International Codes 2004

STAAD.Pro 2004

INTERNATIONAL DESIGN CODES

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STAAD.Pro 2004 is a proprietary computer program of Research Engineers, International (REI), a division of netGuru, Inc. The program and this document have been prepared in accord with established industry engineering principles and guidelines. While believed to be accurate, the information contained herein should never be utilized for any specific engineering application without professional observance and authentication for accuracy, suitability and applicability by a competent and licensed engineer, architect or other professional. REI disclaims any liability arising from the unauthorized and/or improper use of any information contained in this document, or as a result of the usage of the program.

RELEASE 2004

Copyright Research Engineers, Interntional

Division of netGuru, Inc. Published June, 2004

About STAAD.Pro 2004 STAAD.Pro is a widely used software for structural analysis and design from Research Engineers International. The STAAD.Pro software consists of the following: The STAAD.Pro Graphical User Interface (GUI): It is used to generate the model, which can then be analyzed using the STAAD engine. After analysis and design is completed, the GUI can also be used to view the results graphically. The STAAD analysis and design engine: It is a general-purpose calculation engine for structural analysis and integrated Steel, Concrete, Timber and Aluminum design.

About the STAAD.Pro 2004 Documentation

The documentation for STAAD.Pro consists of a set of manuals as described below. Getting Started and Tutorials : This manual contains information on the contents of the STAAD.Pro package, computer system requirements, installation process, copy protection issues and a description on how to run the programs in the package. Tutorials that provide detailed and step-by-step explanation on using the programs are also provided. Examples : This book offers examples of various problems that can be solved using the STAAD engine. The examples represent various structural analyses and design problems commonly encountered by structural engineers. Graphical Environment : This manual contains a detailed description of the Graphical User Interface (GUI) of STAAD.Pro. The topics covered include model generation, structural analysis and design, result verification, and report generation. This manual is generally provided only in the electronic form and can be accessed from the Help facilities of STAAD.Pro. Users who wish to obtain a printed copy of this book may contact Research Engineers. See the back cover of this book for addresses and phone numbers. Technical Reference : This manual deals with the theory behind the engineering calculations made by the STAAD engine. It also includes an explanation of the commands available in the STAAD command file. International Design Codes : This document contains information on the various Concrete, Steel, and Aluminum design codes, of several countries, that are implemented in STAAD. Generally, this book is supplied only to those users who purchase the international codes utilities with STAAD.Pro. OpenSTAAD : This document contains information on the library of functions which enable users to access STAAD.Pro’s input and results data for importing into other applications.

Table of Contents

International Codes

Introduction i

Section 1 Australian Codes 1-

1A Concrete Design Per AS3600 1-1 1A.1 Design Operations 1-1 1A.2 Section Types for Concrete Design 1-1 1A.3 Member Dimensions 1-1 1A.4 Design Parameters 1-2 1A.5 Slenderness Effects and Analysis Consideration 1-2 1A.6 Beam Design 1-3 1A.7 Column Design 1-5 1A.8 Slab/Wall Design 1-6

1B Steel Design Per AS4100-1998 1-9 1B.1 General 1-9 1B.2 Analysis Methodology 1-10 1B.3 Member Property Specifications 1-10 1B.4 Built-in Steel Section Library 1-10 1B.5 Section Classification 1-15 1B.6 Member Resistances 1-15 1B.7 Design Parameters 1-17 1B.8 Code Checking 1-20 1B.9 Member Selection 1-20 1B.10 Tabulated Results of Steel Design 1-21

Section 2 British Codes 2-

2A Concrete Design Per BS8100 2-1 2A.1 Design Operations 2-1 2A.2 Design Parameters 2-1 2A.3 Slenderness Effects and Analysis Considerations 2-4 2A.4 Member Dimensions 2-4 2A.5 Beam Design 2-5 2A.6 Column Design 2-7 2A.7 Slab Design 2-8 2A.8 Shear Wall Design 2-10

2B Steel Design Per BS5950:2000 2-23 2B.1 General 2-23 2B.2 Analysis Methodology 2-25 2B.3 Member Property Specifications 2-25 2B.4 Built-in Steel Section Library 2-25 2B.5 Member Capacities 2-30 2B.6 Design Parameters 2-34 2B.7 Design Operations 2-45 2B.8 Code Checking 2-46 2B.9 Member Selection 2-47 2B.10 Tabulated Results of Steel Design 2-48 2B.11 Plate Girders 2-49 2B.12 Composite Sections 2-50

2B1 Steel Design Per BS5950:1990 2-51

2B1.1 General 2-51 2B1.2 Analysis Methodology 2-52 2B1.3 Member Property Specifications 2-52 2B1.4 Built-in Steel Section Library 2-52 2B1.5 Member Capacities 2-56 2B1.6 Design Parameters 2-61 2B1.7 Design Operations 2-69 2B1.8 Code Checking 2-70 2B1.9 Member Selection 2-70 2B1.10 Tabulated Results of Steel Design 2-71 2B1.11 Plate Girders 2-72 2B1.12 Composite Sections 2-73

2C Design Per BS5400 2-75 2C.1 General Comments 2-75 2C.2 Shape Limitations 2-75 2C.3 Section Class 2-76 2C.4 Moment Capacity 2-76 2C.5 Shear Capacity 2-76 2C.6 Design Parameters 2-77 2C.7 Composite Sections 2-78

2D Design Per BS8007 2-81 2D.1 General Comments 2-81 2D.2 Design Process 2-81 2D.3 Design Parameters 2-83 2D.4 Structural Model 2-83 2D.5 Wood & Armer Moments 2-84

Section 3 Canadian Codes 3-

3A Concrete Design Per CSA Standard A 23.3 94 3-1 3A.1 Design Operations 3-1 3A.2 Section Types for Concrete Design 3-1 3A.3 Member Dimensions 3-1 3A.4 Slenderness Effects and Analysis Consideration 3-2 3A.5 Design Parameters 3-3 3A.6 Beam Design 3-4 3A.7 Column Design 3-6 3A.8 Slab/Wall Design 3-7

3B Steel Design Per CSA Standard CAN/CSA – S16.1-94 3-9

3B.1 General Comments 3-9 3B.2 Analysis Methodology 3-10 3B.3 Member Property Specifications 3-10 3B.4 Built-in Steel Section Library 3-10 3B.5 Section Classification 3-17 3B.6 Member Resistances 3-17 3B.7 Design Parameters 3-21 3B.8 Code Checking 3-23 3B.9 Member Selection 3-24 3B.10 Tabulated Results of Steel Design 3-25

3C Design Per Canadian Cold Formed Steel Code 3-27

3C.1 General 3-27 3C.2 Cross-Sectional Properties 3-27 3C.3 Design Procedure 3-28

Section 4 Chinese Codes 4-

4A Concrete Design Per GBJ 10-89 4-1 4A.1 Design Operations 4-1 4A.2 Section Types for Concrete Design 4-1 4A.3 Member Dimensions 4-1 4A.4 Design Parameters 4-2 4A.5 Beam Design 4-2 4A.6 Column Design 4-6

4B Steel Design Per GBJ 17-88 4-11 4B.1 General 4-11 4B.2 Analysis Methodology 4-12 4B.3 Member Property Specifications 4-12 4B.4 Built-in Chinese Steel Section Library 4-12 4B.5 Member Capacities 4-17 4B.6 Combined Loading 4-18 4B.7 Design Parameters 4-18 4B.8 Code Checking 4-18 4B.9 Member Selection 4-19

Section 5 European Codes 5-

5A Concrete Design Per Eurocode EC2 5-1 5A.1 Design Operations 5-1 5A.2 Eurocode 2 (EC2) 5-1 5A.3 National Application Documents 5-2 5A.4 Material Properties and Load Factors 5-2 5A.5 Columns 5-3 5A.6 Beams 5-3 5A.7 Slabs 5-5 5A.8 Design Parameters 5-5 5A.9 Parameter Definition Table 5-6

5B Steel Design Per Eurocode EC3 5-9 5B.1 General Description 5-9 5B.2 Design Parameters 5-14 5B.3 Worked Examples 5-20 5B.4 User’s Examples 5-37

Section 6 French Codes 6-

6A Concrete Design Per B A E L 6-1 6A.1 Design Operations 6-1 6A.2 Design Parameters 6-1 6A.3 Slenderness Effects and Analysis Consideration 6-1 6A.4 Member Dimensions 6-2 6A.5 Beam Design 6-3 6A.6 Column Design 6-5 6A.7 Slab/Wall Design 6-5

6B Steel Design Per the French Code 6-7 6B.1 General Comments 6-7 6B.2 Basis Of Methodology 6-8 6B.3 Member Capacities 6-8 6B.4 Combined Axial Force and Bending 6-9 6B.5 Design Parameters 6-9 6B.6 Code Checking and Member Selection 6-9 6B.7 Tabulated Results of Steel Design 6-9 6B.8 Built-in French Steel Section Library 6-12

Section 7 German Codes 7-

7A Concrete Design Per DIN 1045 7-1 7A.1 Design Operations 7-1 7A.2 Section Types for Concrete Design 7-1 7A.3 Member Dimensions 7-1 7A.4 Slenderness Effects and Analysis Considerations 7-2 7A.5 Beam Design 7-3 7A.6 Column Design 7-5 7A.7 Slab Design 7-6 7A.8 Design Parameters 7-7

7B Steel Design Per the DIN Code 7-11 7B.1 General 7-11 7B.2 Analysis Methodology 7-12 7B.3 Member Property Specifications 7-12 7B.4 Built-in German Steel Section Library 7-12 7B.5 Member Capacities 7-17 7B.6 Combined Loading 7-18 7B.7 Design Parameters 7-19 7B.8 Code Cecking 7-21 7B.9 Member Selection 7-22

Section 8 Indian Codes 8-

8A Concrete Design Per IS456 8-1 8A.1 Design Operations 8-1 8A.2 Section Types for Concrete Design 8-1 8A.3 Member Dimensions 8-1 8A.4 Design Parameters 8-2 8A.5 Slenderness Effects and Analysis Consideration 8-2 8A.6 Beam Design 8-3 8A.7 Column Design 8-7 8A.8 Bar Combination 8-13

8A1 Concrete Design Per IS13920 8-15 8A1.1 Design Operations 8-15 8A1.2 Section Types for Concrete Design 8-15 8A1.3 Design Parameters 8-16 8A1.4 Beam Design 8-16 8A1.5 Column Design 8-20 8A1.6 Bar Combination 8-31

8B Steel Design Per IS800 8-37 8B.1 Design Operations 8-37 8B.2 General Comments 8-38 8B.3 Allowable Stresses 8-38

8B.3.1 Axial Stress 8-39 8B.3.2 Bending Stress 8-40 8B.3.3 Shear Stress 8-41 8B.3.4 Combined Stress 8-42

8B.4 Design Parameters 8-42 8B.5 Stability Requirements 8-42 8B.6 Truss Members 8-43 8B.7 Deflection Check 8-43 8B.8 Code Checking 8-43 8B.9 Member Selection 8-44 8B.10 Member Selection by Optimization 8-44 8B.11 Tabulated Results of Steel Design 8-45 8B.12 Indian Steel Table 8-47 8B.13 Column with Lacings and Battens 8-55

8C Steel Design Per IS802 8-59 8C.1 General Comments 8-59 8C.2 Allowable Stresses 8-59

8C.2.1 Axial Stress 8-60 8C.3 Stability Requirements 8-62 8C.4 Minimum Thickness Requirement 8-64 8C.5 Code Checking 8-64

8C.5.1 Design Steps 8-65 8C.6 Member Selection 8-66 8C.7 Member Selection by Optimization 8-66 8C.8 Tabulated Results of Steel Design 8-67 8C.9 Parameter Table for IS802 8-69 8C.10 Calculation of Net Section Factor 8-71 8C.11 Example Problem No. 28 8-73

8D Design Per Indian Cold Formed Steel Code 8-81 8D.1 General 8-81 8D.2 Cross-Sectional Properties 8-81 8D.3 Design Procedure 8-82

Section 9 Japanese Codes 9-

9A Concrete Design Per AIJ 9-1 9A.1 Design Operations 9-1 9A.2 Section Types for Concrete Design 9-1 9A.3 Member Dimensions 9-1 9A.4 Slenderness Effects and Analysis Consideration 9-2 9A.5 Beam Design 9-3 9A.6 Column Design 9-5 9A.7 Slab/Wall Design 9-7 9A.8 Design Parameters 9-8

9B Steel Design Per AIJ 9-11 9B.1 General 9-11 9B.2 Analysis Methodology 9-12 9B.3 Member Property Specifications 9-12 9B.4 Built-in Japanese Steel Section Library 9-12 9B.5 Member Capacities 9-18 9B.6 Combined Loading 9-22 9B.7 Design Parameters 9-23 9B.8 Code Checking 9-25 9B.9 Member Selection 9-26

Section 10 American Aluminum Code 10-

10 Design Per American Aluminum Code 10-1 10.1 General 10-1 10.2 Member Properties 10-1 10.3 Design Procedure 10-3 10.4 Design Parameters 10-4 10.5 Code Checking 10-8 10.6 Member Selection 10-8

Section 11 American Transmission Tower Code 11-

11 Steel Design Per ASCE Manuals And Reports 11-1 11.1 General Comments 11-1 11.2 Allowable Stresses Per ASCE (Pub.52) 11-2 11.3 Design Parameters 11-3 11.4 Code Checking and Member Selection 11-3 11.5 Parameter Definition Table 11-4

Section 12 American A.P.I. Code 12-

12 Steel Design Per API 12-1 12.1 Design Operations 12-1 12.2 Allowables Per API Code 12-2

12.2.1 Tension Stress 12-2 12.2.2 Beam Stress 12-2

12.3 Stress due to Compression 12-3 12.4 Bending Stress 12-3 12.5 Combined Compression and Bending 12-4 12.6 Design Parameters 12-4 12.7 Code Checking 12-7 12.8 Member Selection 12-7 12.9 Truss Members 12-8 12.10 Punching Shear 12-8 12.11 Automatic Selection 12-9 12.12 Chord Selection and Qf Parameter 12-10 12.13 External Geometry File 12-11 12.14 Limitations 12-12 12.15 Tabulated Results of Steel Design 12-13 12.16 The Two-Step Process 12-14

Introduction

This publication has been prepared to provide information pertaining to the various international codes supported by STAAD. These codes are provided as additional codes by Research Engineers. In other words, they do not come with the standard package. Hence, information on only some of the codes presented in this document may be actually pertinent to the individual user's package. Users may locate the information for the appropriate code by referring to the Table of Contents shown on the previous few pages. This document is to be used in conjunction with the STAAD Technical Reference Manual and the STAAD Examples Manual. Effort has been made to provide some basic information about the analysis considerations and the logic used in the design approach. A brief outline of the factors affecting the design along with references to the corresponding clauses in the codes is also provided. Examples are provided at the appropriate places to facilitate ease of understanding of the usage of the commands and design parameters. Users are urged to refer to the Examples Manual for solved problems that use the commands and features of STAAD. Since the STAAD output contains references to the clauses in the code that govern the design, users are urged to consult the documentation of the code of that country for additional details on the design criteria.

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Section 1 Australian Codes

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1-1

Concrete Design Per AS3600

1A.1 Design Operations

STAAD has the capabilities of performing concrete design based on the Australian code AS3600-1994.

1A.2 Section Types for Concrete Design

The following types of cross sections for concrete members can be designed. For Beams Prismatic (Rectangular & Square) For Columns Prismatic (Rectangular, Square and Circular)

1A.3 Member Dimensions

Concrete members which will be designed by the program must have certain section properties input under the MEMBER PROPERTY command. The following example shows the required input:

Section 1A

Concrete Design Per AS 3600

Section 1A

1-2

UNIT MM MEMBER PROPERTY 1 3 TO 7 9 PRISM YD 450. ZD 250. 11 13 PR YD 350.

In the above input, the first set of members are rectangular (450 mm depth and 250mm width) and the second set of members, with only depth and no width provided, will be assumed to be circular with 350 mm diameter. It is absolutely imperative that the user not provide the cross section area (AX) as an input.

1A.4 Design Parameters

The program contains a number of parameters which are needed to perform the design. Default parameter values have been selected such that they are frequently used numbers for conventional design requirements. These values may be changed to suit the particular design being performed. Table 1A.1 of this manual contains a complete list of the available parameters and their default values. It is necessary to declare length and force units as Millimeter and Newton before performing the concrete design.

1A.5 Slenderness Effects and Analysis Consideration

Slenderness effects are extremely important in designing compression members. There are two options by which the slenderness effect can be accommodated. One option is to perform an exact analysis which will take into account the influence of axial loads and variable moment of inertia on member stiffness and fixed end moments, the effect of deflections on moment and forces and the effect of the duration of loads. Another option is to approximately magnify design moments.

Section 1A

1-3

STAAD has been written to allow the use of the first option. To perform this type of analysis, use the command PDELTA ANALYSIS instead of PERFORM ANALYSIS. The PDELTA ANALYSIS will accommodate the requirements of the second- order analysis described by AS 3600, except for the effects of the duration of the loads. It is felt that this effect may be safely ignored because experts believe that the effects of the duration of loads is negligible in a normal structural configuration. Although ignoring load duration effects is somewhat of an approximation, it must be realized that the evaluation of slenderness effects is also by an approximate method. In this method, additional moments are calculated based on empirical formula and assumptions on sidesway. Considering all of the above information, a PDELTA ANALYSIS, as performed by STAAD may be used for the design of concrete members. However the user must note that to take advantage of this analysis, all the combinations of loading must be provided as primary load cases and not as load combinations. This is due to the fact that load combinations are just algebraic combinations of forces and moments, whereas a primary load case is revised during the P-delta analysis based on the deflections. Also, note that the proper factored loads (like 1.5 for dead load etc.) should be provided by the user. STAAD does not factor the loads automatically.

1A.6 Beam Design

Beams are designed for flexure, shear and torsion. For all these forces, all active beam loadings are prescanned to identify the critical load cases at different sections of the beams. The total number of sections considered is 13( e.g. 0.,.1,.2,.25,.3,.4,.5,.6,.7,. 75,.8,.9 and 1). All of these sections are scanned to determine the design force envelopes.


Section 1A

1-4 Design for Flexure Maximum sagging (creating tensile stress at the bottom face of the beam) and hogging (creating tensile stress at the top face) moments are calculated for all active load cases at each of the above mentioned sections. Each of these sections are designed to resist both of these critical sagging and hogging moments. Currently, design of singly reinforced sections only is permitted. If the section dimensions are inadequate as a singly reinforced section, such a message will be permitted in the output. Flexural design of beams is performed in two passes. In the first pass, effective depths of the sections are determined with the assumption of single layer of assumed reinforcement and reinforcement requirements are calculated. After the preliminary design, reinforcing bars are chosen from the internal database in single or multiple layers. The entire flexure design is performed again in a second pass taking into account the changed effective depths of sections calculated on the basis of reinforcement provided after the preliminary design. Final provision of flexural reinforcements are made then. Efforts have been made to meet the guideline for the curtailment of reinforcements as per AS 3600. Although exact curtailment lengths are not mentioned explicitly in the design output (finally which will be more or less guided by the detailer taking into account of other practical consideration), user has the choice of printing reinforcements provided by STAAD at 13 equally spaced sections from which the final detailed drawing can be prepared. Design for Shear

Shear reinforcement is calculated to resist both shear forces and torsional moments. Shear design is performed at 13 equally spaced sections (0.to 1.) for the maximum shear forces amongst the active load cases and the associated torsional moments. Shear capacity calculation at different sections without the shear reinforcement is based on the actual tensile reinforcement provided by STAAD program. Two-legged stirrups are provided to take care of the balance shear forces acting on these sections.

Section 1A

1-5

Example of Input Data for Beam Design UNIT NEWTON MMS START CONCRETE DESIGN CODE AUSTRALIAN FYMAIN 415 ALL FYSEC 415 ALL FC 35 ALL CLEAR 25 MEM 2 TO 6 MAXMAIN 40 MEMB 2 TO 6 TRACK 1.0 MEMB 2 TO 9 DESIGN BEAM 2 TO 9 END CONCRETE DESIGN

1A.7 Column Design

Columns are designed for axial forces and biaxial moments at the ends. All active load cases are tested to calculate reinforcement. The loading which yields maximum reinforcement is called the critical load. Column design is done for square, rectangular and circular sections. By default, square and rectangular columns are designed with reinforcement distributed on each side equally. That means the total number of bars will always be a multiple of four (4). This may cause slightly conservative results in some cases. All major criteria for selecting longitudinal and transverse reinforcement as stipulated by AS 3600 have been taken care of in the column design of STAAD.

Example of Input Data for Column Design UNIT NEWTON MMS START CONCRETE DESIGN CODE AUSTRALIAN FYMAIN 415 ALL FC 35 ALL


Section 1A

1-6

CLEAR 25 MEMB 2 TO 6 MAXMAIN 40 MEMB 2 TO 6 DESIGN COLUMN 2 TO 6 END CONCRETE DESIGN

1A.8 Slab/Wall Design

To design a slab or wall, it must be modeled using finite elements. The command specifications are in accordance with Chapter 2, and Chapter 6 of the Technical Reference Manual. Elements are designed for the moments Mx and My. These moments are obtained from the element force output (see Section 3.8 of the Technical Reference Manual). The reinforcement required to resist Mx moment is denoted as longitudinal reinforcement and the reinforcement required to resist My moment is denoted as transverse reinforcement. The parameters FYMAIN, FC, MAXMAIN, MINMAIN and CLEAR listed in Table 1A.1 are relevant to slab design. Other parameters mentioned in Table 1A.1 are not applicable to slab design.

LONG.

TRANS.

X

Y

Z

M

MM

M x

y

x

y

Section 1A

1-7

Example of Input Data for Slab/Wall Design UNIT NEWTON MMS START CONCRETE DESIGN CODE AUSTRALIAN FYMAIN 415 ALL FC 25 ALL CLEAR 40 ALL DESIGN ELEMENT 15 TO 20 END CONCRETE DESIGN

Table 1A.1 Australian Concrete Design-AS 3600- Parameters

Parameter Name

Default Value Description

FYMAIN 415 N/mm2 Yield Stress for main reinforcing steel.

FYSEC 415 N/mm2 Yield Stress for secondary reinforcing steel.

FC 30 N/mm2 Concrete Yield Stress.

CLEAR 25 mm

40 mm

For beam members.

For column members

MINMAIN 10 mm Minimum main reinforcement bar size.

MAXMAIN 60 mm Maximum main reinforcement bar size.

MINSEC 8 mm Minimum secondary reinforcement bar size.

MAXSEC 12 mm Maximum secondary reinforcement bar size.

RATIO 4.0 Maximum percentage of longitudinal reinforcement in columns.

WIDTH ZD Width to be used for design. This value defaults to ZD as provided under MEMBER PROPERTIES.

DEPTH YD Total depth to be used for design. This value defaults to YD as provided under MEMBER PROPERTIES.


Section 1A

1-8

Table 1A.1 Australian Concrete Design-AS 3600- Parameters

Parameter Name


TRACK 0.0 BEAM DESIGN:

For TRACK = 0.0, output consists of reinforcement details at START, MIDDLE and END.

For TRACK = 1.0, critical moments are printed in addition to TRACK 0.0 output.

For TRACK = 2.0, required steel for intermediate sections defined by NSECTION are printed in addition to TRACK 1.0 output.

COLUMN DESIGN:

With TRACK = 0.0, reinforcement details are printed.

REINF 0.0 Tied column. A value of 1.0 will mean spiral reinforcement.

1-9

Steel Design Per AS 4100 - 1998

1B.1 General

This section presents some general statements regarding the implementation of the specifications recommended by Standards Australia for structural steel design (AS 4100) in STAAD. The design philosophy and procedural logistics are based on the principles of elastic analysis and limit state method of design. Facilities are available for member selection as well as code checking. The design philosophy embodied in this specification is based on the concept of limit state design. Structures are designed and proportioned taking into consideration the limit states at which they would become unfit for their intended use. Two major categories of limit-state are recognized - ultimate and serviceability. The primary considerations in ultimate limit state design are strength and stability, while that in serviceability is deflection. Appropriate load and resistance factors are used so that a uniform reliability is achieved for all steel structures under various loading conditions and at the same time the chances of limits being surpassed are acceptably remote. In the STAAD implementation, members are proportioned to resist the design loads without exceeding the limit states of strength, stability and serviceability. Accordingly, the most economic section is selected on the basis of the least weight criteria as augmented by the designer in specification of allowable member depths, desired section type, or other such parameters. The code checking portion of the program checks whether code requirements for each selected section are met and identifies the governing criteria.

Section 1B

Steel Design Per AS 4100-1998

Section 1B

1-10 The following sections describe the salient features of the STAAD implementation of AS 4100. A detailed description of the design process along with its underlying concepts and assumptions is available in the specification document.

1B.2 Analysis Methodology

Elastic analysis method is used to obtain the forces and moments for design. Analysis is done for the primary and combination loading conditions provided by the user. The user is allowed complete flexibility in providing loading specifications and using appropriate load factors to create necessary loading situations. Depending upon the analysis requirements, regular stiffness analysis or P-Delta analysis may be specified. Dynamic analysis may also be performed and the results combined with static analysis results.

1B.3 Member Property Specifications

For specification of member properties, the steel section library available in STAAD may be used. The next section describes the syntax of commands used to assign properties from the built-in steel table. Member properties may also be specified using the User Table facility. For more information on these facilities, refer to the STAAD Technical Reference Manual.

1B.4 Built-in Steel Section Library

The following information is provided for use when the built-in steel tables are to be referenced for member property specification. These properties are stored in a database file. If called for, the properties are also used for member design. Since the shear areas are built into these tables, shear deformation is always considered during the analysis of these members. An example of the member property specification in an input file is provided at the end of this section.

Section 1B

1-11

A complete listing of the sections available in the built-in steel section library may be obtained by using the tools of the graphical user interface. Following are the descriptions of different types of sections. UB Shapes These shapes are designated in the following way.

20 TO 30 TA ST UB150X14.0 36 TO 46 TA ST UB180X16.1

UC Shapes The designation for the UC shapes is similar to that for the UB shapes.

25 TO 35 TA ST UC100X14.8 23 56 TA ST UC310X96.8

Welded Beams Welded Beams are designated in the following way.

25 TO 35 TA ST WB700X115 23 56 TA ST WB1200X455

Welded Columns Welded Columns are designated in the following way.

25 TO 35 TA ST WC400X114 23 56 TA ST WC400X303


Section 1B

1-12 Parallel Flange Channels Shown below is the syntax for assigning names of channel sections.

1 TO 5 TA ST PFC75 6 TO 10 TA ST PFC380

Double Channels Back to back double channels, with or without a spacing between them, are available. The letter D in front of the section name will specify a double channel.

11 TA D PFC230 17 TA D C230X75X25 SP 0.5

In the above set of commands, member 11 is a back to back double channel PFC230 with no spacing in between. Member 17 is a double channel PFC300 with a spacing of 0.5 length units between the channels. Angles Two types of specification may be used to describe an angle. The standard angle section is specified as follows:

16 20 TA ST A30X30X6

The above section signifies an angle with legs of length 30mm and a leg thickness of 6 mm. This specification may be used when the local Z axis corresponds to the z-z axis specified in Chapter 2. If the local Y axis corresponds to the z-z axis, type specification "RA" (reverse angle) may be used.

17 21 TA RA A150X150X16

Section 1B

1-13

Double Angles Short leg back to back or long leg back to back double angles can be specified by means of input of the words SD or LD, respectively, in front of the angle size. In case of an equal angle, either SD or LD will serve the purpose.

33 35 TA SD A65X50X5 SP 0.6 37 39 TA LD A75X50X6 43 TO 47 TA LD A100X75X10 SP 0.75

Tubes (Rectangular or Square Hollow Sections) Tubes can be assigned in 2 ways. In the first method, the designation for the tube is as shown below. This method is meant for tubes whose property name is available in the steel table. In these examples, members 1 to 5 consist of a 2X2X0.5 inch size tube section, and members 6 to 10 consist of 10X5X0.1875 inch size tube section. The name is obtained as 10 times the depth, 10 times the width, and 16 times the thickness.

1 TO 5 TA ST TUB20202.5 6 TO 10 TA ST TUB100503.0

In the second method, tubes are specified by their dimensions. For example,

6 TA ST TUBE DT 8.0 WT 6.0 TH 0.5

is a tube that has a height of 8 length units, width of 6 length units, and a wall thickness of 0.5 length units. Only code checking, no member selection, will be performed for TUBE sections specified in this latter manner.


Section 1B

1-14 Pipes (Circular Hollow Sections) Pipes can be assigned in 2 ways. In the first method, the designation for the pipe is as shown below. This method is meant for pipes whose property name is available in the steel table.

1 TO 5 TA ST PIP180X5 6 TO 10 TA ST PIP273X6.5

In the second method, pipe sections may be provided by specifying the word PIPE followed by the outside and inside diameters of the section. For example,

1 TO 9 TA ST PIPE OD 25.0 ID 20.0

specifies a pipe with outside diameter of 25 length units and inside diameter of 20 length units. Only code checking, no member selection, will be performed on pipes specified in this latter manner.

Sample File Containing Australian Shapes STAAD SPACE UNIT METER KN JOINT COORD 1 0 0 0 11 100 0 0 MEMB INCI 1 1 2 10 UNIT CM MEMBER PROPERTIES AUSTRALIAN * UB SHAPES 1 TA ST UB200X25.4 * UC SHAPES 2 TA ST UC250X89.5 * CHANNELS 3 TA ST PFC125 * DOUBLE CHANNELS

Section 1B

1-15

4 TA D PFC200 * ANGLES 5 TA ST A30X30X6 * REVERSE ANGLES 6 TA RA A150X150X16 * DOUBLE ANGLES - SHORT LEGS BACK TO BACK 7 TA SD A65X50X5 SP 0.6 * DOUBLE ANGLES - LONG LEGS BACK TO BACK 8 TA LD A100X75X10 SP 0.75 * TUBES (RECTANGULAR OR SQUARE HOLLOW SECTIONS) 9 TA ST TUBE DT 8.0 WT 6.0 TH 0.5 * PIPES (CIRCULAR HOLLOW SECTIONS) 10 TA ST PIPE OD 25.0 ID 20.0 PRINT MEMB PROP FINI

1B.5 Section Classification

The AS 4100 specification allows inelastic deformation of section elements. Thus, local buckling becomes an important criterion. Steel sections are classified as compact, non-compact or slender depending upon their local buckling characteristics. This classification is a function of the geometric properties of the section. The design procedures are different depending on the section class. STAAD determines the section classification for the standard shapes and user specified shapes. Design is performed for all three categories of section as mentioned above.

1B.6 Member Resistances

The member resistance is calculated in STAAD according to the procedures outlined in AS 4100. This depends on several factors such as members unsupported lengths, cross-sectional properties, support condition and so on. The procedure adopted in STAAD for calculating the member resistance is explained here.


Section 1B

1-16 Axial Tension

The criteria governing the capacity of tension members is based on two limit states. Limit State of yielding of the gross section is intended to prevent excessive elongation of the member. The second limit state involves fracture at the section with the minimum effective net area. The user through the use of the parameter NSF (see Table 1B.1) may specify the net section area. STAAD calculates the tension capacity of a member based on these two limit states per Cl.7.1 and Cl.7.2 respectively of AS 4100. Parameters FYLD, FU, Kt and NSF are applicable for these calculations. Axial Compression

The compressive strength of members is determined based on Clause 6.1 of the code. It is taken as the lesser of nominal section capacity and nominal member capacity. Nominal section capacity is a function of form factor (Cl.6.2.2), net area of the cross section and yield stress of the material. The user through the use of the parameter NSC (see Table 1B.1) may specify the net section area. Note here, that this parameter is different from that corresponding to tension. The program automatically calculates form factor. Nominal member capacity is a function of nominal section capacity and member slenderness reduction factor (Cl.6.3.3). Here user is required to supply the value of αb (Cl.6.3.3). Table 1B.1 gives the default value of this parameter (named ALB). The effective length for the calculation of compressive strength may be provided through the use of the parameters KY, KZ, LY and LZ (see Table 1B.1). Bending

The allowable bending moment of members is determined as the lesser of nominal section capacity and nominal member capacity (ref. Cl.5.1). The nominal section moment capacity is the capacity to resist cross-section yielding or local buckling and is expressed as the product of yield stress of material and effective section modulus (ref. Cl.5.2). The effective section modulus is a function of section type i.e. compact, non-compact or slender. The nominal

Section 1B

1-17

member capacity depends on overall flexural-torsional buckling of the member (ref.Cl.5.3). Interaction of axial force and bending

The member strength for sections subjected to axial compression and uniaxial or biaxial bending is obtained through the use of interaction equations. Here also the adequacy of a member is examined against both section (ref. Cl.8.3.4) and member capacity (ref.Cl.8.4.5). If the summation of the left hand side of the equations, addressed by the above clauses, exceed 1.0 or the allowable value provided using the RATIO parameter (see Table 1B.1), the member is considered to have FAILed under the loading condition. Shear

Shear capacity of cross section is taken as the shear yield capacity. User may refer to Cl.5.11 in this context. Once the capacity is obtained, the ratio of the shear force acting on the cross section to the shear capacity of the section is calculated. If any of the ratios (for both local Y & Z-axes) exceed 1.0 or the allowable value provided using the RATIO parameter (see Table 1B.1), the section is considered to have failed under shear.

1B.7 Design Parameters

The design parameters outlined in Table 1B.1 may be used to control the design procedure. These parameters communicate design decisions from the engineer to the program and thus allow the engineer to control the design process to suit an application's specific needs. The default parameter values have been selected such that they are frequently used numbers for conventional design. Depending on the particular design requirements, some or all of these parameter values may be changed to exactly model the physical structure.


Section 1B

1-18

Table 1B.1- Australian Steel Design Parameters

Parameter Name


KY 1.0 K value for general column flexural buckling about the local Y-axis. Used to calculate slenderness ratio.

KZ 1.0 K value for general column flexural buckling about the local Z-axis. Used to calculate slenderness ratio.

LY Member Length Length for general column flexural buckling about the local Y-axis. Used to calculate slenderness ratio.

LZ Member Length Length for general column flexural buckling about the local Z-axis. Used to calculate slenderness ratio.

FYLD 250.0 MPa Yield strength of steel.

FU 500.0 MPa Ultimate strength of steel.

NSF 1.0 Net section factor for tension members.

MAIN 0.0 0.0 = Check slenderness ratio against the limits.

1.0 = Suppress the slenderness ratio check.

2.0 = Check slenderness ratio only for column buckling, not for web (See Section 3B.6, Shear)

TRACK 0.0 0.0 = Report only minimum design results.

1.0 = Report design strengths also.

2.0 = Provide full details of design.

DMAX 45.0 in. Maximum allowable depth (Applicable for member selection)

DMIN 0.0 in. Minimum required depth (Applicable for member selection)

RATIO 1.0 Permissible ratio of actual load effect to the design strength.

Section 1B

1-19

Table 1B.1- Australian Steel Design Parameters

Parameter Name


IST 1 Steel type - 1 - SR, 2 - HR, 3 - CF, 4 - LW,

5 - HW

PHI 0.9 Capacity reduction factor

NSC 1.0 Net section factor for compression members = An / Ag

(refer cl. 6.2.1)

ALM 1.0 Moment modification factor (refer cl. 5.6.1.1)

ALB 0.0 Member section constant (refer cl. 6.3.3)

KT 1.0 Correction factor for distribution of forces (refer cl. 7.2)

BEAM 0.0 0.0 = design only for end moments and those at locations specified by SECTION command.

1.0 = Perform design for moments at twelfth points along the beam.

UNT Member Length Unsupported length in bending compression of the top flange for calculating moment resistance.

UNB Member Length Unsupported length in bending compression of the bottom flange for calculating moment resistance.

DFF None (Mandatory for deflection

check)

“Deflection Length”/ Maxm. Allowable local deflection.

DJ1 Start Joint of member

Joint No. denoting start point for calculation of “deflection length”

DJ2 End Joint of member

Joint No. denoting end point for calculation of “deflection length”


Section 1B

1-20

1B.8 Code Checking

The purpose of code checking is to check whether the provided section properties of the members are adequate. The adequacy is checked as per AS 4100 requirements. Code checking is done using forces and moments at every twelfth point along the beam. The code checking output labels the members as PASSed or FAILed. In addition, the critical condition, governing load case, location (distance from the start joint) and magnitudes of the governing forces and moments are also printed. The extent of detail of the output can be controlled by using the TRACK parameter.

Example of commands for CODE CHECKING: UNIT NEWTON METER PARAMETER FYLD 330E6 MEMB 3 4 NSF 0.85 ALL KY 1.2 MEMB 3 4 RATIO 0.9 ALL CHECK CODE MEMB 3 4

Code checking cannot be performed on composite and prismatic sections.

1B.9 Member Selection

The member selection process basically involves determination of the least weight member that PASSes the code checking procedure based on the forces and moments of the most recent analysis. The section selected will be of the same type as that specified initially. For example, a member specified initially as a channel will have a

Section 1B

1-21

channel selected for it. Selection of members whose properties are originally provided from a user table will be limited to sections in the user table. Composite and prismatic sections cannot be selected.

Example of commands for MEMBER SELECTION: UNIT NEWTON METER PARAMETER FYLD 330E6 MEMB 3 4 NSF 0.85 ALL KY 1.2 MEMB 3 4 RATIO 0.9 ALL SELECT MEMB 3 4

1B.10 Tabulated Results of Steel Design

Results of code checking and member selection are presented in a tabular format. The term CRITICAL COND refers to the section of the AS 4100 specification which governs the design.


Section 1B

1-22

Section 2 British Codes

Kjahds;akh

2-1

Concrete Design Per BS8110


It is strongly recommended that the user should perform new concrete design using the RC Designer Module. The following is provided to allow old STAAD files to be run. STAAD has the capability of performing design of concrete beams, columns and slabs according to BS8110. The 1997 revision of the code is currently implemented. Given the width and depth (or diameter for circular columns) of a section, STAAD will calculate the required reinforcement to resist the forces and moments.


The program contains a number of parameters which are needed to perform and control the design to BS8110. These parameters not only act as a method to input required data for code calculations but give the Engineer control over the actual design process. Default values of commonly used parameters for conventional design practice have been chosen as the basis. Table 2A.1 contains a complete list of available parameters with their default values.

Section 2A


Section 2A

2-2

Table 2A.1 – British Concrete Design-BS8110-Parameters

Parameter Name

Default Value

Description

FYMAIN *460 N/mm2 Yield Stress for main reinforcement (For slabs, it is for reinforcement in both directions)

FYSEC *460N/mm2 Yield Stress for secondary reinforcement a. Applicable to shear bars in beams

FC * 30N/mm2 Concrete Yield Stress / cube strength

MINMAIN 8mm Minimum main reinforcement bar size Acceptable bar sizes: 6 8 10 12 16 20 25 32 40 50

MINSEC 8mm Minimum secondary bar size a. Applicable to shear reinforcement in beams

CLEAR * 20mm Clearance of reinforcement measured from concrete surface to closest bar perimeter.

MAXMAIN 50mm Maximum required reinforcement bar size Acceptable bars are per MINMAIN above.

SFACE *0.0 Face of support location at start of beam. (Only applicable for shear - use MEMBER OFFSET for bending )

EFACE *0.0 Face of support location at end of beam. (NOTE : Both SFACE & EFACE must be positive numbers.)

TRACK 0.0 0.0 = Critical Moment will not be printed with beam design report. Column design gives no detailed results.

1.0 = For beam gives min/max steel % and spacing. For columns gives a detailed table of output with additional moments calculated.

2.0 = Output of TRACK 1.0 List of design sag/hog moments and corresponding required steel area at each section of member

MMAG 1.0 Factor by which column design moments are magnified

NSECTION 10 Number of equally-spaced sections to be considered in finding critical moment for beam design. The upper limit is 20.

WIDTH *ZD Width of concrete member. This value default is as provided as ZD in MEMBER PROPERTIES.

DEPTH *YD Depth of concrete member. This value default is as provided as YD in MEMBER PROPERTIES.

Section 2A

2-3

Table 2A.1 – British Concrete Design-BS8110-Parameters

Parameter Name

Default Value

Description

BRACE 0.0 0.0 = Column braced in both directions. 1.0 = Column unbraced about local Z direction only 2.0 = Column unbraced about local Y direction only 3.0 = Column unbraced in both Y and Z directions

ELY 1.0 Member length factor about local Y direction for column design.

ELZ 1.0 Member length factor about local Z direction for column design.

SRA 0.0 0.0 = Orthogonal reinforcement layout without considering torsional moment Mxy -slabs only

-500 = Orthogonal reinforcement layout with Mxy used to calculate WOOD & ARMER moments for design.

A = Skew angle considered in WOOD & ARMER equations where A is the angle in degrees.

SERV 0.0 0.0 = No serviceability check performed. 1.0 = Perform serviceability check for beams as if they

were continuous. 2.0 = Perform serviceability check for beams as if they

were simply supported. 3.0 = Perform serviceability check for beams as if they

were cantilever beams. * Provided in current unit system


Section 2A

2-4

2A.3 Slenderness Effects and Analysis Considerations

STAAD provides the user with two methods of accounting for the slenderness effects in the analysis and design of concrete members. The first method is equivalent to the procedure presented in BS8110 Part 1 1985 Section 3.8.2.2 In this section, the code recognizes that additional moments induced by deflection are present and states that these 'secondary' moments are accounted for by the design formula in Section 3.8.3. This is the method used in the design for concrete in STAAD. Alternatively STAAD houses a PDELTA ANALYSIS facility, which allows the effects of these second order moments to be considered in the analysis rather than the design. In a PDELTA analysis, after solving the joint displacements of the structure, the additional moments induced in the structure are calculated. These can be compared to those calculated using the formulation of BS8110.


Concrete members that are to be designed by STAAD must have certain section properties input under the MEMBER PROPERTIES command. The following example demonstrates the required input:

UNIT MM MEMBER PROPERTIES *RECTANGULAR COLUMN 300mm WIDE X 450mm DEEP 1 3 TO 7 9 PRISM YD 450. ZD 300. *CIRCULAR COLUMN 300mm diameter 11 13 PR YD 300. * T-SECTION - FLANGE 1000.X 200.(YD-YB) * - STEM 250(THICK) X 350.(DEEP) 14 PRISM YD 550. ZD 1000. YB 350. ZB 250.

Section 2A

2-5

In the above input, the first set of members are rectangular (450mm depth x 300mm width) and the second set of members, with only depth and no width provided, will be assumed to be circular with 300mm diameter. Note that area (AX) is not provided for these members. If shear area areas ( AY & AZ ) are to be considered in analysis, the user may provide them along with YD and ZD. Also note that if moments of inertias are not provided, the program will calculate them from YD and ZD. Finally a T section can be considered by using the third definition above.

2A.5 Beam Design

Beam design includes both flexure and shear. For both types of beam action, all active beam loadings are scanned to create moment and shear envelopes and locate the critical sections. The total number of sections considered is ten, unless that number is redefined with the NSECTION parameter. From the critical moment values, the required positive and negative bar pattern is developed with cut-off lengths calculated to include required development length.

Shear design as per BS8110 clause 3.4.5 has been followed and the procedure includes critical shear values plus torsional moments. From these values, stirrup sizes are calculated with proper spacing. The program will scan from each end of the member and provide a total of two shear regions at each, depending on the change of shear distribution along the beam. If torsion is present, the program will also consider the provisions of BS8110 - Part 2 -section 2.4. A table of shear and/or combined torsion is then provided with critical shear. Stirrups not bent up bars are assumed in the design. Table 2A.2 shows a sample output of an actual reinforcement pattern developed by STAAD. The following annotations apply to Table 2A.2


Section 2A

2-6

1) LEVEL - Serial number of the bar centre which may contain one or more bar groups.

2) HEIGHT - Height of bar level from the soffit of the beam in relation to its local y axis.

3) BAR INFO - Reinforcement bar information specifying number of bars and their size.

4) FROM - Distance from the start of the beam to the start of the reinforcing bar.

5) TO - Distance from the start of the beam to the end of the reinforcing bar.

6) ANCHOR - States whether anchorage, either a hook or (STA,END) continuation, is needed at start (STA) or at the

end (END). TABLE 2A.2- ACTUAL DESIGN OUTPUT B E A M N O. 2 D E S I G N R E S U L T S - FLEXURE LEN - 3854. mm FY - 460. FC - 30. SIZE - 300. X 600. mm LEVEL HEIGHT BAR INFO FROM TO ANCHOR mm mm mm STA END 1 29. 6- 8 MM 0. 3854. YES YES CRITICAL POS MOMENT = 55.31 KN-M AT 1927. mm, LOAD 3 REQD STEEL = 261.mm2, ROW = 0.0014, ROWMX= 0.0400, ROWMN = 0.0013 MAX/MIN/ACTUAL BAR SPACING = 189./ 33./ 40. mm 2 565. 6- 8 MM 0. 3854. YES YES CRITICAL NEG MOMENT = 55.31 KN-M AT 1927. mm, LOAD 4 REQD STEEL = 261.mm2, ROW = 0.0014, ROWMX= 0.0400, ROWMN = 0.0013 MAX/MIN/ACTUAL BAR SPACING = 189./ 33./ 40. mm B E A M N O. 2 D E S I G N R E S U L T S - SHEAR PROVIDE SHEAR AND TORSIONAL LINKS AS FOLLOWS FROM - TO SHEAR TORSN LOAD LINK NO. SPACING mm C/C mm kN kNm S T SIZE S T S+T S T S+T END 1 1156 84.4 12 4 2 8 mm 3 5 9 335 199 116 2697 END 2 86.6 12 3 2 8 mm 3 5 9 335 199 116 EXTRA PERIPHERAL LONGITUDINAL TORSION STEEL: 402 mm2 EVENLY DISTRIBUTED * TORSIONAL RIGIDITY SHOULD CONFORM TO CL.2.4.3 - BS8110 *

Section 2A

2-7

2A.6 Column Design

Columns are designed for axial force and biaxial bending at the ends. All active loadings are tested to calculate reinforcement. The loading which produces maximum reinforcement is called the critical load and is displayed. The requirements of BS8110 Part 1 - section 3.8 are followed, with the user having control on the effective length in each direction by using the ELZ and ELY parameters as described in table 2A.1. Bracing conditions are controlled by using the BRACE parameter. The program will then decide whether or not the column is short or slender and whether it requires additional moment calculations. For biaxial bending, the recommendations of 3.8.4.5 of the code are considered. Column design is done for square, rectangular and circular sections. For rectangular and square sections, the reinforcement is always assumed to be arranged symmetrically. This causes slightly conservative results in certain cases. Table 2A.3 shows typical column design results. Using parameter TRACK 1.0, the detailed output below is obtained. TRACK 0.0 would merely give the bar configuration, required steel area and percentage, column size and critical load case.


