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Design of Structural Steel Joints

Dr. Klaus WeynandFeldmann + Weynand GmbH, Aachen, Germany

Prof. Jean-Pierre JaspartUniversity of Liège, Belgium

Design of Structural Steel Joints

• Introduction

• Integration of joints into structural design process

• Moment resistant joints

• Simple joints

• Design tools

Design of Structural Steel Joints

• Introduction• Integration of joints into

structural design process

• Moment resistant joints

• Simple joints

• Design tools

Eurocodes - Design of steel buildings with worked examples Brussels, 16 - 17 October 2014

EN 1993 Part 1.8

Chapter 1 – Introduction

Chapter 2 – Basis of design

Chapter 3 – Connections made with bolts, rivets or pins

Chapter 4 – Welded connections

Chapter 5 – Analysis, classification and modelling

Chapter 6 – Structural joints connecting H or I sections

Chapter 7 – Hollow section joints

Eurocodes - Design of steel buildings with worked examples Brussels, 16 - 17 October 2014

Design of simple joints

ECCS Publication No 126 (EN)

• Background information

• Design guidelines

Eurocodes - Design of steel buildings with worked examples Brussels, 16 - 17 October 2014

2 – Basis of design Partial safety coefficients

Eurocodes - Design of steel buildings with worked examples Brussels, 16 - 17 October 2014

3 – Connections made mechanical fasteners

Eurocodes - Design of steel buildings with worked examples Brussels, 16 - 17 October 2014

4 – Welded connections

Design of Structural Steel Joints

• Introduction

• Integration of joints into structural design process

• Moment resistant joints

• Simple joints

• Design tools

Eurocodes - Design of steel buildings with worked examples Brussels, 16 - 17 October 2014

Actual joint response

Eurocodes - Design of steel buildings with worked examples Brussels, 16 - 17 October 2014

Actual joint response

M

M Rd

S j,inicd

Eurocodes - Design of steel buildings with worked examples Brussels, 16 - 17 October 2014

Influence on the structural response

• Displacements

• Internal forces

• Failure mode and failure load

Eurocodes - Design of steel buildings with worked examples Brussels, 16 - 17 October 2014

M

M

?

?

?

M

Characterization

Modelling

Classification

Idealization

Four successive steps for structural integration

Eurocodes - Design of steel buildings with worked examples Brussels, 16 - 17 October 2014

Characterization

Search for a unified approach whatever the material

M

?

?

?

Eurocodes - Design of steel buildings with worked examples Brussels, 16 - 17 October 2014

Various configurations (1)Continuity

Beam-to-beam

Column bases

Eurocodes - Design of steel buildings with worked examples Brussels, 16 - 17 October 2014

Various configurations (2)Joints in portal frames

Eurocodes - Design of steel buildings with worked examples Brussels, 16 - 17 October 2014

Various configurations (3)

Connections and joints incomposite construction

Eurocodes - Design of steel buildings with worked examples Brussels, 16 - 17 October 2014

Various cross-section shapes (1)

Hot-rolled and

cold-formed

Eurocodes - Design of steel buildings with worked examples Brussels, 16 - 17 October 2014

Various cross-section shapes (2)

Built-up profiles

Eurocodes - Design of steel buildings with worked examples Brussels, 16 - 17 October 2014

Various connection elements

Splices

Cleats

End plates

Eurocodes - Design of steel buildings with worked examples Brussels, 16 - 17 October 2014

Economy

Reduced fabrication, transportation and erection costs

Eurocodes - Design of steel buildings with worked examples Brussels, 16 - 17 October 2014

Specific design criteria

Robustness

Joints as key elements

Eurocodes - Design of steel buildings with worked examples Brussels, 16 - 17 October 2014

Characterization (1)

Search for a unified approach

M

?

?

?

