductility of some individualcomponents are given in SCI (1995a)

Section 631

The UK NA to BS EN 1993-1-8 gives specific rules for the full plasticdistribution of effective design tension resistance The procedure is alsosummarised in SCI (2013a)

Section 633

Where a joint is subjected to combined bending moments and axial forcesthe concept of an applied moment modified by axial load can be used seeSCI (1995a)

UK FOREWORD

_____

xxvi

Section 64

Rotational stiffness is not normally evaluated in UK design practice whichusually relies on past experience

Section 65

Some rules of thumb for the characterisation of the ductility of moment-resisting joints are given in SCI (1995a)

Section 661

With reference to Figure 636 it is noted that this joint configuration ishardly (if ever) used in the UK

Section 663

It should be noted that European sections are not commonly used in the UKalthough there is growing interest in the market Steel grade S235 is not usedin the UK S355 being the current common grade Combinations of plates of15 mm thickness with M24 bolts are common This combination is assumedto provide enough rotation capacity thus satisfying ductility requirementsbecause ductile failure of the plates not brittle failure of the bolts governsthe behaviour

Section 672

Standard practice in the UK does not account for this 25 rule Columnsplices are usually detailed to SCI (2011) to ensure continuity of stiffnessthrough the splice so that the member design is not invalidated

Section 84

The UK Building Regulations require that joints are designed for tyingforces in order to satisfy structural integrity requirements Guidance on thedesign values of tying forces is given in BS EN 1991-1-7 Annex A and itsUK NA (BSI 2014)

Section 91

In the UK the ldquofabricatorsrdquo are known as ldquoSteelwork contractorsrdquo becausethey do more than just fabricate

UK FOREWORD

_____

xxvii

REFERENCES TO NATIONAL FOREWORD

BSI (2000) BS 5950-12000 ndash Structural use of steelwork in building ndash Part1 Code of Practice for Design rolled and welded sections British StandardsInstitution United Kingdom

BSI (2007) BS EN 14399-82007 ndash High-strength structural boltingassemblies for preloading System HV Hexagon fit bolt and nut assembliesBritish Standards Institution United Kingdom

BSI (2009) BS EN 1993-1-122007 ndash Eurocode 3 Design of steel structuresndash Part 112 Additional rules for the extension of EN 1993 up to steel gradesS 700 British Standards Institution United Kingdom

BSI (2010) BS EN 1993-1-82005 ndash Eurocode 3 Design of steel structuresndash Part 18 Design of joints British Standards Institution United Kingdom

BSI (2013) BS EN ISO 898-12013 ndash Mechanical properties of fastenersmade of carbon steel and alloy steel Bolts screws and studs with specifiedproperty classes Coarse thread and fine pitch thread British StandardsInstitution United Kingdom

BSI (2014) BS EN 1991-1-72006+A12014 ndash Eurocode 1 Actions on structuresndash Part 197 General actions British Standards Institution United Kingdom

BSI (2015) BS EN 14399-42015 ndash High-strength structural boltingassemblies for preloading System HV Hexagon bolt and nut assembliesBritish Standards Institution United Kingdom

SCI (1995a) Joints in steel construction Moment connections P207 TheSteel Construction Institute

SCI (1995b) Advisory Desk Notes Bending Moment in a pin AD 172 TheSteel Construction Institute

SCI (2006) Column base stiffness for global analysis NCCI-SN045a TheSteel Construction Institute

SCI (2011) Joints in steel construction Simple joints to Eurocode 3 P358The Steel Construction Institute

SCI (2013a) Joints in steel construction Moment-resisting joints toEurocode 3 P398 The Steel Construction Institute

UK FOREWORD

_____

xxviii

SCI (2013b) Interim Report Design of Portal Frames to Eurocode 3 Anoverview for UK designers P400 The Steel Construction Institute

UK FOREWORD

_____

xix

UK FOREWORD

INTRODUCTION

This book is the second in a series of joint publications of the EuropeanConvention for Constructional Steelwork (ECCS) and The Steel ConstructionInstitute (SCI) It will help provide UK engineers and designers with a betterunderstanding of the design principles in the European Code of Practice for theDesign of Steel Structures (EN 1993 ndash Eurocode 3) and the individual Part 18(EN 1993-1-8) for the design of steel joints in particular Reference will alsobe made to the associated Eurocodes for concrete (EN 1992 ndash Eurocode 2) andearthquake engineering (EN 1998 ndash Eurocode 8) The book complements otherSCI design guides eg SCI (2011 and 2013a)

The current publication is a first UK edition based on the first edition of theECCS manual for the Design of Joints in Steel and Composite Structureswhich was published in 2016 The scope of this UK edition is narrower thanthe original publication in two specific areas that are felt to be of limitedinterest to current practice in the UK there is no content covering compositejoints and chapter 9 (covering frame design strategies) has been shortened tosimply give an overview of strategies In this edition the reader will findinformation that is either of a general nature or relevant to specific sectionsof the publication to facilitate its application in a UK context

The content includes useful background to the code rules and a reminder ofsome engineering principles Information is presented in the context of theEurocodes terminology and notation and with reference to clause numbersetc to help the readerrsquos familiarity with EN 1993-1-8 The document thatserves as the basis for content and numbering of clauses is the UKimplementation of EN 1993-1-82005 incorporating corrigenda December2005 and July 2009 At the time of writing (Autumn 2016) part 1-8 ofEN 1993 is being revised with publication anticipated after 2020

Finally it is noted and should be accepted that there will inevitably be somedifferences of interpretation between the ECCS recommendations and thosepreviously published by the SCI

UK FOREWORD

_____

xx

GENERAL COMMENTS

Design of joints (connections) in steel structures in the UK is covered byBS EN 1993-1-8 and its national Annex (NA) (BSI 2010) BS EN 1993-1-8has clear definitions for connections and joints The term joint refers to thezone where members are interconnected and a connection is the locationwhere elements meet The distinction in terminology is usually emphasised inContinental Europe but traditional practice in the UK is to use the generic termconnection

The following partial safety factors are defined in the UK NA

Partial factor Value Comment

γM2 125 Used for the resistance of bolts pins and welds

γM2 125Used for the resistance of plates in bearing(γM2=15 should be used if deformation control is important)

γM3 125 Used for slip resistance at Ultimate Limit States

γM3serv 110 Used for slip resistance at Serviceability Limit States (SLS)

γM4 100 Used for the resistance of injection bolts

γM5 100 Used for the resistance of joints in hollow section lattice girders

γM6serv 100 Used for the resistance of pins at SLS

γM7

110Used for the preload of high strength steel bolts conforming toBS EN 14399-4 and BS EN 14399-8 (BSI 2015 and 2007)

100 Used for the preload of (other) high strength steel bolts

Specific reference to the UK Building Regulations is also made in this UKedition The UK Building Regulations code has structural integrityrequirements in order to avoid disproportionate collapse and ensure robustnessof the complete structure Disproportionate collapse can be defined as a regionof structural collapse out of proportion to the initiating cause of failure Themost relevant to connectionjoint design is that the detailing for every beam

UK FOREWORD

_____

xxi

member must be adequate to resist a minimum horizontal force at ultimatefailure (or tying resistance) Guidance on the design values of tying forces canbe found in BS EN 1991-1-7 Annex A and its UK annex (BSI 2014)

SECTION SPECIFIC COMMENTS

Section 111

UK practice normally considers only two main forms of joint modellingsimple and continuous Ideally frames designed on the basis of simple jointmodelling should use joints between members that possess negligiblerotational stiffness and transmit the beam reactions in shear into thecolumns without developing significant moments These joints may betreated as perfect pins Members can then be designed in isolation either as(predominantly) axially loaded columns or as simply supported beamsJoints designed within the principles of continuous modelling are capable oftransmitting significant moments and are able to maintain the original anglebetween adjacent members virtually unchanged This form of construction ofsteel frames is particularly advantageous when beam deflections are criticalor if bracing systems are not possible

To comply with one or the other design assumption steelwork connectionsare detailed as simple or moment-resisting joints Because joints in framestructures are often treated by adopting a degree of standardisation thedesigner usually details the connections in accordance with the principlesin the series of SCI Green Books which present this material in the formof step-by-step design procedures and tables covering standardarrangements

Other approximate analysis methods continue to be used among Britishdesigners the most representative being the wind-moment method for thedesign of unbraced multi-storey steel frames The method assumes that(i) under gravity loads the beam-to-column joints act as pinnedconnections and (ii) under horizontal wind loads these joints are rigidalthough it lacks transparency This method can be seen as a manifestationof the semi-continuous principles Wind moment connection details can befound in SCI (1995a) With the now widespread use of software in designoffices for rigorous second-order analysis it is doubtful if the use of the

UK FOREWORD

_____

xxii

wind-moment method should be advocated any longer other than forinitial sizing

Section 13

Although S460 is attracting growing interest S355 is still the dominantgrade of steel used in the UK