Section 2A

2-8

TABLE 2A.3 -COLUMN DESIGN OUTPUT C O L U M N No. 1 D E S I G N R E S U L T S FY - 460. FC -30. N/MM2 RECT SIZE - 300. X 600. MM, AREA OF STEEL REQUIRED = 875. SQ. MM. BAR CONFIGURATION REINF PCT. LOAD LOCATION 8 12 MM 0.486 3 EACH END (ARRANGE COLUMN REINFORCEMENTS SYMMETRICALLY) BRACED /SHORT in z E.L.z = 4500 mm ( 3.8.1.3 & 5 ) BRACED /SLENDER in y E.L.y = 4500 mm ( 3.8.1.3 & 5 ) END MOMS. MZ1 = 1 MZ2 = 25 MY1 = 53 MY2 = 40 SLENDERNESS MOMTS. KNM: MOMZ = 0 MOMY = 2 DESIGN LOADS KN METER: MOM. = 64 AXIAL LOAD = 84 DESIGNED CAP. KN METER: MOM. = 64 AXIAL CAP.= 187

2A.7 Slab Design

Slabs are designed to BS8110 specifications. To design a slab, it must first be modelled using finite elements. The command specifications are in accordance with section 5.51.3 of the Technical Reference Manual. A typical example of element design output is shown in Table 2A.4. The reinforcement required to resist the Mx moment is denoted as longitudinal reinforcement and the reinforcement required to resist the My moment is denoted as transverse reinforcement ( Fig. 4.1 ). The following parameters are those applicable to slab design: 1. FYMAIN - Yield stress for all reinforcing steel 2. FC - Concrete grade 3. CLEAR - Distance from the outer surface to the edge of

the bar. This is considered the same on both surfaces.

Section 2A

2-9

4. SRA - Parameter which denotes the angle of the required transverse reinforcement relative to the longitudinal reinforcement for the calculation of WOOD & ARMER design moments.

Other parameters, as shown in Table 2A.1 are not applicable. WOOD & ARMER equations. Ref: R H WOOD CONCRETE 1968 (FEBRUARY) If the default value of zero is used for the parameter SRA, the design will be based on the Mx and My moments which are the direct results of STAAD analysis. The SRA parameter (Set Reinforcement Angle) can be manipulated to introduce WOOD & ARMER moments into the design replacing the pure Mx, My moments. These new design moments allow the Mxy moment to be considered when designing the section. Orthogonal or skew reinforcement may be considered. SRA set to -500 will assume an orthogonal layout. If however a skew is to be considered, an angle is given in degrees measured anticlockwise (positive) from the element local x-axis to the reinforcement bar. The resulting Mx* and My* moments are calculated and shown in the design format. The design of the slab considers a fixed bar size of 16mm in both directions with the longitudinal bar being the layer closest to the slab exterior face. Typical output is as follows:


Section 2A

2-10

TABLE 2A.4 -ELEMENT DESIGN OUTPUT ELEMENT DESIGN SUMMARY-BASED ON 16mm BARS MINIMUM AREAS ARE ACTUAL CODE MIN % REQUIREMENTS. PRACTICAL LAYOUTS ARE AS FOLLOWS: FY=460, 6No.16mm BARS AT 150mm C/C = 1206mm2/metre FY=250, 4No.16mm BARS AT 250mm C/C = 804mm2/metre ELEMENT LONG. REINF MOM-X /LOAD TRANS. REINF MOM-Y /LOAD (mm2/m) (kN-m/m) (mm2/m) (kN-m/m) WOOD & ARMER RESOLVED MOMENTS FOR ELEMENT: 13 UNITS: METER KN LOAD MX MY MXY MX* MY*/Ma* ANGLE 1 0.619 0.249 0.000 2.226 1.855 30.000 TOP 1 0.619 0.249 0.000 0.000 0.000 30.000 BOTT 3 0.437 0.184 -0.007 1.586 1.358 30.000 TOP 3 0.437 0.184 -0.007 0.000 0.000 30.000 BOTT

13 TOP : 195. 2.23 / 1 195. 1.86 / 1 BOTT : 195. 0.00 / 3 195. 0.00 / 3

2A.8 Shear Wall Design

Purpose

Design of shear walls in accordance with BS 8110 has been added to the features of the program. Description The program implements the provisions of BS 8110 for the design of shear walls. It performs in-plane shear, compression, as well as in-plane and out-of-plane bending design of reinforcing. The shear wall is modeled by a single or a combination of Surface elements. The use of the Surface element enables the designer to treat the entire wall as one entity. It greatly simplifies the modeling of the wall and adds clarity to the analysis and design output. The results are presented in the context of the entire wall rather than individual finite elements thereby allowing users to quickly locate required information.

Section 2A

2-11

The program reports shear wall design results for each load case/combination for user specified number of sections given by SURFACE DIVISION (default value is 10) command. The shear wall is designed at these horizontal sections. The output includes the required horizontal and vertical distributed reinforcing, the concentrated (in-plane bending) reinforcing and the link required due to out-of-plane shear. General format: START SHEARWALL DESIGN CODE BRITISH FYMAIN f1 FC f2 HMIN f3 HMAX f4 VMIN f5 VMAX f6 EMIN f7 EMAX f8 LMIN f9 LMAX f10 CLEAR f11 TWOLAYERED f12 KSLENDER f13 DESIGN SHEARWALL LIST shearwall-list END


Section 2A

2-12 The following table explains parameters used in the shear wall design command block above.

SHEAR WALL DESIGN PARAMETERS

Parameter Name


FYMAIN 460 Mpa Yield strength of steel, in current units.

FC 30 Mpa Compressive strength of concrete, in current units.

HMIN 6 Minimum size of horizontal reinforcing bars (range 6 mm – 36 mm). If input is 6 (integer number) the program will assume 6 mm diameter bar.

HMAX 36 Maximum size of horizontal reinforcing bars (range 6 mm – 36 mm). If input is 6 (integer number) the program will assume 6 mm diameter bar.

VMIN 6 Minimum size of vertical reinforcing bars (range 6mm – 36mm). If input is 6 (integer number) the program will assume 6 mm diameter bar.

VMAX 36 Maximum size of vertical reinforcing bars (range 6mm – 36mm). If input is 6 (integer number) the program will assume 6 mm diameter bar.

EMIN 6 Minimum size of vertical reinforcing bars located in edge zones (range 6mm – 36mm). If input is 6 (integer number) the program will assume 6 mm diameter bar.

EMAX 36 Maximum size of vertical reinforcing bars located in edge zones (range 6mm – 36mm). If input is 6 (integer number) the program will assume 6 mm diameter bar.

LMIN 6 Minimum size of links (range 6mm – 16mm). If input is 6 (integer number) the program will assume 6 mm diameter bar.

LMAX 16 Maximum size of links (range 6mm – 16mm). If input is 6 (integer number) the program will assume 6 mm diameter bar.

Section 2A

2-13

SHEAR WALL DESIGN PARAMETERS

Parameter Name


CLEAR 25 mm Clear concrete cover, in current units. TWOLAYERED 0 Reinforcement placement mode:

0 - single layer, each direction 1 - two layers, each direction

KSLENDER 1.5 Slenderness factor for finding effective height.

The following example starts from the definition of shear wall and ends at the shear wall design. Example

.

. SET DIVISION 12 SURFACE INCIDENCES 2 5 37 34 SUR 1 19 16 65 68 SUR 2 11 15 186 165 SUR 3 10 6 138 159 SUR 4 . . . SURFACE PROPERTY 1 TO 4 THI 18 SUPPORTS 1 7 14 20 PINNED 2 TO 5 GEN PIN 6 TO 10 GEN PIN 11 TO 15 GEN PIN 19 TO 16 GEN PIN . . .


Section 2A

2-14

SURFACE CONSTANTS E 3150 POISSON 0.17 DENSITY 8.68e-005 ALPHA 5.5e-006 . . START SHEARWALL DES CODE BRITISH UNIT NEW MMS FC 25 FYMAIN 460 TWO 1 VMIN 12 HMIN 12 EMIN 12 DESIGN SHEA LIST 1 TO 4 END

Notes 1. Command SET DIVISION 12 indicates that the surface

boundary node-to-node segments will be subdivided into 12 fragments prior to finite element mesh generation.

2. Four surfaces are defined by the SURFACE INCIDENCES command.

3. The SUPPORTS command includes the new support generation routine. For instance, the line 2 TO 5 GEN PIN assigns pinned supports to all nodes between nodes 2 and 5. As the node-to-node distances were previously subdivided by the SET DIVISION 12 command, there will be an additional 11 nodes between nodes 2 and 5. As a result, all 13 nodes will be assigned pinned supports. Please note that the additional 11 nodes are not individually accessible to the user. They are created by the program to enable the finite element mesh generation and to allow application of boundary constraints.

Section 2A

2-15

4. Surface thickness and material constants are specified by the SURFACE PROPERTY and SURFACE CONSTANTS, respectively.

5. The shear wall design commands are listed between lines START SHEARWALL DES and END. The CODE command selects the design code that will be the basis for the design. For British code the parameter is BRTISH. The DESIGN SHEARWALL LIST command is followed by a list of previously defined Surface elements intended as shear walls and/or shear wall components.

Technical Overview The program implements provisions of section 3.9 of BS 8110:Part 1:1997 and relevant provisions as referenced therein, for all active load cases. The wall is designed as unbraced reinforced wall. The following steps are performed for each of the horizontal sections of the wall set using the SURFACE DIVISION command (see Description above). Checking of slenderness limit The slenderness checking is done for out-of-plane direction. For out-of-plane direction, the wall is assumed to be simply supported. Hence, the provisions of clause 3.9.3.2.2 and 3.9.4.2 are applicable. The default effective height is 1.5 times the clear height. User can change the effective height. The limit for slenderness is as per table 3.23 for unbraced wall, which is taken as 30. Design for in-plane bending (denoted by Mz in the shear wall force output) Walls are assumed to be cantilever beams fixed at their base and carrying loads to the foundation. Extreme compression fibre to centroid of tension (concentrated) reinforcement distance, d, is taken as 0.8 horizontal length of the wall. Flexural design of the wall is carried out in accordance with


Section 2A

2-16

the provisions of clause no. 3.4.4. The flexural (concentrated vertical ) reinforcing is located at both ends (edges) of the length of the wall. The edge reinforcement is assumed to be distributed over a length of 0.2 times horizontal length on each side. This length is inclusive of the thickness of the wall. Minimum reinforcements are according to table 3.25. Design for in-plane shear (denoted by Fxy in the shear wall force output) Limit on the nominal shear strength, v is calculated as per clause no. 3.4.5.2. Nominal shear strength of concrete is computed as per table 3.8. The design shear stress is computed as per clause no. 3.4.5.12 taking into consideration the effect of axial load. The area of reinforcement is calculated and checked against the minimum area as per clause no. 3.12.7.4. Design for compression and out-of-plane vertical bending (denoted by Fy and My respectively in the shear wall force output) The wall panel is designed as simply supported (at top and bottom), axially loaded with out-of-plane uniform lateral load, with maximum moments and deflections occurring at mid-height. Design is done as per clause no. 3.8.4 for axially loaded column with uni-axial bending. The minimum reinforcement percentage is as per table 3.25. The maximum reinforcement percentage of vertical reinforcement is as per clause no. 3.12.6.3. Links if necessary are calculated as per the provisions of clause 3.12.7.5. Design for out-of-plane shear (denoted by Qy in the shear wall force output) The out-of-plane shear arises from out-of-plane loading. The design shear stress is calculated as per 3.4.5.2 and shear strength of concrete section is calculated as per table 3.8 considering vertical reinforcement as tension reinforcement. Shear

Section 2A

2-17

reinforcements in the form of links are computed as per table 3.7 and the provisions of clause 3.12.7.5. Design for out-of-plane horizontal bending (denoted by Mx in the shear wall force output) The horizontal reinforcement already calculated from in-plane shear are checked against the whole section subjected to out-of-plane bending and axial load. The axial load in this case is the in-plane shear. The section is again designed as axially loaded column under uni-axial bending as per the provisions of clause 3.8.4. Extra reinforcement in the form of horizontal bars, if necessary, is reported. Shear Wall Design With Opening

The Surface element has been enhanced to allow design of shear walls with rectangular openings. The automatic meshing algorithm has been improved to allow variable divisions along wall and opening(s) edges. Design and output are available for user selected locations. Description Shear walls modeled in STAAD.Pro may include an unlimited number of openings. Due to the presence of openings, the wall may comprise up with different wall panels.

1. Shear wall set-up Definition of a shear wall starts with a specification of the surface element perimeter nodes, meshing divisions along node-to-node segments, opening(s) corner coordinates, and meshing divisions of four edges of the opening(s).

SURFACE INCIDENCE n1, ..., ni SURFACE s DIVISION sd1, ..., sdj - RECOPENING x1 y1 z1 x2 y2 z2 x3 y3 z3 x4 y4 z4 DIVISION od1, ..., odk


Section 2A

2-18 where:

n1, ..., ni - node numbers on the perimeter of the shear wall, s - surface ordinal number, sd1, ..., sdj - number of divisions for each of the node-to-node

distance on the surface perimeter, x1 y1 z1 (...) - coordinates of the corners of the opening, od1, ..., odk - divisions along edges of the opening. Note:

If the sd1, ..., sdj or the od1, ..., odk list does not include all node-to-node segments, or if any of the numbers listed equals zero, then the corresponding division number is set to the default value (=10, or as previously input by the SET DIVISION command). Default locations for stress/force output, design, and design output are set as follows:

SURFACE DIVISION X xd SURFACE DIVISION Y yd

where: xd - number of divisions along X axis, yd - number of divisions along Y axis. Note: xd and yd represent default numbers of divisions for each edge of the surface where output is requested. The output is provided for sections located between division segments. For example, if the number of divisions = 2, then the output will be produced for only one section (at the center of the edge).

Section 2A

2-19

2. Stress/force output printing Values of internal forces may be printed out for any user-defined section of the wall. The general format of the command is as follows:

PRINT SURFACE FORCE (ALONG ξξξξ) (AT a) (BETWEEN d1, d2) LIST s1, ...,si where: ξ - local axis of the surface element (X or Y), a - distance along the � axis from start of the member to

the full cross-section of the wall, d1, d2 - coordinates in the direction orthogonal to �,

delineating a fragment of the full cross-section for which the output is desired.**

s1, ...,si - list of surfaces for output generation ** The range currently is taken in terms of local axis. If the local axis is directed away from the surface, the negative range is to be entered. Note: If command ALONG is omitted, direction Y (default) is assumed. If command AT is omitted, output is provided for all sections along the specified (or default) edge. Number of sections will be determined from the SURFACE DIVISION X or SURFACE DIVISION Y input values. If the BETWEEN command is omitted, the output is generated based on full cross-section width.


Section 2A

2-20

3. Definition of wall panels Input syntax for panel definition is as follows:

START PANEL DEFINITION SURFACE i PANEL j ptype x1 y1 z1 x2 y2 z2 x3 y3 z3 x4 y4 z4 END PANEL DEFINITION

where: i - ordinal surface number, j - ordinal panel number, ptype - panel type, one of: WALL, COLUMN, BEAM x1 y1 z1 (...) - coordinates of the corners of the panel

4. Shear wall design The program implements different provisions of design of walls as per code BS 8110. General syntax of the design command is as follows:

START SHEARWALL DESIGN (...) DESIGN SHEARWALL (AT c) LIST s TRACK tr END SHEARWALL DESIGN

Parameter TRACK specifies how detailed the design output should be: 0 - indicates a basic set of results data (default), 1 - full design output will be generated.

Section 2A

2-21

Note: If the command AT is omitted, the design proceeds for all cross sections of the wall or panels, as applicable, defined by the SURFACE DIVISION X or SURFACE DIVISION Y input values. a. No panel definition.

Design is performed for the specified horizontal full cross-section, located at a distance c from the origin of the local coordinates system. If opening is found then reinforcement is provided along sides of openings. The area of horizontal and vertical bars provided along edges of openings is equal to that of the respective interrupted bars.

b. Panels have been defined.

Design is performed for all panels, for the cross-section located at a distance c from the start of the panel.


Section 2A

2-22

2-23

Steel Design Per BS5950:2000

2B.1 General

The design philosophy embodied in BS5950:2000 is built around the concept of limit state design, used today in most modern steel design codes. Structures are designed and proportioned taking into consideration the limit states at which they become unfit for their intended use. Two major categories of limit state are recognized - serviceability and ultimate. The primary considerations in ultimate limit state design are strength and stability while that in serviceability limit state is deflection. Appropriate safety factors are used so that the chances of limits being surpassed are acceptably remote. In the STAAD implementation of BS5950:2000, members are proportioned to resist the design loads without exceeding the limit states of strength and stability. Accordingly, the most economic section is selected on the basis of the least weight criteria. This procedure is controlled by the designer in specification of allowable member depths, desired section type or other such parameters. The code checking portion of the program checks that code requirements for each selected section are met and identifies the governing criteria. The complete B.S.C. steel tables for both hot rolled and hollow sections are built into the program for use in specifying member properties as well as for the actual design process. See section 2B.4 for information regarding the referencing of these sections. In addition to universal beams, columns, joists, piles, channels, tees, composite sections, beams with cover plates, pipes, tubes and angles, there is a provision for user provided tables.

Section 2B


Section 2B

2-24 Single Angle Sections Angle sections are un-symmetrical and when using BS 5950:2000 table 25 we must consider four axes; two principal, u-u and v-v and two geometric, a-a and b-b. In a TRACK 2.0 design output, the ‘Buckling Calculations’ displays results for the ‘v-v’, ‘a-a’ and ‘b-b’ axes. The effective length for the v-v axis, Lvv, is taken as the LVV parameter or LY * KY, if not specified. The a-a and b-b axes are determined by which leg of the angle is fixed by the connection and should be specified using the LEG parameter, see section 2B6.6 for more information on the LEG parameter. The effective length in the a-a axis is taken as LY * KY and the effective length in the b-b axis as LZ * KZ. The following diagram shows the axes for angles which have been defined with either an ST or RA specification and is connected by its longer leg, i.e. a-a axis is parallel to the longer leg.

Local Z (u-u)

Local Y (v-v)

a

a

b

b

Local Z (v-v)

Local Y (u-u)

a

a

b

b

ST angle RA angle and USER table angles

Section 2B

2-25





2B.4 Built-In Steel Section Library

The following information is provided for use when the built-in steel tables are to be referenced for member property specification. These properties are stored in a database file. If called for, the properties are also used for member design. Since the shear areas are built into these tables, shear deformation is always considered during the analysis of these members. Almost all BSI steel sections are available for input. A complete listing of the sections available in the built-in steel section library may be obtained by using the tools of the graphical user interface.


Section 2B

2-26 Following are the descriptions of different types of sections available: Universal Beams, Columns And Piles All rolled universal beams, columns and pile sections are available. The following examples illustrate the designation scheme.

20 TO 30 TA ST UB305X165X54 33 36 TA ST UC356X406X287 100 102 106 TA ST UP305X305X186

Rolled Steel Joists

Joist sections may be specified as they are listed in BSI-80 with the weight omitted. In those cases where two joists have the same specifications but different weights, the lighter section should be specified with an "A" at the end.

10 TO 20 TA ST JO152X127 1 2 TA ST JO127X114A

Channel Sections

All rolled steel channel sections from the BSI table have been incorporated in STAAD. The designation is similar to that of the joists. The same designation scheme as in BSI tables may be used with the weight omitted.

10 TO 15 TA ST CH305X102 55 57 59 61 TA ST CH178X76

Section 2B

2-27

Double Channels

Back to back double channels, with or without spacing between them, are available. The letter "D" in front of the section name will specify a double channel, e.g. D CH102X51, D CH203X89 etc.

51 52 53 TA D CH152X89 70 TO 80 TA D CH305X102 SP 5. (specifies a double channel with a spacing of 5 length units)

Tee Sections

Tee sections are not input by their actual designations, but instead by referring to the universal beam shapes from which they are cut. For example,

54 55 56 TA T UB254X102X22 (tee cut from UB254X102X22)

Angles

All equal and unequal angles are available for analysis. Two types of specifications may be used to describe an angle section, either a standard, ST specification or reversed angle, RA specification. Note, however, that only angles specified with an RA specification can be designed. The standard angle section is specified as follows:

15 20 25 TA ST UA200X150X18


Section 2B

2-28

This specification may be used when the local STAAD z-axis corresponds to the V-V axis specified in the steel tables. If the local STAAD y-axis corresponds to the V-V axis in the tables, type specification "RA" (reverse angle) may be used.

35 TO 45 TA RA UA200X150X18

Double Angles

Short leg back to back or long leg back to back double angles can be specified by inputting the word SD or LD, respectively, in front of the angle size. In case of an equal angle, either LD or SD will serve the purpose. For example,

14 TO 20 TA LD UA200X200X16 SP 1.5 23 27 TA SD UA80X60X6 "SP" denotes spacing between the individual angle sections.

Note that if the section is defined from a Double Angle User Table, then the section properties must be defined with an 11th value which defines the radius of gyration about an individual sections’ principal v-v axis (See Technical Reference Manual, 5.19 User Steel Table Specification) Pipes (Circular Hollow Sections)

To designate circular hollow sections from BSI tables, use PIP followed by the numerical value of diameter and thickness of the section in mm omitting the decimal section of the value provided for diameter. The following example will illustrate the designation.

10 15 TA ST PIP213.2 (specifies a 21.3 mm dia. pipe with 3.2 mm wall thickness)

Section 2B

2-29

Circular hollow sections may also be provided by specifying the outside and inside diameters of the section. For example,

1 TO 9 TA ST PIPE OD 25.0 ID 20.0 (specifies a pipe with outside dia. of 25 and inside dia. of 20 in current length units)

Only code checking and no member selection will be performed if this type of specification is used. Tubes (Rectangular or Square Hollow Sections)

Designation of tubes from the BSI steel table is illustrated below:

TUB 400 200 12.5

Example: 15 TO 25 TA ST TUB160808.0

Tubes, like pipes, can also be input by their dimensions (Height, Width and Thickness) and not by any table designations.

6 TA ST TUBE DT 8.0 WT 6.0 TH 0.5 (a tube that has a height of 8, a width of 6, and a wall thickness of 0.5 length units)

Note that only code checking and no member selection is performed for TUBE sections specified this way.

Square/Rectangular shape

Height (mm)

Thickness (mm)

Width (mm)


Section 2B

2-30

2B.5 Member Capacities

The basic measure of capacity of a beam is taken as the plastic moment of the section. This is a significant departure from the standard practice followed in BS449, in which the limiting condition was attainment of yield stress at the extreme fibres of a given section. With the introduction of the plastic moment as the basic measure of capacity, careful consideration must be given to the influence of local buckling on moment capacity. To assist this, sections are classified as either Class 1, plastic, Class 2, compact, Class 3, semi-compact or Class 4, slender, which governs the decision whether to use the plastic or the elastic moment capacity. The section classification is a function of the geometric properties of the section. STAAD is capable of determining the section classification for both hot rolled and built up sections. In addition, for slender sections, BS5950 recommends the use of a 'stress reduction factor' to reduce the design strength. This factor is again a function of the geometry of the section and is automatically determined by STAAD for use in the design process. Axial Tension

In members with axial tension, the tensile load must not exceed the tension capacity of the member. The tension capacity of the member is calculated on the basis of the effective area as outlined in Section 4.6 of the code. STAAD calculates the tension capacity of a given member per this procedure, based on a user supplied net section factor (NSF-a default value of 1.0 is present but may be altered by changing the input value - see Table 2B.1 ), proceeding with member selection or code check accordingly. BS5950 does not have any slenderness limitations for tension members. Compression

Compression members must be designed so that the compression resistance of the member is greater than the axial compressive load. Compression resistance is determined according to the compressive strength, which is a function of the slenderness of the

Section 2B

2-31

gross section, the appropriate design strength and the relevant strut characteristics. Strut characteristics take into account the considerable influence residual rolling and welding stresses have on column behaviour. Based on data collected from extensive research, it has been determined that sections such as tubes with low residual stresses and Universal Beams and Columns are of intermediate performance. It has been found that I-shaped sections are less sensitive to imperfections when constrained to fail about an axis parallel to the flanges. These research observations are incorporated in BS5950 through the use of four strut curves together with a selection of tables to indicate which curve to use for a particular case. Compression strength for a particular section is calculated in STAAD according to the procedure outlined in Annex C of BS5950 where compression strength is seen to be a function of the appropriate Robertson constant ( representing Strut Curve) corresponding Perry factor, limiting slenderness of the member and appropriate design strength. A departure from BS5950:1990, generally compression members are no longer required to be checked for slenderness limitations, however, this option can be included by specifying a MAIN parameter. Note, a slenderness limit of 50 is still applied on double angles checked as battened struts as per clause 4.7.9. Axially Loaded Members With Moments

In the case of axially loaded members with moments, the moment capacity of the member must be calculated about both principal axes and all axial forces must be taken into account. If the section is plastic or compact, plastic moment capacities will constitute the basic moment capacities subject to an elastic limitation. The purpose of this elastic limitation is to prevent plasticity at working load. For semi-compact or slender sections, the elastic moment is used. For plastic or compact sections with high shear loads, the plastic modulus has to be reduced to accommodate the shear loads. The STAAD implementation of BS5950 incorporates the procedure outlined in section 4.2.5 and 4.2.6 to calculate the appropriate moment capacities of the section.


Section 2B

2-32 For members with axial tension and moment, the interaction formula as outlined in section 4.8.2 is applied based on effective tension capacity. For members with axial compression and moment, two principal interaction formulae must be satisfied – Cross Section Capacity check (4.8.3.2) and the Member Buckling Resistance check (4.8.3.3 ). Three types of approach for the member buckling resistance check have been outlined in BS5950:2000 - the simplified approach (4.8.3.3.1), the more exact approach (4.8.3.3.2) and Annex I1 for stocky members. As noted in the code, in cases where neither the major axis nor the minor axis moment approaches zero, the more exact approach may be more conservative than the simplified approach. It has been found, however, that this is not always the case and STAAD therefore performs both checks, comparing the results in order that the more appropriate criteria can be used. Additionally the equivalent moment factors, mx my and myx, can be specified by the user or calculated by the program. Members subject to biaxial moments in the absence of both tensile and compressive axial forces are checked using the appropriate method described above with all axial forces set to zero. STAAD also carries out cross checks for compression only, which for compact/plastic sections may be more critical. If this is the case, COMPRESSION will be the critical condition reported despite the presence of moments. Shear Load

A member subjected to shear is considered adequate if the shear capacity of the section is greater than the shear load on the member. Shear capacity is calculated in STAAD using the procedure outlined in section 4.2.3, also 4.4.5 and Annex H3 if appropriate, considering the appropriate shear area for the section specified.

Section 2B

2-33Lateral Torsional Buckling

Since plastic moment capacity is the basic moment capacity used in BS5950, members are likely to experience relatively large deflections. This effect, coupled with lateral torsional buckling, may result in severe serviceability limit state. Hence, lateral torsional buckling must be considered carefully. The procedure to check for lateral torsional buckling as outlined in section 4.3 has been incorporated in the STAAD implementation of BS5950. According to this procedure, for a member subjected to moments about the major axis, the 'equivalent uniform moment' on the section must be less than the lateral torsional buckling resistance moment. For calculation of the buckling resistance moment, the procedure outlined in Annex B.2 has been implemented for all sections with the exception of angles. In Annex B.2., the resistance moment is given as a function of the elastic critical moment, Perry coefficient, and limiting equivalent slenderness, which are calculated within the program; and the equivalent moment factor, mLT, which is determined as a function of the loading configuration and the nature of the load (stabilizing, destabilizing, etc). R. H. S Sections - Additional Provisions Rectangular Hollow sections are treated in accordance with S.C.I. recommendations in cases when the plastic axis is in the flange. In such cases, the following expressions are used to calculate the reduced plastic moduli:

Srx = (A*A/4(B-t))(1-n) [ 2D(B-t)/A + n-1 ]

for n>= 2t(D-2t)/A Sry = (A*A/4(D-t))(1-n) [ 2B(D-t)/A + n-1 ]

for n>= 2t(B-2t)/A


Section 2B

2-34


Available design parameters to be used in conjunction with BS5950 are listed in table 2B.1 along with their default values. The following items should be noted with respect to their use. 1. (PY – Steel Design Strength )

The design parameter PY should only be used when a uniform design strength for an entire structure or a portion thereof is required. Otherwise the value of PY will be set according to the stipulations of BS5950 table 9 in which the design strength is seen as a function of cross sectional thickness for a particular steel grade (SGR parameter) and particular element considered. Generally speaking this option is not required and the program should be allowed to ascertain the appropriate value.

2. (UNL, LY and LZ - Relevant Effective Length) The values supplied for UNL, LY and LZ should be real numbers greater than zero in current units of length. They are supplied along with or instead of UNF, KY and KZ (which are factors, not lengths) to define lateral torsional buckling and compression effective lengths respectively. Please note that both UNL or UNF and LY or KY values are required even though they are often the same values. The former relates to compression flange restraint for lateral torsional buckling while the latter is the unrestrained buckling length for compression checks.

3. (TRACK - Control of Output Formats )

When the TRACK parameter is set to 0.0, 1.0 or 2.0, member capacities will be printed in design related output (code check or member selection) in kilonewtons per square metre. TRACK 4.0 causes the design to carry out a deflection check, usually with a different load list to the main code check. The members that are to be checked must have the parameters, DFF, DJ1 and DJ2 set.

Section 2B

2-35

An example of each TRACK setting follows:-

TRACK 0.0 OUTPUT STAAD CODE CHECKING - (BSI ) --------------------------- ****************************** ALL UNITS ARE - KNS METR (UNLESS OTHERWISE NOTED) MEMBER TABLE RESULT/ CRITICAL COND/ RATIO/ LOADING/ FX MY MZ LOCATION ================================================================= 1 ST UB686X254X170 PASS BS-4.8.3.2 0.036 3 86.72 C 0.00 -22.02 4.50 --------------------------------- TRACK 1.0 OUTPUT STAAD CODE CHECKING - (BSI ) --------------------------- ****************************** ALL UNITS ARE - KNS METR (UNLESS OTHERWISE NOTED) MEMBER TABLE RESULT/ CRITICAL COND/ RATIO/ LOADING/ FX MY MZ LOCATION ================================================================= 1 ST UB686X254X170 PASS BS-4.8.3.2 0.036 3 86.72 C 0.00 -22.02 4.50 CALCULATED CAPACITIES FOR MEMB 1 UNIT - kN,m SECTION CLASS 4 MCZ= 1141.9 MCY= 120.4 PC= 3451.5 PT= 5739.9 MB= 1084.1 PV= 1597.5 BUCKLING CO-EFFICIENTS m AND n : m = 1.000 n = 1.000 PZ= 5739.90 FX/PZ = 0.02 MRZ= 1141.9 MRY= 120.4


Section 2B

2-36 TRACK 2.0 OUTPUT STAAD.Pro CODE CHECKING - (BSI ) --------------------------- *************************** ALL UNITS ARE - KN METE (UNLESS OTHERWISE NOTED) MEMBER TABLE RESULT/ CRITICAL COND/ RATIO/ LOADING/ FX MY MZ LOCATION =================================================================== 1 ST UB533X210X92 PASS BS-4.3.6 0.902 100 0.00 0.00 585.41 0.00 =================================================================== MATERIAL DATA Grade of steel = S 275 Modulus of elasticity = 205 kN/mm2 Design Strength (py) = 275 N/mm2 SECTION PROPERTIES (units - cm) Member Length = 325.00 Gross Area = 117.00 Net Area = 117.00 Major axis Minor axis Moment of inertia : 55229.996 2389.000 Plastic modulus : 2360.000 356.000 Elastic modulus : 2072.031 228.285 Shear Area : 58.771 53.843 DESIGN DATA (units - kN,m) BS5950-1/2000 Section Class : PLASTIC Major axis Minor axis Moment Capacity : 649.0 94.2 Reduced Moment Capacity : 649.0 97.9 Shear Capacity : 969.7 888.4 BUCKLING CALCULATIONS (units - kN,m) (axis nomenclature as per design code) LTB Moment Capacity (kNm) and LTB Length (m): 649.00, 0.001 LTB Coefficients & Associated Moments (kNm):

Section 2B

2-37

mLT = 1.00 : mx = 1.00 : my = 1.00 : myx = 1.00 Mlt = 585.41 : Mx = 585.41 : My = 0.00 : My = 0.00 CRITICAL LOADS FOR EACH CLAUSE CHECK (units- kN,m): CLAUSE RATIO LOAD FX VY VZ MZ MY BS-4.2.3-(Y) 0.329 100 - 292.3 - - - BS-4.3.6 0.902 100 - 292.3 - 585.4 - BS-4.8.3.2 0.814 100 0.0 68.0 0.0 585.4 0.0 BS-4.8.3.3.1 1.027 100 0.0 - - 585.4 0.0 BS-4.8.3.3.2 0.902 100 0.0 - - 585.4 0.0 Annex I.1 0.902 100 0.0 - - 585.4 0.0 Torsion and deflections have not been considered in the design.

_________________________

4. (MX, MY, MYX and MLT – Equivalent Moment Factors)

The values for the equivalent moment factors can either be specified directly by the user as a positive value between 0.4 and 1.0 for MX, MY and MYX and 0.44 and 1.0 for MLT. The program can be used to calculate the values for the equivalent moment factors by defining the design member with a GROUP command (see the Technical Reference Manual section 5.16 Listing of Members/Elements/Joints by Specification of GROUPS). The nodes along the beam can then be defined as the location of restraint points with J settings. Additionally for the MLT parameter, the joint can be defined as having the upper flange restrained (positive local Y) with the a U setting or the lower flange restrained (negative local Y) with a L setting.


Section 2B

2-38 For example, consider a series of 5 beam elements as a single continuous member as shown below:

To enable the steel design, the beam needs to be defined as a group, called MainBeam:

START GROUP DEFINITION MEMBER _MainBeam 11 2 38 12 3 END GROUP DEFINITION

Note that this can be done in the GUI by selecting the beams and clicking on the menu option:

‘Tools | Create New Group…’ Therefore, this 5 beam member has 6 joints such that:-

Joint 1 = Node 3 Joint 2 = Node 1 Joint 3 = Node 33

Section 2B

2-39

Joint 4 = Node 14 Joint 5 = Node 7 Joint 6 = Node 2

a. Consider MX, MY and MYX

Say that this member has been restrained in its’ major axis (local Y) only at the ends. In the minor axis (local Z) it has been restrained at the ends and also at node number 33 (joint 3). For local flexural buckling, it has only been restrained at its ends. Hence:- For the major axis, local Y axis:- MX _MainBeam J1 J6 For the minor axis, local Z axis:- MY _ MainBeam J1 J3 J6 For the lateral flexural buckling, local X axis:- MYX _ MainBeam J1 J6

b. Consider MLT Say that this member has been restrained at its’ ends against lateral torsional buckling and the top flange has been restrained at node number 33 (joint 3) and only the lower flange at node number 7, (joint 5). Hence:- MLT _MainBeam J1 T3 L5 J6 To split the beam into two buckling lengths for Ly at joint 14:- MY _groupname J1 J4 J6


Section 2B

2-40 5. (LEG - Table 25 BS5950 for Fastener Control)

The slenderness of single and double angle, channel and tee sections are specified in BS 5950 table 25 depending on the connection provided at the end of the member. To define the appropriate connection, a LEG parameter should be assigned to the member. The following table indicates the value of the LEG parameter required to match the BS5950 connection definition:- Clause LEG

short leg 1.0 (a) - 2 bolts long leg 3.0 short leg 0.0

4.7.10.2 Single Angle (b) - 1 bolt

long leg 2.0

short leg 3.0 (a) - 2 bolts long leg 7.0 short leg 2.0 (b) - 1 bolt long leg 6.0 long leg 1.0 (c) - 2 bolts short leg 5.0 long leg 0.0

4.7.10.3 Double Angle

(d) - 1 bolt short leg 4.0

(a) - 2 or more rows of bolts 1.0 4.7.10.4

Channels (b) - 1 row of bolts 0.0

(a) - 2 or more rows of bolts 1.0 4.7.10.5 Tee Sections (b) - 1 row of bolts 0.0

For single angles, the slenderness is calculated for the geometric axes, a-a and b-b as well as the weak v-v axis. The effective lengths of the geometric axes are defined as:- La = KY * KY Lb = KZ * LZ

Section 2B

2-41

The slenderness calculated for the v-v axis is then used to calculate the compression strength pc for the weaker principal axis (z-z for ST angles or y-y for RA specified angles). The maximum slenderness of the a-a and b-b axes is used to calculate the compression strength pc for the stronger principal axis. Alternatively for single angles where the connection is not known or Table 25 is not appropriate, by setting the LEG parameter to 10, slenderness is calculated for the two principal axes y-y and z-z only. The LVV parameter is not used. For double angles, the LVV parameter is available to comply with note 5 in table 25. In addition, if using double angles from user tables, (Technical Reference Manual section 5.19) an eleventh value, rvv, should be supplied at the end of the ten existing values corresponding to the radius of gyration of the single angle making up the pair.

6. (SWAY – Sway Loadcase)

This parameter is used to specify a load case that is to be treated as a sway load case in the context of clause 4.8.3.3.4. This load case would be set up to represent the “kampMs” mentioned in this clause and the steel design module would add the forces from this load case to the forces of the other load case it is designed for. Note that the load case specified with this parameter will not be designed as a separate load case. The following is the correct syntax for the parameter:- SWAY

(load case number)

ALL MEMBER (member list) _(group name)

e.g.

SWAY 5 MEM 1 to 10 SWAY 6 _MainBeams


Section 2B

2-42

Table 2B.1 - British Steel Design – BS5950:2000 - Parameters

Parameter Name

Default Value

Description

CODE BS5950 Design Code to follow. See section 5.47.1 of the Technical Reference Manual.

SGR 0.0 Steel Grade per BS4360 0.0 = Grade S 275 1.0 = Grade S 355 2.0 = Grade S 460 3.0 = As per GB 1591 – 16 Mn

PY * Set according to steel grade

(SGR)

Design strength of steel

KY 1.0 K factor value in local y - axis. Usually, this is the minor axis.

KZ 1.0 K factor value in local z - axis. Usually, this is the major axis.

LY * Member Length

Length in local y - axis (current units) to calculate (KY)(LY)/Ryy slenderness ratio.

LZ * Member Length

Length in local z - axis (current units) to calculate (KZ)(LZ)/Rzz slenderness ratio.

UNF 1.0 Factor applied to unsupported length for Lateral Torsional Buckling effective length per section 4.3.7.5 of BS5950.

UNL * Member Length

Unsupported Length for calculating Lateral Torsional Buckling resistance moment section 4.3.7.5 of BS5950.


SBLT 0.0 Identify Section type for section classification 0.0 = Rolled Section 1.0 = Built up Section 2.0 = Cold formed section

MAIN 0.0 Slenderness limit for members with compression forces, effective length/ radius of gyration, for a given axis:- 0.0 = Slenderness not performed. 1.0 = Main structural member (180) 2.0 = Secondary member. (250) 3.0 = Bracing etc (350)

TRACK 0.0 0.0 = Suppress all member capacity info. 1.0 = Print all member capacities. 2.0 = Print detailed design sheet.

Section 2B

2-43


Parameter Name

Default Value

Description

4.0 = Deflection Check (separate check to main select / check code)

BEAM 3.0 0.0 = Design only for end moments or those locations specified by the SECTION command.

1.0 = Calculate forces and moments at 12th points along the member. Establish the location where Mz is the maximum. Use the forces and moments at that location. Clause checks at one location.

2.0 = Same as BEAM = 1.0 but additional checks are carried out for each end.

3.0 = Calculate moments at 12th points along the member. Clause checks at each location including the ends of the member.

LEG 0.0 Valid range from 0 – 7 and 10. See section 2B.6.5 for details. The values correspond to table 25 of BS5950 for fastener conditions.

LVV * Maximum of Lyy and Lzz

(Lyy is a term used

by BS5950)

Used in conjunction with LEG for Lvv as per BS5950 table 25 for double angles, note 5.

CB 1.0 1.0 = BS5950 per clause B.2.5 (continuous) to calculate Mb.

2.0 = To calculate Mbs (simple) as per Clause 4.7.7 as opposed to Mb.

DFF None (Mandatory

for deflection check,

TRACK 4.0)

"Deflection Length" / Maxm. allowable local deflection


Joint No. denoting starting point for calculation of "Deflection Length" (See Note 1)


Joint No. denoting end point for calculation of "Deflection Length" (See Note 1)

ESTIFF 0.0 Clauses 4.8.3.3.1 and 4.8.3.3.2 0.0 = Fail ratio uses MIN of 4.8.3.3.1, 4.8.3.3.2. and

Annex I1 checks. 1.0 = Fail ratio uses MAX of 4.8.3.3.1, 4.8.3.3.2. and

Annex I1 checks.


Section 2B

2-44


Parameter Name

Default Value

Description

WELD 1.0 closed

2.0 open

Weld Type, see AISC steel design 1.0 = Closed sections. Welding on one side only (except

for webs of wide flange and tee sections) 2.0 = Open sections. Welding on both sides (except

pipes and tubes) TB 0.0 0.0 = Elastic stress analysis

1.0 = Plastic stress analysis PNL * 0.0 Transverse stiffener spacing (‘a’ in Annex H1)

0.0 = Infinity Any other value used in the calculations.

SAME** 0.0 Controls the sections to try during a SELECT process.

0.0 = Try every section of the same type as original 1.0 = Try only those sections with a similar name as

original, e.g. if the original is an HEA 100, then only HEA sections will be selected, even if there are HEM’s in the same table.

MX 1.0 Equivalent moment factor for major axis flexural buckling as defined in clause 4.8.3.3.4

MY 1.0 Equivalent moment factor for minor axis flexural buckling as defined in clause 4.8.3.3.4

MYX 1.0 Equivalent moment factor for minor axis lateral flexural buckling as defined in clause 4.8.3.3.4

MLT 1.0 Equivalent moment factor for lateral torsional buckling as defined in clause 4.8.3.3.4

SWAY none Specifies a load case number to provide the sway loading forces in clause 4.8.3.3.4 (See additional notes)

DMAX * 100.0cm Maximum allowable depth

DMIN * 0.0cm Minimum allowable depth

RATIO 1.0 Permissible ratio of the actual capacities.

* current units must be considered. **For angles, if the original section is an equal angle, then the selected section will be an equal angle and vice versa for unequal angles.

Section 2B

2-45

NOTES: 1) "Deflection Length" is defined as the length that is used for

calculation of local deflections within a member. It may be noted that for most cases the "Deflection Length" will be equal to the length of the member. However, in some situations, the "Deflection Length" may be different. For example, refer to the figure below where a beam has been modeled using four joints and three members. Note that the "Deflection Length" for all three members will be equal to the total length of the beam in this case. The parameters DJ1 and DJ2 should be used to model this situation. Also the straight line joining DJ1 and DJ2 is used as the reference line from which local deflections are measured. Thus, for all three members here, DJ1 should be "1" and DJ2 should be "4".

D = Maximum local deflection for members1, 2 and 3.

D

1

2 3

4

1

2 3

EXAMPLE : PARAMETERS DFF 300. ALL DJ1 1 ALL DJ2 4 ALL

2) If DJ1 and DJ2 are not used, "Deflection Length" will default

to the member length and local deflections will be measured from original member line.

3) The above parameters may be used in conjunction with other

available parameters for steel design.

2B.7 Design Operations

STAAD contains a broad set of facilities for the design of structural members as individual components of an analysed structure. The member design facilities provide the user with the ability to carry out a number of different design operations. These facilities may be used selectively in accordance with the requirements of the design problem.


Section 2B

2-46 The operations to perform a design are:

• Specify the load cases to be considered in the design; the

default is all load cases. • Specify design parameter values, if different from the default

values. • Specify whether to perform code checking or member selection

along with the list of members.

These operations may be repeated by the user any number of times depending upon the design requirements.

2B.8 Code Checking

The purpose of code checking is to ascertain whether the provided section properties of the members are adequate. The adequacy is checked as per BS5950. Code checking is done using the forces and moments at specific sections of the members. If no sections are specified, the program uses the start and end forces for code checking. When code checking is selected, the program calculates and prints whether the members have passed or failed the checks; the critical condition of BS5950 code (like any of the BS5950 specifications for compression, tension, shear, etc.); the value of the ratio of the critical condition (overstressed for value more than 1.0 or any other specified RATIO value); the governing load case, and the location (distance from the start of the member of forces in the member where the critical condition occurs). Code checking can be done with any type of steel section listed in Section 2B.4 of the STAAD Technical Reference Manual or any of the user defined sections in section 5.19 with two exceptions; GENERAL and ISECTION. In BS5950, these will not be considered for design along with PRISMATIC sections, which are also not acceptable.

Section 2B

2-47


STAAD is capable of performing design operations on specified members. Once an analysis has been performed, the program can select the most economical section, i.e. the lightest section, which fulfills the code requirements for the specified member. The section selected will be of the same type section as originally designated for the member being designed. Member selection can also be constrained by the parameters DMAX and DMIN, which limits the maximum and minimum depth of the members.

Member selection can be performed with all the types of steel sections with the same limitations as defined in section 2B.8 - CODE CHECKING. Selection of members, whose properties are originally input from a user created table, will be limited to sections in the user table. Member selection cannot be performed on members whose section properties are input as prismatic or as above limitations for code checking.