Eurocodes - Design of steel buildings with worked examples Brussels, 16 - 17 October 2014

Characterization (2)

Eurocode 3 – Part 1-8

• Beam-to-beam joints, splices, beam-to-column joints and column

bases:

welded connections

bolted connections (anchors for column bases)

Background: COMPONENT METHOD

Eurocodes - Design of steel buildings with worked examples Brussels, 16 - 17 October 2014

Three steps

First step

Identification of the

active components

Second step:

Response of the

components

Third step:

“Assembly” of the

components

F F F

E k1 E k2 E k3

F1,RdF2,Rd

F3,Rd

column webin shear

column webin tension

column webin compression

M

Sj,ini

Mj,Rd

cd

, ,minj Rd i RdM F z 2

, 1j ini

i

E zS

k

Characterization (3) - component method

Eurocodes - Design of steel buildings with worked examples Brussels, 16 - 17 October 2014

Characterization (4) - component method

EC3 Part 1-8 provides therefore:

• a library of components

• rules for the evaluation of the properties of the components

(stiffness, resistance, deformation capacity)

• rules for the evaluation of the possible component interactions

• « assembly » rules for components

Applicable for simple joint and moment resistant joint

Eurocodes - Design of steel buildings with worked examples Brussels, 16 - 17 October 2014

Characterization (4) – Hollow section jointsDifferent approach for lattice girder joints

For many types of joint configurations:

• Joints considered as a whole

• Check of relevant failure modes

• Scope of application to be checked

Eurocodes - Design of steel buildings with worked examples Brussels, 16 - 17 October 2014

M

M

?

?

?

M

Characterization

Modelling

Classification

Idealization

Four successive steps for structural integration

Eurocodes - Design of steel buildings with worked examples Brussels, 16 - 17 October 2014

Classification (1)

Stiffness

Sj,ini

Pinned

Semi-rigid

RigidM j

Boundaries for stiffness

Joint initial stiffness

Semi-rigid

Rigid

Pinned

Classification boundariesInitial joint stiffness

Eurocodes - Design of steel buildings with worked examples Brussels, 16 - 17 October 2014

Classification (2)

Resistance

Mj,Rd

Partial-strength

Full-strength

Pinned

Mj

Boundaries for strength

Joint strength

Full resistance

Partial resistance

Pinned

Classification boundariesJoint resistance

Eurocodes - Design of steel buildings with worked examples Brussels, 16 - 17 October 2014

Classification (3)

Ductility

• Brittle

• “Semi-ductile”

• Ductile

Mj

Eurocodes - Design of steel buildings with worked examples Brussels, 16 - 17 October 2014

M

M

?

?

?

M

Characterization

Modelling

Classification

Idealization

Four successive steps for structural integration

Eurocodes - Design of steel buildings with worked examples Brussels, 16 - 17 October 2014

Modelling

JOINT

MODELLING

BEAM-TO-COLUMN JOINTS

MAJOR AXIS BENDING

BEAM

SPLICES

COLUMN

BASES

SIMPLE

SEMI-

CONTINUOUS

CONTINUOUS

Eurocodes - Design of steel buildings with worked examples Brussels, 16 - 17 October 2014

M

M

?

?

?

M

Characterization

Modelling

Classification

Idealization

Four successive steps for structural integration

Design of Structural Steel Joints

• Introduction

• Integration of joints into structural design process

• Moment resistant joints• Simple joints

• Design tools

Eurocodes - Design of steel buildings with worked examples Brussels, 16 - 17 October 2014

ExampleSingle sided beam-to-column joint configuration, bolted end-plate connection

+ +

+ +

M

V

15

3

IPE220

HEB140

120

60 10

8030 30

240

4 M16 8.8

140

u=10p=60

5

w=

To be evaluated:

Design moment resistance , initial stiffness

0

1

1,01,0

M

M

Material: S 235

Eurocodes - Design of steel buildings with worked examples Brussels, 16 - 17 October 2014