Section 161

With reference to Figure 120 it is noted that (site) welded joints and angleflange cleats are rarely if ever used in the UK

Section 162

Hybrid connections are rarely used in the UK for the reasons noted

Section 172

There is not much use of CoPcopy in the UK There are a number of othersoftware tools on the market some more comprehensive than others

Section 22

Although in UK design practice most aspects related to joint modelling havedeveloped to a high degree of sophistication proper consideration of thestructural interaction between the joints and members is rarely fully takeninto account It is indeed very difficult to predict and model the complexbehaviour of a joint (strength stiffness and rotation capacity) TraditionalUK practice is to predict joint behaviour on the basis of past experience

BSI (2010) separates the modelling of the rotational behaviour of theconnection elements (that is the bolts the welds the plates etc) and thatof the column web panel in shear to characterise the overall jointbehaviour As a simplification the two sources of joint deformation arecombined by means of the so-called transformation parameter β Thiscoefficient is related to the web panel internal actions and can be calculatedfrom the moments at each side of the web panel The β parameter iscurrently only defined for same-depth beams which meet at the same levelIn many practical double-sided joints beams will not be of the same depthor at the same height BS EN 1993-1-8 is silent on such joints

UK FOREWORD

_____

xxiii

Section 23

As explained above typical UK design practice does not consider thissophisticated procedure for idealisation of joints

Section 24

The NA to BS EN 1993-1-8 gives practical guidance to classify joints Italso states the following

ldquoUntil experience is gained with the numerical method of calculatingrotational stiffness given in BS EN 1993-1-82005 63 and theclassification by stiffness method given in BS EN 1993-1-82005522 semi-continuous elastic design should only be used where eitherit is supported by test evidence according to BS EN 1993-1-820055221(2) or where it is based on satisfactorily performance in asimilar situationrdquo

Evidence on values of column base stiffness for practical global analysis isgiven in SCI (2006)

Section 25

The concept of ductility classes is not widely applied in the UK It isgenerally assumed that standard connection details to the SCI Green Booksprovide enough rotation capacity and so behave in a ductile manner asevidenced by physical testing and experience

Section 31

The NA to BS EN 1993-1-8 excludes bolts of classes 58 and 68 It alsostates that bolt class 48 may only be used if the manufacturing process (i) isin accordance with BS EN ISO 898-1 (BSI 2013) and (ii) includes suitableprocedures to avoid hydrogen embrittlement

Section 322

The NA to BS EN 1993-1-8 states that if the preload is not explicitly used inthe design calculations then no specific level of preload is required

Section 347

Injection bolts are rarely used in the UK

UK FOREWORD

_____

xxiv

Section 348

Reference is made to SCI (1995b) to calculate the bending moments in thepin of a pin bearing

Section 349

Flow drill blind bolting is not common practice in the UK SHS blind boltingis a common system but there are several manufactures other than thatsuggested in the book

Section 3410

Nails are rarely used in the UK

Section 352

T-stub configurations with four bolts in a row are rarely used in the UK

Section 353

Reference is made to the SCI method for the design of gusset plates seeSCI (2011)

Section 421

It is anticipated that specific rules given in the current BS EN 1993-1-12(BSI 2009) for high strength steels will be incorporated in the revisedBS EN 1993-1-8 to appear after 2020

Section 522

ldquoHeader platesrdquo are known as ldquopartial depth end platesrdquo in the UK Webcleat connections are no longer commonly used in the UK The full depthend plate connection shown on the left of Figure 59 is classified as a simplejoint in the UK (SCI 2011)

Section 523

The UK Building Regulations require that joints are designed for tyingforces in order to satisfy structural integrity requirements Guidance onthe design values of tying forces is given in BS EN 1991-1-7 Annex Aand its UK NA The requirements relate to the building class with a

UK FOREWORD

_____

xxv

design value of horizontal force generally not less than 75 kN andusually significantly higher Simple joints detailed to SCI (2011) satisfythese requirements

Section 525

It is generally safe to assume that the ductility (rotation requirements) aresatisfied provided that joints are detailed in accordance with SCI (2011)

Section 531

The column base detailing on the left of Figure 521 is not commonly used inthe UK We never recommend less than four bolts ndash they are needed toassure stability and facilitate location during erection The anchoringsystems shown in Figure 522 are not usually adopted in the UK Referenceis made to SCI (2013a) for common anchor systems

Section 62

Publication SCI (2013b) summarises the principal differences betweenBS 5950 and BS EN 1993-1-8 (BSI 2000 and 2010) in terms ofcomponent characterisation

With reference to Figure 66 it is anticipated that the revised BS EN1993-1-8will include analytical expressions for the definition of the so-called αcoefficient

Rules of thumb for the characterisation of the ductility of some individualcomponents are given in SCI (1995a)

Section 631

The UK NA to BS EN 1993-1-8 gives specific rules for the full plasticdistribution of effective design tension resistance The procedure is alsosummarised in SCI (2013a)

Section 633

Where a joint is subjected to combined bending moments and axial forcesthe concept of an applied moment modified by axial load can be used seeSCI (1995a)

UK FOREWORD

_____

xxvi

Section 64

Rotational stiffness is not normally evaluated in UK design practice whichusually relies on past experience

Section 65

Some rules of thumb for the characterisation of the ductility of moment-resisting joints are given in SCI (1995a)

Section 661

With reference to Figure 636 it is noted that this joint configuration ishardly (if ever) used in the UK

Section 663

It should be noted that European sections are not commonly used in the UKalthough there is growing interest in the market Steel grade S235 is not usedin the UK S355 being the current common grade Combinations of plates of15 mm thickness with M24 bolts are common This combination is assumedto provide enough rotation capacity thus satisfying ductility requirementsbecause ductile failure of the plates not brittle failure of the bolts governsthe behaviour

Section 672

Standard practice in the UK does not account for this 25 rule Columnsplices are usually detailed to SCI (2011) to ensure continuity of stiffnessthrough the splice so that the member design is not invalidated

Section 84

The UK Building Regulations require that joints are designed for tyingforces in order to satisfy structural integrity requirements Guidance on thedesign values of tying forces is given in BS EN 1991-1-7 Annex A and itsUK NA (BSI 2014)

Section 91

In the UK the ldquofabricatorsrdquo are known as ldquoSteelwork contractorsrdquo becausethey do more than just fabricate

UK FOREWORD

_____

xxvii

REFERENCES TO NATIONAL FOREWORD

BSI (2000) BS 5950-12000 ndash Structural use of steelwork in building ndash Part1 Code of Practice for Design rolled and welded sections British StandardsInstitution United Kingdom

BSI (2007) BS EN 14399-82007 ndash High-strength structural boltingassemblies for preloading System HV Hexagon fit bolt and nut assembliesBritish Standards Institution United Kingdom

BSI (2009) BS EN 1993-1-122007 ndash Eurocode 3 Design of steel structuresndash Part 112 Additional rules for the extension of EN 1993 up to steel gradesS 700 British Standards Institution United Kingdom

BSI (2010) BS EN 1993-1-82005 ndash Eurocode 3 Design of steel structuresndash Part 18 Design of joints British Standards Institution United Kingdom

BSI (2013) BS EN ISO 898-12013 ndash Mechanical properties of fastenersmade of carbon steel and alloy steel Bolts screws and studs with specifiedproperty classes Coarse thread and fine pitch thread British StandardsInstitution United Kingdom

BSI (2014) BS EN 1991-1-72006+A12014 ndash Eurocode 1 Actions on structuresndash Part 197 General actions British Standards Institution United Kingdom

BSI (2015) BS EN 14399-42015 ndash High-strength structural boltingassemblies for preloading System HV Hexagon bolt and nut assembliesBritish Standards Institution United Kingdom

SCI (1995a) Joints in steel construction Moment connections P207 TheSteel Construction Institute

SCI (1995b) Advisory Desk Notes Bending Moment in a pin AD 172 TheSteel Construction Institute

SCI (2006) Column base stiffness for global analysis NCCI-SN045a TheSteel Construction Institute

SCI (2011) Joints in steel construction Simple joints to Eurocode 3 P358The Steel Construction Institute

SCI (2013a) Joints in steel construction Moment-resisting joints toEurocode 3 P398 The Steel Construction Institute

UK FOREWORD

_____

xxviii

SCI (2013b) Interim Report Design of Portal Frames to Eurocode 3 Anoverview for UK designers P400 The Steel Construction Institute

UK FOREWORD

_____

xx

GENERAL COMMENTS

Design of joints (connections) in steel structures in the UK is covered byBS EN 1993-1-8 and its national Annex (NA) (BSI 2010) BS EN 1993-1-8has clear definitions for connections and joints The term joint refers to thezone where members are interconnected and a connection is the locationwhere elements meet The distinction in terminology is usually emphasised inContinental Europe but traditional practice in the UK is to use the generic termconnection