Section 2B

2-48


For code checking or member selection, the program produces the results in a tabulated fashion. The items in the output table are explained as follows: a) MEMBER refers to the member number for which the

design is performed. b) TABLE refers to steel section name, which has been

checked against the steel code or has been selected.

c) RESULTS prints whether the member has PASSED or FAILED. If the RESULT is FAIL, there will be an asterisk (*) mark on front of the member.

d) CRITICAL COND refers to the section of the BS5950 code

which governs the design. e) RATIO prints the ratio of the actual stresses to

allowable stresses for the critical condition. Normally a value of 1.0 or less will mean the member has passed.

f) LOADING provides the load case number, which

governed the design. g) FX, MY, and MZ provide the axial force, moment in local Y-

axis and the moment in local z-axis respectively. Although STAAD does consider all the member forces and moments (except torsion) to perform design, only FX, MY and MZ are printed since they are the ones which are of interest, in most cases.

Section 2B

2-49

h) LOCATION specifies the actual distance from the start of the member to the section where design forces govern.

i) TRACK If the parameter TRACK is set to 1.0, the

program will block out part of the table and will print the allowable bending capacities in compression (MCY & MCZ) and reduced moment capacities (MRY & MRZ), allowable axial capacity in compression (PC) and tension (PT) and shear capacity (PV). TRACK 2.0 will produce the design results as shown in section 2B.9.

2B.11 Plate Girders

Sections will be considered for the Plate Girder checks (BS 5950 Section 4.4) if d/t > 70 ε for ‘rolled sections’ or d/t >62 ε for ‘welded sections’. The parameter SBLT should be used to identify sections as rolled or welded; see the parameter list for more information.

If the plate girder has intermediate stiffeners, the spacing is set with the PNL parameter. These are then used to check against the code clauses ‘4.4.3.2 - Minimum web thickness for serviceability’ and ‘4.4.3.3 - Minimum web thickness to avoid compression flange buckling’. The following printout is then included if a TRACK 2.0 output is selected:-

Shear Buckling check is required: Vb = 1070 kN : qw = 118 N/mm2

d = 900 mm : t = 10 mm : a = 200 mm : pyf = 275 N/mm2

BS-4.4.3.2 status = PASS : BS-4.4.3.3 status = PASS

The section is then checked for shear buckling resistance using clause ‘4.4.5.2 - Simplified method’ and the result is included in the ratio checks.


Section 2B

2-50

2B.12 Composite Sections

Sections that have been defined as acting compositely with a concrete flange either from a standard database section using the CM option, or from a modified user WIDE FLANGE database with the additional composite parameters, cannot be designed with BS5950:2000.

2-51


2B1.1 General

This code has been withdrawn by the British Standards, but has been retained in STAAD.Pro for comparative purposes only. The design philosophy embodied in BS5950 is built around the concept of limit state design, used today in most modern steel design codes. Structures are designed and proportioned taking into consideration the limit states at which they become unfit for their intended use. Two major categories of limit state are recognized - serviceability and ultimate. The primary considerations in ultimate limit state design are strength and stability while that in serviceability limit state is deflection. Appropriate safety factors are used so that the chances of limits being surpassed are acceptably remote. In the STAAD implementation of BS5950, members are proportioned to resist the design loads without exceeding the limit states of strength and stability. Accordingly, the most economic section is selected on the basis of the least weight criteria. This procedure is controlled by the designer in specification of allowable member depths, desired section type or other such parameters. The code checking portion of the program checks that code requirements for each selected section are met and identifies the governing criteria. The complete B.S.C. steel tables for both hot rolled and hollow sections are built into the program for use in specifying member properties as well as for the actual design process. See section 2B.4 for information regarding the referencing of these sections. In addition to universal beams, columns, joists, piles, channels,

Section 2B1


Section 2B1

2-52 tees, composite sections, beams with cover plates, pipes, tubes and angles, there is a provision for user provided tables.

2B1.2 Analysis Methodology


2B1.3 Member Property Specifications

For specification of member properties, the steel section library available in STAAD may be used. The next section describes the syntax of commands used to assign properties from the built-in steel table. Members properties may also be specified using the User Table facility. For more information on these facilities, refer to the STAAD Technical Reference Manual.

2B1.4 Built-In Steel Section Library

The following information is provided for use when the built-in steel tables are to be referenced for member property specification. These properties are stored in a database file. If called for, the properties are also used for member design. Since the shear areas are built into these tables, shear deformation is always considered during the analysis of these members. Almost all BSI steel sections are available for input. A complete listing of the sections available in the built-in steel section library may be obtained by using the tools of the graphical user interface.

Section 2B1

2-53

Following are the descriptions of different types of sections available: Universal Beams, Columns And Piles All rolled universal beams, columns and pile sections are available. The following examples illustrate the designation scheme.

20 TO 30 TA ST UB305X165X54 33 36 TA ST UC356X406X287 100 102 106 TA ST UP305X305X186

Rolled Steel Joists

Joist sections may be specified as they are listed in BSI-80 with the weight omitted. In those cases where two joists have the same specifications but different weights, the lighter section should be specified with an "A" at the end.

10 TO 20 TA ST JO152X127 1 2 TA ST JO127X114A

Channel Sections All rolled steel channel sections from the BSI table have been incorporated in STAAD. The designation is similar to that of the joists. The same designation scheme as in BSI tables may be used with the weight omitted.

10 TO 15 TA ST CH305X102 55 57 59 61 TA ST CH178X76

Double Channels

Back to back double channels, with or without spacing between them, are available. The letter "D" in front of the section name will specify a double channel, e.g. D CH102X51, D CH203X89 etc.


Section 2B1

2-54

51 52 53 TA D CH152X89 70 TO 80 TA D CH305X102 SP 5. (specifies a double channel with a spacing of 5 length units)

Tee Sections

Tee sections are not input by their actual designations, but instead by referring to the universal beam shapes from which they are cut. For example,

54 55 56 TA T UB254X102X22 (tee cut from UB254X102X22)

Angles

All equal and unequal angles are available for input. Two types of specifications may be used to describe an angle. The standard angle section is specified as follows:

15 20 25 TA ST UA200X150X18

This specification may be used when the local STAAD z-axis corresponds to the V-V axis specified in the steel tables. If the local STAAD y-axis corresponds to the V-V axis in the tables, type specification "RA" (reverse angle) may be used.

35 TO 45 TA RA UA200X150X18

Double Angles

Short leg back to back or long leg back to back double angles can be specified by inputting the word SD or LD, respectively, in front of the angle size. In case of an equal angle, either LD or SD will serve the purpose. For example,

Section 2B1

2-55

14 TO 20 TA LD UA200X200X16 SP 1.5 23 27 TA SD UA80X60X6 "SP" denotes spacing between the individual angle sections.

Pipes (Circular Hollow Sections)

To designate circular hollow sections from BSI tables, use PIP followed by the numerical value of diameter and thickness of the section in mm omitting the decimal section of the value provided for diameter. The following example will illustrate the designation.

10 15 TA ST PIP213.2 (specifies a 21.3 mm dia. pipe with 3.2 mm wall thickness)


1 TO 9 TA ST PIPE OD 25.0 ID 20.0 (specifies a pipe with outside dia. of 25 and inside dia. of 20 in current length units)

Only code checking and no member selection will be performed if this type of specification is used. Tubes (Rectangular or Square Hollow Sections)

Designation of tubes from the BSI steel table is illustrated below:

TUB 400 200 12.5

Tube symbol

Height (mm)

Thickness (mm)

Width (mm)


Section 2B1

2-56

Example: 15 TO 25 TA ST TUB160808.0


6 TA ST TUBE DT 8.0 WT 6.0 TH 0.5 is a tube that has a height of 8, a width of 6, and a wall thickness of 0.5 length units.

Note that only code checking and no member selection is performed for TUBE sections specified this way.

2B1.5 Member Capacities

The basic measure of capacity of a beam is taken as the plastic moment of the section. This is a significant departure from the standard practice followed in BS449, in which the limiting condition was attainment of yield stress at the extreme fibres of a given section. With the introduction of the plastic moment as the basic measure of capacity, careful consideration must be given to the influence of local buckling on moment capacity. To assist this, sections are classified as either plastic, compact, semi-compact or slender, which governs the decision whether to use the plastic or the elastic moment capacity. The section classification is a function of the geometric properties of the section. STAAD is capable of determining the section classification for both hot rolled and built up sections. In addition, for slender sections, BS5950 recommends the use of a 'stress reduction factor' to reduce the design strength. This factor is again a function of the geometry of the section and is automatically determined by STAAD for use in the design process. Axial Tension

In members with axial tension, the tensile load must not exceed the tension capacity of the member. The tension capacity of the member is calculated on the basis of the effective area as outlined

Section 2B1

2-57

in Section 4.6 of the code. STAAD calculates the tension capacity of a given member per this procedure, based on a user supplied net section factor (NSF-a default value of 1.0 is present but may be altered by changing the input value - see Table 2B.1 ), proceeding with member selection or code check accordingly. BS5950 does not have any slenderness limitations for tension members. Compression

Compression members must be designed so that the compression resistance of the member is greater than the axial compressive load. Compression resistance is determined according to the compressive strength which is a function of the slenderness of the gross section, the appropriate design strength and the relevant strut characteristics. Strut characteristics take into account the considerable influence residual rolling and welding stresses have on column behaviour. Based on data collected from extensive research, it has been determined that sections such as tubes with low residual stresses and Universal Beams and Columns are of intermediate performance. It has been found that I-shaped sections are less sensitive to imperfections when constrained to fail about an axis parallel to the flanges. These research observations are incorporated in BS5950 through the use of four strut curves together with a selection of tables to indicate which curve to use for a particular case. Compression strength for a particular section is calculated in STAAD according to the procedure outlined in Appendix C of BS5950 where compression strength is seen to be a function of the appropriate Robertson constant ( representing Strut Curve) corresponding Perry factor, limiting slenderness of the member and appropriate design strength. In addition to the compression resistance criteria, compression members are required to satisfy slenderness limitations which are a function of the nature of the use of the member ( main load resisting component, bracing member etc). In both the member selection and the code checking process, STAAD immediately does a slenderness check on appropriate members before continuing with the other procedures for determining the adequacy of a given member.


Section 2B1

2-58 Axially Loaded Members With Moments

In the case of axially loaded members with moments, the moment capacity of the member must be calculated about both axes and all axial forces must be taken into account. If the section is plastic or compact, plastic moment capacities will constitute the basic moment capacities subject to an elastic limitation. The purpose of this elastic limitation is to prevent plasticity at working load. For semi-compact or slender sections, the elastic moment is used. For plastic or compact sections with high shear loads, the plastic modulus has to be reduced to accommodate the shear loads. The STAAD implementation of BS5950 incorporates the procedure outlined in section 4.2.5 and 4.2.6 to calculate the appropriate moment capacities of the section. For members with axial tension and moment, the interaction formula as outlined in section 4.8.2 is applied based on effective tension capacity. For members with axial compression and moment, two principal interaction formulae must be satisfied - local capacity check (4.8.3.2) and overall buckling check (section 4.8.3.3 ). Two types of approach for the overall buckling check have been outlined in BS5950 - the simplified approach and the more exact approach. As noted in the code, in cases where neither the major axis nor the minor axis moment approaches zero, the more exact approach may be more conservative than the simplified approach. It has been found, however, that this is not always the case and STAAD therefore performs both checks, comparing the results in order that the more appropriate criteria be used. Members subject to biaxial moments in the absence of both tensile and compressive axial forces are checked using the appropriate method described above with all axial forces set to zero. STAAD also carries out cross checks for compression only, which for compact/plastic sections may be more critical. If this is the case, COMPRESSION will be the critical condition reported despite the presence of moments.

Section 2B1

2-59Shear Load

A member subjected to shear is considered adequate if the shear capacity of the section is greater than the shear load on the member. Shear capacity is calculated in STAAD using the procedure outlined in section 4.2.3 and considering the appropriate shear area for the section specified. Lateral Torsional Buckling

Since plastic moment capacity is the basic moment capacity used in BS5950, members are likely to experience relatively large deflections. This effect, coupled with lateral torsional buckling, may result in severe serviceability limit state. Hence, lateral torsional buckling must be considered carefully. The procedure to check for lateral torsional buckling as outlined in section 4.3 has been incorporated in the STAAD implementation of BS5950. According to this procedure, for a member subjected to moments about the major axis, the 'equivalent uniform moment' on the section must be less than the lateral torsional buckling resistance moment. For calculation of the buckling resistance moment, the procedure outlined in Appendix B.2 has been implemented for all sections with the exception of angles. In Appendix B.2., the resistance moment is given as a function of the elastic critical moment, Perry coefficient, and limiting equivalent slenderness, which are calculated within the program; and the equivalent moment factor, m, and slenderness correction factor, n, which are determined as a function of the loading configuration and the nature of the load ( stabilizing, destabilizing, etc ). The user is allowed to control these values through the parameters CMM & CMN. If CMM is set to -1, the program automatically calculates the coefficient 'm'. Similarly parameter CMN may be used for the calculation of coefficient 'n'. BS5950 recommends the use of tables 15 & 16 for the calculation of coefficient 'n'. The parameter CMN may be set to -1 or -2 to instruct the program to obtain coefficient 'n' from table 15 or 16 respectively. If a positive value is provided for either CMN or CMM, the program will use this value directly in calculations. The default value for each of


Section 2B1

2-60 these parameters is 1.0 as shown in table 2B.1 of this document. It may be noted that BS5950 recommends the use of either 'm' or 'n' in lateral torsional buckling calculations. If both 'm' and 'n' are set to values less than 1 in error, the program will always reset CMN to 1 and over-ride the provided value. The following table illustrates the use of parameters 'm' and 'n'. PARAMETER VALUE STAAD ACTION CMM ANY POSITIVE Direct use of this value in VALUE calculations. -1 Program calculates 'm' per BS5950 -2 Calculate ‘m’ for both axes CMN ANY POSITIVE Direct use of this value in VALUE calculations. -1 Program calculates 'n' per BS5950 - Table 15 -2 Program calculates 'n' per BS5950 - Table 16 IMPORTANT NOTE: Note that if negative value options are chosen, lateral restraints should be modelled by nodes and the section command incorporated to find Mo. Failure to use the SECTION 0.5 command will cause the program to reset CMN to 1.0 and over-ride any value that may have been provided. In requesting 'n' to be calculated by the program by using a negative CMN value, the member properties must be British ( or British combined with user table sections). If other profiles such as European are being used then 'n' values are reset conservatively to 1.0 by the program. In the case of angles, section 4.3.8 of the code is followed.

R. H. S Sections - Additional Provisions Rectangular Hollow sections are treated in accordance with S.C.I. recommendations in cases when the plastic axis is in the flange. In such cases, the following expressions are used to calculate the reduced plastic moduli:

Section 2B1

2-61

Srx = (A*A/4(B-t))(1-n) [ 2D(B-t)/A + n-1 ] for n>= 2t(D-2t)/A

Sry = (A*A/4(D-t))(1-n) [ 2B(D-t)/A + n-1 ]

for n>= 2t(B-2t)/A

2B1.6 Design Parameters

Available design parameters to be used in conjunction with BS5950 are listed in table 2B.1 along with their default values. The following items should be noted with respect to their use. 1. (PY - STEEL DESIGN STRENGTH )

The design parameter PY should only be used when a uniform design strength for an entire structure or a portion thereof is required. Otherwise the value of PY will be set according to the stipulations of BS5950 table 7 in which the design strength is seen as a function of cross sectional thickness for a particular steel grade and particular element considered. Generally speaking this option is not required and the program should be allowed to ascertain the appropriate value.

2. (UNL, LY and LZ - relevant EFFECTIVE LENGTHS) The values supplied for UNL, LY and LZ should be real numbers greater than zero in current units of length. They are supplied along with or instead of UNF, KY KZ ( which are factors, not lengths) to define lateral torsional buckling and compression effective lengths respectively. Please note that both UNL or UNF and LY or KY values are required even though they are often the same values. The former relates to compression flange restraint for lateral torsional buckling while the latter is the unrestrained buckling length for compression checks.

3. (CMN and CMM - Lateral torsional buckling coefficients)

As per section 2B.7 of this manual CMM and CMN should not both be used in a given design. In such a case the program will reset CMN to 1.0


Section 2B1

2-62 4. (TRACK - control of output formats )

When the TRACK parameter is set to 1.0 or 2.0, member capacities will be printed in design related output ( code check or member selection ) in kilonewtons per square metre. An example of each follows.

TRACK 0.0 OUTPUT STAAD CODE CHECKING - (BSI ) --------------------------- ****************************** ALL UNITS ARE - KNS METR (UNLESS OTHERWISE NOTED) MEMBER TABLE RESULT/ CRITICAL COND/ RATIO/ LOADING/ FX MY MZ LOCATION ================================================================= 1 ST UB686X254X170 PASS BS-4.8.3.2 0.036 3 86.72 C 0.00 -22.02 4.50 ---------------------------------

Section 2B1

2-63 TRACK 1.0 OUTPUT STAAD CODE CHECKING - (BSI ) --------------------------- ****************************** ALL UNITS ARE - KNS METR (UNLESS OTHERWISE NOTED) MEMBER TABLE RESULT/ CRITICAL COND/ RATIO/ LOADING/ FX MY MZ LOCATION ================================================================= 1 ST UB686X254X170 PASS BS-4.8.3.2 0.036 3 86.72 C 0.00 -22.02 4.50 CALCULATED CAPACITIES FOR MEMB 1 UNIT - kN,m SECTION CLASS 4 MCZ= 1141.9 MCY= 120.4 PC= 3451.5 PT= 5739.9 MB= 1084.1 PV= 1597.5 BUCKLING CO-EFFICIENTS m AND n : m = 1.000 n = 1.000 PZ= 5739.90 FX/PZ = 0.02 MRZ= 1141.9 MRY= 120.4 TRACK 2.0 OUTPUT STAAD CODE CHECKING - (BSI ) --------------------------- ****************************** ALL UNITS ARE - KNS METR (UNLESS OTHERWISE NOTED) MEMBER TABLE RESULT/ CRITICAL COND/ RATIO/ LOADING/ FX MY MZ LOCATION ================================================================= 1 ST UB686X254X170 PASS BS-4.8.3.2 0.036 3 86.72 C 0.00 -22.02 4.50 ================================================================= MATERIAL DATA

Grade of steel = 43 Modulus of elasticity = 205 kN/mm2 Design Strength (py) = 265 N/mm2 Reduced = 232N/mm2

SECTION PROPERTIES (units - cm)

Member Length = 450.00 Gross Area = 216.60 Net Area = 216.60

z-axis y-axis

Moment of inertia : 170147.000 6621.000 Plastic modulus : 5624.000 810.000 Elastic modulus : 4911.156 517.670 Shear Area : 109.122 100.470 Radius of gyration : 28.027 5.529 Effective Length : 450.000 450.000


Section 2B1

2-64 DESIGN DATA (units - kN,m) BS5950/1990

Section Class : SLENDER Squash Load : 5739.90 Axial force/Squash load : 0.015

z-axis y-axis

Slenderness ratio (KL/r) : 16.1 81.4 Compression Capacity : 5036.2 3451.5 Tension Capacity : 5739.9 5739.9 Moment Capacity : 1141.9 120.4 Reduced Moment Capacity : 1141.9 120.4 Shear Capacity : 1561.5 1597.5

BUCKLING CALCULATIONS (units - kN,m) Lateral Torsional Buckling Moment (MB = 1084.1) co-efficients m & n : m =1.00 n =1.00, Effective Length =4.500 CRITICAL LOADS FOR EACH CLAUSE CHECK (units- kN,m): CLAUSE RATIO LOAD FX VY VZ MZ MY BS-4.7 (C) 0.025 3 86.7 3.2 0.0 -22.0 0.0 BS-4.8.3.2 0.036 3 86.7 3.2 0.0 -22.0 0.0 BS-4.8.3.3.1 0.047 1 83.3 7.4 0.0 -27.6 0.0 BS-4.8.3.3.2 0.026 1 83.3 7.4 0.0 -27.6 0.0 BS-4.2.3-(Y) 0.005 1 83.3 7.4 0.0 -27.6 0.0 BS-4.3 (LTB) 0.020 4 -86.7 3.2 0.0 22.0 0.0 Torsion and deflections have not been considered in the design 5. ( LEG - table 24/28 BS5950 for fastner control )

The LEG parameter follows the requirements of BS5950 table 28. This table concerns the fastner restraint conditions for angles, double angles, tee sections and channels for slenderness. The following values are available:

Clause 4.7.10.2 (a) Single Angle, short leg 1.0

(b) Single Angle, short leg 0.0 (a) Single Angle, long leg 3.0 (b) Single Angle, long leg 2.0

Section 2B1

2-65

Clause 4.7.10.3 (a) Double angle, short leg 3.0 (b) Double angle, short leg 2.0

(c) Double angle, long leg 1.0 (d) Double angle, long leg 0.0 (a) Double angle, long leg 7.0 (b) Double angle, long leg 6.0 (c) Double angle, short leg 5.0 (d) Double angle, short leg 4.0

Clause 4.7.10.4 (a) Channels, 2 or more rows 1.0 (b) Channels, 1 row 0.0

Clause 4.7.10.5 (a) Tee sections, 2 or more rows 1.0 (b) Tee sections, 1 row 0.0

When defining member properties for single angles, the spec (manual ref: 5.20.1) should be provided as RA and not ST. See fig 1.6 of the Technical Reference Manual. Table 28 may be by-passed in favour of table 24 by using:

10 = Table 24 for equal angles or long legs of unequal angles

11 = Table 24 for short legs of unequal angles For single angles, LY and KY parameters should be provided relative to the raa axis while LZ and KZ are related to rbb. Lvv will be considered as the minimum of the KY*LY and KZ*LZ values. For double angles, the LVV parameter is available to comply with note 5 table 28. In addition, if using double angles from user tables, (Technical Reference Manual section 5.19) an eleventh value, rvv, should be supplied at the end of the ten existing values corresponding to the radius of gyration of the single angle making up the pair.


Section 2B1

2-66

Table 2B1.1 - British Steel Design – BS5950:1990 - Parameters

Parameter Name


KY 1.0 K factor value in local y - axis. Usually, this is the minor axis.

KZ 1.0 K factor value in local z - axis. Usually, this is the major axis.

LY * Member Length

Length in local y - axis (current units) to calculate (KY)(LY)/Ryy slenderness ratio.

LZ * Member Length

Length in local z - axis (current units) to calculate (KZ)(LZ)/Rzz slenderness ratio.

UNF 1.0 Factor applied to unsupported length for Lateral Torsional Buckling effective length per section 4.3.7.5 of BS5950.

UNL * Member Length

Unsupported Length for calculating Lateral Torsional Buckling resistance moment section 4.3.7.5 of BS5950.

PY * Set according to steel grade

(SGR)

Design Strength of steel


SGR 0.0 Steel Grade per BS4360 0.0 = Grade 43 1.0 = Grade 50 2.0 = Grade 55 3.0 = As per GB 1591 – 16 Mn

SBLT 0.0 0.0 = Rolled Section 1.0 = Built up Section

MAIN 1.0 As per BS5950 4.7.3 1.0 = Main structural member (180) 2.0 = Secondary member. (250) 3.0 = Bracing etc (350)

CMM ! 1.0 Coefficient m for lateral torsional buckling. (see section 2B.5)

CMN ! 1.0 Coefficient n for lateral torsional buckling. (see section 2B.5)

TRACK 0.0 0.0 = Suppress all member capacity info. 1.0 = Print all member capacities. 2.0 = Print detailed design sheet. 4.0 = Deflection Check (separate check to main select / check code)

Section 2B1

2-67


Parameter Name


DMAX * 100.0cm Maximum allowable depth

DMIN * 0.0cm Minimum allowable depth

RATIO 1.0 Permissible ratio of the actual capacities.

BEAM 0.0 0.0 = Design only for end moments or those locations specified by the SECTION command.

1.0 = Calculate moments at 12th points along the member and use the maximum Mz value for design. Clause checks at one location

2.0 = Same as BEAM = 1.0 but additional checks are carried out for each end.

3.0 = Calculate moments at 12th points along the member. Clause checks at each location including the ends of the member.

CODE BS5950 Design Code to follow. See section 5.47.1 of the Technical Reference Manual.

LEG 0.0 Values range from 0 - 12. See section 2B.6.5 for details. The values correspond to table 24/28 of BS5950 for fastner conditions.

LVV * Maximum of Lyy and Lzz

(Lyy is a term used

by BS5950)

Used in conjunction with LEG for Lvv as per BS5950 table 28 for double angles, note 5.

CB 1.0 1.0 = BS5950 per clause B.2.5 (continuous) to calculate Mb.

2.0 = To calculate Mbs (simple) as per Clause 4.7.7 as opposed to Mb.

DFF None (Mandatory for

deflection check)






ESTIFF 0.0 Clauses 4.8.3.3.1 and 4.8.3.3.2 1.0 = Pass if member passes EITHER clause. 1.0 = Pass if member passes BOTH clauses.


Section 2B1

2-68


Parameter Name


WELD 1.0 closed

2.0 open

Weld Type, see AISC steel design 1.0 = Welding on one side only (except for webs of wide

flange and tee sections) 2.0 = Welding on both sides (except pipes and tubes)

TB 0.0 2.0 = Elastic stress analysis 3.0 = Plastic stress analysis

PNL * 0.0 Transverse stiffener spacing (‘a’ in Appendix H1) 0.0 = Infinity Any other value used in the calculations.

SAME ** 0.0 Controls the sections to try during a SELECT process.

0.0 = Try every section of the same type as original 1.0 = Try only those sections with a similar name as

original, e.g. if the original is an HEA 100, then only HEA sections will be selected, even if there are HEM’s in the same table.

! CMN & CMM cannot both be provided. * current units must be considered.

**For angles, if the original section is an equal angle, then the selected section will be an equal angle and vice versa for unequal angles.

NOTE: 1) "Deflection Length" is defined as the length that is used for


Section 2B1

2-69


D

1

2 3

4

1

2 3






2B1.7 Design Operations

STAAD contains a broad set of facilities for the design of structural members as individual components of an analysed structure. The member design facilities provide the user with the ability to carry out a number of different design operations. These facilities may be used selectively in accordance with the requirements of the design problem. The operations to perform a design are:

• Specify the load cases to be considered in the design. • Specify design parameter values, if different from the default

values. • Specify whether to perform code checking or member selection

along with the list of members.

These operations may be repeated by the user any number of times depending upon the design requirements.


Section 2B1

2-70

2B1.8 Code Checking

The purpose of code checking is to ascertain whether the provided section properties of the members are adequate. The adequacy is checked as per BS5950. Code checking is done using the forces and moments at specific sections of the members. If no sections are specified, the program uses the start and end forces for code checking. When code checking is selected, the program calculates and prints whether the members have passed or failed the checks; the critical condition of BS5950 code (like any of the BS5950 specifications for compression, tension , shear, etc.); the value of the ratio of the critical condition (overstressed for value more than 1.0 or any other specified RATIO value); the governing load case, and the location (distance from the start of the member of forces in the member where the critical condition occurs). Code checking can be done with any type of steel section listed in Section 2B.4 of the STAAD Technical Reference Manual or any of the user defined sections in section 5.19 with two exceptions ; GENERAL and ISECTION. In BS5950, these will not be considered for design along with PRISMATIC sections which are also not acceptable.

2B1.9 Member Selection

STAAD is capable of performing design operations on specified members. Once an analysis has been performed, the program can select the most economical section, i.e. the lightest section, which fulfills the code requirements for the specified member. The section selected will be of the same type section as originally designated for the member being designed. Member selection can also be constrained by the parameters DMAX and DMIN which limits the maximum and minimum depth of the members.

Section 2B1

2-71

Member selection can be performed with all the types of steel sections with the same limitations as defined in section 2B.8 - CODE CHECKING. Selection of members, whose properties are originally input from a user created table, will be limited to sections in the user table. Member selection can not be performed on members whose section properties are input as prismatic or as above limitations for code checking.

2B1.10 Tabulated Results of Steel Design

For code checking or member selection, the program produces the results in a tabulated fashion. The items in the output table are explained as follows: a) MEMBER refers to the member number for which the

design is performed. b) TABLE refers to steel section name which has been

checked against the steel code or has been selected.

c) RESULTS prints whether the member has PASSED or FAILED. If the RESULT is FAIL, there will be an asterisk (*) mark on front of the member.

d) CRITICAL COND refers to the section of the BS5950 code

which governs the design. e) RATIO prints the ratio of the actual stresses to

allowable stresses for the critical condition. Normally a value of 1.0 or less will mean the member has passed.

f) LOADING provides the load case number which

governed the design.


Section 2B1

2-72 g) FX, MY, and MZ provide the axial force, moment in local Y-

axis and the moment in local z-axis respectively. Although STAAD does consider all the member forces and moments (except torsion) to perform design, only FX, MY and MZ are printed since they are the ones which are of interest, in most cases.

h) LOCATION specifies the actual distance from the start

of the member to the section where design forces govern.

i) TRACK If the parameter TRACK is set to 1.0, the

program will block out part of the table and will print the allowable bending capacities in compression (MCY & MCZ) and reduced moment capacities (MRY & MRZ), allowable axial capacity in compression (PC) and tension (PT) and shear capacity (PV). TRACK 2.0 will produce the design results as shown in section 2B.9.

2B1.11 Plate Girders

Plate girders may be considered for design in BS5950. The "py" used in the calculation of compressive strength is reduced by 20N/mm2 as per the code if parameter SBLT is set to 1.0. The code requires that for d/t >63E, the interaction checks be modified in order to check for shear buckling of the web. This is considered in STAAD ( versions 15.0 and over) following clause 4.4.4.2a and 4.4.4.3 of the code. The shear capacity is found from table 21 of the code and used in clause 4.4.5.3. For plate girders, clauses 4.4.2.2a and 4.4.2.3a are also considered. In order to account for these checks, the output has been modified to show these variations from the more common critical checks. An example is as follows, using TRACK 2.0, showing the bottom part of the output having been modified as follows:

Section 2B1

2-73BS5950 Table 7<note 2>: d/t > 63E Web Is Checked For Shear Buckling d/t =101.7 qcr=191.9 N/mm2 d*t=14639 mm2 (4.4.5.3)Vcr= 2809.4 kN Flange =COMPACT Pyf=344 N/mm2 4.4.2.2 a=PASS 4.4.2.3 a=PASS Flange Ratio 4.4.4.2 (a) =0.20 L= 1 Web Ratio =0.05 L= 1

CRITICAL LOADS FOR EACH CLAUSE CHECK (units- kN,m): CLAUSE RATIO LOAD FX VY VZ MZ MY BS-4.8.3.3.2 0.177 1 0.0 -150.0 0.0 -1125.0 0.0 BS-4.2.3-(Y) 0.049 1 0.0 150.0 0.0 -1125.0 0.0 BS-4.3 (LTB) 0.151 1 0.0 -150.0 0.0 -1125.0 0.0 BS-4.4.5.3 0.053 1 0.0 150.0 0.0 -1125.0 0.0 BS-4.4.4.2 a 0.203 1 0.0 -150.0 0.0 -1125.0 0.0

2B1.12 Composite Sections

The definition of composite sections has been provided for in the standard sections definition - section 5.20.1 of the Technical Reference Manual. This is purely for analysis and for obtaining the right section properties. It uses the American requirement of 18 times depth (CT) as the effective depth. For more control with British sections two new options are available in user provided tables. 1. WIDE FLANGE COMPOSITE:

Using the standard definition of I sections in WIDE FLANGE, 4 additional values can now be provided. The first is the width of concrete to the left of centre of the steel web (b1). The second is the concrete width to the right (b2). The third is the concrete depth (d1) to be considered. The last is the modular ratio. The above values are accepted in the program by adding a '-' at the first position on the first line of data. The program now awaits four extra values on line 2 as described above. If (-) is provided on the second line the program requires another 2 breadths + 1 thickness for the bottom plate.


Section 2B1

2-74 2. ISECTION:

The same is true for ISECTION definition in user table. 3. EXAMPLE INPUT:

UNIT CM WIDE FLANGE C45752 -66.5 44.98 .76 15.24 1.09 21345 645 21.3 34.185 33.223 150 150 30 10 ISECTION PG9144 -92.05 2.15 92.05 42.05 3.66 42.05 3.66 197.9 153.9 1730 40 40 12 1

The larger British sections have been coded as USER TABLES under wide flange and are available on request to any existing user. Please note however that composite design IS NOT available in this portion of STAAD.

2-75

Design Per BS5400

2C.1 General Comments

BS5400 is an additional code available from Research Engineers. It does not come as standard with British versions. The British Standard, BS5400 adopts the limit state design philosophy and is applicable to steel, concrete and composite construction. The code is in 10 parts covering various aspects of bridge design. The implementation of part 3, Code of practice for design of steel bridges, in STAAD is restricted in its scope to simply supported spans. It is assumed that the depth remains constant and both construction and composite stages of steel I-Sections can be checked. The following sections describe in more detail features of the design process currently available in STAAD.

2C.2 Shape Limitations

The capacity of sections could be limited by local buckling if the ratio of flange outstand to thickness is large. In order to prevent this, the code sets limits to the ratio as per clause 9.3.2. In the event of exceeding these limits, the design process will terminate with reference to the clause.

Section 2C

Design Per BS5400

Section 2C

2-76

2C.3 Section Class

Sections are further defined as compact or non-compact. In the case of compact sections, the full plastic moment capacity can be attained. In the case of non compact sections, local buckling of elements may occur prior to reaching the full moment capacity and for this reason the extreme fibre stresses are limited to first yield. In STAAD, section types are determined as per clause 9.3.7 and the checks that follow will relate to the type of section considered.

2C.4 Moment Capacity

Lateral torsional buckling may occur if a member has unrestrained elements in compression. The code deals with this effect by limiting the compressive stress to a value depending on the slenderness parameter which is a modified form of the ratio Le/Ry. Le is the effective length governed by the provision of lateral restraints satisfying the requirements of clause 9.12.1. Once the allowable compressive stress is determined then the moment capacity appropriate to the section type can be calculated. STAAD takes the effective length as that provided by the user, defaulting to the length of the member during construction stage and as zero, assuming full restraint throughout, for the composite stage. The program then proceeds to calculate the allowable compressive stress based on appendix G7 from which the moment capacity is then determined.

2C.5 Shear Capacity

The shear capacity, as outlined in clause is a function of the limiting shear strength, l, which is dependant on the slenderness ratio. STAAD follows the iterative procedure of appendix G8 to determine the limiting shear strength of the web panel. The shear capacity is then calculated based on the formula given under clause 9.9.2.2.

Section 2C

2-77

2C.6 Design Parameters

Available design parameters to be used in conjunction with BS5400 are listed in table 2C.1. Depending on the value assigned to the 'WET' parameter, the users can determine the stage under consideration. For a composite design check, taking into consideration the construction stage, two separate analyses are required. In the first, member properties are non-composite and the WET parameter is set to 1.0 . In the second, member properties should be changed to composite and the WET parameter set to 2.0. Member properties for composite or non-composite sections should be specified from user provided tables (refer to section 5.19 of the manual for specification of user tables). Rolled sections, composite or non-composite, come under WIDE FLANGE section-type and built-up sections under ISECTION. When specifying composite properties the first parameter is assigned a negative value and four additional parameters provided giving details of the concrete section. See user table examples provided.

Table 2C.1 - BS5400 Design Parameters

Parameter Name


UNL* Member Length

Unsupported Length for calculating allowable compressive bending stress.

PY* Set according to Design Strength of steel SGR


SGR* 0.0 Steel Grade per BS4360

0.0 = Grade 43

1.0 = Grade 50

2.0 = Grade 55

SBLT 0.0 0.0 = Rolled Section

1.0 = Built up Section

MAIN 1.0 1.0 = Grade of concrete 30 N/mm2

2.0 = Grade of concrete 40 N/mm2

Design Per BS5400

Section 2C

2-78

Table 2C.1 - BS5400 Design Parameters

Parameter Name


3.0 = Grade of concrete 50 N/mm2

WET 0.0 0.0 = Wet stage with no data saved for composite stage.

1.0 = Wet stage with data saved for composite stage.

2.0 = Composite and wet stage combined.

3.0 = Composite stage only.

TRACK 1.0 1.0 = Print all member capacities.

0.0 = suppress all member capacities.

BEAM 0.0 MUST BE CHANGED TO 1.0 FOR ALL RUNS

LY* Member Length

Length to calculate slenderness ratio for bending about Y-axis.

LZ* Member Length

Length to calculate slenderness ratio for bending about Z-axis.

KY 1.0 K value for bending about Y-axis. Usually this is minor axis.

KZ 1.0 K value for bending about Z-axis. Usually this is major axis.

STIFF 1.0 Factor of length for panel length in the shear calculation.

* Provided in current unit systems.

2C.7 Composite Sections

The definition of composite sections has been provided for in the standard sections definition - section 5.20.1 of the Technical Reference Manual. This is purely for analysis and for obtaining the right section properties. It uses the American requirement of 18 times depth (CT) as the effective depth. For more control with British sections two new options are available in user provided tables.

Section 2C

2-79

1. WIDE FLANGE COMPOSITE: Using the standard definition of I sections in WIDE FLANGE, 4 additional values can now be provided. The first is the width of concrete to the left of centre of the steel web (b1). The second is the concrete width to the right (b2). The third is the concrete depth (d1) to be considered. The last is the modular ratio. The above values are accepted in the program by adding a '-' at the first position on the first line of data. The program now awaits four extra values on line 2 as described above. If (-) is provided on the second line the program requires another 2 breadths + 1 thickness for the bottom plate.

2. ISECTION:

The same is true for ISECTION definition in user table. 3. EXAMPLE INPUT:

UNIT CM WIDE FLANGE C45752 -66.5 44.98 .76 15.24 1.09 21345 645 21.3 34.185 33.223 150 150 30 10 ISECTION PG9144 -92.05 2.15 92.05 42.05 3.66 42.05 3.66 197.9 153.9 1730 40 40 12 1

The larger British sections have been coded as USER TABLES under wide flange and are available on request to any existing user. Please note however that composite design IS NOT available in this portion of STAAD.

Design Per BS5400

Section 2C

2-80

2-81

Design Per BS8007

2D.1 General Comments

BS8007 is an additional code available from Research Engineers. It does not come as standard with British versions. STAAD has the capability of performing concrete slab design according to BS8007. BS8007 provides recommendations for the design of reinforced concrete structures containing aqueous liquids. It is recommended that the design of the structure is carried out according to BS8110, unless modified by the recommendations given in BS8007. Please use the following in conjunction with Section 2A of this Manual - BS8110.

2D.2 Design Process

The design process is carried out in three stages.

1. Ultimate Limit States The program is structured so that ultimate design is first carried out in accordance with recommendations given in BS8110. All active design load cases are considered in turn and a tabulated output is printed showing possible reinforcement arrangements. 12, 16 and 20 mm bars are considered with possible spacings from 100,125,150,175 and 200 mm. Within these spacings, the layout providing the closest area of steel is printed under each bar size. Longitudinal and transverse moments together with critical load

Section 2D

Steel Design Per BS8007

Section 2D

2-82 cases for both hogging and sagging moments are also printed. Minimum reinforcement is in any case checked and provided in each direction. WOOD & ARMER moments may also be included in the design.

2. Serviceability Limit States In the second stage, flexural crack widths under serviceability load cases are calculated. The FIRST and EVERY OTHER OCCURING design load case is considered as a serviceability load case and crack widths are calculated based on bar sizes and spacings proposed at the ultimate limit state check. Crack widths due to longitudinal and transverse moments are calculated directly under bars, midway between and at corners. A tabulated output indicating critical serviceability load cases and moments for top and bottom of the slab is then produced.

3. Thermal crack widths Finally thermal, crack width calculations are carried out. Through available parameters, the user is able to provide information on the type of slab, temperature range and crack width limits. Surface zone depths are determined based on the type of slab and critical areas of reinforcements are calculated and printed in a tabulated form. Four bar sizes are considered and for each, max crack spacing, Smax and crack widths are calculated for the critical reinforcements and printed under each bar size. Maximum bar spacing to limit crack widths to the user's limit is also printed under each bar size.

Section 2D

2-83

2D.3 Design Parameters

The program contains a number of parameters which are needed to perform and control the design to BS8007. These parameters not only act as a method to input required data for code calculations but give the Engineer control over the actual design process. Default values of commonly used values for conventional design practice have been chosen as the basis. Table 2D.1 contains a complete list of available parameters with their default values.

2D.4 Structural Model

Structural slabs that are to be designed to BS8007 must be modelled using finite elements. The manual provides information on the sign convention used in the program for defining elements, (See main manual section 2-6). It is recommended to connect elements in such a way that the positive local z axis points outwards away, from the centre of the container. In this manner the "Top" of elements will consistently fall on the outer surface and internal pressure loads will act in the positive direction of the local z axis. An example of a rectangular tank is provided to demonstrate the above procedure. Element properties are based on the thickness given under ELEMENT PROPERTIES command. The following example demonstrates the required input for a 300 mm slab modelled with 10 elements.


Section 2D

2-84

UNIT MM ELEMENT PROPERTIES 1 TO 10 THI 300.0

2D.5 Wood & Armer Moments

This is controlled by the SRA parameter. If the default value of zero is used, the design will be based on the Mx and My moments which are the direct results of STAAD analysis. The SRA parameter (Set Reinforcement Angle) can be manipulated to introduce WOOD & ARMER moments into the design replacing the pure Mx, My moments. These new design moments allow the Mxy moment to be considered when designing the section. Orthogonal or skew reinforcement may be considered. SRA set to -500 will assume an orthogonal layout. If however a skew is to be considered, an angle is given in degrees, measured between the local element x axis anti-clockwise ( positive ). The resulting Mx* and My* moments are calculated and shown in the design format.

Section 2D

2-85

Table 2D.1 - BS8007 Design Parameters

Parameter Name


FYMAIN * * 460 N/mm2 Yield for all reinforcing steel

FC * 30 N/mm2 Concrete grade.

CLEAR * 20 mm Distance from the outer surface to the edge of the bar. This is considered the same on both surfaces.

SRA 0.0 Orthogonal reinforcement layout without considering torsional moment Mxy - slabs on -500. orthogonal reinforcement layout with Mxy used to calculate WOOD &ARMER moments for design. A* Skew angle considered in WOOD & ARMER EQUATIONS. A* is any angle in degrees.

SCON 1 Parameter which indicates the type of slab ee. ground or suspended as defined in BS8007 1 = Suspended Slab 2 = Ground Slab

TEMP 30°C Temperature range to be considered in thermal crack width calculations

CRACK * 0.2 mm Limiting thermal crack width

* Provided in current unit systems


Section 2D

2-86

Section 3 Canadian Codes

Aksf;ldkjasd

3-1

Concrete Design Per CSA Standard A23.3-94


STAAD can perform design of concrete beams, columns and slabs according to CSA STANDARD A23.3-94. Given the dimensions of a section, STAAD will calculate the required reinforcement necessary to resist the various input loads.


The following types of cross sections for concrete members can be designed. For Beams Prismatic (Rectangular, Square & Tee) For Columns Prismatic (Rectangular, Square and Circular) For Slabs 4-noded Plate Elements



Section 3A


Section 3A

3-2

UNIT MM MEMBER PROPERTIES 1 3 TO 7 9 PRISM YD 450. ZD 300. 11 14 PR YD 300.

In the above input, the first set of members are rectangular (450mm depth and 300mm width) and the second set of members, with only depth and no width provided, will be assumed to be circular with a 300mm diameter.


STAAD provides the user with two methods of accounting for the slenderness effect in the analysis and design of concrete members. The first method is equivalent to the procedure presented in CSA STANDARD A23.3-94 Clause 10.13. STAAD accounts for the secondary moments, due to axial loads and deflections, when the PDELTA ANALYSIS command is used. After solving for the joint displacements of the structure, the program calculates the additional moments induced in the structure due to the P-Delta effect. Therefore, by performing a PDELTA ANALYSIS, member forces are calculated which will require no user modification before beginning member design. The second method by which STAAD allows the user to account for the slenderness effect is through user supplied moment magnification factors (see the parameter MMAG in Table 3A.1). Here the user approximates the additional moment by supplying a factor by which moments will be multiplied before beginning member design. This second procedure allows slenderness to be considered in accordance with Clause 10.14 of the code.

It should be noted that STAAD does not factor loads automatically for concrete design. All the proper factored loads must be provided by the user before the ANALYSIS specification.

Section 3A

3-3

While performing a PDELTA ANALYSIS, all load cases must be defined as primary load cases. If the effects of separate load cases are to be combined, it should be done either by using the REPEAT LOAD command or by specifying the load information of these individual loading cases under one single load case. Usage of the LOAD COMBINATION command will yield incorrect results for PDELTA ANALYSIS.


The program contains a number of parameters which are needed to perform design per CSA STANDARD A23.3-94. These parameters not only act as a method to input required data for code calculations but give the engineer control over the actual design process. Default values, which are commonly used numbers in conventional design practice, have been used for simplicity. Table 3A.1 contains a list of available parameters and their default values. It is necessary to declare length and force units as Millimeter and Newton before performing the concrete design.

Table 3A.1 - Canadian Concrete Design -CSA-A23.3-94 Parameters

Parameter Default Description Name Value

FYMAIN 400N/mm2 Yield Stress for main reinforcing steel.


FC 30 N/mm2 Specified compressive strength of concrete.

CLT 40mm Clear cover to reinforcing bar at top of cross section.

CLB 40mm Clear cover to reinforcing bar at bottom of cross section.

CLS 40mm Clear cover to reinforcing bar along the side of the cross section.

MINMAIN Number 10 bar Minimum main reinforcement bar size

MINSEC Number 10 bar Minimum secondary (stirrup) reinforcement bar size.


Section 3A

3-4

Table 3A.1 - Canadian Concrete Design -CSA-A23.3-94 Parameters


MAXMAIN Number 55 bar Maximum main reinforcement bar size.

SFACE 0.0 Distance of face of support from start node of beam. Used for shear and torsion calculation.

EFACE 0 Face of Support Distance of face of support from end node of beam. Used for shear and torsion calculation. (Note: Both SFACE and EFACE are input as positive numbers).

TRACK 0.0 For TRACK = 0.0, Critical Moment will not be printed out with beam design report. For TRACK=1.0, moments will be printed.

MMAG 1.0 A factor by which the column design moments will be magnified.

NSECTION 12 Number of equally-spaced sections to be considered in finding critical moments for beam design.

WIDTH ZD Width of the concrete member. This value defaults to ZD as provided under MEMBER PROPERTIES.