General data

2 2 140 2 12 2 12 92wc c fc ch h t r mm

2

2 2

4295,6 2 140 12 7 2 12 12 1307,6vc c c fc wc cA A b t t r

mm

80 70,8 0,8 12 26,9

2 2

fc

c

w tm r mm

140 8030

2 2

cb we mm

2 2

,

0

12 2350,25 0,25 8460 /

1,0

fc yc

pl fc

M

t fm Nmm mm

Column

Equivalent T-stub in tension

F /4t

Ft

F /4t

F /4t

F /4t

m e

leff

Eurocodes - Design of steel buildings with worked examples Brussels, 16 - 17 October 2014

General data

+ +

+ +

15

3

IPE220120

60 10

8030 30

240

4 M16 8.8

140

u=10p=60

5

w=

z

9,2220 10 60 165,4

2 2

fb

b

tz h u p mm

6,

,

0

285.406 235 10 (classe 1 section) 67,07

1,0

pl yb yb

c Rd

M

W fM kNm

Lever arm

Beam

Eurocodes - Design of steel buildings with worked examples Brussels, 16 - 17 October 2014

General data

2 2

,

0

15 2350,25 0,25 13.218 /

1,0

p yp

pl p

M

t fm Nmm mm

mp

mp2

80 5,90,8 2 0,8 2 3 33,66

2 2

wbp w

w tm a mm

2 0,8 2 60 10 9,2 0,8 2 5 35,14p fb fm p u t a mm

140 8030

2 2

p

p

b we mm

End plate

Eurocodes - Design of steel buildings with worked examples Brussels, 16 - 17 October 2014

General data

5,5

1

33,660,53

33,66 30

p

p p

m

m e

2

2

35,140,55

33,66 30

p

p p

m

m e

Alpha factor for effective lengths

End plate

Eurocodes - Design of steel buildings with worked examples Brussels, 16 - 17 October 2014

General data

3

,

0,9 0,9 800 157 1090,43

1,25

ub st Rd

Mb

f AF kN

3

,

0,6 0,6 800 157 10 (shear plane in thread) 60,3

1.25

ub sv Rd

Mb

f AF kN

1

0,5 12 15 10 14,8 2 4 47,42

b fc p bolt nutL t t h h mm

Bolts

Eurocodes - Design of steel buildings with worked examples Brussels, 16 - 17 October 2014

Component No 1 – Column web in shear

Vwp

Vwp

F

M

z

F

3,

,

0

0,9 0,9 1307,6 235 10159,7

3 3 1,0

vc y cw

wc Rd

M

A fV kN

Assumption : 1

,

,1

159,7159,7

1

wc Rd

Rd

VF kN

1

0,38 0,38 1307,63,004

1 165,4

vcAk mmh

Resistance

Stiffness coefficient

Transformation parameter

Eurocodes - Design of steel buildings with worked examples Brussels, 16 - 17 October 2014

Component No 2 – Column web in compression

, , min 2 2 2 5 ; 2 5

min 9,2 2 5 2 2 15 5 12 12 ; 9,2 5 2 15 10 5 12 12 161,27

eff c wc fb f p fc fb f p fcb t a t t s t a t u t s

mm

, ,Assumption : min 1,0; 1,7 / 1,0wc com Ed y wck f

, , ,

2

161,27 92 2350,932 0,932 0,543 0,673 1,0

210000 7 7

eff c wc c y wc

p

wc

b d f

E t

1 2 2

, ,

1 10,713

1 1,3 161,27 7 1307,61 1,3 /eff c wc wc vcb t A

3

,2 , , , 1/ 1 0,713 1 161,27 7 235 10 1,0 189,1Rd wc eff c wc wc y wc MF k b t f kN

Resistance

Reduction factors to account for compression stresses and instability

Eurocodes - Design of steel buildings with worked examples Brussels, 16 - 17 October 2014

Component No 2 – Column web in compression

F

F k Ei i i

, ,

2

0,7 0,7 161,27 78,589

92

eff c wc wc

wc

b tk mm

h

Stiffness coefficient

Eurocodes - Design of steel buildings with worked examples Brussels, 16 - 17 October 2014