The following partial safety factors are defined in the UK NA

Partial factor Value Comment

γM2 125 Used for the resistance of bolts pins and welds

γM2 125Used for the resistance of plates in bearing(γM2=15 should be used if deformation control is important)

γM3 125 Used for slip resistance at Ultimate Limit States

γM3serv 110 Used for slip resistance at Serviceability Limit States (SLS)

γM4 100 Used for the resistance of injection bolts

γM5 100 Used for the resistance of joints in hollow section lattice girders

γM6serv 100 Used for the resistance of pins at SLS

γM7

110Used for the preload of high strength steel bolts conforming toBS EN 14399-4 and BS EN 14399-8 (BSI 2015 and 2007)

100 Used for the preload of (other) high strength steel bolts

Specific reference to the UK Building Regulations is also made in this UKedition The UK Building Regulations code has structural integrityrequirements in order to avoid disproportionate collapse and ensure robustnessof the complete structure Disproportionate collapse can be defined as a regionof structural collapse out of proportion to the initiating cause of failure Themost relevant to connectionjoint design is that the detailing for every beam

UK FOREWORD

_____

xxi

member must be adequate to resist a minimum horizontal force at ultimatefailure (or tying resistance) Guidance on the design values of tying forces canbe found in BS EN 1991-1-7 Annex A and its UK annex (BSI 2014)

SECTION SPECIFIC COMMENTS

Section 111

UK practice normally considers only two main forms of joint modellingsimple and continuous Ideally frames designed on the basis of simple jointmodelling should use joints between members that possess negligiblerotational stiffness and transmit the beam reactions in shear into thecolumns without developing significant moments These joints may betreated as perfect pins Members can then be designed in isolation either as(predominantly) axially loaded columns or as simply supported beamsJoints designed within the principles of continuous modelling are capable oftransmitting significant moments and are able to maintain the original anglebetween adjacent members virtually unchanged This form of construction ofsteel frames is particularly advantageous when beam deflections are criticalor if bracing systems are not possible

To comply with one or the other design assumption steelwork connectionsare detailed as simple or moment-resisting joints Because joints in framestructures are often treated by adopting a degree of standardisation thedesigner usually details the connections in accordance with the principlesin the series of SCI Green Books which present this material in the formof step-by-step design procedures and tables covering standardarrangements

Other approximate analysis methods continue to be used among Britishdesigners the most representative being the wind-moment method for thedesign of unbraced multi-storey steel frames The method assumes that(i) under gravity loads the beam-to-column joints act as pinnedconnections and (ii) under horizontal wind loads these joints are rigidalthough it lacks transparency This method can be seen as a manifestationof the semi-continuous principles Wind moment connection details can befound in SCI (1995a) With the now widespread use of software in designoffices for rigorous second-order analysis it is doubtful if the use of the

UK FOREWORD

_____

xxii

wind-moment method should be advocated any longer other than forinitial sizing

Section 13

Although S460 is attracting growing interest S355 is still the dominantgrade of steel used in the UK

Section 161

With reference to Figure 120 it is noted that (site) welded joints and angleflange cleats are rarely if ever used in the UK

Section 162

Hybrid connections are rarely used in the UK for the reasons noted

Section 172

There is not much use of CoPcopy in the UK There are a number of othersoftware tools on the market some more comprehensive than others

Section 22

Although in UK design practice most aspects related to joint modelling havedeveloped to a high degree of sophistication proper consideration of thestructural interaction between the joints and members is rarely fully takeninto account It is indeed very difficult to predict and model the complexbehaviour of a joint (strength stiffness and rotation capacity) TraditionalUK practice is to predict joint behaviour on the basis of past experience

BSI (2010) separates the modelling of the rotational behaviour of theconnection elements (that is the bolts the welds the plates etc) and thatof the column web panel in shear to characterise the overall jointbehaviour As a simplification the two sources of joint deformation arecombined by means of the so-called transformation parameter β Thiscoefficient is related to the web panel internal actions and can be calculatedfrom the moments at each side of the web panel The β parameter iscurrently only defined for same-depth beams which meet at the same levelIn many practical double-sided joints beams will not be of the same depthor at the same height BS EN 1993-1-8 is silent on such joints

UK FOREWORD

_____

xxiii

Section 23

As explained above typical UK design practice does not consider thissophisticated procedure for idealisation of joints

Section 24

The NA to BS EN 1993-1-8 gives practical guidance to classify joints Italso states the following

ldquoUntil experience is gained with the numerical method of calculatingrotational stiffness given in BS EN 1993-1-82005 63 and theclassification by stiffness method given in BS EN 1993-1-82005522 semi-continuous elastic design should only be used where eitherit is supported by test evidence according to BS EN 1993-1-820055221(2) or where it is based on satisfactorily performance in asimilar situationrdquo

Evidence on values of column base stiffness for practical global analysis isgiven in SCI (2006)

Section 25

The concept of ductility classes is not widely applied in the UK It isgenerally assumed that standard connection details to the SCI Green Booksprovide enough rotation capacity and so behave in a ductile manner asevidenced by physical testing and experience

Section 31

The NA to BS EN 1993-1-8 excludes bolts of classes 58 and 68 It alsostates that bolt class 48 may only be used if the manufacturing process (i) isin accordance with BS EN ISO 898-1 (BSI 2013) and (ii) includes suitableprocedures to avoid hydrogen embrittlement

Section 322

The NA to BS EN 1993-1-8 states that if the preload is not explicitly used inthe design calculations then no specific level of preload is required

Section 347

Injection bolts are rarely used in the UK

UK FOREWORD

_____

xxiv

Section 348

Reference is made to SCI (1995b) to calculate the bending moments in thepin of a pin bearing

Section 349

Flow drill blind bolting is not common practice in the UK SHS blind boltingis a common system but there are several manufactures other than thatsuggested in the book

Section 3410

Nails are rarely used in the UK

Section 352

T-stub configurations with four bolts in a row are rarely used in the UK

Section 353

Reference is made to the SCI method for the design of gusset plates seeSCI (2011)

Section 421

It is anticipated that specific rules given in the current BS EN 1993-1-12(BSI 2009) for high strength steels will be incorporated in the revisedBS EN 1993-1-8 to appear after 2020

Section 522

ldquoHeader platesrdquo are known as ldquopartial depth end platesrdquo in the UK Webcleat connections are no longer commonly used in the UK The full depthend plate connection shown on the left of Figure 59 is classified as a simplejoint in the UK (SCI 2011)

Section 523

The UK Building Regulations require that joints are designed for tyingforces in order to satisfy structural integrity requirements Guidance onthe design values of tying forces is given in BS EN 1991-1-7 Annex Aand its UK NA The requirements relate to the building class with a

UK FOREWORD

_____

xxv

design value of horizontal force generally not less than 75 kN andusually significantly higher Simple joints detailed to SCI (2011) satisfythese requirements

Section 525

It is generally safe to assume that the ductility (rotation requirements) aresatisfied provided that joints are detailed in accordance with SCI (2011)

Section 531

The column base detailing on the left of Figure 521 is not commonly used inthe UK We never recommend less than four bolts ndash they are needed toassure stability and facilitate location during erection The anchoringsystems shown in Figure 522 are not usually adopted in the UK Referenceis made to SCI (2013a) for common anchor systems

Section 62

Publication SCI (2013b) summarises the principal differences betweenBS 5950 and BS EN 1993-1-8 (BSI 2000 and 2010) in terms ofcomponent characterisation

With reference to Figure 66 it is anticipated that the revised BS EN1993-1-8will include analytical expressions for the definition of the so-called αcoefficient

Rules of thumb for the characterisation of the ductility of some individualcomponents are given in SCI (1995a)

Section 631

The UK NA to BS EN 1993-1-8 gives specific rules for the full plasticdistribution of effective design tension resistance The procedure is alsosummarised in SCI (2013a)

Section 633

Where a joint is subjected to combined bending moments and axial forcesthe concept of an applied moment modified by axial load can be used seeSCI (1995a)

UK FOREWORD

_____

xxvi

Section 64

Rotational stiffness is not normally evaluated in UK design practice whichusually relies on past experience

Section 65

Some rules of thumb for the characterisation of the ductility of moment-resisting joints are given in SCI (1995a)

Section 661

With reference to Figure 636 it is noted that this joint configuration ishardly (if ever) used in the UK

Section 663

It should be noted that European sections are not commonly used in the UKalthough there is growing interest in the market Steel grade S235 is not usedin the UK S355 being the current common grade Combinations of plates of15 mm thickness with M24 bolts are common This combination is assumedto provide enough rotation capacity thus satisfying ductility requirementsbecause ductile failure of the plates not brittle failure of the bolts governsthe behaviour

Section 672

Standard practice in the UK does not account for this 25 rule Columnsplices are usually detailed to SCI (2011) to ensure continuity of stiffnessthrough the splice so that the member design is not invalidated

Section 84

The UK Building Regulations require that joints are designed for tyingforces in order to satisfy structural integrity requirements Guidance on thedesign values of tying forces is given in BS EN 1991-1-7 Annex A and itsUK NA (BSI 2014)