DEPTH YD Depth of the concrete member. This value defaults to YD as provided under MEMBER PROPERTIES.

3A.6 Beam Design

Beams are designed for flexure, shear and torsion. For all these forces, all active beam loadings are scanned to create moment and shear envelopes, and locate critical sections. The total number of sections considered is thirteen (start, end and 11 intermediate), unless that number is redefined with the NSECTION parameter. Design for Flexure

Design for flexure is performed per the rules of Chapter 2 of CSA Standard A23.3-94. Maximum sagging (creating tensile stress at the bottom face of the beam) and hogging (creating tensile stress at the top face) moments are calculated for all active load cases at each of the thirteen sections. Each of these sections are designed to resist the critical sagging and hogging moments. Currently,

Section 3A

3-5

design of singly reinforced sections only is permitted. If the section dimensions are inadequate as a singly reinforced section, such a message will be printed in the output. Flexural design of beams is performed in two passes. In the first pass, effective depths of the sections are determined with the assumption of single layer of assumed reinforcement and reinforcement requirements are calculated. After the preliminary design, reinforcing bars are chosen from the internal database in single or multiple layers. The entire flexure design is performed again in a second pass taking into account the changed effective depths of sections calculated on the basis of reinforcement provided after the preliminary design. Final provision of flexural reinforcements are made then. Efforts have been made to meet the guideline for the curtailment of reinforcements as per CSA Standard A23.3-94. Although exact curtailment lengths are not mentioned explicitly in the design output (which finally will be more or less guided by the detailer taking into account other practical considerations), the user has the choice of printing reinforcements provided by STAAD at 13 equally spaced sections from which the final detailed drawing can be prepared. The following annotations apply to the output for Beam Design. 1) LEVEL - Serial number of bar level which may

contain one or more bar group. 2) HEIGHT - Height of bar level from the bottom of

beam. 3) BAR INFOrmation - Reinforcement bar information

specifying number of bars and size. 4) FROM - Distance from the start of the beam to

the start of the rebar. 5) TO - Distance from the start of the beam to

the end of the rebar. 6) ANCHOR - States whether anchorage, either a hook (STA,END) or continuation, is needed at start (STA)

or at the end (END) of the bar.


Section 3A

3-6 Design for Shear and Torsion

Design for shear and torsion is performed per the rules of Chapter 4 of CSA Standard A23.3-94. Shear reinforcement is calculated to resist both shear forces and torsional moments. Shear design is performed at the start and end sections. The location along the member span for design is chosen as the effective depth + SFACE at the start, and effective depth + EFACE at the end. The load case which gives rise to the highest stirrup area for shear & torsion is chosen as the critical one. The calculations are performed assuming 2-legged stirrups will be provided. The additional longitudinal steel area required for torsion is reported. The stirrups are assumed to be U-shaped for beams with no torsion, and closed hoops for beams subjected to torsion.

Example of Input Data for Beam Design UNIT NEWTON MMS START CONCRETE DESIGN CODE CANADA FYMAIN 415 ALL FYSEC 415 ALL FC 35 ALL CLEAR 25 MEMB 2 TO 6 MAXMAIN 40 MEMB 2 TO 6 TRACK 1.0 MEMB 2 TO 9 DESIGN BEAM 2 TO 9 END CONCRETE DESIGN

3A.7 Column Design

Column design is performed per the rules of Chapters 7 & 8 of the CSA Standard A23.3-94. Columns are designed for axial force and biaxial moments at the ends. All active loadings are tested to calculate reinforcement. The loading which produces maximum reinforcement is called the critical load. Column design is done for

Section 3A

3-7

square, rectangular and circular sections. For rectangular and square sections, the reinforcement is always assumed to be equally distributed on each side. That means the total number of bars will always be a multiple of four (4). This may cause slightly conservative results in some cases.

Example of Input Data for Column Design UNIT NEWTON MMS START CONCRETE DESIGN CODE CANADIAN FYMAIN 415 ALL FC 35 ALL CLEAR 25 MEMB 2 TO 6 MAXMAIN 40 MEMB 2 TO 6 DESIGN COLUMN 2 TO 6 END CONCRETE DESIGN


To design a slab or wall, it must be modeled using finite elements. The commands for specifying elements are in accordance with the relevant sections of the Technical Reference Manual. Elements are designed for the moments Mx and My using the same principles as those for beams in flexure. The width of the beam is assumed to be unity for this purpose. These moments are obtained from the element force output (see the relevant sections of the Technical Reference Manual). The reinforcement required to resist Mx moment is denoted as longitudinal reinforcement and the reinforcement required to resist My moment is denoted as transverse reinforcement. The effective depth is calculated assuming #10 bars are provided. The parameters FYMAIN, FC, CLT and CLB listed in Table 3A.1 are relevant to slab design. Other parameters mentioned in Table 3A.1 are not applicable to slab design. The output consists only of area of steel required.


Section 3A

3-8 Actual bar arrangement is not calculated because an element most likely represents just a fraction of the total slab area.

LONG.

TRANS.

X

Y

Z

M

MM

M x

y

x

y

Example of Input Data for Slab/Wall Design UNIT NEWTON MMS START CONCRETE DESIGN CODE CANADA FYMAIN 415 ALL FC 35 ALL CLB 40 ALL DESIGN ELEMENT 15 TO 20 END CONCRETE DESIGN

Section 3B

3-9

Steel Design Per CSA Standard CAN/CSA-S16.1-94

3B.1 General Comments

The Canadian Steel Design facility in STAAD is based on the CSA Standard CAN/CSA-S16.1-94, Limit States Design of Steel Structures. A steel section library consisting of Canadian Standards Association (CSA) shapes is available for member property specification. The design philosophy embodied in this specification is based on the concept of limit state design. Structures are designed and proportioned taking into consideration the limit states at which they would become unfit for their intended use. Two major categories of limit-state are recognized - ultimate and serviceability. The primary considerations in ultimate limit state design are strength and stability, while that in serviceability is deflection. Appropriate load and resistance factors are used so that a uniform reliability is achieved for all steel structures under various loading conditions and at the same time the chances of limits being surpassed are acceptably remote. In the STAAD implementation, members are proportioned to resist the design loads without exceeding the limit states of strength, stability and serviceability. Accordingly, the most economic section is selected on the basis of the least weight criteria as augmented by the designer in specification of allowable member depths, desired section type, or other such parameters. The code checking portion of the program checks whether code requirements for each selected section are met and identifies the governing criteria.

Section 3B


Section 3B

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The following sections describe the salient features of the STAAD implementation of CAN/CSA-S16.1-94. A detailed description of the design process along with its underlying concepts and assumptions is available in the specification document.





3B.4 Built-in Steel Section Library

The following information is provided for use when the built-in steel tables are to be referenced for member property specification. These properties are stored in a database file. If called for, the properties are also used for member design. Since the shear areas are built into these tables, shear deformation is always considered during the analysis of these members.

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Almost all Canadian steel sections are available for input. A complete listing of the sections available in the built-in steel section library may be obtained by using the tools of the graphical user interface. Following is the description of the different types of sections available: Welded Wide Flanges (WW shapes)

Welded wide flange shapes listed in the CSA steel tables can be designated using the same scheme used by CSA. The following example illustrates the specification of welded wide flange shapes.

100 TO 150 TA ST WW400X444 34 35 TA ST WW900X347

Wide Flanges (W shapes)

Designation of wide flanges in STAAD is the same as that in CSA tables. For example,

10 TO 75 95 TO 105 TA ST W460X106 100 TO 200 TA ST W610X101

S, M, HP shapes

In addition to welded wide flanges and regular wide flanges, other I shaped sections like S, M and HP shapes are also available. The designation scheme is identical to that listed in the CSA tables. While specifying the sections, it should be remembered that the portion after the decimal point should be omitted. Thus, M310X17.6 should be specified as M310X17 and S180X22.8 should be specified as S180X22. Examples illustrating specifications of these shapes are provided below.


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10 TO 20 BY 2 TA ST S510X98 45 TO 55 TA ST M150X6 88 90 96 TA ST HP310X79

Channel Sections (C & MC shapes)

C and MC shapes are designated as shown in the following example. As in S,M and HP sections, the portion after the decimal point must be omitted in section designations. Thus, MC250X42.4 should be designated as MC250X42.

55 TO 90 TA ST C250X30 30 TO 45 TA ST MC200X33

Double Channels

Back to back double channels, with or without spacing between them, are specified by preceding the section designation by the letter D. For example, a back to back double channel section C200X28 without any spacing in between should be specified as:

100 TO 120 TA D C200X28

If a spacing of 2.5 length units is used, the specification should be as follows:

100 TO 120 TA D C200X28 SP 2.5

Note that the specification SP after the section designation is used for providing the spacing. The spacing should always be provided in the current length unit.

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Angles To specify angles, the angle name is preceded by the letter L. Thus, a 200X200 angle with a 25mm thickness is designated as L200X200X25. The following examples illustrate angle specifications.

75 TO 95 TA ST L100X100X8 33 34 35 TA ST L200X100X20

Note that the above specification is for “standard” angles. In this specification, the local z-axis (see Fig. 2.6 in the Technical Reference Manual) corresponds to the Y’-Y’ axis shown in the CSA table. Another common practice of specifying angles assumes the local y-axis to correspond to the Y’-Y’ axis. To specify angles in accordance with this convention, the reverse angle designation facility has been provided. A reverse angle may be specified by substituting the word ST with the word RA. Refer to the following example for details.

10 TO 15 TA RA L55X35X4

The local axis systems for STANDARD and REVERSE angles is shown in Fig. 2.6 of the STAAD Technical Reference manual. Double Angles To specify double angles, the specification ST should be substituted with LD (for long leg back to back) or SD (short leg back to back). For equal angles, either SD or LD will serve the purpose. Spacing between angles may be provided by using the word SP followed by the value of spacing (in current length unit) after section designation.

25 35 45 TA LD L150X100X16 80 TO 90 TA SD L125X75X6 SP 2.5


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The second example above describes a double angle section consisting of 125X75X6 angles with a spacing of 2.5 length units. Tees

Tee sections obtained by cutting W sections may be specified by using the T specification instead of ST before the name of the W shape. For example:

100 TO 120 TA T W200X42

will describe a T section cut from a W200X42 section. Rectangular Hollow Sections

These sections may be specified in two possible ways. Those sections listed in the CSA tables may be specified as follows.

55 TO 75 TA ST TUB80X60X4

Tube Symbol Thickness (in) X16

Width (in.) X10

TUB 80 X 60 X 4

Height (in) X 10 In addition, any tube section may be specified by using the DT(for depth), WT(for width), and TH(for thickness) specifications.

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For example:

100 TO 200 TA ST TUBE DT 8.0 WT 6.0 TH 0.5

will describe a tube with a depth of 8 in., width of 6 in. and a wall thickness of 0.5 inches. Note that the values of depth, width and thickness must be provided in current length unit. Circular Hollow Sections

Sections listed in the CSA tables may be provided as follows:

15 TO 25 TA ST PIP33X2.5

Pipe Symbol Thickness (mm)

Diameter (mm)

PIP 33 X 2.5

(Upto first decimal place only)

without decimal point In addition to sections listed in the CSA tables, circular hollow sections may be specified by using the OD (outside diameter) and ID (inside diameter) specifications. For example:


will describe a pipe with an outside diameter of 10 length units and inside diameter of 9.0 length units. Note that the values of outside and inside diameters must be provided in terms of current length unit.


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Sample input file to demonstrate usage of Canadian shapes STAAD SPACE UNIT METER KNS JOINT COORD 1 0 0 0 17 160 0 0 MEMBER INCIDENCES 1 1 2 16 UNIT CM MEMBER PROPERTIES CANADIAN * W SHAPES 1 TA ST W250X18 * WW SHAPES 2 TA ST WW700X185 * S SHAPES 3 TA ST S200X27 * M SHAPES 4 TA ST M130X28 * HP SHAPES 5 TA ST HP310X132 * MC CHANNELS 6 TA ST MC150X17 * C CHANNELS 7 TA ST C180X18 * DOUBLE CHANNELS 8 TA D C250X37 SP 1.0 * ANGLES 9 TA ST L55X35X5 * REVERSE ANGLES 10 TA RA L90X75X5 * DOUBLE ANGLES, LONG LEG BACK TO BACK 11 TA LD L100X90X6 SP 2.0 * DOUBLE ANGLES, SHORT LEG BACK TO BACK 12 TA SD L125X75X6 SP 2.5 * TUBES 13 TA ST TUB120807 * TUBES

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14 TA ST TUBE DT 16.0 WT 8.0 TH 0.8 * PIPES 15 TA ST PIP273X6.3 * PIPES 16 TA ST PIPE OD 16.0 ID 13.0 PRINT MEMBER PROPERTIES FINISH

3B.5 Section Classification

The CSA specification allows inelastic deformation of section elements. Thus, local buckling becomes an important criterion. Steel sections are classified as plastic (Class 1), compact (Class 2), non compact (Class 3) or slender element (Class 4) sections depending upon their local buckling characteristics (See Clause 11.2 and Table 1 of CAN/CSA-S16.1-94). This classification is a function of the geometric properties of the section. The design procedures are different depending on the section class. STAAD determines the section classification for the standard shapes and user specified shapes. Design is performed for sections that fall into the category of Class 1,2 or 3 sections only. Class 4 sections are not designed by STAAD.

3B.6 Member Resistances

The member resistances are calculated in STAAD according to the procedures outlined in section 13 of the specification. These depend on several factors such as members unsupported lengths, cross-sectional properties, slenderness factors, unsupported width to thickness ratios and so on. Note that the program automatically takes into consideration appropriate resistance factors to calculate member resistances. Explained here is the procedure adopted in STAAD for calculating the member resistances.


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Axial Tension

The criteria governing the capacity of tension members is based on two limit states. The limit state of yielding in the gross section is intended to prevent excessive elongation of the member. The second limit state involves fracture at the section with the minimum effective net area. The net section area may be specified by the user through the use of the parameter NSF (see Table 3B.1). STAAD calculates the tension capacity of a member based on these two limits states per Cl.13.2 of CAN/CSA-S16.1-94. Parameters FYLD, FU and NSF are applicable for these calculations. Axial Compression

The compressive resistance of columns is determined based on Clause 13.3 of the code. The equations presented in this section of the code assume that the compressive resistance is a function of the compressive strength of the gross section (Gross section Area times the Yield Strength) as well as the slenderness factor (KL/r ratios). The effective length for the calculation of compression resistance may be provided through the use of the parameters KX, KY, KZ, LX, LY and LZ (see Table 3B.1). Some of the aspects of the axial compression capacity calculations are : 1) For frame members not subjected to any bending, and for truss

members, the axial compression capacity in general column flexural buckling is calculated from Cl.13.3.1 using the slenderness ratios for the local Y-Y and Z-Z axis. The parameters KY, LY, KZ and LZ are applicable for this.

2) For single angles, which are frame members not subjected to any bending or truss members, the axial compression capacity in general column flexural buckling and local buckling of thin legs is calculated using the rules of the AISC-LRFD code, 2nd ed., 1994. The reason for this is that the Canadian code doesn’t provide any clear guidelines for calculating this value. The parameters KY, LY, KZ and LZ are applicable for this.

3) The axial compression capacity is also calculated by taking flexural-torsional buckling into account. The rules of Appendix D, page 1-109 of CAN/CSA-S16.1-94 are used for

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this purpose. Parameters KX and LX may be used to provide the effective length factor and effective length value for flexural-torsional buckling. Flexural-torsional buckling capacity is computed for single channels, single angles, Tees and Double angles.

4) The variable “n” in Cl.13.3.1 is assumed as 2.24 for WWF shapes and 1.34 for all other shapes.

5) While computing the general column flexural buckling capacity of sections with axial compression + bending, the special provisions of 13.8.1(a), 13.8.1(b) and 13.8.1(c) are applied. For example, Lambda = 0 for 13.8.1(a), K=1 for 13.8.1(b), etc.)

Bending

The laterally unsupported length of the compression flange for the purpose of computing the factored moment resistance is specified in STAAD with the help of the parameter UNL. If UNL is less than one tenth the member length (member length is the distance between the joints of the member), the member is treated as being continuously laterally supported. In this case, the moment resistance is computed from Clause 13.5 of the code. If UNL is greater than or equal to one tenth the member length, its value is used as the laterally unsupported length. The equations of Clause 13.6 of the code are used to arrive at the moment of resistance of laterally unsupported members. Some of the aspects of the bending capacity calculations are : 1) The weak axis bending capacity of all sections except single

angles is calculated as

For Class 1 & 2 sections, Phi*Py*Fy For Class 3 sections, Phi*Sy*Fy where Phi = Resistance factor = 0.9 Py = Plastic section modulus about the local Y axis Sy = Elastic section modulus about the local Y axis Fy = Yield stress of steel


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2) For single angles, the bending capacities are calculated for the principal axes. The specifications of Section 5, page 6-283 of AISC-LRFD 1994, 2nd ed., are used for this purpose because the Canadian code doesn’t provide any clear guidelines for calculating this value.

3) For calculating the bending capacity about the Z-Z axis of singly symmetric shapes such as Tees and Double angles, CAN/CSA-S16.1-94 stipulates in Clause 13.6(d), page 1-31, that a rational method, such as that given in SSRC’s Guide to Stability Design Criteria of Metal Structures, be used. Instead, STAAD uses the rules of Section 2c, page 6-55 of AISC-LRFD 1994, 2nd ed.

Axial compression and bending

The member strength for sections subjected to axial compression and uniaxial or biaxial bending is obtained through the use of interaction equations. In these equations, the additional bending caused by the action of the axial load is accounted for by using amplification factors. Clause 13.8 of the code provides the equations for this purpose. If the summation of the left hand side of these equations exceed 1.0 or the allowable value provided using the RATIO parameter (see Table 3B.1), the member is considered to have FAILed under the loading condition. Axial tension and bending

Members subjected to axial tension and bending are also designed using interaction equations. Clause 13.9 of the code is used to perform these checks. The actual RATIO is determined as the value of the left hand side of the critical equation. Shear

The shear resistance of the cross section is determined using the equations of Clause 13.4 of the code. Once this is obtained, the ratio of the shear force acting on the cross section to the shear resistance of the section is calculated. If any of the ratios (for both local Y & Z axes) exceed 1.0 or the allowable value provided using the RATIO parameter (see Table 3B.1), the section is

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considered to have failed under shear. The code also requires that the slenderness ratio of the web be within a certain limit (See Cl.13.4.1.3, page 1-29 of CAN/CSA-S16.1-94). Checks for safety in shear are performed only if this value is within the allowable limit. Users may by-pass this limitation by specifying a value of 2.0 for the MAIN parameter.


The design parameters outlined in Table 3B.1 may be used to control the design procedure. These parameters communicate design decisions from the engineer to the program and thus allows the engineer to control the design process to suit an application's specific needs. The default parameter values have been selected such that they are frequently used numbers for conventional design. Depending on the particular design requirements, some or all of these parameter values may be changed to exactly model the physical structure.

Table 3B.1 - Canadian Steel Design Parameters


KT 1.0 K value for flexural torsional buckling.

KY 1.0 K value for general column flexural buckling about the local Y-axis. Used to calculate slenderness ratio.

KZ 1.0 K value for general column flexural buckling about the local Z-axis. Used to calculate slenderness ratio.

LT Member Length Length for flexural torsional buckling.

LY Member Length Length for general column flexural buckling about the local Y-axis. Used to calculate slenderness ratio.

LZ Member Length Length for general column flexural buckling about the local Z-axis. Used to calculate slenderness ratio.


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FU 345.0 MPa Ultimate strength of steel.


UNT Member Length Unsupported length in bending compression of the top flange for calculating moment resistance.

UNB Member Length Unsupported length in bending compression of the bottom flange for calculating moment resistance.

MAIN 0.0 0.0 = Check slenderness ratio against the limits. 1.1 = Suppress the slenderness ratio check.

2.0 = Check slenderness ratio only for column buckling, not for web (See Section 3B.6, Shear)

CB 1.0 Greater than 0.0 and less than 2.5 : Value of Omega_2 (Cl.13.6) to be used for calculation.

Equal to 0.0 : Calculate Omega_2

SSY 0.0 0.0 = Frame subjected to sidesway about local Y axis.

1.0 = Frame not subjected to sidesway about local Y axis.

Used in calculating Omega_2, Cl.13.6 of code

SSZ 0.0 0.0 = Frame subjected to sidesway about local Z axis.

1.0 = Frame not subjected to sidesway about local Z axis.

Used in calculating Omega_2, Cl.13.6 of code

CMY 1.0 1.0 = Do not calculate Omega-1 for local Y axis. 2.0 = Calculate Omega-1 for local Y axis. Used in Cl.13.8.4 of code

CMZ 1.0 1.0 = Do not calculate Omega-1 for local Z axis. 2.0 = Calculate Omega-1 for local Z axis. Used in Cl.13.8.4 of code

TRACK 0.0 0.0 = Report only minimum design results.

1.0 = Report design strengths also.

2.0 = Provide full details of design.

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DMAX 45.0 in. Maximum allowable depth (Applicable for member selection)

DMIN 0.0 in. Minimum required depth (Applicable for member selection)

RATIO 1.0 Permissible ratio of actual load effect to the design strength.

BEAM 0.0 0.0 = design only for end moments and those at locations specified by SECTION command.

1.0 = Perform design for moments at twelfth points along the beam.

DFF None(Mandatory for deflection

check)

“Deflection Length”/Maxm. Allowable local deflection.


Joint No. denoting start point for calculation of “deflection length”


Joint No. denoting end point for calculation of “deflection length”

3B.8 Code Checking

The purpose of code checking is to check whether the provided section properties of the members are adequate. The adequacy is checked as per the CAN/CSA-S16.1-94 requirements. Code checking is done using forces and moments at specified sections of the members. If the BEAM parameter for a member is set to 1, moments are calculated at every twelfth point along the beam. When no sections are specified and the BEAM parameter is set to zero (default), design will be based on member start and end forces only. The code checking output labels the members as PASSed or FAILed. In addition, the critical condition, governing load case, location (distance from the start joint) and magnitudes of the governing forces and moments are also printed. The extent


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of detail of the output can be controlled by using the TRACK parameter. Example of commands for CODE CHECKING:

UNIT NEWTON METER PARAMETER FYLD 330E6 MEMB 3 4 NSF 0.85 ALL KY 1.2 MEMB 3 4 UNL 15 MEMB 3 4 RATIO 0.9 ALL CHECK CODE MEMB 3 4


The member selection process basically involves determination of the least weight member that PASSes the code checking procedure based on the forces and moments of the most recent analysis. The section selected will be of the same type as that specified initially. For example, a member specified initially as a channel will have a channel selected for it. Selection of members whose properties are originally provided from a user table will be limited to sections in the user table. Member selection cannot be performed on TUBES, PIPES or members listed as PRISMATIC.

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Example of commands for MEMBER SELECTION:

UNIT NEWTON METER PARAMETER FYLD 330E6 MEMB 3 4 NSF 0.85 ALL KY 1.2 MEMB 3 4 UNL 15 MEMB 3 4 RATIO 0.9 ALL SELECT MEMB 3 4

Results of code checking and member selection are presented in a tabular format. The term CRITICAL COND refers to the section of the CAN/CSA-S16.1-94 specification which governed the design. If the TRACK parameter is set to 1.0, factored member resistances will be printed out. Following is a description of some of the items printed out. CR = Factored compressive resistance TR = Factored tensile resistance VR = Factored shear resistance MRZ = Factored moment resistance (about z-axis) MRY = Factored moment resistance (about y-axis)

Further details can be obtained by setting TRACK to 2.0.


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Design Per Canadian Cold Formed Steel Code

3C.1 General

Provisions of CSA S136-94, including revisions dated May, 1995, have been implemented. The program allows design of single (non-composite) members in tension, compression, bending, shear, as well as their combinations. For laterally supported members in bending, the Initiation of Yielding method has been used. Cold work of forming strengthening effects have been included as an option.

3C.2 Cross-Sectional Properties

The user specifies the geometry of the cross-section by selecting one of the section shape designations from the Gross Section Property Tables published in the "Cold-Formed Steel Design Manual", AISI, 1996 Edition. The Tables are currently available for the following shapes:

• Channel with Lips • Channel without Lips • Angle with Lips • Angle without Lips • Z with Lips • Z without Lips • Hat

Section 3C

Design Per Canadian Cold Fomed Steel Code

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Shape selection may be done using the member property pages of the graphical user interface (GUI) or by specifying the section designation symbol in the input file. Details of the latter are available in Section AD.2002.4.1.1 of this document. The properties listed in the tables are gross section properties. STAAD.Pro uses unreduced section properties in the structure analysis stage. Both unreduced and effective section properties are used in the design stage, as applicable.

3C.3 Design Procedure

The following two design modes are available:

1. Code Checking

The program compares the resistance of members with the applied load effects, in accordance with CSA 136. Code checking is carried out for locations specified by the user via the SECTION command or the BEAM parameter. The results are presented in a form of a PASS/FAIL identifier and a RATIO of load effect to resistance for each member checked. The user may choose the degree of detail in the output data by setting the TRACK parameter.

2. Member Selection

The user may request that the program search the cold formed steel shapes database (AISI standard sections) for alternative members that pass the code check and meet the least weight criterion. In addition, a minimum and/or maximum acceptable depth of the member may be specified. The program will then evaluate all database sections of the type initially specified (i.e., channel, angle, etc.) and, if a suitable replacement is found, present design results for that section. If no section satisfying the depth restrictions or lighter than the initial one can be found, the program leaves the member unchanged, regardless of whether it passes the code check or not.

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The program calculates effective section properties in accordance with Clauses 5.6.2.1 through 3 and 5.6.2.6 through 8. Cross-sectional properties and overall slenderness of members are checked for compliance with

• Clause 5.3, Maximum Effective Slenderness Ratio for members in Compression

• Clause 5.4, Maximum Flat Width Ratios for Elements in Compression

• Clause 5.5, Maximum Section Depths. The program will check member strength in accordance with Clause 6 of the Standard as follows:

a. Resistance factors listed in Clauses 6.2 (a), (b), and (e) are used, as applicable.

b. Members in tension Resistance is calculated in accordance with Clauses 6.3.1 and 6.3.2.

c. Members in bending and shear Resistance calculations are based on Clauses: a. 6.4.1 General,

b. 6.4.2 and 6.4.2.1 Laterally Supported Members, compressive limit stress based on Initiation of Yielding,

c. 6.4.3 Laterally Unsupported Members,

d. 6.4.4 Channels and Z-Shaped Members with Unstiffened Flanges - additional limitations,

e. 6.4.5 Shear in Webs,

f. 6.4.6 Combined Bending and Shear in Webs.


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a. Members in compression Resistance calculations are based on Clauses: a. 6.6.1.1, 6.6.1.2 (a) and (d), and 6.6.1.3 General,

b. 6.6.2 Sections Not Subject to Torsional-Flexural Buckling,

c. 6.6.3 Singly Symmetric Sections,

d. 6.6.4 Point-Symmetric Sections,

e. 6.6.5 Cylindrical Tubular Sections.

b. Members in compression and bending Resistance calculations are based on Clause 6.7.1, Singly and Doubly Symmetric Sections. Input for the coefficients of uniform bending must be provided by the user. The following table contains the input parameters for specifying values of design variables and selection of design options.

COLD FORMED STEEL DESIGN PARAMETERS

Parameter Name


BEAM 1.0 When this parameter is set to 1.0 (default), the adequacy of the member is determined by checking a total of 13 equally spaced locations along the length of the member. If the BEAM value is 0.0, the 13 location check is not conducted, and instead, checking is done only at the locations specified by the SECTION command (See STAAD manual for details). If neither the BEAM parameter nor any SECTION command is specified, STAAD will terminate the run and ask the user to provide one of those 2 commands. This rule is not enforced for TRUSS members.

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Parameter Name


CMZ 1.0 Coefficient of equivalent uniform bending ωz. See CSA 136, 6.7.2. Used for Combined axial load and bending design. Values range from 0.4 to 1.0.

CMY 0.0 Coefficient of equivalent uniform bending ωy. See CSA 136, 6.7.2. Used for Combined axial load and bending design. Values range from 0.4 to 1.0.

CWY 0 Specifies whether the cold work of forming strengthening effect should be included in resistance computation. See CSA 136, 5.2.

Values: 0 – effect should not be included

1 – effect should be included

DMAX 1000.0 Maximum depth permissible for the section during member selection. This value must be provided in the current units.

DMIN 0.0 Minimum depth required for the section during member selection. This value must be provided in the current units.

FLX 1 Specifies whether torsional-flexural buckling restraint is provided or is not necessary for the member. See CSA 136, 6.6.2

Values:

0 – Section subject to torsional flexural buckling and restraint not provided

1 – restraint provided or unnecessary FU 450 MPa Ultimate tensile strength of steel in current units.

FYLD 350 MPa Yield strength of steel in current units.


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Parameter Name


KT 1.0 Effective length factor for torsional buckling. It is a fraction and is unit-less. Values can range from 0.01 (for a column completely prevented from torsional buckling) to any user specified large value. It is used to compute the KL/R ratio for twisting for determining the capacity in axial compression.

KY 1.0 Effective length factor for overall column buckling about the local Y-axis. It is a fraction and is unit-less. Values can range from 0.01 (for a column completely prevented from buckling) to any user specified large value. It is used to compute the KL/R ratio for determining the capacity in axial compression.

KZ 1.0 Effective length factor for overall column buckling in the local Z-axis. It is a fraction and is unit-less. Values can range from 0.01 (for a column completely prevented from buckling) to any user specified large value. It is used to compute the KL/R ratio for determining the capacity in axial compression.

LT Member length

Unbraced length for twisting. It is input in the current units of length. Values can range from 0.01 (for a column completely prevented from torsional buckling) to any user specified large value. It is used to compute the KL/R ratio for twisting for determining the capacity in axial compression.

LY Member length

Effective length for overall column buckling in the local Y-axis. It is input in the current units of length. Values can range from 0.01 (for a column completely prevented from buckling) to any user specified large value. It is used to compute the KL/R ratio for determining the capacity in axial compression.

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Parameter Name


LZ Member length

Effective length for overall column buckling in the local Z-axis. It is input in the current units of length. Values can range from 0.01 (for a column completely prevented from buckling) to any user specified large value. It is used to compute the KL/R ratio for determining the capacity in axial compression.

NSF 1.0 Net section factor for tension members, See CSA 136, 6.3.1.

STIFF Member length

Spacing in the longitudinal direction of shear stiffeners for stiffened flat webs. It is input in the current units of length. See section CSA 136, 6.4.5

TRACK 0 This parameter is used to control the level of detail in which the design output is reported in the output file. The allowable values are: 0 - Prints only the member number, section name, ratio,

and PASS/FAIL status. 1 - Prints the design summary in addition to that printed

by TRACK 1 2 - Prints member and material properties in addition to

that printed by TRACK 2. TSA 1 Specifies whether bearing and intermediate transverse

stiffeners satisfy the requirements of CSA 136, 6.5. If true, the program uses the more liberal set of interaction equations in 6.4.6.

Values:

0 – stiffeners do not comply with 6.5

1 – stiffeners comply with 6.5


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Section 4 Chinese Codes

Kjahds;akh

4-1

Concrete Design Per GBJ 10-89


STAAD has the capabilities of performing concrete design. It will calculate the reinforcement needed for any concrete section. All the concrete design calculations are based on limit state method of GBJ 10-89.


The following types of cross sections for concrete members can be designed. For Beams Prismatic (Rectangular & Square), and L-shapes For Columns Prismatic (Rectangular, Square and Circular)



Section 4A

Concrete Design Per GBJ 10-89 Section 4A

4-2

UNIT MM MEMBER PROPERTY 1 3 TO 7 9 PRISM YD 450. ZD 250. 11 13 PR YD 350. 14 TO 16 PRIS YD 400. ZD 750. YB 300. ZB 200.

will be done accordingly. In the above input, the first set of members are rectangular (450 mm depth and 250mm width) and the second set of members, with only depth and no width provided, will be assumed to be circular with 350 mm diameter. The third set numbers in the above example represents a T-shape with 750 mm flange width, 200 width, 400 mm overall depth and 100 mm flange depth (See section 6.20.2). The program will determine whether the section is rectangular, flanged or circular and the beam or column design


The program contains a number of parameters which are needed to perform design as per GBJ 10-89. Default parameter values have been selected such that they are frequently used numbers for conventional design requirements. These values may be changed to suit the particular design being performed. Table 9A.1 of this manual contains a complete list of the available parameters and their default values. It is necessary to declare length and force units as Millimeter and Newton before performing the concrete design. Please note as per GBJ 10-89 STAAD supports Characteristic Values of Concrete Strength and Design Value of Strength of Steel Bar only as per Table 2.1.3 and Table 2.2.3-1 respectively.

4A.5 Beam Design

Beams are designed for flexure, shear and torsion. If required the effect the axial force may be taken into consideration. For all

Section 4A

4-3

these forces, all active beam loadings are prescanned to identify the critical load cases at different sections of the beams. The total number of sections considered is 13( e.g. 0., .1, .2, .25, .3, .4, .5, .6, .7, .75, .8, .9 and 1). All of these sections are scanned to determine the design force envelopes. Design for Flexure

Maximum sagging (creating tensile stress at the bottom face of the beam) and hogging (creating tensile stress at the top face) moments are calculated for all active load cases at each of the above mentioned sections. Each of these sections are designed to resist both of these critical sagging and hogging moments. Where ever the rectangular section is inadequate as singly reinforced section, doubly reinforced section is tried. However, presently the flanged section are designed only as singly reinforced section under sagging moment. It may also be noted all flanged sections are automatically designed as rectangular section under hogging moment as the flange of the beam is ineffective under hogging moment. Flexural design of beams are performed in two passes. In the first pass, effective depths of the sections are determined with the assumption of single layer of assumed reinforcement and reinforcement requirements are calculated. After the preliminary design, reinforcing bars are chosen from the internal database in single or multiple layers. The entire flexure design is performed again in a second pass taking into account of the changed effective depths of sections calculated on the basis of reinforcement provide after the preliminary design. Final provision of flexural reinforcements are made then. Efforts have been made to meet the guideline for the reinforcement detailing as per GBJ 10-89 Although exact curtailment lengths are not mentioned explicitly in the design output (finally which will be more or less guided by the detailer taking into account of other practical consideration), user has the choice of printing reinforcements provided by STAAD at 11 equally spaced sections from which the final detail drawing can be prepared.


4-4

Design for Shear

Shear reinforcement is calculated to resist both shear forces and torsional moments. Shear design are performed at 11 equally spaced sections (0.to 1.) for the maximum shear forces amongst the active load cases and the associated torsional moments. Shear capacity calculation at different sections without the shear reinforcement is based on the actual tensile reinforcement provided by STAAD program. Two-legged stirrups are provided to take care of the balance shear forces acting on these sections. Beam Design Output

The default design output of the beam contains flexural and shear reinforcement provided at 5 equally spaced (0,.25,.5,.75 and 1.) sections along the length of the beam. User has option to get a more detail output. All beam design outputs are given in IS units. An example of rectangular beam design output with the default output option (TRACK 0.0) is presented below:

Section 4A

4-5

============================================================================

B E A M N O. 12 D E S I G N R E S U L T S

M20 Fe415 (Main) Fe415 (Sec.)

LENGTH: 4000.0 mm SIZE: 250.0 mm X 350.0 mm COVER: 30.0 mm

DESIGN LOAD SUMMARY (KN MET)----------------------------------------------------------------------------SECTION |FLEXTURE (Maxm. Sagging/Hogging moments)| SHEAR(in mm) | P MZ MX Load Case | VY MX Load Case----------------------------------------------------------------------------

0.0 | 0.00 0.00 0.00 4 | 29.64 1.23 4| 0.00 -25.68 1.23 4 |

400.0 | 0.00 0.00 0.00 4 | 27.97 1.23 4| 0.00 -16.05 1.23 4 |

800.0 | 0.00 0.00 0.00 4 | 25.12 1.23 4| 0.00 -7.17 1.23 4 |

1200.0 | 0.00 0.97 0.49 5 | 21.11 1.23 4| 0.00 -0.14 1.32 6 |

1600.0 | 0.00 6.77 1.23 4 | 15.93 1.23 4| 0.00 0.00 0.00 4 |

2000.0 | 0.00 11.06 1.23 4 | 9.59 1.23 4| 0.00 0.00 0.00 4 |

2400.0 | 0.00 13.04 1.23 4 | 2.08 1.23 4| 0.00 0.00 0.00 4 |

2800.0 | 0.00 12.45 1.23 4 | -5.43 1.23 4| 0.00 0.00 0.00 4 |

3200.0 | 0.00 9.55 1.23 4 | -11.77 1.23 4| 0.00 0.00 0.00 4 |

3600.0 | 0.00 4.73 1.23 4 | -16.95 1.23 4| 0.00 0.00 0.00 4 |

4000.0 | 0.00 0.00 0.00 4 | -25.48 1.23 4| 0.00 -17.36 1.23 4 |

----------------------------------------------------------------------------

SUMMARY OF REINF. AREA (Sq.mm)----------------------------------------------------------------------------SECTION 0.0 mm 1000.0 mm 2000.0 mm 3000.0 mm 4000.0 mm----------------------------------------------------------------------------TOP 259.04 161.29 0.00 0.00 176.31REINF. (Sq. mm) (Sq. mm) (Sq. mm) (Sq. mm) (Sq. mm)

BOTTOM 0.00 160.78 160.78 160.78 0.00REINF. (Sq. mm) (Sq. mm) (Sq. mm) (Sq. mm) (Sq. mm)----------------------------------------------------------------------------

SUMMARY OF PROVIDED REINF. AREA----------------------------------------------------------------------------SECTION 0.0 mm 1000.0 mm 2000.0 mm 3000.0 mm 4000.0 mm----------------------------------------------------------------------------TOP 4-10Ø 3-10Ø 2-10Ø 2-10Ø 3-10ØREINF. 1 layer(s) 1 layer(s) 1 layer(s) 1 layer(s) 1 layer(s)

BOTTOM 2-12Ø 2-12Ø 2-12Ø 2-12Ø 2-12ØREINF. 1 layer(s) 1 layer(s) 1 layer(s) 1 layer(s) 1 layer(s)

SHEAR 2 legged 8Ø 2 legged 8Ø 2 legged 8Ø 2 legged 8Ø 2 legged 8ØREINF. @ 100 mm c/c @ 100 mm c/c @ 100 mm c/c @ 100 mm c/c @ 100 mm c/c----------------------------------------------------------------------------

============================================================================


4-6

4A.6 Column Design

Columns are designed for axial forces and biaxial moments at the ends. All active load cases are tested to calculate reinforcement. The loading which yield maximum reinforcement is called the critical load. Column design is done for square, rectangular and circular sections. By default, square and rectangular columns and designed with reinforcement distributed on each side equally for the sections under biaxial moments and with reinforcement distributed equally in two faces for sections under uniaxial moment. User may change the default arrangement of the reinforcement with the help of the parameter RFACE (see Table 9A.1). Depending upon the member lengths, section dimensions and effective length coefficients specified by the user STAAD automatically determine the criterion (short or long) of the column design. All major criteria for selecting longitudinal and transverse reinforcement as stipulated by GBJ 10-89 have been taken care of in the column design of STAAD. Column Design Output

Default column design output (TRACK 0.0) contains the reinforcement provided by STAAD and the capacity of the section. With the option TRACK 1.0, the output contains intermediate results such as the design forces, effective length coefficients, additional moments etc. A special output TRACK 9.0 is introduced to obtain the details of section capacity calculations. All design output is given in SI units. An example of a long column design output (with option TRACK 1.0) is given below.

Section 4A

4-7

============================================================================

C O L U M N No. 1 D E S I G N R E S U L T S


LENGTH: 3000.0 mm CROSS SECTION: 250.0 mm dia. COVER: 40.0 mm

** GUIDING LOAD CASE: 5 BRACED LONG COLUMN

DESIGN FORCES (KNS-MET)-----------------------DESIGN AXIAL FORCE (Pu) : 62.0

About Z About YINITIAL MOMENTS : 2.21 32.29MOMENTS DUE TO MINIMUM ECC. : 1.24 1.24

SLENDERNESS RATIOS : 12.00 12.00MOMENTS DUE TO SLENDERNESS EFFECT : 1.12 1.12MOMENT REDUCTION FACTORS : 1.00 1.00ADDITION MOMENTS (Maz and May) : 1.12 1.12

TOTAL DESIGN MOMENTS : 3.32 33.40

REQD. STEEL AREA : 1822.71 Sq.mm.MAIN REINFORCEMENT : Provide 17 - 12 dia. (3.92%, 1922.65 Sq.mm.)

(Equally distributed)TIE REINFORCEMENT : Provide 8 mm dia. rectangular ties @ 190 mm c/c

SECTION CAPACITY (KNS-MET)--------------------------Puz : 992.70 Muz1 : 36.87 Muy1 : 36.87

INTERACTION RATIO: 1.00 (as per Cl. 38.6, IS456)

============================================================================


4-8

Table 4A.1 Chinese Concrete Design GBJ 10-89 Parameters





CLEAR 25 mm 40 mm

For beam members. For column members





BRACING 0.0 BEAM DESIGN

A value of 1.0 means the effect of axial force will be taken into account for beam design.

COLUMN DESIGN

A value of 1.0 means the column is unbraced about major axis.

A value of 2.0 means the column is unbraced about minor axis.

A value of 3.0 means the column is unbraced about both axis.


RFACE 4.0 A value of 4.0 means longitudinal reinforcement in column is arranged equally along 4 faces.

A value of 2.0 invokes 2 faced distribution about major axis.

A value of 3.0 invokes 2 faced distribution about minor axis.


Section 4A

4-9

Table 4A.1 Chinese Concrete Design GBJ 10-89 Parameters



TRACK 0.0 BEAM DESIGN: For TRACK = 0.0, output consists of reinforcement details at START, MIDDLE and END. For TRACK = 1.0, critical moments are printed in addition to TRACK 0.0 output. For TRACK = 2.0, required steel for intermediate sections defined by NSECTION are printed in addition to TRACK 1.0 output.

COLUMN DESIGN: With TRACK = 0.0, reinforcement details are printed. With TRACK = 1.0, column interaction analysis results are printed in addition to TRACK 0.0 output. With TRACK = 2.0, a schematic interaction diagram and intermediate interaction values are printed in addition to TRACK 1.0 output.


ELZ 1.0 Ratio of effective length to actual length of column about major axis.

ELY 1.0 Ratio of effective length to actual length of column about minor axis.


4-10

4-11

Steel Design Per GBJ 17- 88

4B.1 General

This section presents some general statements regarding the implementation in STAAD of the National Standard of the People’s Republic of China specifications for Design of Steel Structures (GBJ 17-88). The design philosophy and procedural logistics are based on the principles of limit state design method. Facilities are available for member selection as well as code checking. The following sections describe the salient features of the design approach. Members are proportioned to resist the design loads without exceedance of the capacities. The most economical section is selected on the basis of the least weight criteria. The code checking part of the program also checks the slenderness requirements and the stability criteria. It is generally assumed that the user will take care of the detailing requirements like flange buckling, web crippling etc. Users are recommended to adopt the following steps in performing the steel design: 1) Specify the geometry and factored loads. Perform the analysis. 2) Specify the design parameter values if different from the

default values. 3) Specify whether to perform code checking or member

selection.

Section 4B

Steel Design Per GBJ 17-88 Section 4B

4-12


Analysis is done for the primary and combination loading conditions provided by the user. The user is allowed complete flexibility in providing loading specifications and using appropriate load factors to create necessary loading situations. Depending upon the analysis requirements, regular stiffness analysis, P-Delta analysis or Non-linear analysis may be specified. Dynamic analysis may also be performed and the results combined with static analysis results. Please note that STAAD does not automatically factor any loads. The responsibility of creating load combinations with factored loads is entirely upon the user.


For specification of member properties, the steel section library available in STAAD may be used. The next section describes the syntax of commands used to assign properties from the built-in steel table. Member properties may also be specified using the User Table facility. For more information on these facilities, refer to the STAAD Program Technical Reference manual.

4B.4 Built-in Chinese Steel Section Library

The following information is provided for use when the built-in steel tables are to be referenced for member property specification. These properties are stored in a database file. If called for, the properties are also used for member design. Since the shear areas are built into these tables, shear deformation is always considered for these members. An example of the member property specification in an input file is provided at the end of this section.

Section 4B

4-13

A complete listing of the sections available in the built-in steel section library may be obtained by using the tools of the graphical user interface. Following are the descriptions of different types of sections. B Shapes These shapes are designated in the following way.

20 TO 30 TA ST I14 33 36 TO 46 TA ST I63C

Channels Channels are specified in the following way.

11 TA ST CH5 17 TA ST CH40C

Double Channels Back to back double channels, with or without a spacing between them, are available. The letter D in front of the section name will specify a double channel.

11 TA D CH22B 17 TA D CH40C SP 0.5

In the above set of commands, member 11 is a back to back double channel CH22B with no spacing in between. Member 17 is a double channel CH40C with a spacing of 0.5 length units between the channels.


4-14

Angles Two types of specifications may be used to describe an angle. The standard angle section is specified as follows:

16 20 TA ST L25X16X3

The above section signifies an angle with legs of length 25mm and 16mm and a leg thickness of 3 mm. This specification may be used when the local Z axis corresponds to the z-z axis specified in Chapter 2. If the local Y axis corresponds to the z-z axis, type specification "RA" (reverse angle) may be used.

17 21 TA RA L100X80X6

Double Angles Short leg back to back or long leg back to back double angles can be specified by means of input of the words SD or LD, respectively, in front of the angle size. In case of an equal angle, either SD or LD will serve the purpose.

33 35 TA SD L25X16X4 SP 0.6 37 39 TA LD L100X80X6 43 TO 47 TA LD L32X20X3 SP 0.75

Tubes (Rectangular or Square Hollow Sections) Tubes can be assigned in 2 ways. In the first method, the designation for the tube is as shown below. This method is meant for tubes whose property name is available in the steel table. In these examples, members 1 to 5 consist of a 2X2X0.5 inch size tube section, and members 6 to 10 consist of 10X5X0.1875 inch size tube section. The name is obtained as 10 times the depth, 10 times the width, and 16 times the thickness.