Component No 3 – Column web in tension

, , min 2 ;4 1,25 min 2 26,9;4 26,9 1,25 30 145,10eff t wcb m m e mm

1 2 2

, ,

1 10,749

1 1,3 145,1 7 1307,61 1,3 /eff t wc wc vcb t A

3

,3 , , , 0/ 0,749 145,1 7 235 10 1,0 178,7Rd eff t wc wc y wc MF b t f kN

, ,

3

0,7 0,7 145,1 77,728

92

eff t wc wc

wc

b tk mm

h

Resistance

Stiffness coefficient

Eurocodes - Design of steel buildings with worked examples Brussels, 16 - 17 October 2014

Equivalent T-stub in tension

Component No 4 – Column flange in bendingComponent No 5 – End plate in bending

F /4t

Ft

F /4t

F /4t

F /4t

m e

leff

Eurocodes - Design of steel buildings with worked examples Brussels, 16 - 17 October 2014

T-stub – Effective length

Distinction between circular and non-circular yield line patterns

Circular patterns Non-circular patterns

Eurocodes - Design of steel buildings with worked examples Brussels, 16 - 17 October 2014

T-stub – Effective length

Groups effects to consider in addition to the individual response of each bolt-row

Group 1+2 Group 2+3 Group 1+2+3

Row 1

Row 2

Row 3

Eurocodes - Design of steel buildings with worked examples Brussels, 16 - 17 October 2014

T-stub – Effective length

Groups effects to consider in addition to the individual response of each bolt-row

Row 3

,3 ,3, ,3, ;( )Rd Rd indiv Rd groupF min F F

Eurocodes - Design of steel buildings with worked examples Brussels, 16 - 17 October 2014

Bolt rows consideredIn this example: only bolt row 1 is considered for tension forces

+ +

+ +

M

V

15

3

IPE220

HEB140

120

60 10

8030 30

240

4 M16 8.8

140

u=10p=60

5

w=

Row 1

Row 2

Eurocodes - Design of steel buildings with worked examples Brussels, 16 - 17 October 2014

Component No 4 – Column flange in bending

, , , , 145,1 (see column web in tension)eff t fc eff t wcl b mm

min ;1,25 ; / 2 min 30;1,25 26,9;30 30pn e m b w mm

Resistance

Eurocodes - Design of steel buildings with worked examples Brussels, 16 - 17 October 2014

3, , , , 3

, , 2

2 2 2 145,1 8460 2 90,4 10 3010 138,5

26,9 30

eff t fc pl fc t Rd

fc Rd t

l m B nF kN

m n

, , 3 ,2 2 90,43 180,9fc Rd t t RdF B kN

Mode 1 - Complete yielding of the flange

Mode 2 - Bolt failure with yielding of the flange

Mode 3 - Bolt failure

Component No 4 – Column flange in bending

, , , 3

, , 1

4 4 145,1 846010 182,5

26,9

eff t fc pl fc

fc Rd t

l mF kN

m

Eurocodes - Design of steel buildings with worked examples Brussels, 16 - 17 October 2014

Component No 4 – Column flange in bending

,4 , , 1 , , 2 , , 3min ; ; 138,5Rd fc Rd t fc Rd t fc Rd tF F F F kN

3 3, ,

4 3 3

0,9 0,9 145,1 1211,59

26,9

eff fc t fcl tk mm

m

Resistance

Stiffness coefficient

Eurocodes - Design of steel buildings with worked examples Brussels, 16 - 17 October 2014

Component No 5 – End plate in bending

, , min 2 ; min 2 33,66; 5,5 33,66 185eff t p p pl m m mm

min ;1,25 ; min 30;1,25 33,66;30 30p p pn e m e mm

, , , 3

, ,1

4 4 185 13.218Mode 1: 10 291

33,66

eff t p pl p

ep Rd

p

l mF kN

m

3, , , , 3

, ,2

2 2 2 185 13.218 2 90,43 10 30Mode 2: 10 162,1

33,66 30

eff p t pl p t Rd p

ep Rd

p p

l m B nF kN

m n

,5 , ,1 , ,2 , ,3min ; ; 162,1Rd ep Rd ep Rd ep RdF F F F kN

Resistance

Eurocodes - Design of steel buildings with worked examples Brussels, 16 - 17 October 2014