Section 91

In the UK the ldquofabricatorsrdquo are known as ldquoSteelwork contractorsrdquo becausethey do more than just fabricate

UK FOREWORD

_____

xxvii

REFERENCES TO NATIONAL FOREWORD

BSI (2000) BS 5950-12000 ndash Structural use of steelwork in building ndash Part1 Code of Practice for Design rolled and welded sections British StandardsInstitution United Kingdom

BSI (2007) BS EN 14399-82007 ndash High-strength structural boltingassemblies for preloading System HV Hexagon fit bolt and nut assembliesBritish Standards Institution United Kingdom

BSI (2009) BS EN 1993-1-122007 ndash Eurocode 3 Design of steel structuresndash Part 112 Additional rules for the extension of EN 1993 up to steel gradesS 700 British Standards Institution United Kingdom

BSI (2010) BS EN 1993-1-82005 ndash Eurocode 3 Design of steel structuresndash Part 18 Design of joints British Standards Institution United Kingdom

BSI (2013) BS EN ISO 898-12013 ndash Mechanical properties of fastenersmade of carbon steel and alloy steel Bolts screws and studs with specifiedproperty classes Coarse thread and fine pitch thread British StandardsInstitution United Kingdom

BSI (2014) BS EN 1991-1-72006+A12014 ndash Eurocode 1 Actions on structuresndash Part 197 General actions British Standards Institution United Kingdom

BSI (2015) BS EN 14399-42015 ndash High-strength structural boltingassemblies for preloading System HV Hexagon bolt and nut assembliesBritish Standards Institution United Kingdom

SCI (1995a) Joints in steel construction Moment connections P207 TheSteel Construction Institute

SCI (1995b) Advisory Desk Notes Bending Moment in a pin AD 172 TheSteel Construction Institute

SCI (2006) Column base stiffness for global analysis NCCI-SN045a TheSteel Construction Institute

SCI (2011) Joints in steel construction Simple joints to Eurocode 3 P358The Steel Construction Institute

SCI (2013a) Joints in steel construction Moment-resisting joints toEurocode 3 P398 The Steel Construction Institute

UK FOREWORD

_____

xxviii

SCI (2013b) Interim Report Design of Portal Frames to Eurocode 3 Anoverview for UK designers P400 The Steel Construction Institute

UK FOREWORD

_____

xxi

member must be adequate to resist a minimum horizontal force at ultimatefailure (or tying resistance) Guidance on the design values of tying forces canbe found in BS EN 1991-1-7 Annex A and its UK annex (BSI 2014)

SECTION SPECIFIC COMMENTS

Section 111

UK practice normally considers only two main forms of joint modellingsimple and continuous Ideally frames designed on the basis of simple jointmodelling should use joints between members that possess negligiblerotational stiffness and transmit the beam reactions in shear into thecolumns without developing significant moments These joints may betreated as perfect pins Members can then be designed in isolation either as(predominantly) axially loaded columns or as simply supported beamsJoints designed within the principles of continuous modelling are capable oftransmitting significant moments and are able to maintain the original anglebetween adjacent members virtually unchanged This form of construction ofsteel frames is particularly advantageous when beam deflections are criticalor if bracing systems are not possible

To comply with one or the other design assumption steelwork connectionsare detailed as simple or moment-resisting joints Because joints in framestructures are often treated by adopting a degree of standardisation thedesigner usually details the connections in accordance with the principlesin the series of SCI Green Books which present this material in the formof step-by-step design procedures and tables covering standardarrangements

Other approximate analysis methods continue to be used among Britishdesigners the most representative being the wind-moment method for thedesign of unbraced multi-storey steel frames The method assumes that(i) under gravity loads the beam-to-column joints act as pinnedconnections and (ii) under horizontal wind loads these joints are rigidalthough it lacks transparency This method can be seen as a manifestationof the semi-continuous principles Wind moment connection details can befound in SCI (1995a) With the now widespread use of software in designoffices for rigorous second-order analysis it is doubtful if the use of the

UK FOREWORD

_____

xxii

wind-moment method should be advocated any longer other than forinitial sizing

Section 13

Although S460 is attracting growing interest S355 is still the dominantgrade of steel used in the UK

Section 161

With reference to Figure 120 it is noted that (site) welded joints and angleflange cleats are rarely if ever used in the UK

Section 162

Hybrid connections are rarely used in the UK for the reasons noted

Section 172

There is not much use of CoPcopy in the UK There are a number of othersoftware tools on the market some more comprehensive than others

Section 22

Although in UK design practice most aspects related to joint modelling havedeveloped to a high degree of sophistication proper consideration of thestructural interaction between the joints and members is rarely fully takeninto account It is indeed very difficult to predict and model the complexbehaviour of a joint (strength stiffness and rotation capacity) TraditionalUK practice is to predict joint behaviour on the basis of past experience

BSI (2010) separates the modelling of the rotational behaviour of theconnection elements (that is the bolts the welds the plates etc) and thatof the column web panel in shear to characterise the overall jointbehaviour As a simplification the two sources of joint deformation arecombined by means of the so-called transformation parameter β Thiscoefficient is related to the web panel internal actions and can be calculatedfrom the moments at each side of the web panel The β parameter iscurrently only defined for same-depth beams which meet at the same levelIn many practical double-sided joints beams will not be of the same depthor at the same height BS EN 1993-1-8 is silent on such joints

UK FOREWORD

_____

xxiii

Section 23

As explained above typical UK design practice does not consider thissophisticated procedure for idealisation of joints

Section 24

The NA to BS EN 1993-1-8 gives practical guidance to classify joints Italso states the following

ldquoUntil experience is gained with the numerical method of calculatingrotational stiffness given in BS EN 1993-1-82005 63 and theclassification by stiffness method given in BS EN 1993-1-82005522 semi-continuous elastic design should only be used where eitherit is supported by test evidence according to BS EN 1993-1-820055221(2) or where it is based on satisfactorily performance in asimilar situationrdquo

Evidence on values of column base stiffness for practical global analysis isgiven in SCI (2006)

Section 25

The concept of ductility classes is not widely applied in the UK It isgenerally assumed that standard connection details to the SCI Green Booksprovide enough rotation capacity and so behave in a ductile manner asevidenced by physical testing and experience

Section 31

The NA to BS EN 1993-1-8 excludes bolts of classes 58 and 68 It alsostates that bolt class 48 may only be used if the manufacturing process (i) isin accordance with BS EN ISO 898-1 (BSI 2013) and (ii) includes suitableprocedures to avoid hydrogen embrittlement

Section 322

The NA to BS EN 1993-1-8 states that if the preload is not explicitly used inthe design calculations then no specific level of preload is required

Section 347

Injection bolts are rarely used in the UK

UK FOREWORD

_____

xxiv

Section 348

Reference is made to SCI (1995b) to calculate the bending moments in thepin of a pin bearing

Section 349

Flow drill blind bolting is not common practice in the UK SHS blind boltingis a common system but there are several manufactures other than thatsuggested in the book

Section 3410

Nails are rarely used in the UK

Section 352

T-stub configurations with four bolts in a row are rarely used in the UK

Section 353

Reference is made to the SCI method for the design of gusset plates seeSCI (2011)

Section 421

It is anticipated that specific rules given in the current BS EN 1993-1-12(BSI 2009) for high strength steels will be incorporated in the revisedBS EN 1993-1-8 to appear after 2020

Section 522

ldquoHeader platesrdquo are known as ldquopartial depth end platesrdquo in the UK Webcleat connections are no longer commonly used in the UK The full depthend plate connection shown on the left of Figure 59 is classified as a simplejoint in the UK (SCI 2011)

Section 523

The UK Building Regulations require that joints are designed for tyingforces in order to satisfy structural integrity requirements Guidance onthe design values of tying forces is given in BS EN 1991-1-7 Annex Aand its UK NA The requirements relate to the building class with a

UK FOREWORD

_____

xxv

design value of horizontal force generally not less than 75 kN andusually significantly higher Simple joints detailed to SCI (2011) satisfythese requirements

Section 525

It is generally safe to assume that the ductility (rotation requirements) aresatisfied provided that joints are detailed in accordance with SCI (2011)

Section 531

The column base detailing on the left of Figure 521 is not commonly used inthe UK We never recommend less than four bolts ndash they are needed toassure stability and facilitate location during erection The anchoringsystems shown in Figure 522 are not usually adopted in the UK Referenceis made to SCI (2013a) for common anchor systems

Section 62

Publication SCI (2013b) summarises the principal differences betweenBS 5950 and BS EN 1993-1-8 (BSI 2000 and 2010) in terms ofcomponent characterisation

With reference to Figure 66 it is anticipated that the revised BS EN1993-1-8will include analytical expressions for the definition of the so-called αcoefficient

Rules of thumb for the characterisation of the ductility of some individualcomponents are given in SCI (1995a)