Section 4B

4-15

1 TO 5 TA ST TUB20202.5 6 TO 10 TA ST TUB100503.0

In the second method, tubes are specified by their dimensions. For example,


is a tube that has a height of 8 length units, width of 6 length units, and a wall thickness of 0.5 length units. Only code checking, no member selection, will be performed for TUBE sections specified in this latter manner. Pipes (Circular Hollow Sections) Pipes can be assigned in 2 ways. In the first method, the designation for the pipe is as shown below. This method is meant for pipes whose property name is available in the steel table.

1 TO 5 TA ST PIP180X5 6 TO 10 TA ST PIP273X6.5

In the second method, pipe sections may be provided by specifying the word PIPE followed by the outside and inside diameters of the section. For example,


specifies a pipe with outside diameter of 25 length units and inside diameter of 20 length units. Only code checking, no member selection, will be performed on pipes specified in this latter manner.


4-16

Sample File Containing Chinese Shapes STAAD SPACE UNIT METER KN JOINT COORD 1 0 0 0 12 110 0 0 MEMB INCI 1 1 2 11 UNIT CM MEMBER PROPERTIES CHINESE * B SHAPES 1 TA ST I10 * CHANNELS 2 TA ST CH16A * DOUBLE CHANNELS 3 TA D CH22B SP 1.0 * ANGLES 4 TA ST L25X25X4 * REVERSE ANGLES 5 TA RA L25X16X3 * DOUBLE ANGLES - SHORT LEGS BACK TO BACK 6 TA SD L25X16X3 SP 0.6 * DOUBLE ANGLES - LONG LEGS BACK TO BACK 7 TA LD L32X20X3 SP 0.75 * TUBES (RECTANGULAR OR SQUARE HOLLOW SECTIONS) 8 TA ST TUB50252.5 * TUBES (RECTANGULAR OR SQUARE HOLLOW SECTIONS) 9 TA ST TUBE DT 8.0 WT 6.0 TH 0.5 * PIPES (CIRCULAR HOLLOW SECTIONS) 10 TA ST PIP180X5 * PIPES (CIRCULAR HOLLOW SECTIONS) 11 TA ST PIPE OD 18.0 ID 10.0 PRINT MEMB PROP FINI

Section 4B

4-17


The basic measure of member capacities are the allowable stresses on the member under various conditions of applied loading such as allowable tensile stress, allowable compressive stress etc. These depend on several factors such as cross sectional properties, slenderness factors, unsupported width to thickness ratios and so on. Explained here is the procedure adopted in STAAD for calculating such capacities. Allowable stress for Axial Tension In members with axial tension, the tensile load must not exceed the tension capacity of the member. The tension capacity of the member is calculated on the basis of allowable tensile stresses provided in Table 3.2.1-2 of the code. STAAD calculates the tension capacity of a given member per this allowable stress value and a user supplied net section factor (NSF-a default value of 1.0 is present but may be altered by changing the input value, see Table 1) and proceeds with member selection or code checking. Allowable stress for Axial Compression The allowable stress for members in compression is determined according to Table 3.2.1-2. Compressive resistance is a function of the slenderness of the cross-section (Kl/r ratio) and the user may control the slenderness value by modifying parameters such as KY, LY, KZ and LZ. The provisions of Section 5 are used to check the adequacy of sections in compression. Allowable stress for Bending and Shear Sections subjected to bending moments and shear forces are to be designed according to the provisions of section 5. The permissible bending compressive and tensile stresses are dependent on such factors as outstanding legs and thickness of flanges, unsupported length of the compression flange (UNL, defaults to member length) etc. Shear capacities are calculated according to Table 3.2.1-2 and Section 5 and are a function of web depth, web


4-18

thickness etc. Users may use a value of 1.0 or 2.0 for the TRACK parameter to obtain a listing of the bending and shear capacities.

4B.6 Combined Loading

For members experiencing combined loading (axial force, bending and shear), applicable interaction formulas are checked at different locations of the member for all modeled loading situations. The procedure of Section 5 is implemented for combined axial load and bending.


The user is allowed complete control over the design process through the use of parameters mentioned in Table 1 of this chapter. These parameters communicate design decisions from the engineer to the program. The default parameter values have been selected such that they are frequently used numbers for conventional design. Depending on the particular design requirements of an analysis, some or all of these parameter values may have to be changed to exactly model the physical structure.

4B.8 Code Checking

The purpose of code checking is to check whether the provided section properties of the members are adequate. The adequacy is checked per the GBJ 17-88 requirements. Code checking is done using forces and moments at specified sections of the members. If the BEAM parameter for a member is set to 1, moments are calculated at every twelfth point along the beam, and the maximum moment about the major axis is used. When no sections are specified and the BEAM parameter is set to zero (default), design will be based on member start and end

Section 4B

4-19

forces. The code checking output labels the members as PASSed or FAILed. In addition, the critical condition, governing load case, location (distance from start joint) and magnitudes of the governing forces and moments are also printed.


The member selection process basically involves determination of the least weight member that PASSes the code checking procedure based on the forces and moments of the most recent analysis. The section selected will be of the same type as that specified initially. For example, a member specified initially as a channel will have a channel selected for it. Selection of members whose properties are originally provided from a user table will be limited to sections in the user table.

Table 4B.1 Chinese Steel Design Parameters


KY 1.0 K value in local y-axis. Usually, this is the minor axis.

KZ 1.0 K value in local z-axis. Usually, this is the major axis.

LY Member Length

Length in local y-axis to calculate slenderness ratio.

LZ Member Length

Same as above except in z-axis (major).

GRADE 1.0 Grade of steel as explained in Table 3.2.1-2 of Code. The following values represent the various grades of steel: Grade 3 group 1 - 1 Grade 3 group 2 - 2 Grade 3 group 3 - 3 16Mn and 16Mnq - 4 15MnV and 15MnVq - 5


COMPRESSION 150 Allowable KL/r value in compression.


4-20

Table 4B.1 Chinese Steel Design Parameters


TENSION 300 Allowable KL/r value in tension.

MAIN 0.0 0.0 = Check Slenderness ratio against allowable values.

1.0 = Do not check for slenderness.

PFY 1.2 Plasticity adaptation factor for Y direction.

PFZ 1.05 Plasticity adaptation factor for Z direction.

SFY 1.0 Stability factor for Y direction.

SFZ 1.0 Stability factor for Z direction.

TRACK 1.0 1.0 = Print all critical member stresses. 0.0 = Suppress critical member stresses.

DMAX 100.0 cm. Maximum allowable depth.

DMIN 0.0 cm. Minimum allowable depth.

RATIO 1.0 Permissible ratio of the actual to allowable stresses.

BEAM 0.0 0.0 = design only for end moments and those at locations specified by the SECTION command.

1.0 = calculate moments at twelfth points along the beam, and use the maximum, Mz for design.

Sample Input data for Steel Design UNIT METER PARAMETER CODE CHINESE NSF 0.85 ALL GRADE 3.0 MEMBER 7 KY 1.2 MEMBER 3 4 RATIO 0.9 ALL TRACK 1.0 ALL CHECK CODE ALL

Section 5 European Codes

5-1

Concrete Design Per Eurocode EC2


STAAD provides a comprehensive set of national codes for the design of concrete structures. In general, all the available codes, including EC2, follow the same procedure for the design of the concrete members. The main steps in performing a design operation are: 1. Selecting the applicable load cases to be considered in the

design process. 2. Providing appropriate parameter values if different from the

default values. 3. Perform the design for the member as appropriate. These operations can be repeated by the user any number of times depending on the design requirements. The parameters referred to above provide the user with the ability to allocate specific design properties to individual members considered in the design operation.

5A.2 Eurocode 2 (EC2)

Eurocode 2, Design of concrete structures, Part 1, General rules and rules for buildings, provides design rules applicable to plain, reinforced or prestressed concrete used in buildings and civil engineering works. It is based on the limit state philosophy common to modern standards.

Section 5A

Concrete Design Per Eurocode EC2 Section 5A

5-2

The objective of this method of design is to ensure that possibility of failure is reduced to a negligible level. This is achieved through application of factors to both the applied loads and the material properties. The code also provides guidelines on the global method of analysis to be used for calculating internal member forces and moments. STAAD provides a number of methods for analysis, allowing Geometric Nonlinearity as well as P-Delta effects to be considered.

5A.3 National Application Documents

Various authorities of the CEN member countries have prepared National Application Documents to be used with EC2. These documents provide alternative factors for loads and may also provide supplements to the rules in EC2. The current version of EC2 implemented in STAAD adheres to the factors and rules provided in EC2 and has not been modified by any National Application Documents.

5A.4 Material Properties and Load Factors

Design resistances are obtained by dividing the characteristic yield strengths, as given in table 2.3 of EC2, by the material partial safety factors γc for concrete and γs for reinforcements. The magnitude in STAAD is 1.5 for concrete and 1.15 for reinforcements. Material coefficients in STAAD take the following default values unless replaced by user's numerical values provided in the input file. Modulus of Elasticity E = 21.71 KN/mm2 Shear Modulus G = E / 2 (1 + v) Poisson's Ratio v = 0.25 Unit weight ρ = 23.56 KN/m3

Section 5A

5-3

The magnitude of design loads is dependent on γF, the partial safety factor for the action under consideration. In STAAD the user is allowed total control in providing applicable values for the factors and their use in various load combinations.

5A.5 Columns

Columns are designed for axial compressive loads and possible moments at the ends of the member. If a particular load case causes tension in the column being designed that load case is ignored, the design proceeds with a warning message given to that affect. All active load cases will be considered in the design and reinforcements are assumed symmetrically arranged in the cross section. The maximum reinforcement calculated after all design load cases have been considered is then reported as the critical required area of reinforcement.

Slender columns are also covered in the design process, the program will make due allowance for the additional moment that has to be considered in the design. Please note that sway type structures are not directly covered in the current implementation of EC2. This effect, however, can be catered for by the P-DELTA analysis option.

5A.6 Beams

Beams are designed for flexure, shear and torsion. For all these actions active load cases are scanned to create appropriate envelopes for the design process. Maximum torsional moment is also identified and incorporated in the design.


5-4

Design for flexure

Reinforcement for both positive and negative moments is calculated on the basis of the section properties provided by the user. If the required reinforcement exceeds the maximum allowable then the section size is inadequate and a massage to that effect is given in the output. Parabolic-rectangular stress distribution for the concrete section is adopted and as moment redistribution is not available in STAAD analysis, the limit for N.A to depth ratio is set according to clause 2.5.3.4.2 (5) of the code. If required, compression reinforcement will be provided in order to satisfy the above limits. It is important to know that beams are designed for the flexural moment MZ only. The moment MY is not considered in the design at all. Design for Shear

Shear reinforcement design is based on the standard method mentioned in clause 4.3.2.4.3 where it is assumed the notional strut inclination is constant. Depending on the shear distribution within the member it may be possible that nominal shear reinforcement will be sufficient to cater for the design shear forces. If this is not the case an attempt is made to identify regions where nominal reinforcement is insufficient and appropriate reinforcement is then calculated to cover the excess design shear force. The maximum shear force that can be carried without crushing the concrete is also checked and if exceeded, a message to revise the section size is given in the output file. Design for Torsion

Torsional moments arising as a result of equilibrium requirements need to be designed for at the ultimate limit state. Reinforcement for torsional moments consists of stirrups combined with longitudinal bars. The combined magnitude of shear stress arising from shear forces and torsional moments are checked in order to establish whether the section size is adequate. If section size is inadequate a massage is given in the output file, otherwise, full

Section 5A

5-5

design is carried out and both shear links and longitudinal bars required are calculated and, where necessary, links are combined with the shear force links and printed in a tabulated manner in the output file.

5A.7 Slabs

Slabs can only be designed for if finite elements are used to represent them in the model of the structure. In the main the design follows the same procedure as for flexure except that shear forces are assumed to be resisted without the provision of shear reinforcements. In cases where this may not be the case users must ensure that necessary checks are carried out. The output for the slab design refers to longitudinal reinforcements, which coincides with the local x direction of the element, and, transverse reinforcement, which coincides with the local y direction of the element. Also, reference is made to 'TOP' and BOTT' reinforcement which relates to the element's 'TOP' and 'BOTTOM' as determined from the connectivity of the element. This may not coincide with the slab's actual top and bottom and, if desired, users must ensure this through the numbering scheme of the elements (see figure 1.13 in the STAAD Technical Reference Manual). The design of the slab considers a fixed bar size of 16mm in both directions with the longitudinal bar being the layer closest to the slab exterior faces.


Design parameters communicate specific design decisions to the program. They are set to default values to begin with and may be altered to suite the particular structure. Depending on the model being designed, the user may have to change some or all of the parameter default values. Some parameters are unit dependent and when altered, the new setting must be compatible with the active "unit" specification. Table 5A.1 lists all the relevant EC2 parameters together with description and default values.


5-6

5A.9 Parameter Definition Table

Table 5A.1 – Concrete Design Parameters-EC2


FYMAIN *460 N/mm2 Yield Stress for main reinforcement (For slabs, it is for reinforcement in both directions)

FYSEC *460N/mm2 Yield Stress for secondary reinforcement. Applicable to shear bars in beams

FC * 30N/mm2 Concrete Yield Stress / cube strength

MINMAIN 8mm Minimum main reinforcement bar size Acceptable bar sizes: 6 8 10 12 16 20 25 32 40 50

MINSEC 8mm Minimum secondary bar size a. Applicable to shear reinforcement in beams

CLEAR * 20mm Clearance of reinforcement measured from concrete surface to closest bar perimeter.

MAXMAIN 50mm Maximum required reinforcement bar size Acceptable bars are per MINMAIN above.

SFACE *0.0 Face of support location at start of beam. (Only applicable for shear - use MEMBER OFFSET for bending )

EFACE *0.0 Face of support location at end of beam. (NOTE : Both SFACE & EFACE must be positive numbers.)

TRACK 0.0 0.0 = Critical Moment will not be printed with beam design report. Column design gives no detailed results.


2.0 = Output of TRACK 1.0 List of design sag/hog moments and corresponding required steel area at each section of member

MMAG 1.0 Factor by which column design moments are magnified

Section 5A

5-7

Table 5A.1 – Concrete Design Parameters-EC2


NSECTION 10 Number of equally-spaced sections to be considered in finding critical moment for beam design. The upper limit is 20.

WIDTH *ZD Width of concrete member. This value default is as provided as ZD in MEMBER PROPERTIES.

DEPTH *YD Depth of concrete member. This value default is as provided as YD in MEMBER PROPERTIES.

BRACE 0.0 0.0 = Column braced in both directions. 1.0 = Column unbraced about local Z direction

only 2.0 = Column unbraced about local Y

direction only 3.0 = Column unbraced in both Y and Z

directions

ELY 1.0 Member length factor about local Y direction for column design.

ELZ 1.0 Member length factor about local Z direction for column design.


-500 = Orthogonal reinforcement layout with Mxy used to calculate WOOD & ARMER moments for design.

A = Skew angle considered in WOOD & ARMER equations where A is the angle in degrees.

SERV 0.0 0.0 = No serviceability check performed. 1.0 = Perform serviceability check for beams

as if they were continuous. 2.0 = Perform serviceability check for beams

as if they were simply supported. 3.0 = Perform serviceability check for beams

as if they were cantilever beams. * Provided in current unit system


5-8

5-9

Steel Design Per Eurocode EC3

5B.1 General Description

Introduction STAAD provides a comprehensive set of national codes for the design of steel structures. In general, all the available codes, including EC3, follow the same procedure to perform either code-check of members or select optimum cross sections for members of an analyzed structure.

The main steps in performing a design operation are:

1. Selecting the applicable load cases to be

considered in the design process.

2. Providing appropriate parameter values if different from the default values.

3. Specify whether to perform code-checking and/or member selection.

These operations can be repeated by the user any number of times depending on the design requirements.

The parameters, referred to above, provide the user with the ability to allocate specific design properties to individual members considered in the design operation.

Section 5B

Steel Design Per Eurocode EC3 Section 5B

5-10

Eurocode (EC3)

Eurocode 3, Design of steel structures, Part 1.1 General rules and rules for buildings (EC3) provides design rules applicable to structural steel used in buildings and civil engineering works. It is based on the limit states philosophy common to modern standards. The objective of this method of design is to ensure that possibility of failure is reduced to a negligible level. This is achieved through application of factors to both the applied loads and the material properties. The code also provides guidelines on the global method of analysis to be used for calculating internal member forces and moments. STAAD uses the elastic method of analysis which may be used in all cases. Also there are three types of framing referred to in EC3. These are “Simple”, “Continuous”, and “Semi-continuous” which reflect the ability of the joints in developing moments. In STAAD, only “Simple” and “Continuous” joint types can be assumed when carrying out global analysis. Axes convention in STAAD and EC3

By default, STAAD defines the major axis of the cross-section as zz and the minor axis as yy. A special case where zz is the minor axis and yy is the major axis is available if the “SET Z UP” command is used and is discussed in the Technical Reference Manual. The longitudinal axis of the member is defined as x and joins the start joint of the member to the end with the same positive direction. EC3, however, defines the principal cross-section axes in reverse to that of STAAD, but the longitudinal axis is defined in the same way. Both of these axes definitions follow the orthogonal right hand rule. See figure below. Users must bear this difference in mind when examining the code-check output from STAAD.

Section 5B

5-11

STAAD EC3

Figure 1 Axes Convention in STAAD and EC3. National Application Documents

Various authorities of the CEN member countries have prepared National Application Documents to be used with EC3. These documents provide alternative factors for loads and may also provide supplements to the rules in EC3. The current version of EC3 implemented in STAAD adheres to the factors and rules provided in EC3 and has not been modified by any National Application Documents. Section Classification

The occurrence of local buckling of the compression elements of a cross-section prevents the development of full section capacity. It is therefore imperative to establish this possibility prior to determining the section capacities. Cross sections are classified in accordance with their geometrical properties and the stress pattern on the compression elements. For each load case considered in the design process, STAAD determines the section class and calculates the capacities accordingly. Material Properties and Load Factors

Design resistances are obtained by dividing the characteristic yield strength, as given in table 3.1, by the material partial safety factor gm. The magnitude of gm in STAAD is 1.1 which is applicable to all section types.


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Material coefficients in STAAD take the following default values unless replaced by user’s numerical values provided in the input file. Modulus of Elasticity E = 205 N/mm2 Shear Modulus G = E / 2 (1+v) Poisson’s Ratio v = 0.3 Unit weight r = 76.8 KN/m3 The magnitude of design loads is dependent on gf, the partial safety factor for the action under consideration. In STAAD, the user is allowed total control in providing applicable values for the factors and their use in various load combinations. Axially Loaded Members

For members subject to tension loads only, tension capacity is calculated based on yield strength, material factor gm and cross-sectional area of the member with possible reduction due to bolt holes. When bolt holes need to be considered in the capacity calculations, the value used for gm is 1.2 and the yield strength is replaced with the ultimate tensile strength of the material. The tension capacity is then taken as the smaller of the full section capacity and the reduced one. For members subject to compression only, cross-section resistance as well as buckling resistance must be checked. The latter is often more critical as it is influenced by a number of factors including the section type and member unbraced length. Beams

The main requirement for a beam is to have sufficient cross-section resistance to the applied bending moment and shear force. Also the possibility of lateral-torsional buckling must be taken into consideration when the full length of the member is not laterally restrained. The bending capacity is primarily a function of the section type and the material yield strength. There are four classes of cross-

Section 5B

5-13

sections defined in EC3. Class 1 and 2 sections can both attain full plastic capacity with the exception that the class 2 sections cannot sustain sufficient rotation required for plastic analysis of the model. Class 3 sections, due to local buckling, cannot develop plastic moment capacity and the yield stress is limited to the extreme compression fiber of the section. The elastic section modulus is used to determine the moment capacity. Class 4 sections do suffer from local buckling and explicit allowance must be made for the reduction in section properties before the moment capacity can be determined. Further, because of interaction between shear force and bending moment, the moment resistance of the cross-section may be reduced. This, however, does not occur unless the value of applied shear forces exceeds 50% of the plastic shear capacity of the section. In such cases the web is assumed to resist the applied shear force as well as contributing towards the moment resistance of the cross-section. The plastic shear capacity is calculated using the appropriate shear

area for the section and the yield strength in shear, taken as 3

f y .

As mentioned earlier, lateral-torsional buckling must also be considered whenever the full length of the member is not laterally restrained. The buckling capacity is dependent on the section type as well as the unrestrained length, restraint conditions and type of applied loading. Axially Loaded Members With Moments

The bending resistance of members subject to coexistent axial load is reduced by the presence of the axial load. The presence of large shear, as mentioned above, can also reduce the bending resistance of the section under consideration. If the shear load is large enough to cause a reduction in bending resistance, then the reduction due to shear has to be taken into


5-14

account before calculating the effect of the axial load on the bending resistance of the section. Generally, EC3 requires to check cross-section resistance for local capacity and also check the overall buckling capacity of the member. In the case of members subject to axial tension and bending, there is provision to take the stabilizing effect of the tension load into consideration. This is achieved by modifying the extreme compression fiber stress and calculating an effective applied moment for the section. This is then checked against the lateral-torsional buckling resistance of the section.


Introduction Design parameters communicate specific design decisions to the program. They are set to default values to begin with and may be altered to suite the particular structure. Depending on the model being designed, the user may have to change some or all of the parameter default values. Some parameters are unit dependent and when altered, the new setting must be compatible with the active “unit” specification. Table 5B.1 lists all the relevant EC3 parameters together with description and default values.

Section 5B

5-15

Parameter Definition Table

Table 5B.1 – Steel Design Parameters EC3

Parameter Default Definition Name Value

KY 1.0 K factor in local y axis.

KZ 1.0 K factor in local z axis.

LY Member Length Compression length in local y axis, Slenderness ratio = (KY)*(LY)/(Ryy)

LZ Member Length Compression length in local z axis, Slenderness ratio = (KZ)*(LZ)/(Rzz)

UNL Member Length Unrestraint length of member used in calculating the lateral-torsional resistance moment of the member.

PY Yield Strength The yield strength default value is set based on the default value of the “SGR” parameter.

NSF 1.0 Net tension factor for tension capacity calculation.

SGR 0.0 Steel grade as per table 3.1 in EC3. 0.0 = Fe 360 1.0 = Fe 430 2.0 = Fe 510

SBLT 0.0 Indicates if the section is rolled or built-up. 0.0 = Rolled 1.0 = Built-up.

CMM 1.0 Indicates type of loading on member. Can take a value from 1 to 6. Refer to Table 5B.2 for more information on its use.

CMN 1.0 Indicates the level of End-Restraint. 1.0 = No fixity 0.5 = Full fixity

0.7 = One end free and other end fixed

DMAX 100.0 cm Maximum allowable depth for the member.

DMIN 0 Minimum required depth for the member.

RATIO 1 Permissible ratio of loading to capacity.

BEAM 0 Indicates the number of sections to be checked for during the design.

= Check the end sections only or the locations specified by the SECTION command.


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Table 5B.1 – Steel Design Parameters EC3

Parameter Default Definition Name Value

= Consider 13 sections along the member and select the maximum Mz location for the design check.

= Same as BEAM = 1.0 but checks the end sections of the member as well.

= Consider 13 sections along the member and design check every section.

CODE Undefined User must specify EC3.

TRACK 0 Controls the level of descriptivity of output. 0 = Minimum 1 = Intermediate 2 = Maximum 4 = option 4 for performing a deflection check

UNF 1.0 Unsupported buckling length as a factor of the beam length

LEG 0.0 Connection type

LVV Maximum of Lyy and Lzz

(Lyy is a term used by BS5950)

Buckling length for angle about its principle axis

FU Ultimate tensile strength of steel


deflection check)

Deflection limit


Joint No. denoting starting point for calculation of "Deflection Length"


Joint No. denoting end point for calculation of "Deflection Length"

Section 5B

5-17

Notes: 1. LEG - Table 25 BS5950 for Fastener Control

The slenderness of single and double angle, channel and tee sections are specified in BS 5950 table 25 depending on the connection provided at the end of the member. To define the appropriate connection, a LEG parameter should be assigned to the member. The following table indicates the value of the LEG parameter required to match the BS5950 connection definition:- Clause LEG

short leg 1.0 (a) - 2 bolts long leg 3.0 short leg 0.0

4.7.10.2 Single Angle (b) - 1 bolt

long leg 2.0

short leg 3.0 (a) - 2 bolts long leg 7.0 short leg 2.0 (b) - 1 bolt long leg 6.0 long leg 1.0 (c) - 2 bolts short leg 5.0 long leg 0.0

4.7.10.3 Double Angle

(d) - 1 bolt short leg 4.0

(a) - 2 or more rows of bolts 1.0 4.7.10.4

Channels (b) - 1 row of bolts 0.0

(a) - 2 or more rows of bolts 1.0 4.7.10.5 Tee Sections (b) - 1 row of bolts 0.0


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For single angles, the slenderness is calculated for the geometric axes, a-a and b-b as well as the weak v-v axis. The effective lengths of the geometric axes are defined as:- La = KY * KY Lb = KZ * LZ The slenderness calculated for the v-v axis is then used to calculate the compression strength pc for the weaker principal axis (z-z for ST angles or y-y for RA specified angles). The maximum slenderness of the a-a and b-b axes is used to calculate the compression strength pc for the stronger principal axis. Alternatively for single angles where the connection is not known or Table 25 is not appropriate, by setting the LEG parameter to 10, slenderness is calculated for the two principal axes y-y and z-z only. The LVV parameter is not used. For double angles, the LVV parameter is available to comply with note 5 in table 25. In addition, if using double angles from user tables, (Technical Reference Manual section 5.19) an eleventh value, rvv, should be supplied at the end of the ten existing values corresponding to the radius of gyration of the single angle making up the pair.

2. BEAM Ensure that the “BEAM” parameter is set to either 1 or 2 while performing code checking for members susceptible to Lateral - Torsional Buckling.

Section 5B

5-19

Table 5B.2


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5B.3 Worked Examples

Example 1: Restrained simply supported beam.

The figure below shows a simply supported beam spanning 7 meters and assumed to be fully restrained laterally. Fe 430 steel is assumed and the beam will be checked to the clauses of EC3 currently implemented in STAAD.

Unfactored Loading Permanent Load: UDL including selfweight assume 20 KN/m Variable Load: UDL load assume 25 KN/m Partial safety factor for permanent load (ULS) 1.35 Partial safety factor for variable load (ULS) 1.5 Factored Load: 1.35 X 15 + 1.5 X 25 = 64.5 KN/m 64.5 KN/m

Section 5B

5-21

Try 457 X 191 X 82UB. h = 460.2 mm d = 407.9mm tw = 9.9 mm b = 191.3 mm tf = 16.0 mm A = 104.5cm2

ly = 37103 cm4 Wpl.y = 1833 cm3 Av

= 48.13 cm2

Grade Fe 430 Fy = 275 N/mm2 Section Classification Outstand Flanges in Compression, limit for rolled section c/t = 10e = 9.2 c/t ratio for the selected section is 95.65/16 = 5.9 < 9.2 Flange is therefore a class 1 element. Web with N.A. at mid depth, limit for rolled section d/tw = 72e = 66.6 d/ tw ratio for the selected section is 407.9/9.9 = 41.2 < 66.6 Web is therefore a class 1 element.

Shear Resistance Maximum design shear force (64.5 X 7) / 2 = 225.7 KN Plastic shear resistance Vpl.Rd = (Av / gM0) (fy / 3 ) = (4813 / 1.1) (275 / 1.732) / 1000 = 694.7 KN Maximum design shear force = 225.7 KN < 694.7 KN Therefore shear resistance is satisfactory.

Section is class 1


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Moment Resistance Maximum design moment at mid-span of beam (wl2 / 8) = 395 Knm Maximum resistance of section Mc.Rd = ( Wpl.yfy) / gM0 = (1833 X 103 X 275) / (1.1 X 106) = 458.2KNm

Lateral Torsional Buckling As it is assumed that the full length of member is restrained laterally there is no need to check for Lateral Torsional Buckling of the member.

Maximum design moment = 395 KNm < 458.2 KNm Therefore moment resistance is satisfactory.

457 X 191 X 82 UB In Fe 430 Steel is satisfactory.

Section 5B

5-23

Example 2: Unrestrained simply supported beam. Figure 2 shows a simply supported beam spanning 5 meters and assumed to be laterally unrestrained. Fe 430 steel is assumed and the beam will be checked to the clauses of EC3 currently implemented in STAAD.

5m Unfactored Loading Permanent Load: UDL including selfweight assume 15 KN/m Variable Load: UDL load assume 20 KN/m Partial safety factor for permanent load (ULS) 1.35 Partial safety factor for variable load (ULS) 1.5 Factored Load: 1.35 X 15 + 1.5 X 20 = 50.3 KN/m 50.3 KN/m

5m


5-24

Try 457 X 191 X 82 UB. h = 460.2 mm d = 407.9 mm tw = 9.9 mm b = 191.3 mm tf = 16.0 mm A = 104.5 cm2 ly = 37103cm4 Wpl.y = 1833cm3 Av = 48.13cm2 Grade Fe 430fy = 275 N/mm2

Section Classification Outstand Flanges in compression, limit for rolled section c/t = 10e = 9.2 c/t ratio for the selected section is 95.65/16 = 5.9 < 9.2 Flange is therefore a class 1 element. Web with N.A. at mid depth, limit for rolled section d/tw = 72e = 66.6 d/ tw ratio for the selected section is 407.9/9.9 = 41.2 < 66.6 Web is therefore a class 1 element.

Shear Resistance Maximum design shear force (50.3 X 5) / 2 = 120.8 KN Plastic shear resistance Vpl.Rd = (Av / gM0) (fy / 3 ) = (4813 / 1.1) (275 / 1.732) / 1000 = 694.7 KN Maximum design shear force = 120.8 KN < 694.7 KN Therefore shear resistance is satisfactory.

Section is class 1

Section 5B

5-25

Moment Resistance Maximum design moment at mid-span of beam (wl2 / 8) = 157.2 KNm Maximum resistance of section Mc.Rd = ( Wpl.yfy) / gM0 = (1833 X 103 X 275) / (1.1 X 106) = 458.2KNm

Lateral Torsional Buckling Buckling resistance moment Mb.Rd = XLTbwWPl.yfy / gM1 bw = 1 for Class 1 or Class 2 sections.

XLT = 0.5LT

2LT

2LT ]l[ff

1−+

fLT = 0.5 [1 + aLT( lLT – 0.2 ) + l2

LT ] aLT = 0.21 for rolled sections. lLT = [ lLT / l1 ] [bw]0.5

l1 = 93.9e lLT is the geometrical slenderness ratio for lateral-torsional buckling.

lLT = /25.66])(L/a[1)(C

L/i2

LT0.5

1

LT

+

aLT = ( Iw / lt ) 0.5

Maximum design moment = 157.2 KNm < 458.2 KNm Therefore moment resistance is satisfactory.


5-26

lw = lzhs2 / 4

hs = h - tf

iLT = [lzIw / Wpl.y2]0.25

C1 is a factor depending on transverse loading type. For the selected section: hs = 460.2 – 16.0 = 444.2 mm lw = 1871 X 44.422 / 4 = 922934.6 cm6 iLT = [1871 X 922934.6 / (18332) ]0.25 = 4.76 cm aLT = ( 922934.6 / 69.2 ) 0.5 = 115.4 cm C1 = 1.132 (From EC3 Table F.1.2)

lLT = 0.2520.5 /25.66])(500/115.4[11.132500/4.76

+ = 86.06

l1 = 93.9 (235 / 275)0.5 86.8 lLT = 86.06 / 86.8 0.99 fLT = 0.5 [1 + 0.21 (0.99 – 0.2) + 0.992] 1.07 XLT = 1 / { 1.07 + [ 1.072 – 0.992 ] 0.5} 0.67 Mb.Rd = 0.67 X 1 X 1833 X 103 X 275 / 1.1 X 106

Mb.Rd = 307.0 KNm

Maximum design moment = 157.2 KNm < 307.0 KNm Therefore buckling resistance moment is satisfactory.

Section 5B

5-27

Example 3: Axially Loaded Column. Figure 3 shows a pinned end column 5m long subject to a factored load of 3500 kN. Fe 430 steel is assumed and the column will be checked to the clauses of EC3 currently implemented in STAAD. 3500 KN 5m 3500 KN Try 305 X 305 X 158 UC h = 327.2 mm d = 246.6 mm tw = 15.7 mm b = 310.6 mm tf = 25.0 mm A = 210.2 cm2

iy = 13.9 cm iz = 7.89 cm fy = 275 N/ mm2 Section Classification Outstand flanges in compression, limit for rolled section c/t = 10e = 9.2 c/t ratio for the selected section is 155.3/25 = 6.21 < 9.2 Flange is therefore a class 1 element.


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Web with N.A. at mid depth, limit for rolled section d/tw = 33e = 30.5 d/ tw ratio for the selected section is 246.6/15.7 = 15.7 < 30.5 Web is therefore a class 1 element.

Compressive resistance Design compression resistance of the cross-section, Nc.Rd = ( Afy) / gM0 Nc.Rd = ( 210.2 X 102 X 275 ) / ( 1.1 X 103 ) Nc.Rd = 5255 KN

Buckling resistance The design buckling resistance of the member Nb.Rd = XbAAfy / gM0 bA = 1 for class 1, 2 or 3 cross-sections. X is a reduction factor for the relevant buckling mode.

X = 5.0

2_2 ]lf[f

1

−+

f = 0.5 [ 1 + a (_l – 0.2) +

2_l ]

a is an imperfection factor. _l = [ l / l1 ] [ bA ]0.5

l is the slenderness for the relevant buckling mode.

Section is class 1

Applied design load NSd = 3500 KN < 5255 Therefore compression resistance is satisfactory.

Section 5B

5-29

l1 = 93.9 e From table 5.5.3 for buckling about y-y-axis, a is 0.34. From table 5.5.3 for buckling about z-z axis, a is 0.49. ly = 500 / 13.9 ly = 35.97 lz = 500 / 7.89 lz = 63.37 Consider buckling about the y-y axis. _l y = [ ly / l1] [bA]0.5

l1 = 93.9 X 0.924 = 86.8 _l y = [35.9 / 86.8 ] = 0.41

fy = 0.5 [1 + ay (_l y – 0.2) + l2

y] fy = 0.5 [1 + 0.34 (0.41 – 0.2) + 0.412] fy = 0.62

Xy = 0.5

y

2_y

2y ]l[ff

1

−+

= 0.522 ]0.41[0.620.621

−+

Xy = 0.92 but cannot be greater than 1, therefore Xy = 0.92. Nb.Rdy = XyAfy / gM0 = (0.92 X 275 X 201.2 X 102) / (1.1 X 103)

= 4627KN


5-30

Consider buckling about the z-z axis. _l z = [ lz / l1] [bA]0.5

l1 = 93.9 X 0.924 = 86.8 _l z = [63.37 / 86.8 ] = 0.73

fz = 0.5 [1 + az (_l z – 0.2) +

2_l z]

fz = 0.5 [1 + 0.49 (0.73 – 0.2) + 0.732] fz = 0.89

Xz = 5.0

z

2_z

2z ]lf[f

1

−+

= 0.522 ]0.73[0.890.891

−+

Xz = 0.71 but cannot be greater than 1, therefore Xz = 0.71. Nb.Rdz = XzAfz / gM0 = (0.71 X 275 X 201.2 X 102) / (1.1 X 103)

= 3571KN

3400 KN design load is less than 3571 KN, therefore section is satisfactory.

Section 5B

5-31

Example 4: Column subject to axial load and bending The figure below shows a pinned end column 5m long subject to a factored load of 1500 KN and factored bending moment of 250 KNm about the major axis. Fe 430 steel is assumed and the column will be checked to the clauses of EC3 currently implemented in STAAD.

Try 305 X 305 X 137 UC h = 320.5 mm d = 246.6 mm tw = 13.8 mm b = 308.7mm tf = 21.7 mm A = 174.6cm2

Wpl.y = 2298cm3 Wel.y= 2049 cm3 Av = 50.6 cm2

iy = 13.7 cm iz = 7.82 cm fy = 275 N/mm2


5-32

Section classification

Shear Resistance Maximum design shear force 250 / 5 = 50 KN Plastic shear resistance Vpl.Rd = ( Av / gM0 ) ( fy / 3 ) = (5060 / 1.1) (275 / 1.732) / 1000 = 730 KN

Moment Resistance Design bending moment must not exceed the reduced plastic resistance moment of the section given by the following equations. MNy.Rd = Mpl.y.Rd ( 1 – n ) / ( 1 – 0.5 a ) a = ( A – 2btf ) / A but ‘a’ must not exceed 0.5. n = Nsd / Npl.Rd

If ‘n’ does not exceed ‘a’ then MNy.Rd = Mpl.y.Rd a = ( 17460 – 2 X 308.7 X 21.7 ) / 17460 a = 0.232 Npl.Rd = ( 275 X 17460 ) ( 1.1 X 1000 ) = 4365 KN n = 1500 / 4365 = 0.343

Section by inspection is class 1.

Design shear force is less than 730 KN. Shear resistance is satisfactory.

Section 5B

5-33

Mpl.y.Rd = ( 275 X 2298 ) / ( 1.1 X 1000 ) = 574.5 KN MNy.Rd = 574.5 ( 1 – 0.343 ) / ( 1 – 0.5 X 0.232 ) MNy.Rd = 426.97 KNm

Flexural Buckling and Bending Check Members subject to axial load and bending must satisfy:

/gM1AfXN

ymin

sd + /gM1fW

MK

ypl.y

y.sdy ≤ 1

Ky = 1 - yy

sdy

AfXNm

but Ky ≤ 1.5

my = _l y (2bMy – 4) +

el.y

el.ypl.y

WWW −

but my ≤ 0.90

Xmin is the lesser of Xy and Xz, where Xy and Xz are reduction factors as calculated in the previous example. bMy is equivalent moment factor for flexural buckling. From Figure 5.5.3 in EC3, bMy = 1.8 – 0.7 y but in this example, y = 0.0 bMy = 1.8

The design bending moment is less than the reduced moment capacity. The section therefore has sufficient moment resistance.


5-34

Consider buckling about the y-y axis. _l y = [ ly / l1] [bA]0.5 bA = 1.0 for class 1 sections.

l1 = 93.9 X 0.924 = 86.8 ly = [500 / 13.7 ] = 36.5 _l y = [36.5 / 86.8 ] = 0.42

fy = 0.5 [1 + ay (_l y – 0.2) + l2

y] fy = 0.5 [1 + 0.34 (0.42 – 0.2) + 0.422] fy = 0.62

Xy = 0.5y

2y

2y ]l[ff

1−+

= 0.522 ]0.42[0.620.621

−+

Xy = 0.93 but ≤ 1, therefore Xy = 0.93. Consider buckling about the z-z axis. _l z = [ lz / l1] [bA]0.5 bA = 1.0 for class 1 sections.

l1 = 93.9 X 0.924 = 86.8 lz = [500 / 7.82 ] = 63.9 _l z = [63.9 / 86.8] = 0.73

fz = 0.5 [1 + az (_l z – 0.2) +

_l 2

z] fz = 0.5 [1 + 0.49 (0.73 – 0.2) + 0.732] fz = 0.89

Section 5B

5-35

Xz = 0.5

z

2_z

2z ]l[ff

1

−+

= 0.522 ]0.73[0.890.891

−+

Xz = 0.71 but ≤ 1, therefore Xz = 0.71. Xmin is therefore 0.71. _l y = 0.42

my = 0.42 (2 X 1.8 – 4) + 2049

20492298 − = - 0.046

Ky = 1 - X2750.93X17.46

0.046X1500− = 1.015 ≤ 1.5

/gM1AfXN

ymin

sd + /gM1fW

MK

ypl.y

y.sdy ≤ 1

X275/1.10.71X17.461500 +

1.12.298X275/1.015X250 = 0.92 ≤ 1

Members for which lateral-torsional buckling is a potential problem must also satisfy:

/gM1AfXN

yz

sd + /gM1fWX

MK

ypl.yLT

y.sdLT ≤ 1

KLT = 1 - yz

sdLT

AfXNm

but KLT ≤ 1

mLT = 0.15 lzbM.LT – 0.15, but mLT ≤ 0.90 Using the equations used in Example 2, we have the following.


5-36

For the selected selection: iLT = 8.33 cm aLT = 97.6 cm C1 = 1.879 (From EC3 Table F.1.2)

lLT = 0.2520.5 /25.66](500/97.6)[11.879500/8.33

+ = 36.71

l1 = 93.9 (235 / 275)0.5 = 86.8 lLT = 36.71 / 86.8 = 0.42 fLT = 0.5 [ 1 + 0.21 (0.42 – 0.2) + 0.422 ] = 0.61 XLT = 1 / { 0.61 + [ 0.612 – 0.422 ]0.5 } = 0.95 bMLT = 1.8 lz = 0.73 mLT = 0.15 X 0.73 X 1.8 – 0.15 = 0.047

KLT = 1 - X2750.71X17.46

0.047X1500 = 0.98

/gM1AfXN

yz

sd + /gM1fWX

MK

ypl.yLT

y.sdLT ≤ 1

X275/1.10.71X17.461500 +

X275/1.10.95X2.2980.98X250 = 0.932

305X305X137UC is therefore satisfactory.

Section 5B

5-37

5B.4 User’s Examples Example 1. The following input file is for the single beam in example 1. Only code check related output is enclosed. STAAD PLANE INPUT FILE FOR EX.1 IN THE EC3 MANUAL. INPUT WIDTH 79 UNIT METER KNS JOINT COORDINATES

1 0.000 0.000 0.000 2 5.000 0.000 0.000 MEMBER INCIDENCES 1 1 2 MEMBER PROPERTY BRITISH 1 TABLE ST UB457X191X82 CONSTANTS E STEEL ALL SUPPORTS 1 PINNED 2 FIXED BUT FX MZ LOAD 1 MEMBER LOAD 1 UNI GY-20.0 LOAD 2 MEMBER LOAD 1 UNI GY -25.0 LOAD COMBINATION 3 1 1.35 2 1.5 PERFORM ANALYSIS LOAD LIST 3 PARAMETER CODE EC3 UNL 0.0 ALL BEAM 2.0 ALL TRACK 2 .ALL SGR 1 .ALL CHECK CODE ALL FINISH


5-38

Section 5B

5-39

Example 2. The following input file is for the beam in example 2. Only code check related output is enclosed. STAAD PLANE INPUT FILE FOR EXAMPLE 2 INPUT WIDTH 79 UNIT METER KNS JOINT COORDINATES

1 0.000 0.000 0.000 2 5.000 0.000 0.000 MEMBER INCIDENCES 1 1 2 MEMBER PROPERTY BRITISH 1 TABLE ST UB457X191X82 CONSTANTS E STEEL ALL SUPPORTS 1 PINNED 2 FIXED BUT FX MZ LOAD 1 MEMBER LOAD 1 UNI GY -15.0 LOAD 2 MEMBER LOAD 1 UNI GY -20.0 LOAD COMBINATION 3 1 1.35 2 1.5 PERFORM ANALYSIS LOAD LIST 3 PARAMETER CODE EC3 BEAM 2.0 ALL TRACK 2. ALL SGR 1. ALL CHECK CODE ALL FINISH


5-40

Section 5B

5-41

Example 3. The following input file is for the simple column in example 3. Only code check related output is enclosed. STAAD PLANE INPUT FILE FOR EXAMPLE 3. UNIT METER KNS JOINT COORDINATES 1 0 0 0 2 0 5 0 MEMBER INCIDENCES 1 1 2 MEMBER PROPERTIES BRITISH 1 TA ST UC305X305X158 CONSTANTS E STEEL ALL SUPPORT 1 FIXED LOAD 1 JOINT LOAD 2 FY -3500 PERFORM ANALYSIS PARAMETERS CODE EC3 TRACK 2.0 ALL SGR 1. ALL CHECK CODE ALL FINISH


5-42

Section 5B

5-43

Example 4. The following input file is for the column in example 4. Only code check related output is enclosed. STAAD PLANE INPUT FILE FOR EXAMPLE 4. UNIT METER KNS JOINT COORDINATES 1 0 0 0 2 0 5 0 MEMBER INCIDENCES 1 1 2 MEMBER PROPERTIES BRITISH 1 TA ST UC305X305X137 CONSTANTS E STEEL ALL SUPPORT 1 PINNED 2 FIXED BUT FY MZ LOAD 1 JOINT LOAD 2 FY -1500 2 MZ 250 PERFORM ANALYSIS PARAMETERS CODE EC3 BEAM 2.0 ALL TRACK 2.0 ALL CMM 6 SGR 1.0 ALL CHECK CODE ALL FINISH


5-44

Section 6 French Codes

A’lkjdfl’akjsfd

6-1

Concrete Design Per B.A.E.L.


STAAD has the capabilities for performing design of concrete beams, columns and slabs according to B.A.E.L. - 1983. Given the width and depth (or diameter for circular columns) of a section, STAAD will calculate the required reinforcing to resist the various input loads.


The program contains a number of parameters which are needed to perform design per B.A.E.L. These parameters not only act as a method to input required data for code calculations but give the engineer control over the actual design process. Default values, of commonly used numbers in conventional design practice, have been used for simplicity. Table 5A.1 contains a complete list of available parameters and their default values.


STAAD provides the user two methods of accounting for the slenderness effect in the analysis and design of concrete members. The first method is a procedure which takes into account second order effects. Here, STAAD accounts for the secondary moments, due to axial loads and deflections, when the PDELTA ANALYSIS command is used. STAAD, after solving for the joint displacements of the structure, calculates the additional moments induced in the structure. Therefore, by using PDELTA

Section 6A


Section 6A

6-2 ANALYSIS, member forces are calculated which will require no user modification before beginning member design. The second method by which STAAD allows the user to account for the slenderness effect is through user supplied moment magnification factors. Here the user approximates the additional moment by supplying a factor by which moments will be multiplied before beginning member design.



UNIT MM MEMBER PROPERTIES 1 3 to 7 9 PRISM YD 450 ZD 300. 11 13 PR YD 300.

In the above input, the first set of members are rectangular (450 mm depth and 300 mm width) and the second set of members, with only depth and no width provided, will be assumed to be circular with a 300 mm diameter. Note that area (AX) is not provided for these members. If shear areas (AY & AZ) are to be considered in analysis, the user may provide them along with YD and ZD. Also note that moments of inertia may be provided, but if not provided, the program will calculate values from YD and ZD.