Component No 5 – End plate in bending

3 3, ,

5 3 3

0,9 0,9 185,0 1514,73

33,66

eff t p p

p

l tk mm

m

Stiffness coefficient

Eurocodes - Design of steel buildings with worked examples Brussels, 16 - 17 October 2014

Component No 7 – Beam flange and web in compression

,7 , 367,07

/ 318,2210,8 10

Rd c Rd b fbF M h t kN

7k

Resistance

Stiffness coefficient

Eurocodes - Design of steel buildings with worked examples Brussels, 16 - 17 October 2014

Component No 8 – Beam web in tension

, , , , 185eff t wb eff t pb l mm

3

,8 , , 0/ 185 5,9 235 10 1,0 256,5Rd eff t wb wb yb MF b t f kN

8k

Resistance

Stiffness coefficient

Eurocodes - Design of steel buildings with worked examples Brussels, 16 - 17 October 2014

Component No 10 – Bolts in tension

,10 ,2 2 90,43 180,9Rd t RdF B kN

10

1571,6 1,6 5,30

47,4

s

b

Ak mm

L

Mode 3 in T-stubs for components:

• “column flange in bending”

• “end plate in bending”

Resistance

Stiffness coefficient

Eurocodes - Design of steel buildings with worked examples Brussels, 16 - 17 October 2014

Mj,Rd

Design moment resistance

,min 138,5 (Column flange in bending)Rd Rd iF F kN

3

, 138,5 165,4 10 22,91j Rd RdM F z kNm

, , ,

215,27

3j el Rd j RdM M kNm

Design plastic moment resistance

Relevant component

Design elastic moment resistance

Eurocodes - Design of steel buildings with worked examples Brussels, 16 - 17 October 2014

Stiffness

Sj,ini

2 62

,

210000 165,4 10/ 1 6234 /

1 1 1 1 1 1

3,004 8,589 7,728 11,59 14,73 5,30

j ini i

i

S E h k kNm rad

, / 2 3117 /j j iniS S kNm rad

Initial stiffness

Secant stiffness

Eurocodes - Design of steel buildings with worked examples Brussels, 16 - 17 October 2014

Design moment-rotation characteristic

M

Sj,ini

Sj,ini

SjS

j= /

Ersatzsteifigkeit:

M j,Rd

2/3Mj,Rd

Secant stiffness

Design of Structural Steel Joints

• Introduction

• Integration of joints into structural design process

• Moment resistant joints

• Simple joints• Design tools

Eurocodes - Design of steel buildings with worked examples Brussels, 16 - 17 October 2014

Nominally pinned joints

Braced frame

Eurocodes - Design of steel buildings with worked examples Brussels, 16 - 17 October 2014

Nominally pinned joints

V 0 M = 0

Eurocodes - Design of steel buildings with worked examples Brussels, 16 - 17 October 2014

Design of simple joints

ECCS Publication No 126 (EN)

• Background information

• Design guidelines

Eurocodes - Design of steel buildings with worked examples Brussels, 16 - 17 October 2014

Classification and modelling of joints

Limits for classification of joints by stiffness

Nominally pinned

Semi-rigid

RigidMj

Initial stiffness of the joint

Sj,ini

Eurocodes - Design of steel buildings with worked examples Brussels, 16 - 17 October 2014

Classification and modelling of joints

Sj,ini

Limits for classification of joints by stiffness

Nominally pinned

Semi-rigid

RigidMj

Initial stiffness of the joint

“Semi-rigid” joints :

Eurocodes - Design of steel buildings with worked examples Brussels, 16 - 17 October 2014

Classification and modelling of joints

As an alternative to a semi-continuous modelling (semi-rigid joints), is it safe to

model the joints as nominally pinned whilst they are actually semi-rigid?