Section 631

The UK NA to BS EN 1993-1-8 gives specific rules for the full plasticdistribution of effective design tension resistance The procedure is alsosummarised in SCI (2013a)

Section 633

Where a joint is subjected to combined bending moments and axial forcesthe concept of an applied moment modified by axial load can be used seeSCI (1995a)

UK FOREWORD

_____

xxvi

Section 64

Rotational stiffness is not normally evaluated in UK design practice whichusually relies on past experience

Section 65

Some rules of thumb for the characterisation of the ductility of moment-resisting joints are given in SCI (1995a)

Section 661

With reference to Figure 636 it is noted that this joint configuration ishardly (if ever) used in the UK

Section 663

It should be noted that European sections are not commonly used in the UKalthough there is growing interest in the market Steel grade S235 is not usedin the UK S355 being the current common grade Combinations of plates of15 mm thickness with M24 bolts are common This combination is assumedto provide enough rotation capacity thus satisfying ductility requirementsbecause ductile failure of the plates not brittle failure of the bolts governsthe behaviour

Section 672

Standard practice in the UK does not account for this 25 rule Columnsplices are usually detailed to SCI (2011) to ensure continuity of stiffnessthrough the splice so that the member design is not invalidated

Section 84

The UK Building Regulations require that joints are designed for tyingforces in order to satisfy structural integrity requirements Guidance on thedesign values of tying forces is given in BS EN 1991-1-7 Annex A and itsUK NA (BSI 2014)

Section 91

In the UK the ldquofabricatorsrdquo are known as ldquoSteelwork contractorsrdquo becausethey do more than just fabricate

UK FOREWORD

_____

xxvii

REFERENCES TO NATIONAL FOREWORD

BSI (2000) BS 5950-12000 ndash Structural use of steelwork in building ndash Part1 Code of Practice for Design rolled and welded sections British StandardsInstitution United Kingdom

BSI (2007) BS EN 14399-82007 ndash High-strength structural boltingassemblies for preloading System HV Hexagon fit bolt and nut assembliesBritish Standards Institution United Kingdom

BSI (2009) BS EN 1993-1-122007 ndash Eurocode 3 Design of steel structuresndash Part 112 Additional rules for the extension of EN 1993 up to steel gradesS 700 British Standards Institution United Kingdom

BSI (2010) BS EN 1993-1-82005 ndash Eurocode 3 Design of steel structuresndash Part 18 Design of joints British Standards Institution United Kingdom

BSI (2013) BS EN ISO 898-12013 ndash Mechanical properties of fastenersmade of carbon steel and alloy steel Bolts screws and studs with specifiedproperty classes Coarse thread and fine pitch thread British StandardsInstitution United Kingdom

BSI (2014) BS EN 1991-1-72006+A12014 ndash Eurocode 1 Actions on structuresndash Part 197 General actions British Standards Institution United Kingdom

BSI (2015) BS EN 14399-42015 ndash High-strength structural boltingassemblies for preloading System HV Hexagon bolt and nut assembliesBritish Standards Institution United Kingdom

SCI (1995a) Joints in steel construction Moment connections P207 TheSteel Construction Institute

SCI (1995b) Advisory Desk Notes Bending Moment in a pin AD 172 TheSteel Construction Institute

SCI (2006) Column base stiffness for global analysis NCCI-SN045a TheSteel Construction Institute

SCI (2011) Joints in steel construction Simple joints to Eurocode 3 P358The Steel Construction Institute

SCI (2013a) Joints in steel construction Moment-resisting joints toEurocode 3 P398 The Steel Construction Institute

UK FOREWORD

_____

xxviii

SCI (2013b) Interim Report Design of Portal Frames to Eurocode 3 Anoverview for UK designers P400 The Steel Construction Institute

UK FOREWORD

_____

xxii

wind-moment method should be advocated any longer other than forinitial sizing

Section 13

Although S460 is attracting growing interest S355 is still the dominantgrade of steel used in the UK

Section 161

With reference to Figure 120 it is noted that (site) welded joints and angleflange cleats are rarely if ever used in the UK

Section 162

Hybrid connections are rarely used in the UK for the reasons noted

Section 172

There is not much use of CoPcopy in the UK There are a number of othersoftware tools on the market some more comprehensive than others

Section 22

Although in UK design practice most aspects related to joint modelling havedeveloped to a high degree of sophistication proper consideration of thestructural interaction between the joints and members is rarely fully takeninto account It is indeed very difficult to predict and model the complexbehaviour of a joint (strength stiffness and rotation capacity) TraditionalUK practice is to predict joint behaviour on the basis of past experience

BSI (2010) separates the modelling of the rotational behaviour of theconnection elements (that is the bolts the welds the plates etc) and thatof the column web panel in shear to characterise the overall jointbehaviour As a simplification the two sources of joint deformation arecombined by means of the so-called transformation parameter β Thiscoefficient is related to the web panel internal actions and can be calculatedfrom the moments at each side of the web panel The β parameter iscurrently only defined for same-depth beams which meet at the same levelIn many practical double-sided joints beams will not be of the same depthor at the same height BS EN 1993-1-8 is silent on such joints

UK FOREWORD

_____

xxiii

Section 23

As explained above typical UK design practice does not consider thissophisticated procedure for idealisation of joints

Section 24

The NA to BS EN 1993-1-8 gives practical guidance to classify joints Italso states the following

ldquoUntil experience is gained with the numerical method of calculatingrotational stiffness given in BS EN 1993-1-82005 63 and theclassification by stiffness method given in BS EN 1993-1-82005522 semi-continuous elastic design should only be used where eitherit is supported by test evidence according to BS EN 1993-1-820055221(2) or where it is based on satisfactorily performance in asimilar situationrdquo

Evidence on values of column base stiffness for practical global analysis isgiven in SCI (2006)

Section 25

The concept of ductility classes is not widely applied in the UK It isgenerally assumed that standard connection details to the SCI Green Booksprovide enough rotation capacity and so behave in a ductile manner asevidenced by physical testing and experience

Section 31

The NA to BS EN 1993-1-8 excludes bolts of classes 58 and 68 It alsostates that bolt class 48 may only be used if the manufacturing process (i) isin accordance with BS EN ISO 898-1 (BSI 2013) and (ii) includes suitableprocedures to avoid hydrogen embrittlement

Section 322

The NA to BS EN 1993-1-8 states that if the preload is not explicitly used inthe design calculations then no specific level of preload is required

Section 347

Injection bolts are rarely used in the UK

UK FOREWORD

_____

xxiv

Section 348

Reference is made to SCI (1995b) to calculate the bending moments in thepin of a pin bearing

Section 349

Flow drill blind bolting is not common practice in the UK SHS blind boltingis a common system but there are several manufactures other than thatsuggested in the book

Section 3410

Nails are rarely used in the UK

Section 352

T-stub configurations with four bolts in a row are rarely used in the UK

Section 353

Reference is made to the SCI method for the design of gusset plates seeSCI (2011)

Section 421

It is anticipated that specific rules given in the current BS EN 1993-1-12(BSI 2009) for high strength steels will be incorporated in the revisedBS EN 1993-1-8 to appear after 2020

Section 522

ldquoHeader platesrdquo are known as ldquopartial depth end platesrdquo in the UK Webcleat connections are no longer commonly used in the UK The full depthend plate connection shown on the left of Figure 59 is classified as a simplejoint in the UK (SCI 2011)

Section 523

The UK Building Regulations require that joints are designed for tyingforces in order to satisfy structural integrity requirements Guidance onthe design values of tying forces is given in BS EN 1991-1-7 Annex Aand its UK NA The requirements relate to the building class with a

UK FOREWORD

_____

xxv

design value of horizontal force generally not less than 75 kN andusually significantly higher Simple joints detailed to SCI (2011) satisfythese requirements

Section 525

It is generally safe to assume that the ductility (rotation requirements) aresatisfied provided that joints are detailed in accordance with SCI (2011)

Section 531

The column base detailing on the left of Figure 521 is not commonly used inthe UK We never recommend less than four bolts ndash they are needed toassure stability and facilitate location during erection The anchoringsystems shown in Figure 522 are not usually adopted in the UK Referenceis made to SCI (2013a) for common anchor systems

Section 62

Publication SCI (2013b) summarises the principal differences betweenBS 5950 and BS EN 1993-1-8 (BSI 2000 and 2010) in terms ofcomponent characterisation

With reference to Figure 66 it is anticipated that the revised BS EN1993-1-8will include analytical expressions for the definition of the so-called αcoefficient

Rules of thumb for the characterisation of the ductility of some individualcomponents are given in SCI (1995a)

Section 631

The UK NA to BS EN 1993-1-8 gives specific rules for the full plasticdistribution of effective design tension resistance The procedure is alsosummarised in SCI (2013a)

Section 633

Where a joint is subjected to combined bending moments and axial forcesthe concept of an applied moment modified by axial load can be used seeSCI (1995a)