Section 6A

6-3

6A.5 Beam Design

Beam design includes both flexure and shear. For both types of beam action, all active beam loadings are scanned to create moment and shear envelopes, and locate critical sections. The total number of sections considered is twelve, unless that number is redefined with the NSECTION parameter. From the critical moment values, the required positive and negative bar pattern is developed, with cut-off lengths calculated to include required development length. Shear design includes critical shear values plus torsional moments. From these values, stirrup sizes are calculated with proper spacing. The stirrups are assumed to be U-shaped for beams with no torsion, and closed hoops for beams subject to torsion.

Table 6A.1 French Concrete Design Parameters


FYMAIN * 300 N/mm2 Yield Stress for main reinforcing steel.

FYSEC * 300 N/mm2 Yield Stress for secondary reinforcing steel.

FC * 30 N/mm2 Concrete Yield Stress.

CLEAR * 20 mm Clearance of reinforcing bar. Value is automatically set to 20 mm for C35 and higher.

MINMAIN 8 mm Minimum main reinforcement bar size. (8mm - 60mm).

MINSEC 8 mm Minimum secondary reinforcement bar size. (8mm - 60mm).

MAXMAIN 50 mm Maximum main reinforcement bar size. (8mm - 60mm).

SFACE *0.0 Face of support location at start of beam. (Only considers shear - use MEMBER OFFSET for bending).


Section 6A

6-4

Table 6A.1 French Concrete Design Parameters


EFACE *0.0 Face of Support Location at end of beam. (Note: Both SFACE and EFACE are input as positive numbers.).

TRACK 0.0 Critical Moment will not be printed out with beam design report. A value of 1.0 will mean a print out.

MMAG 1.0 A factor by which the design moments will be magnified.


WIDTH ZD Width of the concrete member. This value defaults to ZD as provided under MEMBER PROPERTIES.

DEPTH YD Depth of concrete member. This value defaults to YD as provided under MEMBER PROPERTIES.

* These values must be provided in the units the user is currently using for input.

Example of Input Data for Beam Design UNIT NEWTON MMS START CONCRETE DESIGN CODE FRENCH FYMAIN 415 ALL FYSEC 415 ALL FC 35 ALL CLEAR 25 MEM 2 TO 6 MAXMAIN 40 MEMB 2 TO 6 SFACE 100 MEMB 7 TO 9 EFACE 100 MEMB 7 TO 9 TRACK 1.0 MEMB 2 TO 6 TRACK 2.0 MEMB 7 TO 9 DESIGN BEAM 2 TO 9 END CONCRETE DESIGN

Section 6A

6-5

6A.6 Column Design

Columns are designed for axial force and biaxial moments at the ends. All active loadings are tested to calculate reinforcement. The loading which produces maximum reinforcement is called the critical load. Column design is done for square, rectangular and circular sections. For rectangular and square sections, the reinforcement is always assumed to be equally distributed on each side. That means the total number of bars will always be a multiple of four (4). This may cause slightly conservative results in some cases.

Example of Input Data for Column Design UNIT NEWTON MMS START CONCRETE DESIGN CODE FRENCH FYMAIN 415 ALL FC 35 ALL CLEAR 25 MEMB 2 TO 6 MMAG 1.5 MEMB 4 5 MAXMAIN 40 MEMB 2 TO 6 DESIGN COLUMN 2 TO 6 END CONCRETE DESIGN


Slab and walls are designed per BAEL 1983 specifications. To design a slab or wall, it must be modeled using finite elements. The command specifications are in accordance with Chapter II, section 6.40. Elements are designed for the moments Mx and My. These moments are obtained from the element force output (see Chapter 2 of the Technical Reference Manual). The reinforcement required


Section 6A

6-6 to resist Mx moment is denoted as longitudinal reinforcement and the reinforcement required to resist My moment is denoted as transverse reinforcement. The parameters FYMAIN, FC, and CLEAR listed in Table 5A.1 are relevant to slab design. Other parameters mentioned in Table 5A.1 are not applicable to slab design.

LONG.

TRANS.

X

Y

Z

M

MM

M x

y

x

y

Example of Input Data for Slab/Wall Design UNIT NEWTON MMS START CONCRETE DESIGN CODE FRENCH FYMAIN 415 ALL FC 25 ALL CLEAR 40 ALL DESIGN ELEMENT 15 TO 20 END CONCRETE DESIGN

6-7

Steel Design Per the French Code


STAAD implementation of French Steel Design is based on Centre Technique Industriel de la Construction Metallique publication entitled "Design Rules for Structural Steelwork." The design philosophy embodied in this specification is based on the concept of limit state design. Structures are designed and proportioned according to the limit states of which they would become unfit for their intended use. Two major categories of limit-states are recognized: ultimate and serviceability. The primary considerations in ultimate limit state design are strength and stability; that in serviceability is deflection. Appropriate load and resistance factors are used so that uniform reliability is achieved for all steel structures under various loading conditions and at the same time the chances of limits being surpassed are acceptably remote. In the STAAD implementation, members are proportioned to resist the design loads without exceeding the limit states of strength, stability and serviceability. Accordingly, the most economic section is selected on the basis of the least weight criteria, as augmented by the designer in specification of allowable member depths, desired section type, or other related parameters. The code checking portion of the program verifies that code requirements for each selected section are met and also identifies the governing criteria.

Section 6B

Steel Design per the French Code

Section 6B

6-8 The following sections describe the salient features of STAAD implementation of "Design Rules for Structural Steelwork." A detailed description of the design process, along with its underlying concepts and assumptions, is available in the specification document.

6B.2 Basis of Methodology

The "Design Rules for Structural Steelwork (Revision 80)" permits the usage of elastic analysis. Thus, in STAAD, linear elastic analysis method is used to obtain the forces and moments in the members. However, strength and stability considerations are based on the principles of plastic behaviour. Axial compression buckling and lateral torsional buckling are taken into consideration for calculation of axial compression resistance and flexural resistance of members. Slenderness calculations are made and overall geometric stability is checked for all members.


The member strengths are calculated in STAAD according to the procedures outlined in section 4 of this specification. Note that the program automatically considers co-existence of axial force, shear and bending in calculating section capacities. For axial tension capacity, procedures of section 4.2 are followed. For axial compression capacity, formulas of section 5.3 are used. Moment capacities about both axes are calculated using the procedures of sections 4.5 and 4.6. Lateral torsional buckling is considered in calculating ultimate twisting moment per section 5.22 of the specification. The parameter UNL (see Table 6B.1) must be used to specify the unsupported length of the compression flange for a laterally unsupported member. Note that this length is also referred to as twisting length.

Section 6B

6-9

6B.4 Combined Axial Force and Bending

The procedures of sections 4.55 and 5.32 are implemented for interaction of axial forces and bending. Appropriate interaction equations are used and the governing criteria is determined.


The design parameters outlined in Table 6B.1 may be used to control the design procedure. These parameters communicate design decisions from the engineer to the program, thus allowing the engineer to control the design process to suit an application's specific needs. The default parameter values have been selected as frequently used numbers for conventional design. Depending on the particular design requirements, some or all of these parameter values may be changed to exactly model the physical structure.

6B.6 Code Checking and Member Selection

Both code checking and member selection options are available in STAAD implementation of CM 66 (Revn. 80). For general information on these options, refer to Chapter II, sections 3.4 and 3.5. For information on specification of these commands, refer to Chapter II, and section 6.46.


Results of code checking and member selection are presented in the output file in a tabular format. Please note the following: COND CRITIQUE refers to the section of the CM 66 (Revn. 80) specification which governed the design.


Section 6B

6-10 If the TRACK parameter is set to 1.0, calculated member capacities will be printed. The following is a detailed description of printed items: PC = Member Compression Capacity TR = Member Tension Capacity MUZ = Member Moment Capacity (about z-axis) MUY = Member Moment Capacity (about y-axis) VPZ = Member Shear Capacity (z-axis) VPY = Member Shear Capacity (y-axis)

Table 6B.1 French Steel Design Parameters


KY 1.0 K value for axial compression buckling about local Y-axis. Usually, this is the minor axis.

KZ 1.0 K value for axial compression buckling about local Z-axis. Usually, this is the major axis.

LY Member Length Length to calculate slenderness ratio about Y-axis for axial compression.

LZ Member Length Length to calculate slenderness ratio about Z-axis for axial compression.



UNL Member Length Unsupported length of compression flange for calculating moment resistance.

UNF 1.0 Same as above provided as a fraction of member length.

TRACK 0.0 0.0 = Suppress printing of all design strengths. 1.0 = Print all design strengths.

DMAX 100.0 cm. Maximum allowable depth (used in member selection).

DMIN 0.0 cm. Minimum allowable depth (used in member selection).

RATIO 1.0 Permissible ratio of actual load effect and design strength.

Section 6B

6-11

Table 6B.1 French Steel Design Parameters


BEAM 0.0 0.0 = design only for end moments and those at locations specified by SECTION command. 1.0 = calculate moments at tenth points along the beam, and use maximum Mz for design.

STAAD contains a broad set of facilities for designing structural members as individual components of an analyzed structure. The member design facilities provide the user with the ability to carry out a number of different design operations. These facilities may be used selectively in accordance with the requirements of the design problem. The operations to perform a design are: • Specify the members and the load cases to be considered in the

design. • Specify whether to perform code checking or member

selection. • Specify design parameter values, if different from the default

values. These operations may be repeated by the user any number of times depending upon the design requirements. Currently STAAD supports steel design of wide flange, S, M, HP shapes, angle, double angle, channel, double channel, beams with cover plate, composite beams and code checking of prismatic properties.


Section 6B

6-12

Sample Input data for Steel Design UNIT METER PARAMETER CODE FRENCH NSF 0.85 ALL UNL 10.0 MEMBER 7 KY 1.2 MEMBER 3 4 RATIO 0.9 ALL TRACK 1.0 ALL CHECK CODE ALL

6B.8 Built-in French Steel Section Library

The following information is provided for use when the built-in steel tables are to be referenced for member property specification. These properties are stored in a database file. If called for, the properties are also used for member design. Since the shear areas are built into these tables, shear deformation is always considered for these members. An example of the member property specification in an input file is provided at the end of this section. A complete listing of the sections available in the built-in steel section library may be obtained by using the tools of the graphical user interface. Following are the descriptions of different types of sections.

Section 6B

6-13

IPE Shapes These shapes are designated in the following way.

10 15 TA ST IPE140 20 TO 30 TA ST IPEA120 33 36 TO 46 BY 2 TA ST IPER180

HE shapes HE shapes are specified as follows.

3 5 TA ST HEA120A 7 10 TA ST HEM140 13 14 TA ST HEB100

IPN Shapes The designation for the IPN shapes is similar to that for the IPE shapes.

25 TO 35 TA ST IPN200 23 56 TA ST IPN380

T Shapes Tee sections are not input by their actual designations, but instead by referring to the I beam shapes from which they are cut. For example,

1 5 TA T IPE140 2 8 TA T HEM120


Section 6B

6-14 U Channels Shown below is the syntax for assigning 4 different names of channel sections.

1 TO 5 TA ST UAP100 6 TO 10 TA ST UPN220 11 TO 15 TA ST UPN240A 16 TO 20 TA ST UAP250A

Double U Channels Back to back double channels, with or without a spacing between them, are available. The letter D in front of the section name will specify a double channel.

11 TA D UAP150 17 TA D UAP250A SP 0.5

In the above set of commands, member 11 is a back to back double channel UAP150 with no spacing in between. Member 17 is a double channel UAP250A with a spacing of 0.5 length units between the channels. Angles Two types of specification may be used to describe an angle. The standard angle section is specified as follows:

16 20 TA ST L30X30X2.7

The above section signifies an angle with legs of length 30mm and a leg thickness of 2.7mm. This specification may be used when the local Z axis corresponds to the z-z axis specified in Chapter 2. If the local Y axis corresponds to the z-z axis, type specification "RA" (reverse angle) should be used instead of ST.

17 21 TA RA L25X25X4

Section 6B

6-15

22 24 TA RA L100X100X6.5 Note that if the leg thickness is a round number such as 4.0, only the number 4 appears in the section name, the decimal part is not part of the section name. Double Angles Short leg back to back or long leg back to back double angles can be specified by means of input of the words SD or LD, respectively, in front of the angle size. In case of an equal angle, either SD or LD will serve the purpose.

33 35 TA SD L30X20X4 SP 0.6 37 39 TA LD L80X40X6 43 TO 47 TA LD L80X80X6.5 SP 0.75

Tubes (Rectangular or Square Hollow Sections) Section names of tubes, just like angles, consist of the depth, width and wall thickness as shown below.

64 78 TA ST TUB50252.7 66 73 TA ST TUB2001008.0

Members 64 and 78 are tubes with a depth of 50mm, width of 25mm and a wall thickness of 2.7mm. Members 66 and 73 are tubes with a depth of 200mm, width of 100mm and a wall thickness of 8.0mm. Unlike angles, the ".0" in the thickness is part of the section name. Tubes can also be input by their dimensions instead of by their table designations. For example,



Section 6B

6-16 is a tube that has a depth of 8 length units, width of 6 length units, and a wall thickness of 0.5 length units. Only code checking, no member selection, will be performed for TUBE sections specified in this way. Pipes (Circular Hollow Sections) To designate circular hollow sections, use PIP followed by numerical value of the diameter and thickness of the section in mm omitting the decimal portion of the value provided for the diameter. The following example illustrates the designation.

8 TO 28 TA ST PIP422.6 3 64 78 TA ST PIP21912.5

Members 8 to 28 are pipes 42.4mm in dia, having a wall thickness of 2.6mm. Members 3, 64 and 78 are pipes 219.1mm in dia, having a wall thickness of 12.5mm. Circular hollow sections may also be provided by specifying the outside and inside diameters of the section. For example,


specifies a pipe with outside dia. of 25 length units and inside dia. of 20 length units. Only code checking, no member selection will be performed if this type of specification is used.

SAMPLE FILE CONTAINING FRENCH SHAPES STAAD SPACE UNIT METER KN JOINT COORD 1 0 0 0 15 140 0 0 MEMB INCI 1 1 2 14 UNIT CM

Section 6B

6-17

MEMBER PROPERTIES FRENCH * IPE SHAPES 1 TA ST IPEA120 * IPN SHAPES 2 TA ST IPN380 *HE SHAPES 3 TA ST HEA200 * T SHAPES 4 TA T HEM120 * U CHANNELS 5 TA ST UAP100 * DOUBLE U CHANNELS 6 TA D UAP150 SP 0.5 * ANGLES 7 TA ST L30X30X2.7 * REVERSE ANGLES 8 TA RA L25X25X4 * DOUBLE ANGLES - SHORT LEGS BACK * TO BACK 9 TA SD L30X20X4 SP 0.25 * DOUBLE ANGLES - LONG LEGS BACK * TO BACK 10 TA LD L80X40X6 SP 0.75 * TUBES (RECTANGULAR OR SQUARE * HOLLOW SECTIONS) 11 TA ST TUB50252.7 * TUBES (RECTANGULAR OR SQUARE * HOLLOW SECTIONS) 12 TA ST TUBE DT 8.0 WT 6.0 TH 0.5 * PIPES (CIRCULAR HOLLOW SECTIONS) 13 TA ST PIP422.6 * PIPES (CIRCULAR HOLLOW SECTIONS) 14 TA ST PIPE OD 25.0 ID 20.0 PRINT MEMB PROP FINI


Section 6B

6-18

Section 7 German Codes

Aslkdfj;alskjdf’

7-1

Concrete Design Per DIN 1045


STAAD has the capabilities of performing concrete design based on the DIN 1045 - November 1989. Slab design is also available but this follows the requirements of Baumann, Munich, which is the basis for Eurocode 2. Design for a member involves calculation of the amount of reinforcement required for the member. Calculations are based on the user specified properties and the member forces obtained from the analysis. In addition, the details regarding placement of the reinforcement on the cross section are also reported in the output.


The following types of cross sections for concrete members can be designed. For Beams - Prismatic (Rectangular & Square) For Columns - Prismatic (Rectangular, Square and Circular)



Section 7A


Section 7A 7-2


In the above input, the first set of members are rectangular (450 mm depth and 250mm width) and the second set of members, with only depth and no width provided, will be assumed to be circular with 350mm diameter. It is absolutely imperative that the user not provide the cross section area (AX) as an input.


Slenderness effects are extremely important in designing compression members. There are two options by which the slenderness effect can be accommodated. The first method is equivalent to the procedure presented in DIN 1045 17.4.3/17.4.4 which is used as the basis for commonly used design charts considering e/d and sk/d for conditions where the slenderness moment exceeds 70. This method has been adopted in the column design in STAAD per the DIN code. The second option is to compute the secondary moments through an analysis. Secondary moments are caused by the interaction of the axial loads and the relative end displacements of a member. The axial loads and joint displacements are first determined from an elastic stiffness analysis and the secondary moments are then evaluated. To perform this type of analysis, use the command PDELTA ANALYSIS instead of PERFORM ANALYSIS in the input file. The user must note that to take advantage of this analysis, all the combinations of loading must be provided as primary load cases and not as load combinations. This is due to the fact that load combinations are just algebraic combinations of forces and moments, whereas a primary load case is revised during

Section 7A

7-3

the P-delta analysis based on the deflections. Also, note that the proper factored loads (like 1.5 for dead load etc.) should be provided by the user. STAAD does not factor the loads automatically. The column is designed for the total moment which is the sum of the primary and secondary forces. The secondary moments can be compared to those calculated using the charts of DIN 1045.

7A.5 Beam Design

Beams are designed for flexure, shear and torsion. For all these forces, all active beam loadings are prescanned to identify the critical load cases at different sections of the beams. The total number of sections considered is 13 (e.g. 0., .1, .2, .25, .3, .4, .5, .6, .7, .75, .8, .9 and 1). All of these sections are scanned to determine the design force envelopes. Design for Flexure

Maximum sagging (creating tensile stress at the bottom face of the beam) and hogging (creating tensile stress at the top face) moments are calculated for all active load cases at each of the above mentioned sections. Each of these sections is designed to resist these critical sagging and hogging moments. Currently, design of singly reinforced sections only is permitted. If the section dimensions are inadequate as a singly reinforced section, such a message will be printed in the output. Flexural design of beams is performed in two passes. In the first pass, effective depths of the sections are determined with the assumption of single layer of assumed reinforcement and reinforcement requirements are calculated. After the preliminary design, reinforcing bars are chosen from the internal database in single or multiple layers. The entire flexural design is performed again in a second pass taking into account the changed effective depths of sections calculated on the basis of reinforcement provided after the preliminary design. Final provision of flexural reinforcements are made then. Efforts have been made to meet the guideline for the curtailment of reinforcements as per the DIN code. Although exact curtailment lengths are not mentioned explicitly in the design output (finally which will be more or less guided by the


Section 7A 7-4 detailer taking into account of other practical considerations), the user has the choice of printing reinforcements provided by STAAD at 13 equally spaced sections from which the final detailed drawing can be prepared. Design for Shear and Torsion

Shear design in STAAD conforms to the specifications of section 17.5 of DIN 1045. Shear reinforcement is calculated to resist both shear forces and torsional moments. Shear and torsional design is performed at the start and end sections of the member at a distance "d" away from the node of the member where "d" is the effective depth calculated from flexural design. The maximum shear forces from amongst the active load cases and the associated torsional moments are used in the design. The capacity of the concrete in shear and torsion is determined at the location of design and the balance, if any, is carried by reinforcement. It is assumed that no bent-up bars are available from the flexural reinforcement to carry and "balance" shear. Two-legged stirrups are provided to take care of the balance shear forces acting on these sections. Stirrups are assumed to be U-shaped for beams with no torsion, and closed hoops for beams subject to torsion.

Example of Input Data for Beam Design UNIT NEWTON MMS START CONCRETE DESIGN CODE GERMAN FYMAIN 415 ALL FYSEC 415 ALL FC 35 ALL CLEAR 25 MEM 2 TO 6 MAXMAIN 40 MEMB 2 TO 6 TRACK 1.0 MEMB 2 TO 9 DESIGN BEAM 2 TO 9 END CONCRETE DESIGN

Section 7A

7-5

7A.6 Column Design

Columns are designed for axial forces and biaxial moments at the ends. All active load cases are tested to calculate reinforcement. The loading which yields maximum reinforcement is called the critical load. The requirements of DIN 1045-figure 13, for calculating the equilibrium equations for rectangular and circular sections from first principles, is implemented in the design. The user has control of the effective length (sk) in each direction by using the ELZ and ELY parameters as described on Table 6A.1. This means that the slenderness will be evaluated along with e/d to meet the requirements of DIN 1045 section 17.4.3 and 17.4.4. Column design is done for square, rectangular and circular sections. Square and rectangular columns are designed with reinforcement distributed on all four sides equally. That means the total number of bars will always be a multiple of four (4). This may cause slightly conservative results in some cases. The TRACK parameter may be used to obtain the design details in various levels of descriptivity.

Example of Input Data for Column Design UNIT NEWTON MMS START CONCRETE DESIGN CODE GERMAN FYMAIN 415 ALL FC 35 ALL CLEAR 25 MEMB 2 TO 6 MAXMAIN 40 MEMB 2 TO 6 DESIGN COLUMN 2 TO 6 END CONCRETE DESIGN


Section 7A 7-6

7A.7 Slab Design

To design a slab, it must first be modeled using finite elements and analysed. The command specifications are in accordance with Chapter 2 and Chapter 6 of the Technical Reference Manual. Slabs are designed to specifications as described by BAUMANN of MUNICH which is the basis for Eurocode 2. Elements are designed for the moments Mx and My. These moments are obtained from the element force output (see Chapter 2 of the Technical Reference Manual). The reinforcement required to resist the Mx moment is denoted as longitudinal reinforcement and the reinforcement required to resist the My moment is denoted as transverse reinforcement. The following parameters are those applicable to slab design: 1. FYMAIN Yield stress for all reinforcing steel 2. FC Concrete grade 3. CLEAR Distance from the outer surface of the element to

the edge of the bar. This is considered the same on both top and bottom surfaces of the element.

4. SRA Parameter which denotes the angle of direction of the required transverse reinforcement relative to the direction of the longitudinal reinforcement for the calculation of BAUMANN design forces.

The other parameters shown in Table 7A.1 are not applicable to slab design. BAUMANN equations

If the default value of zero is used, the design will be based on Mx and My forces which are obtained from the STAAD analysis. The SRA parameter (Set Reinforcement Angle) can be manipulated to introduce resolved BAUMANN forces into the design replacing the pure Mx and My moments. These new design moments allow the Mxy moment to be considered when designing the section, resolved as an axial force. Orthogonal or skew reinforcement may

Section 7A

7-7

be considered. If SRA is set to -500, an orthogonal layout will be assumed. If however a skew is to be considered, an angle is given in degrees measured from the local element X axis anticlockwise (positive). The resulting Mx* and My* moments are calculated and shown in the design format. The design of the slab considers a fixed bar size of 10mm in the longitudinal direction and 8mm in the transverse. The longitudinal bar is the layer closest to the slab exterior face.


The program contains a number of parameters which are needed to perform the design. Default parameter values have been selected such that they are frequently used numbers for conventional design requirements. These values may be changed to suit the particular design being performed. Table 7A.1 of this manual contains a complete list of the available parameters and their default values. It is necessary to declare length and force units as Millimeter and Newton before performing the concrete design.

Table 7A.1 German Concrete Design Parameters

Parameter Name


FYMAIN 420 N/mm2 Yield Stress for main reinforcement (For slabs it is 500 N/mm2 for both directions)

FYSEC 420N/mm2 Yield Stress for secondary reinforcement. Applicable to shear and torsion reinforcement in beams

FC 25N/mm2 Concrete Yield Stress/ cube strength

MINMAIN 16mm Minimum main reinforcement bar size [Acceptable bar sizes: 6 8 10 12 14 16 20 25 32 40 50]

MINSEC 8mm Minimum secondary reinforcement bar size. Applicable to shear and torsion reinforcement in beams.


Section 7A 7-8


Parameter Name


CLEAR 25mm Clear cover for reinforcement measured from concrete surface to closest bar perimeter.

MAXMAIN 50 mm Maximum required reinforcement bar size. Acceptable bars are per MINMAIN above.

SFACE 0.0 Face of support location at start of beam, measured from the start joint. (Only applicable for shear - use MEMBER OFFSET for bending)

EFACE 0.0 Face of support location at end of beam, measured from the end joint. (NOTE: Both SFACE & EFACE must be positive numbers.)

TRACK 0.0 0.0 = Critical Moment will not be printed with beam design report.


2.0 = For beams gives area of steel required at intermediate sections. (see NSECT)

MMAG 1.0 Factor by which design moments are magnified for column design

NSECTION 10 Number of equally-spaced sections to be considered in finding critical moment for beam design. The upper limit is 20

WIDTH ZD Width of concrete member. The default value is as provided as ZD in MEMBER PROPERTIES.

DEPTH YD Depth of concrete member. The default value is as provided as YD in MEMBER PROPERTIES.

ELY 1.0 Member length factor about local Y direction for column design

ELZ 1.0 Member length factor about local Z direction for column design

Section 7A

7-9


Parameter Name



-500 = Orthogonal reinforcement layout considering Mxy

A = Skew angle considered in BAUMANN equations. A is the angle in degrees.


Section 7A 7-10

7-11

Steel Design Per the DIN Code

7B.1 General

This section presents some general statements regarding the implementation of the DIN code of practice for structural steel design (DIN 18800 and DIN 4114) in STAAD. The design philosophy and procedural logistics are based on the principles of elastic analysis and allowable stress design. Facilities are available for member selection as well as code checking. Two major failure modes are recognized: failure by overstressing and failure by stability considerations. The following sections describe the salient features of the design approach. Members are proportioned to resist the design loads without exceedance of the allowable stresses or capacities and the most economical section is selected on the basis of the least weight criteria. The code checking part of the program also checks the slenderness requirements and the stability criteria. Users are recommended to adopt the following steps in performing the steel design:

1) Specify the geometry and loads and perform the analysis. 2) Specify the design parameter values if different from the

default values. 3) Specify whether to perform code checking or member

selection.

Section 7B

Steel Design per the DIN Code

Section 7B 7-12


Elastic analysis method is used to obtain the forces and moments for design. Analysis is done for the primary and combination loading conditions provided by the user. The user is allowed complete flexibility in providing loading specifications and in using appropriate load factors to create necessary loading situations. Depending upon the analysis requirements, regular stiffness analysis or P-Delta analysis may be specified. Dynamic analysis may also be performed and the results combined with static analysis results.


For specification of member properties of standard German steel sections, the steel section library available in STAAD may be used. The next section describes the syntax of commands used to assign properties from the built-in steel table. Members properties may also be specified using the User Table facility. For more information on these facilities, refer to the STAAD Program User's manual.

7B.4 Built-in German Steel Section Library

The following information is provided for use when the built-in steel tables are to be referenced for member property specification. These properties are stored in a database file. If called for, these properties are also used for member design. Since the shear areas are built into these tables, shear deformation is always considered for these members during the analysis. An example of member property specification in an input file is provided at the end of this section.

Section 7B

7-13

A complete listing of the sections available in the built-in steel section library may be obtained using the tools of the graphical user interface. Following are the descriptions of different types of sections. IPE Shapes These shapes are designated in the following way:

20 TO 30 TA ST IPEA120 33 36 TO 46 BY 2 TA ST IPER140

HE Shapes The designation for HE shapes is similar to that for IPE shapes.

25 TO 35 TA ST HEB300 23 56 TA ST HEA160

I Shapes I shapes are identified by the depth of the section. The following example illustrates the designation.

14 15 TA ST I200 (indicates an I-section with 200mm depth)

T Shapes Tee sections are not input by their actual designations, but instead by referring to the I beam shapes from which they are cut. For example,

1 5 TA T HEA220 2 8 TA T IPE120


Section 7B 7-14 U Channels The example below provides the command for identifying two channel sections. The former (U70X40) has a depth of 70mm and a flange width of 40mm. The latter (U260) has a depth of 260mm.

11 TA D U70X40 27 TA D U260

Double Channels Back to back double channels, with or without spacing between them, are available. The letter “D” in front of the section name will specify a double channel, e.g. D U180. The spacing between the double channels is provided following the expression “SP”.

11 TA D U180 27 TA D U280 SP 0.5 (Indicates 2 channels back to back spaced at 0.5 length units)

Angles Two types of specifications may be used to describe an angle. The standard angle section is specified as follows:

16 20 TA ST L20X20X2.5

The above section signifies an angle with legs of length 20mm and a leg thickness of 2.5mm. The above specification may be used when the local z-axis corresponds to the Z-Z axis specified in Chapter 2. If the local y-axis corresponds to the Z-Z axis, type specification "RA" (reverse angle) may be used.

17 21 TA RA L40X20X5

Section 7B

7-15

Double Angles Short leg back to back or long leg back to back double angles can be specified by using the word SD or LD, respectively, in front of the angle size. In case of an equal angle, either SD or LD will serve the purpose. Spacing between the angles is provided by using the word SP and the spacing value following the section name.

14 TO 20 TA SD L40X20X4 SP 0.5 21 TO 27 TA LD L40X20X4 SP 0.5

Pipes (Circular Hollow Sections) To designate circular hollow sections, use PIP followed by numerical value of the diameter and thickness of the section in mm omitting the decimal section of the value provided for diameter. The following example will illustrate the designation.

8 TO 28 TA ST PIP602.9 (60.3mm dia, 2.9mm wall thickness) 3 64 67 TA ST PIP40612.5 (406.4mm dia, 12.5mm wall thickness)



specifies a pipe with outside dia. of 25 and inside dia. of 20 in current length units. Only code checking and no member selection will be performed if this type of specification is used.


Section 7B 7-16 Tubes (Rectangular or Square Hollow Sections) Tube names are input by their dimensions. For example,

15 TO 25 TA ST TUB100603.6

is the specification for a tube having sides of 100mmX60mm and the wall thickness of 3.6mm. Tubes, like pipes can also be input by their dimensions (Height, Width and Thickness) instead of by their table designations.


is a tube that has a height of 8, a width of 6, and a wall thickness of 0.5 in current length units. Only code checking and no member selection will be performed for TUBE sections specified this way.

SAMPLE INPUT FILE CONTAINING GERMAN SHAPES STAAD SPACE UNIT METER KN JOINT COORDINATES 1 0 0 0 15 140 0 0 MEMBER INCIDENCES 1 1 2 14 UNIT CM MEMBER PROPERTIES GERMAN * IPE SHAPES 1 TA ST IPEA120 * HE SHAPES 2 TA ST HEB300 * I SHAPES 3 TA ST I200 * T SHAPES 4 TA T HEA220

Section 7B

7-17

* U CHANNELS 5 TA ST U70X40 * DOUBLE U CHANNELS 6 TA D U260 * ANGLES 7 TA ST L20X20X2.5 * REVERSE ANGLES 8 TA RA L40X20X5 * DOUBLE ANGLES - LONG LEGS BACK TO BACK 9 TA LD L40X20X4 SP 0.5 * DOUBLE ANGLES - SHORT LEGS BACK TO BACK 10 TA SD L40X20X4 SP 0.5 * PIPES 11 TA ST PIP602.9 * PIPES 12 TA ST PIPE OD 25.0 ID 20.0 * TUBES 13 TA ST TUB100603.6 * TUBES 14 TA ST TUBE DT 8.0 WT 6.0 WT 0.5 * PRINT MEMBER PROPERTIES FINISH


The allowable stresses used in the implementation are based on DIN 18800 (Part 1) - Section 7. The procedures of DIN 4114 are used for stability analysis. The basic measure of member capacities are the allowable stresses on the member under various conditions of applied loading such as allowable tensile stress, allowable compressive stress etc. These depend on several factors such as cross sectional properties, slenderness factors, unsupported width to thickness ratios and so on. Explained here is the procedure adopted in STAAD for calculating such capacities.


Section 7B 7-18 Allowable stress for Axial Tension

In members with axial tension, the tensile load must not exceed the tension capacity of the member. The tension capacity of the member is calculated on the basis of the member area. STAAD calculates the tension capacity of a given member based on a user supplied net section factor (NSF-a default value of 1.0 is present but may be altered by changing the input value, see Table 6B.1) and proceeds with member selection or code checking. Allowable stress for Axial Compression

The allowable stress for members in compression is determined according to the procedure of DIN 4114 (Part 1) - Section 7. Compressive resistance is a function of the slenderness of the cross-section (Kl/r ratio) and the user may control the slenderness value by modifying parameters such as KY, LY, KZ and LZ. Allowable stress for Bending and Shear

The permissible bending compressive and tensile stresses are dependent on such factors as length of outstanding legs, thickness of flanges, unsupported length of the compression flange (UNL, defaults to member length) etc. Shear capacities are a function of web depth, web thickness etc. Users may use a value of 1.0 or 2.0 for the TRACK parameter to obtain a listing of the bending and shear capacities.


For members experiencing combined loading (axial force, bending and shear), applicable interaction formulas are checked at different locations of the member for all modeled loading situations. Members subjected to axial force and bending are checked using the criteria of DIN 18800 (Part 1) - Section 6.1.6. In addition, for members with compression and bending, the criteria of DIN 4114 (Part 1) - Section 10 is used. Similarly, for members with axial tension and bending, the criteria of DIN 4114 (Part 1) - Section 15 is used.

Section 7B

7-19


The user is allowed complete control over the design process through the use of parameters mentioned in Table 7B.1 of this chapter. These parameters communicate design decisions from the engineer to the program. The default parameter values have been selected such that they are frequently used numbers for conventional design. Depending on the particular design requirements of the situation, some or all of these parameter values may have to be changed to exactly model the physical structure.

Table 7B.1 German Steel Design Parameters

Parameter Name




LY Member Length Length in local y-axis to calculate slenderness ratio.

LZ Member Length Length in local z-axis to calculate slenderness ratio.

PY 240 N/sq.mm Strength of steel.


UNL Member Length Unrestrained member length in lateral torsional buckling checks.

UNF 1.0 Same as above provided as a factor of actual member length.

BEAM 0.0 Number of sections to be checked per member: 0.0 = Design only for end sections. 1.0 = Check at location of maximum MZ

along member.

2.0 = Check ends plus location of beam 1.0 check.


Section 7B 7-20


Parameter Name


3.0 = Check at every 1/13th of the member length and report the maximum.

TRACK 0.0 Level of detail in output file: 0.0 = Output summary of results 1.0 = Output summary of results plus

member capacities

2.0 = Output detailed results

RATIO 1.0 Permissible ratio of actual to allowable stresses

SGR 0.0 Grade of steel:

0.0 = St 37-2

1.0 = St 52-3

2.0 = StE 355

SBLT 0 Specify section as either rolled or built-up:

0 = Rolled

1 = Built-up

Cb 0 Beam coefficient n, defined in Table 9: If Cb = 0, program will use n = 2.5 for rolled sections and 2.0 for welded sections.

Cmm 1.0 Moment factor, Zeta, defined in Table 10:

1.0 = fixed ended member with constant moment, Zeta = 1.0

2.0 = pin ended member with UDL, Zeta = 1.12

3.0 = pin ended member with central point load, Zeta = 1.35

4.0 = fixed ended member, Zeta calculated from end moments.

DMAX 1.0 m Maximum allowable depth during member selection

DMIN 0.0 m Minimum required depth during member selection

Section 7B

7-21


Parameter Name


SAME 0.0 Control of sections to try during a SELECT process:

0.0 = Try every section of the same type as the original.

1.0 = Try only those with a similar name.

7B.8 Code Checking

The purpose of code checking is to check whether the provided section properties of the members are adequate to carry the forces transmitted to it by the loads on the structure. The adequacy is checked per the DIN requirements. Code checking is done using forces and moments at specified sections of the members. If the BEAM parameter for a member is set to 1, moments are calculated at every twelfth point along the beam, and the maximum moment about the major axis is used. When no sections are specified and the BEAM parameter is set to zero (default), design will be based on member start and end forces. The code checking output labels the members as PASSed or FAILed. In addition, the critical condition, governing load case, location (distance from start joint) and magnitudes of the governing forces and moments are also printed.


Section 7B 7-22


The member selection process basically involves determination of the least weight member that PASSes the code checking procedure based on the forces and moments of the most recent analysis. The section selected will be of the same type as that specified initially. For example, a member specified initially as a channel will have a channel selected for it. Selection of members whose properties are originally provided from a user table will be limited to sections in the user table. Member selection cannot be performed on TUBES, PIPES or members listed as PRISMATIC.

Sample Input data for Steel Design UNIT METER PARAMETER CODE GERMAN NSF 0.85 ALL UNL 10.0 MEMBER 7 KY 1.2 MEMBER 3 4 RATIO 0.9 ALL TRACK 1.0 ALL CHECK CODE ALL

Section 8 Indian Codes

Ad;flaksd;lfka

8-1

Concrete Design Per IS456


STAAD has the capabilities of performing concrete design. It will calculate the reinforcement needed for any concrete section. All the concrete design calculations are based on limit state method of IS: 456 (2000).


The following types of cross sections for concrete members can be designed. For Beams Prismatic (Rectangular & Square), T-Beams and

L-shapes For Columns Prismatic (Rectangular, Square and Circular)



Section 8A


Section 8A

8-2

UNIT MM MEMBER PROPERTY 1 3 TO 7 9 PRISM YD 450. ZD 250. 11 13 PR YD 350. 14 TO 16 PRIS YD 400. ZD 750. YB 300. ZB 200.

will be done accordingly. In the above input, the first set of members are rectangular (450 mm depth and 250mm width) and the second set of members, with only depth and no width provided, will be assumed to be circular with 350 mm diameter. The third set numbers in the above example represents a T-shape with 750 mm flange width, 200 width, 400 mm overall depth and 100 mm flange depth (See section 6.20.2). The program will determine whether the section is rectangular, flanged or circular and the beam or column design


The program contains a number of parameters which are needed to perform design as per IS:456(2000). Default parameter values have been selected such that they are frequently used numbers for conventional design requirements. These values may be changed to suit the particular design being performed. Table 8A.1 of this manual contains a complete list of the available parameters and their default values. It is necessary to declare length and force units as Millimeter and Newton before performing the concrete design.


Slenderness effects are extremely important in designing compression members. The IS:456 code specifies two options by which the slenderness effect can be accommodated (Clause 39.7).

Section 8A

8-3

One option is to perform an exact analysis which will take into account the influence of axial loads and variable moment of inertia on member stiffness and fixed end moments, the effect of deflections on moment and forces and the effect of the duration of loads. Another option is to approximately magnify design moments. STAAD has been written to allow the use of the first options. To perform this type of analysis, use the command PDELTA ANALYSIS instead of PERFORM ANALYSIS. The PDELTA ANALYSIS will accommodate all requirements of the second- order analysis described by IS:456, except for the effects of the duration of the loads. It is felt that this effect may be safely ignored because experts believe that the effects of the duration of loads is negligible in a normal structural configuration. Although ignoring load duration effects is somewhat of an approximation, it must be realized that the approximate evaluation of slenderness effects is also an approximate method. In this method, additional moments are calculated based on empirical formula and assumptions on sidesway (Clause 39.7.1 and 39.7.1.1,IS: 456 - 2000). Considering all these information, a PDELTA ANALYSIS, as performed by STAAD may be used for the design of concrete members. However the user must note, to take advantage of this analysis, all the combinations of loading must be provided as primary load cases and not as load combinations. This is due to the fact that load combinations are just algebraic combinations of forces and moments, whereas a primary load case is revised during the P-delta analysis based on the deflections. Also note that the proper factored loads (like 1.5 for dead load etc.) should be provided by user. STAAD does not factor the loads automatically.

8A.6 Beam Design

Beams are designed for flexure, shear and torsion. If required the effect the axial force may be taken into consideration. For all


Section 8A

8-4 these forces, all active beam loadings are prescanned to identify the critical load cases at different sections of the beams. The total number of sections considered is 13 ( e.g. 0.,.1,.2,.25,.3,.4,.5,.6,.7,. 75,.8,.9 and 1). All of these sections are scanned to determine the design force envelopes. Design for Flexure

Maximum sagging (creating tensile stress at the bottom face of the beam) and hogging (creating tensile stress at the top face) moments are calculated for all active load cases at each of the above mentioned sections. Each of these sections are designed to resist both of these critical sagging and hogging moments. Where ever the rectangular section is inadequate as singly reinforced section, doubly reinforced section is tried. However, presently the flanged section are designed only as singly reinforced section under sagging moment. It may also be noted all flanged sections are automatically designed as rectangular section under hogging moment as the flange of the beam is ineffective under hogging moment. Flexural design of beams are performed in two passes. In the first pass, effective depths of the sections are determined with the assumption of single layer of assumed reinforcement and reinforcement requirements are calculated. After the preliminary design, reinforcing bars are chosen from the internal database in single or multiple layers. The entire flexure design is performed again in a second pass taking into account of the changed effective depths of sections calculated on the basis of reinforcement provide after the preliminary design. Final provision of flexural reinforcements are made then. Efforts have been made to meet the guideline for the curtailment of reinforcements as per IS:456-2000 (Clause 26.2.3). Although exact curtailment lengths are not mentioned explicitly in the design output (finally which will be more or less guided by the detailer taking into account of other practical consideration), user has the choice of printing reinforcements provided by STAAD at 11 equally spaced sections from which the final detail drawing can be prepared.

Section 8A

8-5

Design for Shear

Shear reinforcement is calculated to resist both shear forces and torsional moments. Shear design are performed at 11 equally spaced sections (0.to 1.) for the maximum shear forces amongst the active load cases and the associated torsional moments. Shear capacity calculation at different sections without the shear reinforcement is based on the actual tensile reinforcement provided by STAAD program. Two-legged stirrups are provided to take care of the balance shear forces acting on these sections. As per Clause 40.5 of IS:456-2000 shear strength of sections (< 2d where d is the effective depth) close to support has been enhanced, subjected to a maximum value of τcmax. Beam Design Output The default design output of the beam contains flexural and shear reinforcement provided at 5 equally spaced (0,.25,.5,.75 and 1.) sections along the length of the beam. User has option to get a more detail output. All beam design outputs are given in IS units. An example of rectangular beam design output with the default output option (TRACK 0.0) is presented below:


Section 8A

8-6 ============================================================================




DESIGN LOAD SUMMARY (KN MET)----------------------------------------------------------------------------SECTION |FLEXTURE (Maxm. Sagging/Hogging moments)| SHEAR(in mm) | P MZ MX Load Case | VY MX Load Case----------------------------------------------------------------------------

0.0 | 0.00 0.00 0.00 4 | 29.64 1.23 4| 0.00 -25.68 1.23 4 |

400.0 | 0.00 0.00 0.00 4 | 27.97 1.23 4| 0.00 -16.05 1.23 4 |

800.0 | 0.00 0.00 0.00 4 | 25.12 1.23 4| 0.00 -7.17 1.23 4 |

1200.0 | 0.00 0.97 0.49 5 | 21.11 1.23 4| 0.00 -0.14 1.32 6 |

1600.0 | 0.00 6.77 1.23 4 | 15.93 1.23 4| 0.00 0.00 0.00 4 |

2000.0 | 0.00 11.06 1.23 4 | 9.59 1.23 4| 0.00 0.00 0.00 4 |

2400.0 | 0.00 13.04 1.23 4 | 2.08 1.23 4| 0.00 0.00 0.00 4 |

2800.0 | 0.00 12.45 1.23 4 | -5.43 1.23 4| 0.00 0.00 0.00 4 |

3200.0 | 0.00 9.55 1.23 4 | -11.77 1.23 4| 0.00 0.00 0.00 4 |

3600.0 | 0.00 4.73 1.23 4 | -16.95 1.23 4| 0.00 0.00 0.00 4 |

4000.0 | 0.00 0.00 0.00 4 | -25.48 1.23 4| 0.00 -17.36 1.23 4 |

----------------------------------------------------------------------------



SUMMARY OF PROVIDED REINF. AREA----------------------------------------------------------------------------SECTION 0.0 mm 1000.0 mm 2000.0 mm 3000.0 mm 4000.0 mm----------------------------------------------------------------------------TOP 4-10Ø 3-10Ø 2-10Ø 2-10Ø 3-10ØREINF. 1 layer(s) 1 layer(s) 1 layer(s) 1 layer(s) 1 layer(s)

BOTTOM 2-12Ø 2-12Ø 2-12Ø 2-12Ø 2-12ØREINF. 1 layer(s) 1 layer(s) 1 layer(s) 1 layer(s) 1 layer(s)

SHEAR 2 legged 8Ø 2 legged 8Ø 2 legged 8Ø 2 legged 8Ø 2 legged 8ØREINF. @ 100 mm c/c @ 100 mm c/c @ 100 mm c/c @ 100 mm c/c @ 100 mm c/c----------------------------------------------------------------------------

============================================================================

Section 8A

8-7

8A.7 Column Design

Columns are designed for axial forces and biaxial moments at the ends. All active load case are tested to calculate reinforcement. The loading which yield maximum reinforcement is called the critical load. Column design is done for square, rectangular and circular sections. By default, square and rectangular columns and designed with reinforcement distributed on each side equally for the sections under biaxial moments and with reinforcement distributed equally in two faces for sections under uniaxial moment. User may change the default arrangement of the reinforcement with the help of the parameter RFACE (see Table 8A.1). Depending upon the member lengths, section dimensions and effective length coefficients specified by the user STAAD automatically determine the criterion (short or long) of the column design. All major criteria for selecting longitudinal and transverse reinforcement as stipulated by IS:456 have been taken care of in the column design of STAAD. Default clear spacing between main reinforcing bars is taken to be 25 mm while arrangement of longitudinal bars. Column Design Output Default column design output (TRACK 0.0) contains the reinforcement provided by STAAD and the capacity of the section. With the option TRACK 1.0, the output contains intermediate results such as the design forces, effective length coefficients, additional moments etc. A special output TRACK 9.0 is introduced to obtain the details of section capacity calculations. All design output is given in SI units. An example of a long column design (Ref. Example 9 of SP:16, Design Aids For Reinforced Concrete to IS:456-1978) output (with option TRACK 1.0) is given below.