Semi-rigid Sj,ini > 0,5EIb/Lb

Partial strength Mj,Rd > 0,25 Mfull-strength

Nominally pinned Sj,ini = 0

Nominally pinned Mj,Rd = 0??

Eurocodes - Design of steel buildings with worked examples Brussels, 16 - 17 October 2014

Classification and modelling of joints

Yes, …under the reservation the joint has:

• a sufficient rotation capacity

= capacity to “rotate”

• a sufficient ductility

= capacity to follow the actual

loading path in a ductile way

VRd

V

M

Yielding criterionMRd

Supposed

loading path

Actual loading

path

Eurocodes - Design of steel buildings with worked examples Brussels, 16 - 17 October 2014

Supplementary design requirement

Sufficient resistance to «catenary effects» so as to provide required structural

robustness

Eurocodes - Design of steel buildings with worked examples Brussels, 16 - 17 October 2014

Example: Partial depth end-plate

Components

• Bolts in shear

• End-plate in bearing

• End-plate in shear (gross section)

• End-plate in shear (net section)

• End-plate in shear block

• End-plate in bending

• Beam web in shear

• Welds in shear

• Column flange in bearing

Eurocodes - Design of steel buildings with worked examples Brussels, 16 - 17 October 2014

Partial depth end-plate

Strength requirement

• Use of “component method” for the assessment of VRd

Assessment of the strength of all the constitutive components of the joint

+

“Assembly” of these components

Eurocodes - Design of steel buildings with worked examples Brussels, 16 - 17 October 2014

Partial depth end-plate

Rotation capacity requirement

Bending moment

Rotationavail

Contact between supported beam and supporting element

Compression force

Bendingmoment

Bolts in tension

Eurocodes - Design of steel buildings with worked examples Brussels, 16 - 17 October 2014

Partial depth end-plate

Rotation capacity requirement

hp

he

tp

hbdb

avail

p bh d

p

avail

e

t

h

Eurocodes - Design of steel buildings with worked examples Brussels, 16 - 17 October 2014

Partial depth end-plate

Ductility requirement

• Prevent premature fracture of the bolts

• Prevent premature fracture of the welds

under unavoidable bending moment in the joint

Eurocodes - Design of steel buildings with worked examples Brussels, 16 - 17 October 2014

Partial depth end-plate

Ductility requirements

• Prevent premature collapse of the bolts

2,8yp

p ub

fd

t f

2,8ycf

p ub

fd

t f for the supporting column

d and fub : diameter and tensile strength of bolts

for the end-plate

Yielding of end-plate prior to tensile fracture of bolts

Design of Structural Steel Joints

• Introduction

• Integration of joints into structural design process

• Moment resistant joints

• Simple joints

• Design tools

Eurocodes - Design of steel buildings with worked examples Brussels, 16 - 17 October 2014

Practical design tools

• Tables of standardized joints

• Dedicated software

Eurocodes - Design of steel buildings with worked examples Brussels, 16 - 17 October 2014

Worked Example Configuration Beam IPE 500 Column HEA 340 End plate connection

Design assumption Rigid joint

Frame analysisMEd = 220 kNm

CoP software used for this example: http://cop.fw-ing.com

Eurocodes - Design of steel buildings with worked examples Brussels, 16 - 17 October 2014

Design resistance: MRd = 196 kNm < 220 kNmClassification: Semi-rigidFailure mode: Column web in compression

Eurocodes - Design of steel buildings with worked examples Brussels, 16 - 17 October 2014

Failure mode:End plate in bending

Eurocodes - Design of steel buildings with worked examples Brussels, 16 - 17 October 2014

Failure mode:Column web panel in shear

Eurocodes - Design of steel buildings with worked examples Brussels, 16 - 17 October 2014

Failure mode:Column web panel in shear

Eurocodes - Design of steel buildings with worked examples Brussels, 16 - 17 October 2014

Failure mode:Column web panel in shear

Design of Structural Steel Joints

Dr. Klaus WeynandFeldmann + Weynand GmbH, Aachen, Germany

Prof. Jean-Pierre JaspartUniversity of Liège, Belgium