UK FOREWORD

_____

xxvi

Section 64

Rotational stiffness is not normally evaluated in UK design practice whichusually relies on past experience

Section 65

Some rules of thumb for the characterisation of the ductility of moment-resisting joints are given in SCI (1995a)

Section 661

With reference to Figure 636 it is noted that this joint configuration ishardly (if ever) used in the UK

Section 663

It should be noted that European sections are not commonly used in the UKalthough there is growing interest in the market Steel grade S235 is not usedin the UK S355 being the current common grade Combinations of plates of15 mm thickness with M24 bolts are common This combination is assumedto provide enough rotation capacity thus satisfying ductility requirementsbecause ductile failure of the plates not brittle failure of the bolts governsthe behaviour

Section 672

Standard practice in the UK does not account for this 25 rule Columnsplices are usually detailed to SCI (2011) to ensure continuity of stiffnessthrough the splice so that the member design is not invalidated

Section 84

The UK Building Regulations require that joints are designed for tyingforces in order to satisfy structural integrity requirements Guidance on thedesign values of tying forces is given in BS EN 1991-1-7 Annex A and itsUK NA (BSI 2014)

Section 91

In the UK the ldquofabricatorsrdquo are known as ldquoSteelwork contractorsrdquo becausethey do more than just fabricate

UK FOREWORD

_____

xxvii

REFERENCES TO NATIONAL FOREWORD

BSI (2000) BS 5950-12000 ndash Structural use of steelwork in building ndash Part1 Code of Practice for Design rolled and welded sections British StandardsInstitution United Kingdom

BSI (2007) BS EN 14399-82007 ndash High-strength structural boltingassemblies for preloading System HV Hexagon fit bolt and nut assembliesBritish Standards Institution United Kingdom

BSI (2009) BS EN 1993-1-122007 ndash Eurocode 3 Design of steel structuresndash Part 112 Additional rules for the extension of EN 1993 up to steel gradesS 700 British Standards Institution United Kingdom

BSI (2010) BS EN 1993-1-82005 ndash Eurocode 3 Design of steel structuresndash Part 18 Design of joints British Standards Institution United Kingdom

BSI (2013) BS EN ISO 898-12013 ndash Mechanical properties of fastenersmade of carbon steel and alloy steel Bolts screws and studs with specifiedproperty classes Coarse thread and fine pitch thread British StandardsInstitution United Kingdom

BSI (2014) BS EN 1991-1-72006+A12014 ndash Eurocode 1 Actions on structuresndash Part 197 General actions British Standards Institution United Kingdom

BSI (2015) BS EN 14399-42015 ndash High-strength structural boltingassemblies for preloading System HV Hexagon bolt and nut assembliesBritish Standards Institution United Kingdom

SCI (1995a) Joints in steel construction Moment connections P207 TheSteel Construction Institute

SCI (1995b) Advisory Desk Notes Bending Moment in a pin AD 172 TheSteel Construction Institute

SCI (2006) Column base stiffness for global analysis NCCI-SN045a TheSteel Construction Institute

SCI (2011) Joints in steel construction Simple joints to Eurocode 3 P358The Steel Construction Institute

SCI (2013a) Joints in steel construction Moment-resisting joints toEurocode 3 P398 The Steel Construction Institute

UK FOREWORD

_____

xxviii

SCI (2013b) Interim Report Design of Portal Frames to Eurocode 3 Anoverview for UK designers P400 The Steel Construction Institute

UK FOREWORD

_____

xxiii

Section 23

As explained above typical UK design practice does not consider thissophisticated procedure for idealisation of joints

Section 24

The NA to BS EN 1993-1-8 gives practical guidance to classify joints Italso states the following

ldquoUntil experience is gained with the numerical method of calculatingrotational stiffness given in BS EN 1993-1-82005 63 and theclassification by stiffness method given in BS EN 1993-1-82005522 semi-continuous elastic design should only be used where eitherit is supported by test evidence according to BS EN 1993-1-820055221(2) or where it is based on satisfactorily performance in asimilar situationrdquo

Evidence on values of column base stiffness for practical global analysis isgiven in SCI (2006)

Section 25

The concept of ductility classes is not widely applied in the UK It isgenerally assumed that standard connection details to the SCI Green Booksprovide enough rotation capacity and so behave in a ductile manner asevidenced by physical testing and experience

Section 31

The NA to BS EN 1993-1-8 excludes bolts of classes 58 and 68 It alsostates that bolt class 48 may only be used if the manufacturing process (i) isin accordance with BS EN ISO 898-1 (BSI 2013) and (ii) includes suitableprocedures to avoid hydrogen embrittlement

Section 322

The NA to BS EN 1993-1-8 states that if the preload is not explicitly used inthe design calculations then no specific level of preload is required

Section 347

Injection bolts are rarely used in the UK

UK FOREWORD

_____

xxiv

Section 348

Reference is made to SCI (1995b) to calculate the bending moments in thepin of a pin bearing

Section 349

Flow drill blind bolting is not common practice in the UK SHS blind boltingis a common system but there are several manufactures other than thatsuggested in the book

Section 3410

Nails are rarely used in the UK

Section 352

T-stub configurations with four bolts in a row are rarely used in the UK

Section 353

Reference is made to the SCI method for the design of gusset plates seeSCI (2011)

Section 421

It is anticipated that specific rules given in the current BS EN 1993-1-12(BSI 2009) for high strength steels will be incorporated in the revisedBS EN 1993-1-8 to appear after 2020

Section 522

ldquoHeader platesrdquo are known as ldquopartial depth end platesrdquo in the UK Webcleat connections are no longer commonly used in the UK The full depthend plate connection shown on the left of Figure 59 is classified as a simplejoint in the UK (SCI 2011)

Section 523

The UK Building Regulations require that joints are designed for tyingforces in order to satisfy structural integrity requirements Guidance onthe design values of tying forces is given in BS EN 1991-1-7 Annex Aand its UK NA The requirements relate to the building class with a

UK FOREWORD

_____

xxv

design value of horizontal force generally not less than 75 kN andusually significantly higher Simple joints detailed to SCI (2011) satisfythese requirements

Section 525

It is generally safe to assume that the ductility (rotation requirements) aresatisfied provided that joints are detailed in accordance with SCI (2011)

Section 531

The column base detailing on the left of Figure 521 is not commonly used inthe UK We never recommend less than four bolts ndash they are needed toassure stability and facilitate location during erection The anchoringsystems shown in Figure 522 are not usually adopted in the UK Referenceis made to SCI (2013a) for common anchor systems

Section 62

Publication SCI (2013b) summarises the principal differences betweenBS 5950 and BS EN 1993-1-8 (BSI 2000 and 2010) in terms ofcomponent characterisation

With reference to Figure 66 it is anticipated that the revised BS EN1993-1-8will include analytical expressions for the definition of the so-called αcoefficient

Rules of thumb for the characterisation of the ductility of some individualcomponents are given in SCI (1995a)

Section 631

The UK NA to BS EN 1993-1-8 gives specific rules for the full plasticdistribution of effective design tension resistance The procedure is alsosummarised in SCI (2013a)

Section 633

Where a joint is subjected to combined bending moments and axial forcesthe concept of an applied moment modified by axial load can be used seeSCI (1995a)

UK FOREWORD

_____

xxvi

Section 64

Rotational stiffness is not normally evaluated in UK design practice whichusually relies on past experience

Section 65

Some rules of thumb for the characterisation of the ductility of moment-resisting joints are given in SCI (1995a)

Section 661

With reference to Figure 636 it is noted that this joint configuration ishardly (if ever) used in the UK

Section 663

It should be noted that European sections are not commonly used in the UKalthough there is growing interest in the market Steel grade S235 is not usedin the UK S355 being the current common grade Combinations of plates of15 mm thickness with M24 bolts are common This combination is assumedto provide enough rotation capacity thus satisfying ductility requirementsbecause ductile failure of the plates not brittle failure of the bolts governsthe behaviour

Section 672

Standard practice in the UK does not account for this 25 rule Columnsplices are usually detailed to SCI (2011) to ensure continuity of stiffnessthrough the splice so that the member design is not invalidated

Section 84

The UK Building Regulations require that joints are designed for tyingforces in order to satisfy structural integrity requirements Guidance on thedesign values of tying forces is given in BS EN 1991-1-7 Annex A and itsUK NA (BSI 2014)

Section 91

In the UK the ldquofabricatorsrdquo are known as ldquoSteelwork contractorsrdquo becausethey do more than just fabricate

UK FOREWORD

_____

xxvii

REFERENCES TO NATIONAL FOREWORD

BSI (2000) BS 5950-12000 ndash Structural use of steelwork in building ndash Part1 Code of Practice for Design rolled and welded sections British StandardsInstitution United Kingdom

BSI (2007) BS EN 14399-82007 ndash High-strength structural boltingassemblies for preloading System HV Hexagon fit bolt and nut assembliesBritish Standards Institution United Kingdom