Section 8A

8-8 ============================================================================

C O L U M N N O. 1 D E S I G N R E S U L T S


LENGTH: 3000.0 mm CROSS SECTION: 250.0 mm dia. COVER: 40.0 mm

** GUIDING LOAD CASE: 5 BRACED LONG COLUMN



SLENDERNESS RATIOS : 12.00 12.00MOMENTS DUE TO SLENDERNESS EFFECT : 1.12 1.12MOMENT REDUCTION FACTORS : 1.00 1.00ADDITION MOMENTS (Maz and May) : 1.12 1.12



(Equally distributed)TIE REINFORCEMENT : Provide 8 mm dia. rectangular ties @ 190 mm c/c


INTERACTION RATIO: 1.00 (as per Cl. 38.6, IS456)

============================================================================

Section 8A

8-9

Table 8A.1 Indian Concrete Design IS456 Parameters

Parameter Name Default Value Description




CLEAR 25 mm 40 mm

For beam members. For column members





BRACING

0.0

BEAM DESIGN


COLUMN DESIGN











Section 8A

8-10



TRACK 0.0 BEAM DESIGN: For TRACK = 0.0, output consists of reinforcement details at START, MIDDLE and END. For TRACK = 1.0, critical moments are printed in addition to TRACK 0.0 output. For TRACK = 2.0, required steel for intermediate sections defined by NSECTION are printed in addition to TRACK 1.0 output.

COLUMN DESIGN: With TRACK = 0.0, reinforcement details are printed. With TRACK = 1.0, column interaction analysis results are printed in addition to TRACK 0.0 output. With TRACK = 2.0, a schematic interaction diagram and intermediate interaction values are printed in addition to TRACK 1.0 output.

With TRACK = 9.0, the details of section capacity calculations are printed.




TORSION 0.0 A value of 0.0 means torsion to be considered in beam design. A value of 1.0 means torsion to be neglected in beam design.

SPSMAIN 25 mm Minimum clear distance between main reinforcing bars in beam and column. For column centre to centre distance between main bars cannot exceed 300mm.

SFACE 0.0 Face of support location at start of beam. It is used to check against shear at the face of the support in beam design. The parameter can also be used to check against shear at any point from the start of the member.

Section 8A

8-11



EFACE 0.0 Face of support location at end of beam. The parameter can also be used to check against shear at any point from the end of the member. (Note: Both SFACE and EFACE are input as positive numbers).

ENSH 0.0 Perform shear check against enhanced shear strength as per Cl. 40.5 of IS456:2000.

ENSH = 1.0 means ordinary shear check to be performed ( no enhancement of shear strength at sections close to support)

For ENSH = a positive value(say x ), shear strength will be enhanced up to a distance x from the start of the member. This is used only when a span of a beam is subdivided into two or more parts. (Refer note )

For ENSH = a negative value(say –y), shear strength will be enhanced up to a distance y from the end of the member. This is used only when a span of a beam is subdivided into two or more parts.(Refer note)

If default value (0.0) is used the program will calculate Length to Overall Depth ratio. If this ratio is greater than 2.5, shear strength will be enhanced at sections (<2d) close to support otherwise ordinary shear check will be performed.

RENSH 0.0 Distance of the start or end point of the member

from its nearest support. This parameter is used only when a span of a beam is subdivided into two or more parts. (Refer note)

Bar combination has been introduced for detailing. Please refer section 8A.8 for details.

Note: Value of ENSH parameter (other than 0.0 and 1.0) is used only when the span of a beam is subdivided into two or more parts. When this condition is aroused RENSH parameter is also to be used.


Section 8A

8-12

The span of the beam is subdivided four parts, each of length L metre. The shear strength will be enhanced up to X metre from both supports. The input should be the following: Steps: ENSH L MEMB 1 => Shear strength will be enhanced

throughout the length of the member 1, positive sign indicates length measured from start of the member

ENSH (X-L) MEMB 2 => Shear strength will be enhanced up to a

length (X-L) of the member 2, length measured from the start of the member

ENSH –L MEMB 4 => Shear strength will be enhanced

throughout the length of the member 4, negative sign indicates length measured from end of the member

ENSH –(X-L) MEMB 3 => Shear strength will be enhanced up to

a length (X-L) of the member 3, length measured from the end of the member

RENSH L MEMB 2 3 => Nearest support lies at a distance L

from both the members 2 and 3.

Section 8A

8-13

DESIGN BEAM 1 TO 4 => This will enhance the shear strength up to length X from both ends of the beam consisting of members 1 to 4 and gives spacing accordingly.

At section = y1 from start of member 1 av = y1 At section = y2 from the start of member 2 av = y2+L At section = y3 from the end of member 3 av = y3+L At section = y4 from end of member 4 av = y4 where τc, enhanced = 2dτc/av At section 0.0, av becomes zero. Thus enhanced shear strength will become infinity. However for any section shear stress cannot exceed τc, max. Hence enhanced shear strength is limited to a maximum value of τc, max.

8A.8 Bar Combination

Initially, the program selects only one bar to calculate the number of bars required and area of steel provided at each section along the length of the beam. Now, two bar diameters can be specified to calculate a combination of each bar to be provided at each section. The syntax for bar combination is given below.

START BAR COMBINATION MD1 <bar diameter> MEMB <member list> MD2 <bar diameter> MEMB <member list> END BAR COMBINATION


Section 8A

8-14 MD2 bar diameter should be greater than MD1 bar diameter. The typical output for bar combination is shown below:

OUTPUT FOR BAR COMBINATION

----------------------------------------------------------------------------

| M A I N R E I N F O R C E M E N T |

----------------------------------------------------------------------------SECTION | 0.0- 2166.7 | 2166.7- 6500.0 | 6500.0- 8666.7 |

| mm | mm | mm |----------------------------------------------------------------------------TOP | 6-20í + 1-25í | 2-20í + 1-25í | 2-20í |

| in 2 layer(s) | in 1 layer(s) | in 1 layer(s) |Ast Reqd| 2330.22 | 1029.90 | 582.55 |

Prov| 2376.79 | 1119.64 | 628.57 |Ld (mm) | 940.2 | 940.2 | 940.2 |----------------------------------------------------------------------------BOTTOM | 4-20í | 2-20í | 2-20í |


Prov| 1257.14 | 628.57 | 628.57 |Ld (mm) | 940.2 | 940.2 | 940.2 |----------------------------------------------------------------------------

The beam length is divided into three parts, two at its ends and one at span. Ld gives the development length to be provided at the two ends of each section.

8-15


8A1.1 Design Operations

Earthquake motion often induces force large enough to cause inelastic deformations in the structure. If the structure is brittle, sudden failure could occur. But if the structure is made to behave ductile, it will be able to sustain the earthquake effects better with some deflection larger than the yield deflection by absorption of energy. Therefore ductility is also required as an essential element for safety from sudden collapse during severe shocks. STAAD has the capabilities of performing concrete design as per IS 13920. While designing it satisfies all provisions of IS 456 – 2000 and IS 13920 for beams and columns.

8A1.2 Section Types for Concrete Design

The following types of cross sections for concrete members can be designed. For Beams Prismatic (Rectangular & Square) & T-shape For Columns Prismatic (Rectangular, Square and Circular)

Section 8A1


Section 8A1

8-16

8A1.3 Design Parameters

The program contains a number of parameters that are needed to perform design as per IS 13920. It accepts all parameters that are needed to perform design as per IS:456. Over and above it has some other parameters that are required only when designed is performed as per IS:13920. Default parameter values have been selected such that they are frequently used numbers for conventional design requirements. These values may be changed to suit the particular design being performed. Table 8A1.1 of this manual contains a complete list of the available parameters and their default values. It is necessary to declare length and force units as Millimeter and Newton before performing the concrete design.

8A1.4 Beam Design

Beams are designed for flexure, shear and torsion. If required the effect of the axial force may be taken into consideration. For all these forces, all active beam loadings are prescanned to identify the critical load cases at different sections of the beams. The total number of sections considered is 13. All of these sections are scanned to determine the design force envelopes. For design to be performed as per IS:13920 the width of the member shall not be less than 200mm(Clause 6.1.3). Also the member shall preferably have a width-to depth ratio of more than 0.3 (Clause 6.1.2). The factored axial stress on the member should not exceed 0.1fck (Clause 6.1.1) for all active load cases. If it exceeds allowable axial stress no design will be performed.

Section 8A1

8-17

Design for Flexure

Design procedure is same as that for IS 456. However while designing following criteria are satisfied as per IS-13920:

1. The minimum grade of concrete shall preferably be M20. (Clause 5.2)

2. Steel reinforcements of grade Fe415 or less only shall be used. (Clause 5.3)

3. The minimum tension steel ratio on any face, at any section, is given by

ρmin = 0.24√fck/fy (Clause 6.2.1b) The maximum steel ratio on any face, at any section, is given by ρmax = 0.025 (Clause 6.2.2)

4. The positive steel ratio at a joint face must be at least equal to half the negative steel at that face. (Clause 6.2.3)

5. The steel provided at each of the top and bottom face, at any section, shall at least be equal to one-fourth of the maximum negative moment steel provided at the face of either joint. (Clause 6.2.4) Design for Shear

The shear force to be resisted by vertical hoops is guided by the Clause 6.3.3 of IS 13920:1993 revision. Elastic sagging and hogging moments of resistance of the beam section at ends are considered while calculating shear force. Plastic sagging and hogging moments of resistance can also be considered for shear design if PLASTIC parameter is mentioned in the input file. (Refer Table 8A1.1) Shear reinforcement is calculated to resist both shear forces and torsional moments. Procedure is same as that of IS 456.


Section 8A1

8-18 The following criteria are satisfied while performing design for shear as per Cl. 6.3.5 of IS-13920: The spacing of vertical hoops over a length of 2d at either end of the beam shall not exceed a) d/4 b) 8 times the diameter of the longitudinal bars In no case this spacing is less than 100 mm. The spacing calculated from above, if less than that calculated from IS 456 consideration is provided. Beam Design Output The default design output of the beam contains flexural and shear reinforcement provided at 5 equally spaced sections along the length of the beam. User has option to get a more detail output. All beam design outputs are given in IS units. An example of rectangular beam design output with the default output option (TRACK 1.0) is presented below:

Section 8A1

8-19============================================================================




DESIGN LOAD SUMMARY (KN MET)----------------------------------------------------------------------------SECTION |FLEXTURE (Maxm. Sagging/Hogging moments)| SHEAR(in mm) | P MZ MX Load Case | VY MX Load Case----------------------------------------------------------------------------0.0 | 0.00 0.00 0.00 4 | 17.67 0.00 4

| 0.00 -2.74 0.00 5 |291.7 | 0.00 1.15 0.00 5 | 16.26 0.00 4

| 0.00 0.00 0.00 4 |583.3 | 0.00 4.61 0.00 5 | 13.97 0.00 4

| 0.00 0.00 0.00 4 |875.0 | 0.00 7.44 0.00 5 | 10.78 0.00 4

| 0.00 0.00 0.00 4 |1166.7 | 0.00 9.41 0.00 5 | 6.69 0.00 4

| 0.00 0.00 0.00 4 |1458.3 | 0.00 10.33 0.00 5 | 1.10 0.00 5

| 0.00 0.00 0.00 4 |1750.0 | 0.00 9.98 0.00 5 | -3.60 0.00 5

| 0.00 0.00 0.00 4 |2041.7 | 0.00 8.23 0.00 5 | -10.02 0.00 4

| 0.00 0.00 0.00 4 |2333.3 | 0.00 5.21 0.00 5 | -15.00 0.00 4

| 0.00 0.00 0.00 4 |2625.0 | 0.00 1.14 0.00 5 | -19.08 0.00 4

| 0.00 0.00 0.00 4 |2916.7 | 0.00 0.00 0.00 4 | -22.27 0.00 4

| 0.00 -3.79 0.00 5 |3208.3 | 0.00 0.00 0.00 4 | -24.57 0.00 4

| 0.00 -9.35 0.00 5 |3500.0 | 0.00 0.00 0.00 4 | -25.97 0.00 4

| 0.00 -15.34 0.00 5 |

*** DESIGN SHEAR FORCE AT SECTION 0.0 IS 68.60 KN.- CLAUSE 6.3.3 OF IS-

13920*** DESIGN SHEAR FORCE AT SECTION 3500.0 IS 75.24 KN.

- CLAUSE 6.3.3 OF IS-13920

----------------------------------------------------------------------------



SUMMARY OF PROVIDED REINF. AREA----------------------------------------------------------------------------SECTION 0.0 mm 875.0 mm 1750.0 mm 2625.0 mm 3500.0 mm----------------------------------------------------------------------------TOP 3-10í 2-10í 2-10í 2-10í 3-10íREINF. 1 layer(s) 1 layer(s) 1 layer(s) 1 layer(s) 1 layer(s)

BOTTOM 2-12í 2-12í 2-12í 2-12í 2-12íREINF. 1 layer(s) 1 layer(s) 1 layer(s) 1 layer(s) 1 layer(s)

SHEAR 2 legged 8í 2 legged 8í 2 legged 8í 2 legged 8í 2 legged 8íREINF. @ 100 mm c/c @ 150 mm c/c @ 150 mm c/c @ 150 mm c/c @ 100 mm c/c----------------------------------------------------------------------------

============================================================================


Section 8A1

8-20

8A1.5 Column Design

Columns are designed for axial forces and biaxial moments per IS 456:2000. Columns are also designed for shear forces as per Clause 7.3.4. All major criteria for selecting longitudinal and transverse reinforcement as stipulated by IS:456 have been taken care of in the column design of STAAD. However following clauses have been satisfied to incorporate provisions of IS 13920: 1. The minimum grade of concrete shall preferably be M20.

(Clause 5.2)

2. Steel reinforcements of grade Fe415 or less only shall be used. (Clause 5.3)

3. The minimum dimension of column member shall not be less than 200 mm. For columns having unsupported length exceeding 4m, the shortest dimension of column shall not be less than 300 mm. (Clause 7.1.2)

4. The ratio of the shortest cross-sectional dimension to the perpendicular dimension shall preferably be not less than 0.4. (Clause 7.1.3)

5. The spacing of hoops shall not exceed half the least lateral dimension of the column, except where special confining reinforcement is provided. (Clause 7.3.3)

6. Special confining reinforcement shall be provided over a length lo from each joint face, towards mid span, and on either side of any section, where flexural yielding may occur. The length lo shall not be less than a) larger lateral dimension of the member at the section where yielding occurs, b) 1/6 of clear span of the member, and c) 450 mm. (Clause 7.4.1)

7. The spacing of hoops used as special confining reinforcement shall not exceed ¼ of minimum member dimension but need not be less than 75 mm nor more than 100 mm. (Clause 7.4.6)

Section 8A1

8-21

8. The area of cross-section of hoops provided are checked against the provisions for minimum area of cross-section of the bar forming rectangular, circular or spiral hoops, to be used as special confining reinforcement. (Clause 7.4.7 and 7.4.8)

Column Design Output Default column design output (TRACK 0.0) contains the reinforcement provided by STAAD and the capacity of the section. With the option TRACK 1.0, the output contains intermediate results such as the design forces, effective length coefficients, additional moments etc. A special output TRACK 9.0 is introduced to obtain the details of section capacity calculations. All design output is given in SI units. An example of a column design output (with option TRACK 1.0) is given below. ============================================================================

C O L U M N N O. 3 D E S I G N R E S U L T S


LENGTH: 3000.0 mm CROSS SECTION: 350.0 mm X 400.0 mm COVER: 40.0 mm

** GUIDING LOAD CASE: 5 END JOINT: 2 SHORT COLUMN



SLENDERNESS RATIOS : - -MOMENTS DUE TO SLENDERNESS EFFECT : - -MOMENT REDUCTION FACTORS : - -ADDITION MOMENTS (Maz and May) : - -


** GUIDING LOAD CASE: 5Along Z Along Y

DESIGN SHEAR FORCES : 43.31 76.08


(Equally distributed)CONFINING REINFORCEMENT : Provide 10 mm dia. rectangular ties @ 85 mm c/c

over a length 500.0 mm from each joint face towardsmidspan as per Cl. 7.4.6 of IS-13920.

TIE REINFORCEMENT : Provide 10 mm dia. rectangular ties @ 175 mm c/c


INTERACTION RATIO: 1.00 (as per Cl. 39.6, IS456:2000)============================================================================

********************END OF COLUMN DESIGN RESULTS********************


Section 8A1

8-22

Table 8A1.1 Indian Concrete Design IS13920 Parameters

Parameter Name





CLEAR 25 mm

40 mm

For beam members.

For column members





BRACING 0.0 BEAM DESIGN


COLUMN DESIGN








Section 8A1

8-23


Parameter Name







TORSION 0.0 A value of 0.0 means torsion to be considered in beam design.

A value of 1.0 means torsion to be neglected in beam design.

TRACK 0.0 BEAM DESIGN:

For TRACK = 0.0, output consists of reinforcement details at START, MIDDLE and END.

For TRACK = 1.0, critical moments are printed in addition to TRACK 0.0 output.

For TRACK = 2.0, required steel for intermediate sections defined by NSECTION are printed in addition to TRACK 1.0 output.

COLUMN DESIGN:

With TRACK = 0.0, reinforcement details are printed.

With TRACK = 1.0, column interaction analysis results are printed in addition to TRACK 0.0 output.

With TRACK = 2.0, a schematic interaction diagram and intermediate interaction values are printed in addition to TRACK 1.0 output.


Section 8A1

8-24


Parameter Name


SPSMAIN 25 mm Minimum clear distance between main reinforcing bars in beam and column. For column centre to centre distance between main bars cannot exceed 300mm.

SFACE 0.0 Face of support location at start of beam. It is used to check against shear at the face of the support in beam design. The parameter can also be used to check against shear at any point from the start of the member.*

EFACE 0.0 Face of support location at end of beam. The parameter can also be used to check against shear at any point from the end of the member. (Note: Both SFACE and EFACE are input as positive numbers).*

ENSH 0.0 Perform shear check against enhanced shear strength as per Cl. 40.5 of IS456:2000.

ENSH = 1.0 means ordinary shear check to be performed ( no enhancement of shear strength at sections close to support)

For ENSH = a positive value(say x ), shear strength will be enhanced up to a distance x from the start of the member. This is used only when a span of a beam is subdivided into two or more parts. (Refer note after Table 8A.1 )

For ENSH = a negative value(say –y), shear strength will be enhanced up to a distance y from the end of the member. This is used only when a span of a beam is subdivided into two or more parts.(Refer note after Table 8A.1)

If default value (0.0) is used the program will calculate Length to Overall Depth ratio. If this ratio is greater than 2.5, shear strength will be enhanced at sections (<2d) close to support otherwise ordinary shear check will be performed.

RENSH 0.0 Distance of the start or end point of the member from its nearest support. This

Section 8A1

8-25


Parameter Name


parameter is used only when a span of a beam is subdivided into two or more parts. (Refer note after Table 8A.1)

EUDL None Equivalent u.d.l on span of the beam. This load value must be the unfactored load on span. During design the load value is multiplied by a factor 1.2. If no u.d.l is defined factored shear force due to gravity load on span will be taken as zero. No elastic or plastic moment will be calculated. Shear design will be performed based on analysis result.(Refer note)

GLD None Gravity load number to be considered for calculating equivalent u.d.l on span of the beam, in case no EUDL is mentioned in the input. This loadcase can be any static loadcase containing MEMBER LOAD on the beam which includes UNI, CON, LIN and TRAP member loading. CMOM member loading is considered only when it is specified in local direction. FLOOR LOAD is also considered.

The load can be primary or combination load. For combination load only load numbers included in load combination is considered. The load factors are ignored. Internally the unfactored load is multiplied by a factor 1.2 during design.

If both EUDL and GLD parameters are mentioned in the input mentioned EUDL will be considered in design

Note :

No dynamic (Response spectrum, 1893, Time History) and moving load cases are considered.

CMOM member loading in global direction is not considered.

UMOM member loading is not considered.


Section 8A1

8-26


Parameter Name


PLASTIC 0.0 Default value calculates elastic hogging and sagging moments of resistance of beam at its ends.

A value of 1.0 means plastic hogging and sagging moments of resistance of beam to be calculated at its ends.

IPLM 0.0 Default value calculates elastic/plastic hogging and sagging moments of resistance of beam at its ends.

A value of 1.0 means calculation of elastic/plastic hogging and sagging moments of resistance of beam to be ignored at start node of beam. This implies no support exists at start node.

A value of -1.0 means calculation of elastic/plastic hogging and sagging moments of resistance of beam to be considered at start node of beam. . This implies support exists at start node.

A value of 2.0 means calculation of elastic/plastic hogging and sagging moments of resistance of beam to be ignored at end node of beam. This implies no support exists at end node.

A value of -2.0 means calculation of elastic/plastic hogging and sagging moments of resistance of beam to be considered at end node of beam. . This implies support exists at end node. **

IMB 0.0 Default value calculates elastic/plastic hogging and sagging moments of resistance of beam at its ends.

A value of 1.0 means calculation of elastic/plastic hogging and sagging moments of resistance of beam to be ignored at both ends of beam. This implies no support exist at either end of the member.

A value of -1.0 means calculation of

Section 8A1

8-27


Parameter Name


elastic/plastic hogging and sagging moments of resistance of beam to be considered at both ends of beam. This implies support exist at both ends of the member.**

COMBINE 0.0 Default value means there will be no member combination.

A value of 1.0 means there will be no printout of sectional force and critical load for combined member in the output.

A value of 2.0 means there will be printout of sectional force for combined member in the output.

A value of 3.0 means there will be printout of both sectional force and critical load for combined member in the output. ***

HLINK Spacing of longitudinal bars measured to the

outer face

Longer dimension of the rectangular confining hoop measured to its outer face. It shall not exceed 300 mm as per Cl. 7.4.8. If hlink value as provided in the input file does not satisfy the clause the value will be internally assumed as the default one. This parameter is valid for rectangular column.

Bar combination has been introduced for detailing. Please refer section 8A1.6 for details.

* EFACE and SFACE command is not valid for member combination. ** IPLM and IMB commands are not valid for member combination. These commands are ignored for members forming physical member.


Section 8A1

8-28 *** The purpose of COMBINE command is the following:

1. If a beam spanning between two supports is subdivided into many

sub-beams this parameter will combine them into one member. It can also be used to combine members to form one continuous beam spanning over more than two supports.

2. When two or more members are combined during design plastic or elastic moments will be calculated at the column supports. At all the intermediate nodes (if any) this calculation will be ignored. Please note that the program only recognizes column at right angle to the beam. Inclined column support is ignored.

3. It will calculate sectional forces at 13 sections along the length of the combined member.

4. It will calculate critical loads (similar to that of Design Load Summary) for all active load cases during design. Beams will be combined only when DESIGN BEAM command is issued. The following lines should be satisfied during combination of members:

1. Members to be combined should have same sectional properties if any single span between two column supports of a continuous beam are subdivided into several members.

2. Members to be combined should have same constants (E, Poi ratio, alpha, density and beta angle)

3. Members to be combined should lie in one straight line. 4. Members to be combined should be continuous. 5. Vertical members (i.e. columns) cannot be combined. 6. Same member cannot be used more than once to form two different

combined members. 7. The maximum number of members that can be combined into one

member is 299.

Section 8A1

8-29

Note: Sectional forces and critical load for combined member output will only be available when all the members combined are successfully designed in both flexure and shear. ENSH and RENSH parameters will have to be provided (as and when necessary) even if physical member has been formed. The following lines show a standard example for design to be performed in IS 13920. STAAD SPACE UNIT METER MTON JOINT COORDINATES ………………………………….. MEMBER INCIDENCES ………………………………….. MEMBER PROPERTY INDIAN ………………………………….. CONSTANTS ……………………. SUPPORTS ……………………. DEFINE 1893 LOAD ZONE 0.05 I 1 K 1 B 1 SELFWEIGHT JOINT WEIGHT ………………………. LOAD 1 SEISMIC LOAD IN X DIR 1893 LOAD X 1 LOAD 2 SEISMIC LOAD IN Z DIR 1893 LOAD Z 1 LOAD 3 DL MEMBER LOAD …… UNI GY -5 LOAD 4 LL


Section 8A1

8-30 MEMBER LOAD ……. UNI GY -3 LOAD COMB 5 1.5(DL+LL) 3 1.5 4 1.5 LOAD COMB 6 1.2(DL+LL+SLX) 1 1.2 3 1.2 4 1.2 LOAD COMB 7 1.2(DL+LL-SLX) 1 1.2 3 1.2 4 -1.2 LOAD COMB 8 1.2(DL+LL+SLZ) 2 1.2 3 1.2 4 1.2 LOAD COMB 9 1.2(DL+LL-SLZ) 2 1.2 3 1.2 4 -1.2 PDELTA ANALYSIS LOAD LIST 5 TO 9 START CONCRETE DESIGN CODE IS13920 UNIT MMS NEWTON FYMAIN 415 ALL FC 20 ALL MINMAIN 12 ALL MAXMAIN 25 ALL TRACK 2.0 ALL *** Unfactored gravity load on members 110 to 112 is 8 t/m (DL+LL) i.e. 78.46 New/mm EUDL 78.46 MEMB 110 TO 112

** Members to be combined into one physical member COMBINE 3.0 MEMB 110 TO 112

*** Plastic moment considered PLASTIC 1.0 MEMB 110 TO 112 DESIGN BEAM 110 TO 112 DESIGN COLUMN ……… END CONCRETE DESIGN FINISH

Section 8A1

8-31

8A1.6 Bar Combination

Initially the program selects only one bar to calculate the number of bars required and area of steel provided at each section along the length of the beam. Now two bar diameters can be specified to calculate a combination of each bar to be provided at each section. The syntax for bar combination is given below.

START BAR COMBINATION MD1 <bar diameter> MEMB <member list> MD2 <bar diameter> MEMB <member list> END BAR COMBINATION

MD2 bar diameter should be greater than MD1 bar diameter. The typical output for bar combination is shown below:

OUTPUT FOR BAR COMBINATION

----------------------------------------------------------------------------

| M A I N R E I N F O R C E M E N T |

----------------------------------------------------------------------------SECTION | 0.0- 2166.7 | 2166.7- 6500.0 | 6500.0- 8666.7 |

| mm | mm | mm |----------------------------------------------------------------------------TOP | 6-20í + 1-25í | 2-20í + 1-25í | 2-20í |


Prov| 2376.79 | 1119.64 | 628.57 |Ld (mm) | 940.2 | 940.2 | 940.2 |----------------------------------------------------------------------------BOTTOM | 4-20í | 2-20í | 2-20í |


Prov| 1257.14 | 628.57 | 628.57 |Ld (mm) | 940.2 | 940.2 | 940.2 |----------------------------------------------------------------------------

The beam length is divided into three parts, two at its ends and one at span. Ld gives the development length to be provided at the two ends of each section.


Section 8A1

8-32

Sample example showing calculation of design shear force as per Clause 6.3.3

For Beam No. 1 and 2 Section Width b 250 mm Depth D 500 mm Characteristic Strength of Steel fy 415 N/sq. mm Characteristic Strength of Concrete fck 20 N/sq. mm Clear Cover 25 mm Bar Diameter 12 mm Effective Depth d 469 mm Eudl w 6.5 N/sq. mm Length L 4000 mm Ast_Top_A 339.29 sq. mm Ast_Bot_A 226.19 sq. mm Ast_Top_B 226.19 sq. mm Ast_Bot_B 339.29 sq. mm

Section 8A1

8-33

Steps Calculation of Simple Shear Simple shear from gravity load on span =

Va = Vb = 1.2 * w * L / 2 = 15600N

Calculation of Moment Of Resistances Based On Area Of Steel Provided Sagging Moment Of Resistance of End A Mu,as =

0.87 * fy * Ast_Bot_A * d * ( 1 - Ast_Bot_A * fy / b * d * fck)

= 36768130.05 N

Hogging Moment Of Resistance of End A Mu,ah =

0.87 * fy * Ast_Top_A * d * ( 1 - Ast_Top_A * fy / b * d * fck)

= 54003057.45 N

Sagging Moment Of Resistance of End A Mu,bs =

0.87 * fy * Ast_Bot_B * d * ( 1 - Ast_Bot_B * fy / b * d * fck)

= 54003057.45 N

Hogging Moment Of Resistance of End A Mu,bh =

0.87 * fy * Ast_Top_B * d * ( 1 - Ast_Top_B* fy / b * d * fck)

= 36768130.05 N

Calculation of Shear Force Due To Formation Of Plastic Hinge At Both Ends Of The Beam Plus The Factored Gravity Load On Span

FIG1: SWAY TO RIGHT

Vur,a = Va - 1.4 [ ( Mu,as + Mu,bh ) / L ] = -10137.69104 N

Vur,b = Va + 1.4 [ ( Mu,as + Mu,bh ) / L ] = 41337.69104 N


Section 8A1

8-34

FIG2: SWAY TO LEFT Vul,a = Va + 1.4 [ ( Mu,ah + Mu,bs ) / L ] = 53402.14022 N

Vul,b = Va - 1.4 [ ( Mu,ah + Mu,bs ) / L ] = - 22202.14022 N Design Shear Force Shear Force From Analysis At End A , Va,anl = 11.56 N Design Shear Force At End A, Vu,a = Max ( Va,anl, Vur,a, Vul,a) = 53402.14022 N Shear Force From Analysis At End B , Vb,anl = -6.44 N Design Shear Force At End B, Vu,b = Max ( Vb,anl, Vur,b, Vul,b) = 41337.69104 N

For Beam No. 3 Section Width b 300 mm Depth D 450 mm Characteristic Strength of Steel fy 415 N/sq. mm Characteristic Strength of Concrete fck 20 N/sq. mm Clear Cover 25 mm Bar Diameter 12 mm Effective Depth d 419 mm Eudl w 6.5 N/sq. mm Length L 3000 mm Ast_Top_A 226.19 sq. mm Ast_Bot_A 339.29 sq. mm Ast_Top_B 452.39 sq. mm Ast_Bot_B 226.19 sq. mm

Section 8A1

8-35

Calculation of Simple Shear Simple shear from gravity load on span =

Va = Vb = 1.2 * w * L / 2 = 11700N

Calculation of Moment Of Resistances Based On Area Of Steel Provided Sagging Moment Of Resistance of End A Mu,as =

0.87 * fy * Ast_Bot_A * d * ( 1 - Ast_Bot_A * fy / b * d * fck)

= 48452983 N

Hogging Moment Of Resistance of End A Mu,ah =

0.87 * fy * Ast_Top_A * d * ( 1 - Ast_Top_A * fy / b * d * fck)

= 32940364.5 N

Sagging Moment Of Resistance of End A Mu,bs =

0.87 * fy * Ast_Bot_B * d * ( 1 - Ast_Bot_B * fy / b * d * fck)

= 32940364.5 N

Hogging Moment Of Resistance of End A Mu,bh =

0.87 * fy * Ast_Top_B * d * ( 1 - Ast_Top_B* fy / b * d * fck) = 63326721.3 N

Calculation of Shear Force Due To Formation Of Plastic Hinge At Both Ends Of The Beam Plus The Factored Gravity Load On Span

FIG1: SWAY TO RIGHT

Vur,a = Va - 1.4 [ ( Mu,as + Mu,bh ) / L ] = -40463.862 N

Vur,b = Va + 1.4 [ ( Mu,as + Mu,bh ) / L ] = 63863.862 N


Section 8A1

8-36

Vul,a = Va + 1.4 [ ( Mu,ah + Mu,bs ) / L ] = 42444.3402 N

Vul,b = Va - 1.4 [ ( Mu,ah + Mu,bs ) / L ] = -15144.34 N Design Shear Force Shear Force From Analysis At End A , Va,anl = -10.31 N Design Shear Force At End A, Vu,a = Max ( Va,anl, Vur,a, Vul,a) = 42444.3402 N Shear Force From Analysis At End B , Vb,anl = -23.81 N Design Shear Force At End B, Vu,b = Max ( Vb,anl, Vur,b, Vul,b) = 63863.862 N

8-37

Steel Design Per IS800

8B.1 Design Operations

STAAD contains a broad set of facilities for designing structural members as individual components of an analyzed structure. The member design facilities provide the user with the ability to carry out a number of different design operations. These facilities may be used selectively in accordance with the requirements of the design problem. The operations to perform a design are: • Specify the members and the load cases to be considered in the

design. • Specify whether to perform code checking or member

selection. • Specify design parameter values, if different from the default

values. • Specify whether to perform member selection by optimization.

These operations may be repeated by the user any number of times depending upon the design requirements. The entire ISI steel section table is supported. Section 8B.13 describes the specification of steel sections.

Section 8B


Section 8B

8-38


This section presents some general statements regarding the implementation of Indian Standard code of practice (IS:800-1984) for structural steel design in STAAD. The design philosophy and procedural logistics for member selection and code checking are based upon the principles of allowable stress design. Two major failure modes are recognized: failure by overstressing, and failure by stability considerations. The flowing sections describe the salient features of the allowable stresses being calculated and the stability criteria being used. Members are proportioned to resist the design loads without exceeding the allowable stresses and the most economic section is selected on the basis of least weight criteria. The code checking part of the program checks stability and strength requirements and reports the critical loading condition and the governing code criteria. It is generally assumed that the user will take care of the detailing requirements like provision of stiffeners and check the local effects such as flange buckling and web crippling.

8B.3 Allowable Stresses

The member design and code checking in STAAD are based upon the allowable stress design method as per IS:800 (1984). It is a method for proportioning structural members using design loads and forces, allowable stresses, and design limitations for the appropriate material under service conditions. It would not be possible to describe every aspect of IS:800 in this manual. This section, however, will discuss the salient features of the allowable stresses specified by IS:800 and implemented in STAAD. Appropriate sections of IS:800 will be referenced during the discussion of various types of allowable stresses.

Section 8B

8-39

8B.3.1 Axial Stress

Tensile Stress The allowable tensile stress, as calculated in STAAD as per IS:800 is described below. The permissible stress in axial tension, σat in MPa on the net effective area of the sections shall not exceed

σat = 0.6 fy Where, fy = minimum yield stress of steel in Mpa Compressive Stress Allowable compressive stress on the gross section of axially loaded compression members shall not exceed 0.6fy nor the permissible stress σac calculated based on the following formula: (Clause: 5.1.1)

accc y

nf fnccf nyf

σ =⋅

+0 6 1.

[( ) ( ) ]/

Where, σac = Permissible stress in axial compression, in Mpa fy = Yield stress of steel, in Mpa fcc = Elastic critical stress in compression = π2 E/λ2 E = Modulus of elasticity of steel, 2 X 105 Mpa λ=l/r = Slenderness ratio of the member, ratio of the effective

length to appropriate radius of gyration n = A factor assumed as 1.4.


Section 8B

8-40

8B.3.2 Bending Stress

The allowable bending stress in a member subjected to bending is calculated based on the following formula: (Clause: 6.2.1)

σbt or σbc = 0.66 fy Where, σbt = Bending stress in tension σbc = Bending stress in compression fy = Yield stress of steel, in MPa For an I-beam or channel with equal flanges bent about the axis of maximum strength (z-z axis), the maximum bending compressive stress on the extreme fibre calculated on the effective section shall not exceed the values of maximum permissible bending compressive stress. The maximum permissible bending compressive stress shall be obtained by the following formula: (Clause: 6.2.2)

6.2.3) :(Clause

])f y(n

)f cb(n

[

1/nf yfcb0.66σbc

+

⋅=

Where, fy = Yield stress of steel, in Mpa n = A factor assumed as 1.4. fcb = Elastic critical stress in bending, calculated by the

following formula:

cbf k X k Y cc

= +1 22

1 [ ]

Section 8B

8-41

Where,

X Y ITr D

MPyry

a= +1 120 1

2

2 Y = 26.5x105

( / )

k1 = a coefficient to allow for reduction in thickness or

breadth of flanges between points of effective lateral restraint and depends on ψ, the ratio of the total area of both flanges at the point of least bending moment to the corresponding area at the point of greatest bending moment between such points of restraint.

k2 = a coefficient to allow for the inequality of flanges, and

depends on ω, the ratio of the moment of inertia of the compression flange alone to that of the sum of the moment of the flanges each calculated about its own axis parallel to the y-yaxis of the girder, at the point of maximum bending moment.

1 = effective length of compression flange ry = radius of gyration of the section about its axis of

minimum strength (y-y axis) T = mean thickness of the compression flange, is equal to the

area of horizontal portion of flange divided by width. D = overall depth of beam c1 ,c2 = respectively the lesser and greater distances from the

section neutral axis to the extreme fibres.

8B.3.3 Shear Stress

Allowable shear stress calculations are based on Section 6.4 of IS:800. For shear on the web, the gross section taken into consideration consist of the product of the total depth and the web thickness. For shear parallel to the flanges, the gross section is taken as 2/3 times the total flange area.


Section 8B

8-42

8B.3.4 Combined Stress

Members subjected to both axial and bending stresses are proportioned accordingly to section 7 of IS:800. All members subject to bending and axial compression are required to satisfy the equation of Section 7.1.1.(a) for intermediate points, and equation of Section 7.1.1.(b) for support points. For combined axial tension and bending the equation of Section 7.1.2. is required to be satisfied. Cm coefficients are calculated according to the specifications of Section 7.1.3. information regarding occurrence of sidesway can be provided through the use of parameters SSY and SSZ. In the absence of any user provided information, sidesway will be assumed.


In STAAD implementation of IS:800, the user is allowed complete control of the design process through the use of design parameters. Available design parameters to be used in conjunction with IS:800 are listed in Table 7B.1 of this section along with their default values and applicable restrictions. Users should note that when the TRACK parameter is set to 1.0 and use in conjunction with this code, allowable bending stresses in compression (FCY & FCZ), tension (FTY & FTZ), and allowable shear stress (FV) will be printed out in Member Selection and Code Check output in Mpa. When TRACK is set to 2.0, detailed design output will be provided.

8B.5 Stability Requirements

Slenderness ratios are calculated for all members and checked against the appropriate maximum values. Section 3.7 of IS:800

Section 8B

8-43

summarizes the maximum slenderness ratios for different types of members. In STAAD implementation of IS:800, appropriate maximum slenderness ratio can be provided for each member. If no maximum slenderness ratio is provided, compression members will be checked against a maximum value of 180 and tension members will be checked against a maximum value of 400.

8B.6 Truss Members

As mentioned earlier, a truss member is capable of carrying only axial forces. So in design no time is wasted in calculating bending or shear stresses, thus reducing design time considerably. Therefore, if there is any truss member in an analysis (like bracing or strut, etc.), it is wise to declare it as a truss member rather than as a regular frame member with both ends pinned.

8B.7 Deflection Check

This facility allows the user to consider deflection as a criteria in the CODE CHECK and MEMBER SELECTION processes. The deflection check may be controlled using three parameters which are described in Table 7B.1. Note that deflection is used in addition to other strength and stability related criteria. The local deflection calculation is based on the latest analysis results.

8B.8 Code Checking

The purpose of code checking is to verify whether the specified section is capable of satisfying applicable design code requirements. The code checking is based on the IS:800 (1984) requirements. Forces and moments at specified sections of the members are utilized for the code checking calculations. Sections may be specified using the BEAM parameter or the SECTION command. If no sections are specified, the code checking is based on forces and moments at the member ends.


Section 8B

8-44 The code checking output labels the members as PASSed or FAILed. In addition, the critical condition (applicable IS:800 clause no.), governing load case, location (distance from the start) and magnitudes of the governing forces and moments are also printed out.


STAAD is capable of performing design operations on specified members. Once an analysis has been performed, the program can select the most economical section, that is the lightest section, which satisfies the applicable code requirements. The section selected will be of the same type (I-Section, Channel etc.) as originally specified by the user. Member selection may be performed with all types of steel sections listed in Section 7B.13 and user provided tables. Selection of members, whose properties are originally provided from user specified table, will be limited to sections in the user provided table. Member selection can not be performed on members whose cross sectional properties are specified as PRISMATIC. The process of MEMBER SELECTION may be controlled using the parameters listed in Table 8B.1. It may be noted that the parameters DMAX and DMIN may be used to specify member depth constraints for selection. If PROFILE parameter is provided, the search for the lightest section is restricted to that profile. Up to three (3) profiles may be provided for any member with a section being selected from each one.

8B.10 Member Selection By Optimization

Steel section selection of the entire structure may be optimized. The optimization method utilizes a state-of-the -art numerical technique which requires automatic multiple analysis. The user may start without a specifically designated section. However, the section profile type (BEAM, COLUMN, CHANNEL, ANGLE etc.) must be specified using the ASSIGN command (see Chapter 6).

Section 8B

8-45

The optimization is based on member stiffness contributions and corresponding force distributions. An optimum member size is determined through successive analysis/design iterations. This method requires substantial computer time and hence should be used with caution.


For code checking or member selection, the program produces the result in a tabulated fashion. The items in the output table are explained as follows: a) MEMBER refers to the member number for which the design

is performed b) TABLE refers to the INDIAN steel section name which has

been checked against the steel code or has been selected. c) RESULT prints whether the member has PASSED or FAILed.

If the RESULT is FAIL, there will be an asterisk (*) mark in front of the member number.

d) CRITICAL COND refers to the section of the IS:800 code

which governs the design. e) RATIO prints the ratio of the actual stresses to allowable

stresses for the critical condition. Normally a value of 1.0 or less will mean the member has passed.

f) LOADING provides the load case number which governs the design.

g) FX, MY and MZ provide the axial force, moment in local y-

axis and moment in local z-axis respectively. Although STAAD does consider all the member forces and moments (except torsion) to perform design, only FX,MY and MZ are printed since they are the ones which are of interest, in most cases.


Section 8B

8-46 h) LOCATION specifies the actual distance from the start of the

member to the section where design forces govern.

i) If the parameter TRACK is set to 1.0, the program will blockout part of the table and will print allowable bending stresses in compression (FCY & FCZ) and tension (FTY & FTZ), allowable axial stress in compression (FA), and allowable shear stress (FV). When the parameter TRACK is set to 2.0 for all members parameter code values as shown in Fig 8B.1.

STAAD.Pro CODE CHECKING - (ISA )

***********************

|--------------------------------------------------------------------------|| Y PROPERTIES ||************* | IN CM UNIT || * |=============================| ===|=== ------------ ||MEMBER 7 * | | | AX = 72.4 || * | ST ISLB400 | | --Z AY = 32.0 ||DESIGN CODE * | | | AZ = 27.5 || IS-800 * =============================== ===|=== SY = 86.8 || * SZ = 965.3 || * |<---LENGTH (ME= 3.00 --->| RY = 3.1 ||************* RZ = 16.3 || || 104.6( KN-METR) ||PARAMETER |L1 STRESSES ||IN NEWT MM | IN NEWT MM||--------------- + -------------|| KL/R-Y= 95.4 | FA = 84.8 || KL/R-Z= 18.4 + fa = 1.6 || UNL = 3000.0 | FCZ = 116.6 || C = 400.0 + FTZ = 165.0 || CMY = 0.85 | FCY = 165.0 || CMZ = 0.85 + FTY = 165.0 || FYLD = 249.9 | L3 fbz = 108.4 || NSF = 0.9 +---+---+---+---+---+---+---+---+---+---| fby = 0.0 || DFF = 325.0 92.7 FV = 100.0 || dff = 4383.0 ABSOLUTE MZ ENVELOPE || (WITH LOAD NO.) || || MAX FORCE/ MOMENT SUMMARY ( KN-METR) || ------------------------- || || AXIAL SHEAR-Y SHEAR-Z MOMENT-Y MOMENT-Z || || VALUE -23.7 61.3 0.0 0.0 104.6 || LOCATION 0.0 0.0 0.0 0.0 0.0 || LOADING 3 1 0 0 1 || ||**************************************************************************||* *||* DESIGN SUMMARY ( KN-METR) *||* -------------- *||* *||* RESULT/ CRITICAL COND/ RATIO/ LOADING/ *|| FX MY MZ LOCATION || ====================================================== || PASS IS-7.1.2 0.667 1 || 9.62 T 0.0 -104.6 0.00 || || DEFLECTION * PASS || RATIO: 0.074 LOADING: 3 LOCATION: 0.67 ||* *||**************************************************************************|

Section 8B

8-47

8B.12 Indian Steel Table

This is an important feature of the program since the program will read section properties of a steel member directly from the latest ISI steel tables (as published in ISI-800). These properties are stored in memory corresponding to the section designation (e.g. ISMB250, etc.). If called for, the properties are also used for member design. Since the shear areas are built in to these tables, shear deformation is always considered for these members. Almost all ISI steel tables are available for input. A complete listing of the sections available in the built-in steel section library may be obtained using the tools of the graphical user interface. Following are the descriptions of all the types of sections available: Rolled Steel Beams (ISJB, ISLB, ISMB and ISHB). All rolled steel beam sections are available the way they are designated in the ISI handbook., e.g. ISJB225, ISWB400, etc.

20 TO 30 TA ST ISLB325

NOTE: In case of two identical beams, the heavier beam is designated with an ‘A” on the end., e.g. ISHB400 A, etc.

1 TO 5 TA ST ISHB400A


Section 8B

8-48 Rolled Steel Channels (ISJC, ISLC and ISMC) All these shapes are available as listed in ISI section handbook. Designation of the channels are per the scheme used by ISI.

10 TO 20 BY 2 TA ST ISMC125 12 TA ST ISLC300

Double Channels Back to back double channels, with or without spacing between them, are available. The letter D in front of the section name will specify a double channel, e.g. D ISJC125, D ISMC75 etc.

21 22 24 TA D ISLC225

Rolled Steel Angles Both rolled steel equal angles and unequal angles are available for use in the STAAD implementation of ISI steel tables. The following example with explanations will be helpful in understanding the input procedure:

ISA 150 X 75 X 8 Angle symbol Thickness in mm Long leg length in mm Short leg length in mm

At present there is no standard way to define the local y and z axes for an angle section. The standard section has local axis system as illustrated in Fig.2.4 of this manual. The standard angle is specified as:

51 52 53 TA ST ISA60X60X6

Section 8B

8-49

This specification has the local z-axis ( i.e., the minor axis corresponding to the V-V axis specified in the steel tables. Many engineers are familiar with a convention used by some other programs in which the local y-axis is the minor axis. STAAD provides for this convention by accepting the command:

54 55 56 TA RA ISA50X30X6 (RA denotes reverse angle)

Double Angles Short leg back to back or long leg back to back double angles can be specified by inputting the word SD or LD, respectively, in front of the angle size. In case of an equal angle either LD or SD will serve the purpose. For example,

14 TO 20 TA LD ISA50X30X5 SP 1.5 23 27 TA SD ISA75X50X6

Rolled Tees (ISHT, ISST, ISLT and ISJT) All the rolled tee sections are available for input as they are specified in the ISI handbook. Following example illustrates the designated method.