BSI (2009) BS EN 1993-1-122007 ndash Eurocode 3 Design of steel structuresndash Part 112 Additional rules for the extension of EN 1993 up to steel gradesS 700 British Standards Institution United Kingdom

BSI (2010) BS EN 1993-1-82005 ndash Eurocode 3 Design of steel structuresndash Part 18 Design of joints British Standards Institution United Kingdom

BSI (2013) BS EN ISO 898-12013 ndash Mechanical properties of fastenersmade of carbon steel and alloy steel Bolts screws and studs with specifiedproperty classes Coarse thread and fine pitch thread British StandardsInstitution United Kingdom

BSI (2014) BS EN 1991-1-72006+A12014 ndash Eurocode 1 Actions on structuresndash Part 197 General actions British Standards Institution United Kingdom

BSI (2015) BS EN 14399-42015 ndash High-strength structural boltingassemblies for preloading System HV Hexagon bolt and nut assembliesBritish Standards Institution United Kingdom

SCI (1995a) Joints in steel construction Moment connections P207 TheSteel Construction Institute

SCI (1995b) Advisory Desk Notes Bending Moment in a pin AD 172 TheSteel Construction Institute

SCI (2006) Column base stiffness for global analysis NCCI-SN045a TheSteel Construction Institute

SCI (2011) Joints in steel construction Simple joints to Eurocode 3 P358The Steel Construction Institute

SCI (2013a) Joints in steel construction Moment-resisting joints toEurocode 3 P398 The Steel Construction Institute

UK FOREWORD

_____

xxviii

SCI (2013b) Interim Report Design of Portal Frames to Eurocode 3 Anoverview for UK designers P400 The Steel Construction Institute

UK FOREWORD

_____

xxiv

Section 348

Reference is made to SCI (1995b) to calculate the bending moments in thepin of a pin bearing

Section 349

Flow drill blind bolting is not common practice in the UK SHS blind boltingis a common system but there are several manufactures other than thatsuggested in the book

Section 3410

Nails are rarely used in the UK

Section 352

T-stub configurations with four bolts in a row are rarely used in the UK

Section 353

Reference is made to the SCI method for the design of gusset plates seeSCI (2011)

Section 421

It is anticipated that specific rules given in the current BS EN 1993-1-12(BSI 2009) for high strength steels will be incorporated in the revisedBS EN 1993-1-8 to appear after 2020

Section 522

ldquoHeader platesrdquo are known as ldquopartial depth end platesrdquo in the UK Webcleat connections are no longer commonly used in the UK The full depthend plate connection shown on the left of Figure 59 is classified as a simplejoint in the UK (SCI 2011)

Section 523

The UK Building Regulations require that joints are designed for tyingforces in order to satisfy structural integrity requirements Guidance onthe design values of tying forces is given in BS EN 1991-1-7 Annex Aand its UK NA The requirements relate to the building class with a

UK FOREWORD

_____

xxv

design value of horizontal force generally not less than 75 kN andusually significantly higher Simple joints detailed to SCI (2011) satisfythese requirements

Section 525

It is generally safe to assume that the ductility (rotation requirements) aresatisfied provided that joints are detailed in accordance with SCI (2011)

Section 531

The column base detailing on the left of Figure 521 is not commonly used inthe UK We never recommend less than four bolts ndash they are needed toassure stability and facilitate location during erection The anchoringsystems shown in Figure 522 are not usually adopted in the UK Referenceis made to SCI (2013a) for common anchor systems

Section 62

Publication SCI (2013b) summarises the principal differences betweenBS 5950 and BS EN 1993-1-8 (BSI 2000 and 2010) in terms ofcomponent characterisation

With reference to Figure 66 it is anticipated that the revised BS EN1993-1-8will include analytical expressions for the definition of the so-called αcoefficient

Rules of thumb for the characterisation of the ductility of some individualcomponents are given in SCI (1995a)

Section 631

The UK NA to BS EN 1993-1-8 gives specific rules for the full plasticdistribution of effective design tension resistance The procedure is alsosummarised in SCI (2013a)

Section 633

Where a joint is subjected to combined bending moments and axial forcesthe concept of an applied moment modified by axial load can be used seeSCI (1995a)

UK FOREWORD

_____

xxvi

Section 64

Rotational stiffness is not normally evaluated in UK design practice whichusually relies on past experience

Section 65

Some rules of thumb for the characterisation of the ductility of moment-resisting joints are given in SCI (1995a)

Section 661

With reference to Figure 636 it is noted that this joint configuration ishardly (if ever) used in the UK

Section 663

It should be noted that European sections are not commonly used in the UKalthough there is growing interest in the market Steel grade S235 is not usedin the UK S355 being the current common grade Combinations of plates of15 mm thickness with M24 bolts are common This combination is assumedto provide enough rotation capacity thus satisfying ductility requirementsbecause ductile failure of the plates not brittle failure of the bolts governsthe behaviour

Section 672

Standard practice in the UK does not account for this 25 rule Columnsplices are usually detailed to SCI (2011) to ensure continuity of stiffnessthrough the splice so that the member design is not invalidated

Section 84

The UK Building Regulations require that joints are designed for tyingforces in order to satisfy structural integrity requirements Guidance on thedesign values of tying forces is given in BS EN 1991-1-7 Annex A and itsUK NA (BSI 2014)

Section 91

In the UK the ldquofabricatorsrdquo are known as ldquoSteelwork contractorsrdquo becausethey do more than just fabricate

UK FOREWORD

_____

xxvii

REFERENCES TO NATIONAL FOREWORD

BSI (2000) BS 5950-12000 ndash Structural use of steelwork in building ndash Part1 Code of Practice for Design rolled and welded sections British StandardsInstitution United Kingdom

BSI (2007) BS EN 14399-82007 ndash High-strength structural boltingassemblies for preloading System HV Hexagon fit bolt and nut assembliesBritish Standards Institution United Kingdom

BSI (2009) BS EN 1993-1-122007 ndash Eurocode 3 Design of steel structuresndash Part 112 Additional rules for the extension of EN 1993 up to steel gradesS 700 British Standards Institution United Kingdom

BSI (2010) BS EN 1993-1-82005 ndash Eurocode 3 Design of steel structuresndash Part 18 Design of joints British Standards Institution United Kingdom

BSI (2013) BS EN ISO 898-12013 ndash Mechanical properties of fastenersmade of carbon steel and alloy steel Bolts screws and studs with specifiedproperty classes Coarse thread and fine pitch thread British StandardsInstitution United Kingdom

BSI (2014) BS EN 1991-1-72006+A12014 ndash Eurocode 1 Actions on structuresndash Part 197 General actions British Standards Institution United Kingdom

BSI (2015) BS EN 14399-42015 ndash High-strength structural boltingassemblies for preloading System HV Hexagon bolt and nut assembliesBritish Standards Institution United Kingdom

SCI (1995a) Joints in steel construction Moment connections P207 TheSteel Construction Institute

SCI (1995b) Advisory Desk Notes Bending Moment in a pin AD 172 TheSteel Construction Institute

SCI (2006) Column base stiffness for global analysis NCCI-SN045a TheSteel Construction Institute

SCI (2011) Joints in steel construction Simple joints to Eurocode 3 P358The Steel Construction Institute

SCI (2013a) Joints in steel construction Moment-resisting joints toEurocode 3 P398 The Steel Construction Institute

UK FOREWORD

_____

xxviii

SCI (2013b) Interim Report Design of Portal Frames to Eurocode 3 Anoverview for UK designers P400 The Steel Construction Institute

UK FOREWORD

_____

xxv

design value of horizontal force generally not less than 75 kN andusually significantly higher Simple joints detailed to SCI (2011) satisfythese requirements

Section 525

It is generally safe to assume that the ductility (rotation requirements) aresatisfied provided that joints are detailed in accordance with SCI (2011)

Section 531

The column base detailing on the left of Figure 521 is not commonly used inthe UK We never recommend less than four bolts ndash they are needed toassure stability and facilitate location during erection The anchoringsystems shown in Figure 522 are not usually adopted in the UK Referenceis made to SCI (2013a) for common anchor systems

Section 62

Publication SCI (2013b) summarises the principal differences betweenBS 5950 and BS EN 1993-1-8 (BSI 2000 and 2010) in terms ofcomponent characterisation

With reference to Figure 66 it is anticipated that the revised BS EN1993-1-8will include analytical expressions for the definition of the so-called αcoefficient

Rules of thumb for the characterisation of the ductility of some individualcomponents are given in SCI (1995a)

Section 631

The UK NA to BS EN 1993-1-8 gives specific rules for the full plasticdistribution of effective design tension resistance The procedure is alsosummarised in SCI (2013a)

Section 633

Where a joint is subjected to combined bending moments and axial forcesthe concept of an applied moment modified by axial load can be used seeSCI (1995a)

UK FOREWORD

_____

xxvi

Section 64

Rotational stiffness is not normally evaluated in UK design practice whichusually relies on past experience

Section 65

Some rules of thumb for the characterisation of the ductility of moment-resisting joints are given in SCI (1995a)

Section 661

With reference to Figure 636 it is noted that this joint configuration ishardly (if ever) used in the UK

Section 663

It should be noted that European sections are not commonly used in the UKalthough there is growing interest in the market Steel grade S235 is not usedin the UK S355 being the current common grade Combinations of plates of15 mm thickness with M24 bolts are common This combination is assumedto provide enough rotation capacity thus satisfying ductility requirementsbecause ductile failure of the plates not brittle failure of the bolts governsthe behaviour

Section 672

Standard practice in the UK does not account for this 25 rule Columnsplices are usually detailed to SCI (2011) to ensure continuity of stiffnessthrough the splice so that the member design is not invalidated

Section 84

The UK Building Regulations require that joints are designed for tyingforces in order to satisfy structural integrity requirements Guidance on thedesign values of tying forces is given in BS EN 1991-1-7 Annex A and itsUK NA (BSI 2014)

Section 91

In the UK the ldquofabricatorsrdquo are known as ldquoSteelwork contractorsrdquo becausethey do more than just fabricate

UK FOREWORD

_____

xxvii

REFERENCES TO NATIONAL FOREWORD

BSI (2000) BS 5950-12000 ndash Structural use of steelwork in building ndash Part1 Code of Practice for Design rolled and welded sections British StandardsInstitution United Kingdom

BSI (2007) BS EN 14399-82007 ndash High-strength structural boltingassemblies for preloading System HV Hexagon fit bolt and nut assembliesBritish Standards Institution United Kingdom

BSI (2009) BS EN 1993-1-122007 ndash Eurocode 3 Design of steel structuresndash Part 112 Additional rules for the extension of EN 1993 up to steel gradesS 700 British Standards Institution United Kingdom

BSI (2010) BS EN 1993-1-82005 ndash Eurocode 3 Design of steel structuresndash Part 18 Design of joints British Standards Institution United Kingdom

BSI (2013) BS EN ISO 898-12013 ndash Mechanical properties of fastenersmade of carbon steel and alloy steel Bolts screws and studs with specifiedproperty classes Coarse thread and fine pitch thread British StandardsInstitution United Kingdom

BSI (2014) BS EN 1991-1-72006+A12014 ndash Eurocode 1 Actions on structuresndash Part 197 General actions British Standards Institution United Kingdom

BSI (2015) BS EN 14399-42015 ndash High-strength structural boltingassemblies for preloading System HV Hexagon bolt and nut assembliesBritish Standards Institution United Kingdom

SCI (1995a) Joints in steel construction Moment connections P207 TheSteel Construction Institute

SCI (1995b) Advisory Desk Notes Bending Moment in a pin AD 172 TheSteel Construction Institute

SCI (2006) Column base stiffness for global analysis NCCI-SN045a TheSteel Construction Institute

SCI (2011) Joints in steel construction Simple joints to Eurocode 3 P358The Steel Construction Institute

SCI (2013a) Joints in steel construction Moment-resisting joints toEurocode 3 P398 The Steel Construction Institute

UK FOREWORD

_____

xxviii

SCI (2013b) Interim Report Design of Portal Frames to Eurocode 3 Anoverview for UK designers P400 The Steel Construction Institute

UK FOREWORD

_____

xxvi

Section 64

Rotational stiffness is not normally evaluated in UK design practice whichusually relies on past experience

Section 65

Some rules of thumb for the characterisation of the ductility of moment-resisting joints are given in SCI (1995a)

Section 661

With reference to Figure 636 it is noted that this joint configuration ishardly (if ever) used in the UK

Section 663

It should be noted that European sections are not commonly used in the UKalthough there is growing interest in the market Steel grade S235 is not usedin the UK S355 being the current common grade Combinations of plates of15 mm thickness with M24 bolts are common This combination is assumedto provide enough rotation capacity thus satisfying ductility requirementsbecause ductile failure of the plates not brittle failure of the bolts governsthe behaviour

Section 672

Standard practice in the UK does not account for this 25 rule Columnsplices are usually detailed to SCI (2011) to ensure continuity of stiffnessthrough the splice so that the member design is not invalidated

Section 84

The UK Building Regulations require that joints are designed for tyingforces in order to satisfy structural integrity requirements Guidance on thedesign values of tying forces is given in BS EN 1991-1-7 Annex A and itsUK NA (BSI 2014)

Section 91

In the UK the ldquofabricatorsrdquo are known as ldquoSteelwork contractorsrdquo becausethey do more than just fabricate

UK FOREWORD

_____

xxvii

REFERENCES TO NATIONAL FOREWORD

BSI (2000) BS 5950-12000 ndash Structural use of steelwork in building ndash Part1 Code of Practice for Design rolled and welded sections British StandardsInstitution United Kingdom

BSI (2007) BS EN 14399-82007 ndash High-strength structural boltingassemblies for preloading System HV Hexagon fit bolt and nut assembliesBritish Standards Institution United Kingdom

BSI (2009) BS EN 1993-1-122007 ndash Eurocode 3 Design of steel structuresndash Part 112 Additional rules for the extension of EN 1993 up to steel gradesS 700 British Standards Institution United Kingdom

BSI (2010) BS EN 1993-1-82005 ndash Eurocode 3 Design of steel structuresndash Part 18 Design of joints British Standards Institution United Kingdom

BSI (2013) BS EN ISO 898-12013 ndash Mechanical properties of fastenersmade of carbon steel and alloy steel Bolts screws and studs with specifiedproperty classes Coarse thread and fine pitch thread British StandardsInstitution United Kingdom

BSI (2014) BS EN 1991-1-72006+A12014 ndash Eurocode 1 Actions on structuresndash Part 197 General actions British Standards Institution United Kingdom

BSI (2015) BS EN 14399-42015 ndash High-strength structural boltingassemblies for preloading System HV Hexagon bolt and nut assembliesBritish Standards Institution United Kingdom

SCI (1995a) Joints in steel construction Moment connections P207 TheSteel Construction Institute

SCI (1995b) Advisory Desk Notes Bending Moment in a pin AD 172 TheSteel Construction Institute

SCI (2006) Column base stiffness for global analysis NCCI-SN045a TheSteel Construction Institute

SCI (2011) Joints in steel construction Simple joints to Eurocode 3 P358The Steel Construction Institute

SCI (2013a) Joints in steel construction Moment-resisting joints toEurocode 3 P398 The Steel Construction Institute

UK FOREWORD

_____

xxviii

SCI (2013b) Interim Report Design of Portal Frames to Eurocode 3 Anoverview for UK designers P400 The Steel Construction Institute

UK FOREWORD

_____

xxvii

REFERENCES TO NATIONAL FOREWORD

BSI (2000) BS 5950-12000 ndash Structural use of steelwork in building ndash Part1 Code of Practice for Design rolled and welded sections British StandardsInstitution United Kingdom

BSI (2007) BS EN 14399-82007 ndash High-strength structural boltingassemblies for preloading System HV Hexagon fit bolt and nut assembliesBritish Standards Institution United Kingdom

BSI (2009) BS EN 1993-1-122007 ndash Eurocode 3 Design of steel structuresndash Part 112 Additional rules for the extension of EN 1993 up to steel gradesS 700 British Standards Institution United Kingdom

BSI (2010) BS EN 1993-1-82005 ndash Eurocode 3 Design of steel structuresndash Part 18 Design of joints British Standards Institution United Kingdom

BSI (2013) BS EN ISO 898-12013 ndash Mechanical properties of fastenersmade of carbon steel and alloy steel Bolts screws and studs with specifiedproperty classes Coarse thread and fine pitch thread British StandardsInstitution United Kingdom

BSI (2014) BS EN 1991-1-72006+A12014 ndash Eurocode 1 Actions on structuresndash Part 197 General actions British Standards Institution United Kingdom

BSI (2015) BS EN 14399-42015 ndash High-strength structural boltingassemblies for preloading System HV Hexagon bolt and nut assembliesBritish Standards Institution United Kingdom

SCI (1995a) Joints in steel construction Moment connections P207 TheSteel Construction Institute

SCI (1995b) Advisory Desk Notes Bending Moment in a pin AD 172 TheSteel Construction Institute

SCI (2006) Column base stiffness for global analysis NCCI-SN045a TheSteel Construction Institute

SCI (2011) Joints in steel construction Simple joints to Eurocode 3 P358The Steel Construction Institute

SCI (2013a) Joints in steel construction Moment-resisting joints toEurocode 3 P398 The Steel Construction Institute

UK FOREWORD

_____

xxviii

SCI (2013b) Interim Report Design of Portal Frames to Eurocode 3 Anoverview for UK designers P400 The Steel Construction Institute

UK FOREWORD

_____

xxviii

SCI (2013b) Interim Report Design of Portal Frames to Eurocode 3 Anoverview for UK designers P400 The Steel Construction Institute