1 2 5 8 TA ST ISNT100 67 68 TA ST ISST250

Pipes (Circular Hollow Sections) To designate circular hollow sections from ISI tables, use PIP followed by the numerical value of diameter and thickness of the section in mm omitting the decimal section of the value provided for diameter. Following example will illustrate the designation.


Section 8B

8-50

10 15 TA ST PIP 213.2 (Specifies a 213 mm dia. pipe with 3.2 mm wall thickness)

Circular pipe sections can also be specified by providing the outside and inside diameters of the section. For example,

1 TO 9 TA ST PIPE OD 25.0ID 20.0 (specifies a pipe with outside dia. of 25 and inside dia. of 20 in current length units)

Only code checking and no member selection will be performed if this type of specification is used. Tubes (Rectangular or Square Hollow Sections) Designation of tubes from the ISI steel table is illustrated below. TUB 400 200 12.5 Tube Symbol Thickness in mm Height in mm Width in mm

Example:

15 TO 25 TA ST TUB 160808


6 TA ST TUBE DT 8.0 WT 6.0 TH 0.5 is a tube that has a height of 8, a width of 6, and a wall thickness of 0.5.

Section 8B

8-51

Note that only code checking and no member selection is performed for TUBE sections specified this way. Plate And Angle Girders (With Flange Plates) All plate and angle grinders (with flange plates) are available as listed in ISI section handbook. The following example with explanations will be helpful in understanding the input procedure.

I 1000 12 A 400 12 A F B E C D A Plate and angle girder symbol. B Web plate width in mm. C Web plate thickness in mm. D Flange angle (Flange angle key below): E Flange plate width in mm. F Flange plate thickness in mm. SYMBOL ANGLE(A X B X t)(all in mm) A 150X150X18 B 200X100X15 C 200X150X18 E 200X200X18


Section 8B

8-52 SINGLE JOIST WITH CHANNELS AND PLATES ON THE FLANGES TO BE USED AS GIRDERS All single joist with channel and plates on the flanges to be used as girders are available as listed in ISI section handbook. The following example with explanations will be helpful in understanding the input procedure.

IW 450 350 X 10 20 A E B D C A Joist Designation: IW450=ISWB450 B Top flange channel designation: 350=ISMC350 C Constant (always X). D Top flange plate thickness in mm. NOTE: D is 0 for no plate. E Bottom flange plate thickness in mm. NOTE: The heavier ISWB600 has been omitted, since the lighter ISWB600 is more efficient.

Section 8B

8-53

Table 8B.1 Indian Steel Design - IS : 800 Parameters

Parameter Name


KY 1.0 K value in local y-axis. Usually, this is minor axis.

KZ 1.0 K value in local z-axis. Usually, this is major axis.

LY Member Length Length in local y-axis to calculate slenderness ratio.

LZ Member Length Same as above except in local z-axis (major).

FYLD 250 MPA

(36.25 KSI) Yield strength of steel.


UNL Member Length Unsupported length for calculating allowable bending stress.

UNF 1.0 Same as above provided as a fraction of actual member length.

SSY 0.0 0.0 = Sidesway in local y-axis. 1.0 = No sidesway

SSZ 0.0 Same as above except in local z-axis.

CMY

CMZ

0.85 for sidesway and

calculated for no sidesway

Cm value in local y & z axes

MAIN 180 (Comp. Memb.)

Allowable Kl/r for slenderness calculations for compression members.

TMAIN 400 (Tension Memb)

Allowable Kl/r for slenderness calculations for tension members.

TRACK 0.0

0.0 = Suppress critical member stresses 1.0 = Print all critical member stresses 2.0 = Print expanded output. If there is

deflection check it will also print the governing load case number for deflection check whenever critical condition for design is not DEFLECTION. (see fig.8B.1)




Section 8B

8-54

Table 8B.1 Indian Steel Design - IS : 800 Parameters

Parameter Name



BEAM 3.0

0.0 = design only for end moments and those at locations specified by the SECTION command.

1.0 = calculate section forces at twelfth points along the beam, design at each intermediate location and report the critical location where ratio is maximum.

PROFILE - Search for the lightest section for the profile mentioned.

DFF None

(Mandatory for deflection check)






NOTES: 1) "Deflection Length" is defined as the length that is used for


Section 8B

8-55

D = Maximum local deflection for members1 2 and 3.

D

1

2 3

4

1

2 3






8B.13 Column With Lacings And Battens

For columns with large loads it is desirable to build rolled sections at a distance and inter-connect them. The joining of element sections is done by two ways: a) Lacing and b) Batten Double channel sections (back-to-back and face-to-face) can be joined either by lacing or by batten plates having rivetted or welded connection. Table 8B.2 gives the parameters that are required for Lacing or batten design. These parameters will have to be provided in unit NEW MMS along with parameters defined in Table 8B.1.


Section 8B

8-56

Table 8B.2 Indian Concrete Design IS800 Parameters

Parameter Name


CTYPE 1 Type of joining

CTYPE = 1 implies single lacing with rivetted connection

CTYPE = 2 implies double lacing with rivetted connection

CTYPE = 3 implies single lacing with welded connection

CTYPE = 4 implies double lacing with welded connection

CTYPE = 5 implies batten with rivetted connection

CTYPE = 6 implies batten with welded connection

THETA 50 degree Angle of inclination of lacing bars. It should lie between 40 degree and 70 degree.

DBL 20 mm Nominal diameter of rivet

FVB 100 N/mm2 Allowable shear stress in rivet

FYB 300 N/mm2 Allowable bearing stress in rivet

WMIN 6 mm Minimum thickness of weld

WSTR 108 N/mm2 Allowable welding stress

EDIST 32 mm (Rivetted Connection)

25 mm (Welded Connection)

Edge Distance

Section 8B

8-57

Table 8B.2 Indian Concrete Design IS800 Parameters

Parameter Name


DCFR 0.0 0.0 implies double channel back-to-back.

1.0 Implies double channel face-to-face.

This parameter is used when member properties are defined through user provided table using GENERAL option.

COG 0.0 mm Centre of gravity of the channel. This parameter is used when member properties are defined through user provided table using GENERAL option.

SPA 0.0 mm Spacing between double channels. This parameter is used when member properties are defined through user provided table using GENERAL option.


Section 8B

8-58

8-59


8C.1 General Comments

This section presents some general statements regarding the implementation of Indian Standard code of practice (IS:802-1995 – Part 1) for structural steel design for overhead transmission line towers in STAAD. The design philosophy and procedural logistics for member selection and code checking are based upon the principles of allowable stress design. Two major failure modes are recognized: failure by overstressing, and failure by stability considerations. The flowing sections describe the salient features of the allowable stresses being calculated and the stability criteria being used. Members are proportioned to resist the design loads without exceeding the allowable stresses and the most economic section is selected on the basis of least weight criteria. The code checking part of the program checks stability and strength requirements and reports the critical loading condition and the governing code criteria.

8C.2 Allowable Stresses

The member design and code checking in STAAD are based upon the allowable stress design method as per IS:802 (1995). It is a method for proportioning structural members using design loads and forces, allowable stresses, and design limitations for the appropriate material under service conditions. This section discusses the salient features of the allowable stresses specified by IS:802 and implemented in STAAD.

Section 8C

Steel Design Per IS802 Section 8C

8-60

8C.2.1 Axial Stress

Tensile Stress

The allowable tensile stress, as calculated in STAAD as per IS:802 is described below. The estimated tensile stresses on the net effective sectional area in various members, multiplied by the appropriate factor of safety shall not exceed minimum guaranteed yield stress of the material. Thus, the permissible stress in axial tension, σat in MPa on the net effective area of the sections shall not exceed

σat = fy Where, fy = minimum yield stress of steel in Mpa Compressive Stress

The estimated compressive stresses in various members multiplied by the appropriate factor of safety shall not exceed the value given by the formulae described below.

Condition 1: If

=

≤

yFtb

tb 210

lim

CCr/KL ≤

Stress Fa= yFCc

r/KL211

2

×

− N/mm2

CCr/KL >

Section 8C

8-61

Stress Fa = ( )2

2

/ rKLE×π

N/mm2

Condition 2: If lim

tb

≤

tb

≤ yF

378 when Fy is the N/mm2

formulae given in condition 1 shall be used substituting for Fy the value Fcr given by:

Fcr = y

lim

F

tb

tb677.0

677.1

−

Condition 3:

tb >

yF378 when Fy is the N/mm2 formulae given in

condition 1 shall be used substituting for Fy the value Fcr given by

Fcr = 2

tb

65550

In which CC = yFE2π

Where Fa = allowable unit stress in compression, Mpa Fy = minimum guaranteed yield stress of the material, Mpa K = restraint factor, L = unbraced length of the compression member in cm, and R = appropriate radius of gyration in cm. E = modulus of elasticity of steel in N/mm2


8-62

rKL = largest effective slenderness ratio of any unbraced segment

of the member, b = distance from edge of the fillet to the extreme fibre in mm, and t = thickness of flange in mm. Note : The maximum permissible value of b/t for any type of steel shall not exceed 25.

8C.3 Stability Requirements

Slenderness ratios are calculated for all members and checked against the appropriate maximum values. Following are the default values used in STAAD: Compression Members:

Members Slenderness value

Leg Members, ground wire peak member and lower members of cross arms in compression

120

Other members carrying computed stress 200

Redundant members and those carrying nominal stresses

250

Section 8C

8-63

Slenderness ratios of compression members are determined as follows:

If ELA number given in the input for any particular member is such that condition for L/r ratio to fall within the specified range is not satisfied, STAAD goes on by the usual way of finding slenderness ratio using K*L/r formula.

ELA NO.

Type of members

Value of KL/r

1 Leg sections or joint members bolted at connections in both faces

L/r

2 Members with concentric loading at both ends of the unsupported panel with values of L/r up to and including 120

L/r

3 Member with concentric loading at one end and normal eccentricities at the other end of the unsupported panel for value of L/r up to and including 120

30 + 0.75L/r

4 Members with normal framing eccentricities at both ends of the unsupported panel for values of L/r up to and including 120

60 + 0.5L/r

5 Member unrestrained against rotation at both ends of the unsupported panel for value of L/r from 120 to 200

L/r

6 Members partially restrained against rotation at one end of the unsupported panel for values of L/r over 120 and up to and including 225

28.6 + 0.762L/r

7 Members partially restrained against rotation at both ends of the unsupported panel for values of L/r over 120 and up to and including 250

46.2 + 0.615L/r


8-64

Tension Members:

Slenderness ratio KL/r of a member carrying axial tension only, shall not exceed 400.

8C.4 Minimum Thickness Requirement

As per Clause7.1 of IS: 802-1995 minimum thickness of different tower members shall be as follows:

Minimum Thickness, mm Members Galvanized Painted

Leg Members, ground wire peak member and lower members of cross arms in compression

5 6

Other members

4 5

8C.5 Code Checking

The purpose of code checking is to verify whether the specified section is capable of satisfying applicable design code requirements. The code checking is based on the IS:802 (1995) requirements. Axial forces at two ends of the members are utilized for the code checking calculations. The code checking output labels the members as PASSed or FAILed. In addition, the critical condition, governing load case, location (distance from the start) and magnitudes of the governing forces are also printed out. Using TRACK 9 option calculation steps are also printed.

Section 8C

8-65

8C.5.1 Design Steps

The following are the steps followed in member design. Step 1 Thickness of the member (maximum of web and flange thicknesses) is checked against minimum allowable thickness, depending upon whether the member is painted or galvanised. Step 2 If the minimum thickness criterion is fulfilled, the program determines whether the member is under compression or tension for the loadcase under consideration. Depending upon whether the member is under tension or compression the slenderness ratio of the member is calculated. This calculated ratio is checked against allowable slenderness ratio. Step 3 If the slenderness criterion is fulfilled check against allowable stress is performed. Allowable axial and tensile stresses are calculated. If the member is under tension and there is no user defined net section factor (NSF), the net section factor is calculated by the program itself (Refer Section 8C.10). Actual axial stress in the member is calculated. The ratio for actual stress to allowable stress, if less than 1.0 or user defined value, the member has passed the check. Step 4 Number of bolts required for the critical loadcase is calculated.


8-66

8C.6 Member Selection

STAAD is capable of performing design operations on specified members. Once an analysis has been performed, the program can select the most economical section, that is the lightest section, which satisfies the applicable code requirements. The section selected will be of the same type (either angle or channel) as originally specified by the user. Member selection may be performed with all angle or channel sections and user provided tables. Selection of members, whose properties are originally provided from user specified table, will be limited to sections in the user provided table. The process of MEMBER SELECTION may be controlled using the parameters listed in Table 8B.1. It may be noted that the parameters DMAX and DMIN may be used to specify member depth constraints for selection. If PROFILE parameter is provided, the search for the lightest section is restricted to that profile. Up to three (3) profiles may be provided for any member with a section being selected from each one.

8C.7 Member Selection by Optimization

Steel section selection of the entire structure may be optimized. The optimization method utilizes a state-of-the -art numerical technique which requires automatic multiple analysis. The optimization is based on member stiffness contributions and corresponding force distributions. An optimum member size is determined through successive analysis/design iterations. This method requires substantial computer time and hence should be used with caution.

Section 8C

8-67

8C.8 Tabulated Results of Steel Design

DETAILS OF CALCULATION ---------------------- CHECK FOR MINIMUM THICKNESS --------------------------- TYPE : GALVANISED MIN. ALLOWABLE THICKNESS : 5.0 MM ACTUAL THICKNESS : 10.0 MM RESULT : PASS


8-68

CHECK FOR SLENDERNESS RATIO --------------------------- VALUE OF L/r : 90.16 EQN. USED TO FIND KL/r : 60.0 + 0.5*L/r ACTUAL VALUE OF KL/r : 105.08 ALLOWABLE KL/r : 120.00 RESULT : PASS

CALCULATION OF ALLOWABLE STRESS -------------------------------- CRITICAL CONDITION : COMPRESSION Cc : sqrt(2*3.141592*3.141592*E/fy) : 127.22 b : LENGTH OF LEG - WEB THICKNESS - ROOT RADIUS : 150.0 - 10.0 - 11.0 : 129.0 MM (b/t)lim : 210/sqrt(fy) : 13.28 (b/t)cal : 12.90 (b/t)cal <= (b/t)lim AND KL/r <= Cc ALLOWABLE AXIAL COMP. STRESS : (1-0.5*(KL/r/Cc)*(KL/r/Cc))*fy : 164.72 MPA CHECK AGAINST PERMISSIBLE STRESS -------------------------------- DESIGN AXIAL FORCE : 250000.00 N ACTUAL AXIAL COMP. STRESS : 250000.00 / 2552.0 : 97.96 MPA RESULT : PASS BOLTING ------- BOLT DIA : 16 MM SHEARING CAP : 20.11 KN BEARING CAP : 38.40 KN BOLT CAP : 20.11 KN NO. OF BOLTS REQD. : 13

Section 8C

8-69

8C.9 Parameter Table for IS 802

Table 8C.1 Indian Steel Design - IS 802 Parameters

Parameter Name


KY 1.0 K value in local y-axis. Usually, this is minor axis.

KZ 1.0 K value in local z-axis. Usually, this is major axis.

LY Member Length Unbraced length in local z-axis to calculate slenderness ratio.

LZ Member Length Unbraced length in local z-axis to calculate slenderness ratio.

FYLD 250 MPA Yield Strength of steel

MAIN 1.0 Type of member to find allowable Kl/r for slenderness calculations for members.

1.0 = Leg, Ground wire peak and lower members of cross arms in compression (KL/r = 120)

2.0 = Members carrying computed stress (KL/r = 200)

3.0 = Redundant members and members carrying nominal stresses (KL/r = 250)

4.0 = Tension members (KL/r = 400)

10.0 = Do not perform KL/r check

Any value greater than 10.0 indicates user defined allowable KL/r ratio. For this case KY and KZ values are must to find actual KL/r ratio of the member.




8-70


Parameter Name


TRACK 0.0 0.0 = Suppress critical member stresses

1.0 = Print all critical member stresses

2.0 = Print expanded output.

9.0 = Print design calculations along with expanded output.

LEG 1.0 This parameter is meant for plain angles.

0.0 = indicates the angle is connected by shorter leg

1.0 = indicates the angle is connected by longer leg

ELA 1.0 This parameter indicates what type of end conditions is to be used. Refer Section 8C.3.

NSF 1.0 Net section factor for tension members

CNSF 0.0 This parameter indicates whether user has defined NSF or the program will calculate it.

0.0 = User has defined NSF

1.0 = Program has to calculate it

DANGLE 0.0 This parameter indicates how the pair of angles are connected to each other. This is required to find whether the angle is in single or double shear and the net section factor.

0.0 = Double angle placed back to back and connected to each side of a gusset plate

1.0 = Pair of angle placed back-to-back connected by only one leg of each angle to the same side of a gusset plate�

DBL 12 mm Diameter of bolt for calculation of number of bolts and net section factor.

FVB 218 MPA Allowable shear stress in bolt

FYB 436 MPA Allowable bearing stress in bolt

Section 8C

8-71


Parameter Name


GUSSET 5 mm Thickness of gusset plate.

Minimum of the thicknesses of the gusset plate and the leg is used for calculation of the capacity of bolt in bearing

NHL 0.0 mm Deduction for holes.

Default value is one bolt width plus 1.5 mm. If the area of holes cut by any straight, diagonal or zigzag line across the member is different from the default value, this parameter is to be defined.

8C.10 Calculation of Net Section Factor

The procedure for calculating net section factor for angle section is described below. Single angle connected by only one leg

Anet = A1 + A2 x K1 Where A1 = net cross-sectional area of the connected leg A2 = gross cross-sectional area of the unconnected leg

And K1 = A2 A13

A13+x

x

The area of a leg of an angle = Thickness of angle x (length of leg – 0.5x thickness of leg)


8-72

Pair of angles placed back-to-back connected by only one leg of each angle to the same side of a gusset plate Anet = A1 + A2 x K1 Where A1 = net cross-sectional area of the connected leg A2 = gross cross-sectional area of the unconnected leg

And K1 = A2 A15

A15+x

x

The area of a leg of an angle = Thickness of angle x (length of leg – 0.5x thickness of leg) Double angles placed back to back and connected to each side of a gusset plate Anet = gross area – deduction for holes Net Section Factor For angle section it is the ratio of the net effective area, Anet to the gross area. For channel section net section factor is taken to be 1.0.

Section 8C

8-73

8C.11 Example Problem No. 28

A transmission line tower is subjected to different loading conditions. Design some members as per IS-802 and show detailed calculation steps for the critical loading condition.

Given: End Condition = Members with normal framing

eccentricities at both ends of the unsupported panel for values of L/r up to and including 120 Diameter of the bolt = 16 mm Thickness of the gusset plate = 8 mm Net Section Factor is to be calculated.


8-74

STAAD TRUSS INPUT WIDTH 79 UNIT METER KN JOINT COORDINATES 1 3 0 3; 2 1.2 27 1.2; 3 2.8 3 2.8; 4 2.6 6 2.6; 5 2.4 9 2.4; 6 2.2 12 2.2; 7 2 15 2; 8 1.8 18 1.8; 9 1.6 21 1.6; 10 1.4 24 1.4; 11 -3 0 3; 12 -1.2 27 1.2; 13 -2.8 3 2.8; 14 -2.6 6 2.6; 15 -2.4 9 2.4; 16 -2.2 12 2.2; 17 -2 15 2; 18 -1.8 18 1.8; 19 -1.6 21 1.6; 20 -1.4 24 1.4; 21 3 0 -3; 22 1.2 27 -1.2; 23 2.8 3 -2.8; 24 2.6 6 -2.6; 25 2.4 9 -2.4; 26 2.2 12 -2.2; 27 2 15 -2; 28 1.8 18 -1.8; 29 1.6 21 -1.6; 30 1.4 24 -1.4; 31 -3 0 -3; 32 -1.2 27 -1.2; 33 -2.8 3 -2.8; 34 -2.6 6 -2.6; 35 -2.4 9 -2.4; 36 -2.2 12 -2.2; 37 -2 15 -2; 38 -1.8 18 -1.8; 39 -1.6 21 -1.6; 40 -1.4 24 -1.4; 41 1.2 30 1.2; 42 -1.2 30 1.2; 43 1.2 30 -1.2; 44 -1.2 30 -1.2; 45 4.2 27 1.2; 46 7.2 27 1.2; 47 4.2 30 1.2; 48 4.2 27 -1.2; 49 7.2 27 -1.2; 50 4.2 30 -1.2; 51 -4.2 27 1.2; 52 -7.2 27 1.2; 53 -4.2 30 1.2; 54 -4.2 27 -1.2; 55 -7.2 27 -1.2; 56 -4.2 30 -1.2; 57 1.2 33 1.2; 58 -1.2 33 1.2; 59 1.2 33 -1.2; 60 -1.2 33 -1.2; 61 0 35 0; MEMBER INCIDENCES 1 1 3; 2 3 4; 3 4 5; 4 5 6; 5 6 7; 6 7 8; 7 8 9; 8 9 10; 9 10 2; 10 11 13; 11 13 14; 12 14 15; 13 15 16; 14 16 17; 15 17 18; 16 18 19; 17 19 20; 18 20 12; 19 13 3; 20 14 4; 21 15 5; 22 16 6; 23 17 7; 24 18 8; 25 19 9; 26 20 10; 27 12 2; 28 11 3; 29 1 13; 30 13 4; 31 3 14; 32 14 5; 33 15 4; 34 15 6; 35 16 5; 36 16 7; 37 17 6; 38 17 8; 39 18 7; 40 18 9; 41 19 8; 42 19 10; 43 20 9; 44 20 2; 45 12 10; 46 21 23; 47 23 24; 48 24 25; 49 25 26; 50 26 27; 51 27 28; 52 28 29; 53 29 30; 54 30 22; 55 3 23; 56 4 24; 57 5 25; 58 6 26; 59 7 27; 60 8 28; 61 9 29; 62 10 30; 63 2 22; 64 1 23; 65 21 3; 66 3 24; 67 23 4; 68 4 25; 69 5 24; 70 5 26; 71 6 25; 72 6 27; 73 7 26; 74 7 28; 75 8 27; 76 8 29; 77 9 28; 78 9 30; 79 10 29; 80 10 22; 81 2 30; 82 31 33; 83 33 34; 84 34 35; 85 35 36; 86 36 37; 87 37 38; 88 38 39; 89 39 40; 90 40 32; 91 23 33; 92 24 34; 93 25 35; 94 26 36; 95 27 37; 96 28 38; 97 29 39; 98 30 40; 99 22 32; 100 21 33; 101 31 23; 102 23 34; 103 33 24; 104 24 35; 105 25 34; 106 25 36; 107 26 35; 108 26 37; 109 27 36; 110 27 38; 111 28 37; 112 28 39; 113 29 38; 114 29 40; 115 30 39; 116 30 32; 117 22 40; 118 33 13; 119 34 14; 120 35 15; 121 36 16; 122 37 17; 123 38 18; 124 39 19; 125 40 20; 126 32 12; 127 31 13; 128 11 33; 129 33 14; 130 13 34; 131 34 15; 132 35 14; 133 35 16; 134 36 15; 135 36 17; 136 37 16; 137 37 18; 138 38 17; 139 38 19; 140 39 18; 141 39 20; 142 40 19; 143 40 12; 144 32 20; 145 32 44; 146 12 42; 147 2 41; 148 22 43; 149 42 41; 150 41 43; 151 43 44; 152 44 42; 153 12 41; 154 42 2; 155 22 41; 156 43 2; 157 43 32; 158 44 22; 159 12 44; 160 32 42; 161 41 47; 162 47 45; 163 45 2; 164 47 46; 165 46 45; 166 41 45; 167 43 50; 168 50 48; 169 48 22; 170 50 49; 171 49 48; 172 43 48; 173 47 50; 174 46 49; 175 45 48; 176 41 50; 177 50 46; 178 43 47; 179 47 49; 180 22 50; 181 2 47; 182 22 45; 183 2 48; 184 47 48; 185 50 45; 186 45 49; 187 48 46; 188 42 53; 189 53 51; 190 51 12; 191 53 52; 192 52 51; 193 42 51; 194 44 56; 195 56 54; 196 54 32; 197 56 55; 198 55 54; 199 44 54; 200 53 56; 201 52 55; 202 51 54; 203 42 56; 204 56 52; 205 44 53; 206 53 55; 207 32 56; 208 12 53; 209 32 51; 210 12 54; 211 53 54; 212 56 51; 213 51 55; 214 54 52; 215 44 60; 216 42 58; 217 41 57; 218 43 59; 219 60 59; 220 59 57; 221 57 58; 222 58 60; 223 44 58; 224 42 60; 225 42 57; 226 41 58; 227 44 59; 228 43 60; 229 43 57; 230 41 59; 231 60 57; 232 59 58; 235 33 3; 236 13 23; 237 34 4; 238 14 24; 239 35 5; 240 15 25; 241 36 6; 242 16 26; 243 37 7; 244 17 27; 245 38 8; 246 18 28; 247 39 9; 248 19 29; 249 40 10; 250 20 30; 251 32 2; 252 22 12; 253 44 41; 254 43 42;

Section 8C

8-75

255 60 61; 256 58 61; 257 57 61; 258 59 61; MEMBER PROPERTY INDIAN 1 TO 18 46 TO 54 82 TO 90 145 TO 148 215 TO 218 TA LD ISA200X150X18 SP 0.01 19 TO 26 28 TO 45 55 TO 62 64 TO 81 91 TO 98 100 TO 125 127 TO 144 155 156 - 159 160 223 224 229 230 235 TO 250 TA ST ISA150X150X10 27 63 99 126 149 TO 154 157 158 161 TO 214 219 TO 222 225 TO 228 231 232 251 - 252 TO 258 TA ST ISA80X50X6 CONSTANTS E 2.05e+008 ALL POISSON 0.3 ALL DENSITY 76.8195 ALL ALPHA 6.5e-006 ALL SUPPORTS 1 11 21 31 FIXED UNIT METER KG LOAD 1 VERT SELFWEIGHT Y -1 JOINT LOAD 61 FX 732 46 49 52 55 FX 153 61 FX 1280 FY -1016 FZ 160 46 49 52 55 FX 9006 FY -7844 FZ 1968 2 12 22 32 FX 4503 FY -3937 FZ 1968 LOAD 2 GWBC SELFWEIGHT Y -1 JOINT LOAD 61 FX 549 46 49 52 55 FX 1148 61 FX 515 FY -762 FZ 2342 46 49 52 55 FX 6755 FY -5906 2 12 22 32 FX 3378 FY -2953 LOAD 3 LEFT PCBC SELFWEIGHT Y -1 JOINT LOAD 61 FX 549 46 49 52 55 FX 1148 61 FX 960 FY -762 46 49 FX 6755 FY -5906 52 55 FX 4211 FY -4551 FZ 13293 2 12 22 32 FX 3378 FY -2953 LOAD 4 RIGHT PCBC SELFWEIGHT Y -1 JOINT LOAD 61 FX 549 46 49 52 55 FX 1148 61 FX 960 FY -762 52 55 FX 6755 FY -5906 46 49 FX 4211 FY -4551 FZ 13293 2 12 22 32 FX 3378 FY -2953 PERFORM ANALYSIS UNIT NEW MMS PARAMETER CODE IS802


8-76

LY 2800 MEMB 28 LZ 2800 MEMB 28 MAIN 1.0 MEMB 1 ELA 4 MEMB 1 CNSF 1.0 MEMB 28 DBL 16 ALL GUSSET 8 ALL TRACK 9 ALL CHECK CODE MEMB 1 28

FINISH

Output of design result

Section 8C

8-77 DETAILS OF CALCULATION ---------------------- CHECK FOR MINIMUM THICKNESS --------------------------- TYPE : PAINTED MIN. ALLOWABLE THICKNESS : 6.0 MM ACTUAL THICKNESS : 18.0 MM RESULT : PASS CHECK FOR SLENDERNESS RATIO --------------------------- VALUE OF L/r : 48.49 EQN. USED TO FIND KL/r : 60.0 + 0.5*L/r ACTUAL VALUE OF KL/r : 84.25 ALLOWABLE KL/r : 120.00 RESULT : PASS CALCULATION OF ALLOWABLE STRESS --------------------------------- CRITICAL CONDITION : COMPRESSION Cc : sqrt (2*3.141592*3.141592*E/fy) : 127.24 b : LENGTH OF LEG - WEB THICKNESS - ROOT RADIUS : 200.0 - 18.0 - 13.5 : 168.5 MM (b/t)lim : 210/sqrt(fy) : 13.28 (b/t)cal : 9.36 (b/t)cal <= (b/t)lim AND KL/r <= Cc ALLOWABLE AXIAL COMP. STRESS : (1- 0.5*(KL/r/Cc)*(KL/r/Cc))*fy :

195.15 MPA CHECK AGAINST PERMISSIBLE STRESS -------------------------------- LOAD NO. : 1 DESIGN AXIAL FORCE : 1742002.38 N ACTUAL AXIAL COMP. STRESS :1742002.38 / 11952.0 : 145.75 MPA RESULT : PASS


8-78

BOLTING ------- BOLT DIA : 16 MM SHEARING CAP : 87.66 KN BEARING CAP : 55.81 KN BOLT CAP : 55.81 KN NO. OF BOLTS REQD. : 32

Section 8C

8-79 DETAILS OF CALCULATION ---------------------- CHECK FOR MINIMUM THICKNESS --------------------------- TYPE : PAINTED MIN. ALLOWABLE THICKNESS : 6.0 MM ACTUAL THICKNESS : 10.0 MM RESULT : PASS CHECK FOR SLENDERNESS RATIO --------------------------- VALUE OF L/r : 95.56 EQN. USED TO FIND KL/r : K*L/r ACTUAL VALUE OF KL/r : 95.56 ALLOWABLE KL/r : 400.00 RESULT : PASS CALCULATION OF ALLOWABLE STRESS --------------------------------- CRITICAL CONDITION : TENSION ALLOWABLE AXIAL TENSILE STRESS : 249.94 MPA CHECK AGAINST PERMISSIBLE STRESS -------------------------------- LOAD NO. : 3 DESIGN AXIAL FORCE : 112909.27 N ACTUAL AXIAL TENSILE STRESS : 112909.27 / ( 2903.0*0.801 ) : 48.53 MPA RESULT : PASS BOLTING ------- BOLT DIA : 16 MM SHEARING CAP : 43.83 KN BEARING CAP : 55.81 KN BOLT CAP : 43.83 KN NO. OF BOLTS REQD. : 3 ********** END OF TABULATED RESULT OF DESIGN ***********


8-80

8-81

Design Per Indian Cold Formed Steel Code

8D.1 General

Provisions of IS:801-1975, including revisions dated May, 1988, have been implemented. The program allows design of single (non-composite) members in tension, compression, bending, shear, as well as their combinations. Cold work of forming strengthening effects have been included as an option.

8D.2 Cross-Sectional Properties

The user specifies the geometry of the cross-section by selecting one of the section shape designations from the Gross Section Property Tables from IS:811-1987(Specification for cold formed light gauge structural steel sections). The Tables are currently available for the following shapes:

• Channel with Lips • Channel without Lips • Angle without Lips • Z with Lips • Hat

Shape selection may be done using the member property pages of the graphical user interface (GUI) or by specifying the section designation symbol in the input file.

Section 8D

Design Per Indian Cold Formed Steel Code Section 8D

8-82

The properties listed in the tables are gross section properties. STAAD.Pro uses unreduced section properties in the structure analysis stage. Both unreduced and effective section properties are used in the design stage, as applicable.

8D.3 Design Procedure

The following two design modes are available:

1. Code Checking

The program compares the resistance of members with the applied load effects, in accordance with IS:801-1975. Code checking is carried out for locations specified by the user via the SECTION command or the BEAM parameter. The results are presented in a form of a PASS/FAIL identifier and a RATIO of load effect to resistance for each member checked. The user may choose the degree of detail in the output data by setting the TRACK parameter.

2. Member Selection

The user may request that the program search the cold formed steel shapes database (IS standard sections) for alternative members that pass the code check and meet the least weight criterion. In addition, a minimum and/or maximum acceptable depth of the member may be specified. The program will then evaluate all database sections of the type initially specified (i.e., channel, angle, etc.) and, if a suitable replacement is found, presents design results for that section. If no section satisfying the depth restrictions or lighter than the initial one can be found, the program leaves the member unchanged, regardless of whether it passes the code check or not. The program calculates effective section properties in accordance with Clause 5.2.1.1. Cross-sectional properties and overall slenderness of members are checked for compliance with

Section 8D

8-83

• Clause 6.6.3, Maximum Effective Slenderness Ratio for members in Compression

• Clause 5.2.3, Maximum Flat Width Ratios for Elements in Compression

• Clause 5.2.4, Maximum Section Depths. The program will check member strength in accordance with Clause 6 of the Standard as follows: Members in tension

Resistance is calculated in accordance with Clauses 6.1 Members in bending and shear Resistance calculations are based on Clauses:

a) 6.4.1 Shear stress in webs,

b) 6.4.2 Bending stress in webs

c) 6.4.3 Combined Bending and Shear in Webs. Members in compression Resistance calculations are based on Clauses:

a) 6.2 Compression on flat unstiffened element,

b) 6.6.1.1 Shapes not subject to torsional-flexural buckling,

c) 6.6.1.2 Singly-symmetric sections and nonsymmetrical shapes of open cross section or intermittently fastened singly-symmetrical components of built-up shapes having Q = 1.0 which may be subject to torsional-flexural buckling,


8-84

d) 6.6.1.3 Singly-symmetric sections and nonsymmetrical shapes or intermittently fastened singly-symmetrical components of built-up shapes having Q < 1.0 which may be subject to torsional-flexural buckling,

e) 6.8 Cylindrical Tubular Sections. Members in compression and bending Resistance calculations are based on Clauses:

a) All clauses for members in compression

&

b) 6.3 Laterally Unsupported Members,

c) 6.7.1 Doubly-symmetric shapes or Shapes not subjected to torsional or torsional-flexural buckling

d) 6.7.2. Singly-symmetric shapes or Intermittently fastened

singly-symmetric components of built-up shapes having Q=1.0 which may be subjected to torsional-flexural buckling

e) 6.7.3. Singly-symmetric shapes or Intermittently fastened

singly-symmetric components of built-up shapes having Q<1.0 which may be subjected to torsional-flexural buckling.

Input for the coefficients of uniform bending must be provided by the user.

Section 8D

8-85

The following table contains the input parameters for specifying values of design variables and selection of design options.


Parameter Name

Default Value

Description

BEAM 1.0 When this parameter is set to 1.0 (default), the adequacy of the member is determined by checking a total of 13 equally spaced locations along the length of the member. If the BEAM value is 0.0, the 13 location check is not conducted, and instead, checking is done only at the locations specified by the SECTION command (See STAAD manual for details. For TRUSS members only start and end locations are designed.

CMZ 1.0 Coefficient of equivalent uniform bending ωz. See IS:801-1975, 6.7. Used for Combined axial load and bending design. Values range from 0.4 to 1.0.

CMY 0.85 Coefficient of equivalent uniform bending ωy. See IS:801-1975, 6.7. Used for Combined axial load and bending design. Values range from 0.4 to 1.0.

CWY 0.85 Specifies whether the cold work of forming strengthening effect should be included in resistance computation. See IS:801-1975, 6.1.1

Values: 0 – effect should not be included

1 – effect should be included

FLX 1 Specifies whether torsional-flexural buckling restraint is provided or is not necessary for the member. See IS:801-1975, 6.6.1

Values:

0 – Section not subject to torsional flexural buckling 1 – Section subject to torsional flexural buckling

FU 450 MPa (4588.72 kg/cm2)

Ultimate tensile strength of steel in current units.


8-86


Parameter Name

Default Value

Description

FYLD 353.04 MPa

(3600.0 kg/cm2)

Yield strength of steel in current units.

KX 1.0 Effective length factor for torsional buckling. It is a fraction and is unit-less. Values can range from 0.01 (for a column completely prevented from buckling) to any user specified large value. It is used to compute the KL/R ratio for twisting for determining the capacity in axial compression.

KY 1.0 Effective length factor for overall buckling about the local Y-axis. It is a fraction and is unit-less. Values can range from 0.01 (for a column completely prevented from buckling) to any user specified large value. It is used to compute the KL/R ratio for determining the capacity in axial compression.

KZ 1.0 Effective length factor for overall buckling in the local Z-axis. It is a fraction and is unit-less. Values can range from 0.01 (for a member completely prevented from buckling) to any user specified large value. It is used to compute the KL/R ratio for determining the capacity in axial compression.

LX Member length

Unbraced length for twisting. It is input in the current units of length. Values can range from 0.01 (for a member completely prevented from torsional buckling) to any user specified large value. It is used to compute the KL/R ratio for twisting for determining the capacity in axial compression.

LY Member length

Effective length for overall buckling in the local Y-axis. It is input in the current units of length. Values can range from 0.01 (for a member completely prevented from buckling) to any user specified large value. It is used to compute the KL/R ratio for determining the capacity in axial compression.

LZ Member length

Effective length for overall buckling in the local Z-axis. It is input in the current units of length. Values can range from

Section 8D

8-87


Parameter Name

Default Value

Description

0.01 (for a member completely prevented from buckling) to any user specified large value. It is used to compute the KL/R ratio for determining the capacity in axial compression.

MAIN 0 0 – Check slenderness ratio

0 – Do not check slenderness ratio

NSF 1.0 Net section factor for tension members DMAX

2540.0 cm. Maximum allowable depth. It is input in the current units of

length.

RATIO 1.0 Permissible ratio of actual to allowable stresses

TRACK 0 This parameter is used to control the level of detail in which the design output is reported in the output file. The allowable values are: 0 - Prints only the member number, section name, ratio, and

PASS/FAIL status. 1 - Prints the design summary in addition to that printed by

TRACK 1 2 - Prints member and material properties in addition to that

printed by TRACK 2. TSA 1 Specifies whether webs of flexural members are adequately

stiffened to satisfy the requirements of IS:801-1975, 5.2.4.

Values:

0 – Do not comply with 5.2.4

1 – Comply with 5.2.4


8-88

Section 9 Japanese Codes

;alksdf;lkajf

9-1

Concrete Design Per AIJ


STAAD has the capabilities of performing concrete design based on the AIJ standard for structural calculation of Reinforced Concrete Structures (1985 edition). Design for a member involves calculation of the amount of reinforcement required for the member. Calculations are based on the user specified properties and the member forces obtained from the analysis. In addition, the details regarding placement of the reinforcement on the cross section are also reported in the output.


The following types of cross sections for concrete members can be designed. For Beams Prismatic (Rectangular & Square) For Columns Prismatic (Rectangular, Square and Circular)



Section 9A

Concrete Design Per AIJ Section 9A

9-2


In the above input, the first set of members are rectangular (450 mm depth and 250mm width) and the second set of members, with only depth and no width provided, will be assumed to be circular with 350mm diameter. It is absolutely imperative that the user not provide the cross section area (AX) as an input.


Slenderness effects are extremely important in designing compression members. Slenderness effects result in additional forces being exerted on the column over and above those obtained from the elastic analysis. There are two options by which the slenderness effects can be accommodated. The first option is to compute the secondary moments through an exact analysis. Secondary moments are caused by the interaction of the axial loads and the relative end displacements of a member. The axial loads and joint displacements are first determined from an elastic stiffness analysis and the secondary moments are then evaluated. The second option is to approximately magnify the moments from the elastic analysis and design the column for the magnified moment. It is assumed that the magnified moment is equivalent to the total moment comprised of the sum of primary and secondary moments. STAAD provides facilities to design according to both of the above methods. To utilize the first method, the command PDELTA ANALYSIS must be used instead of PERFORM ANALYSIS in the

Section 9A

9-3

input file. The user must note that to take advantage of this analysis, all the combinations of loading must be provided as primary load cases and not as load combinations. This is due to the fact that load combinations are just algebraic combinations of forces and moments, whereas a primary load case is revised during the P-delta analysis based on the deflections. Also, note that the proper factored loads (like 1.5 for dead load etc.) should be provided by the user. STAAD does not factor the loads automatically. The second method mentioned above is utilized by providing the magnification factor as a concrete design parameter (See the parameter MMAG in Table 9A.1). The column is designed for the axial load and total of primary and secondary biaxial moments if the first method is used and for the axial load and magnified biaxial moments if the second method is used.

9A.5 Beam Design

Beams are designed for flexure, shear and torsion. Program considers 12 equally spaced sections of the beam member. However this number can be redefined by NSECTION parameter. All these sections are designed for flexure, shear and torsion for all the load cases and print out the design results for most critical load case. Design for Flexure

Reinforcement for positive and negative moments are calculated on the basis of section properties provided by the user. Program first try to design the section for γ=0 and pt = balanced reinforcement ratio. If allowable moment is lower than the actual moment program increases γ value for same pt and checks the satisfactory conditions. If conditions are not satisfied this procedure continues until γ reaches to 1.0 and then pt value is increased keeping γ = 1.0. This procedure continues until pt reaches to its maximum value( 2 % ). But if the allowable moment for pt = maximum value and γ = 1.0 is lower than the actual moment the program gives message that the section fails. This program automatically calculates the Bar size and no. of bars needed to design the section. It arranges the bar in layers as per


9-4

the requirements and recalculate the effective depth and redesign the sections for this effective depth. Please note,

• Beams are designed for MZ only. The moment MY is not considered in flexure design

• MMAG parameter can be used to increase design moment

• 1.4 cm. is added to the clear cover to take stirrup size into consideration for flexure design.

• STAAD beam design procedure is based on the local practice and considering the fact that Japan is a high seismic zone area.

Design for Shear

Shear design of beam is done for Qy value. The update effective depth is used for allowable shear stress calculation. Allowable shear stress of concrete is automatically calculated from design load type (permanent or temporary) and given density of concrete. Program calculates required Bar size and spacing of stirrups. Pw is calculated for design Bar size and spacing and all the necessary checking is done. For seismic load it is needed to increase shear force 1.5 times the actual value and this can be done utilizing SMAG parameter. Please note, • SMAG parameter can be used if its needed to increase the

Design Shear Force without changing Design Moment.

• Stirrups are always assumed to be 2-legged

• Governing density to determine Light weight or Normal Weight Concrete is 2.3 kg/sq. cm

Section 9A

9-5

Example of Input Data for Beam Design UNIT KG CM START CONCRETE DESIGN CODE JAPAN FYMAIN SRR295 ALL FYSEC SRR295 ALL FC 350 ALL CLEAR 2.5 MEM 2 TO 6 TRACK 1.0 MEMB 2 TO 9 DESIGN BEAM 2 TO 9 END CONCRETE DESIGN

Design for Torsion

Torsion design for beam is optional. If TORSION parameter value is 1.0, program design that beam for torsion. Program first checks whether extra reinforcement is needed for torsion or not. If additional reinforcement is needed, this additional pt is added to flexure pt and additional Pw is added to shear design Pw.

9A.6 Column Design

Columns are designed for axial force, MZ moment, MY moment and shear force. Both the ends of the members are designed for all the load cases and the loading which produces largest amount of reinforcement is called as critical load. If Track 0 or Track 1 is used, design results will be printed for critical load only. But if Track 2 is used user can get details design results of that member. Pt needed for minimum axial force, maximum axial force, maximum MZ, maximum MY among all the load cases for both the ends will be printed. If MMAG parameter is used, the column moments will be multiplied by that value. If SMAG parameter is used, column shear force will be multiplied by that value. Column design is done for Rectangular, Square and Circular sections. For rectangular and square sections Pt value is calculated


9-6

separately for MZ and MY, while for circular sections Pg value is calculated for MZ and MY separately. Column design for biaxial moments is optional. If BIAXIAL parameter value 1.0, program will design the column for biaxial moments. Otherwise column design is always uniaxial type. Steps involved : 1) Depending on the axial force zone is determined for Pt = 0.0 . 2) If the column is in "zone A", design is performed by

increasing Pt and checking allowable load for that known Pt and known actual eccentricity of the column.

3) If the column is in "zone B" or in "zone C", xn is calculated

for given P and Pt and checking is done for allowable moment, if allowable moment is less than the actual moment, program increases Pt and this procedure continues until the column design conditions are satisfied or the column fails as the required Pt is higher than Pt maximum value.

4) If the column is in tension, design is done by considering

allowable tensile stress of steel only. 5) If biaxial design is requested program solve the following

interaction equation

0.1Mzcap

MzMycap

My ≤

+

αα

where, α = 1.0+1.66666666 × (ratio-0.2), ratio = P/Pcap & 1.0 ≤ α ≤ 2.0, Mycap, Mzcap & Pcap represents section capacity

6) If the interaction equation is not satisfied program increases Pt and calculates Pcap, Mycap and Mzcap and solve the interaction equation again and this process continues until the

Section 9A

9-7

eqn. is satisfied or the column fails as Pt exceeds its maximum limit.

7) If biaxial design is not requested program assumes that

interaction equation is satisfied ( if uniaxial design is performed successfully ).

8) If the interaction equation is satisfied program determines bar

size and calculates no. of bars and details output is written.

Example of Input Data for Column Design UNIT KGS CMS START CONCRETE DESIGN CODE JAPAN FYMAIN SRR295 ALL FC 210 ALL CLEAR 2.5 MEMB 2 TO 6 DESIGN COLUMN 2 TO 6 END CONCRETE DESIGN


To design a slab or a wall, it must first be modelled using finite elements and analysed. The command specifications are in accordance with Chapter 2 and Chapter 6 of the Technical Reference Manual. Elements are designed for the moments Mx and My. These moments are obtained from the element force output (see Chapter 2 of the Technical Reference Manual). The reinforcement required to resist the Mx moment is denoted as longitudinal reinforcement and the reinforcement required to resist the My moment is denoted as transverse reinforcement.


9-8

The longitudinal bar is the layer closest to the exterior face of the slab or wall. The following parameters are those applicable to slab and wall design: 1. FYMAIN Yield stress for reinforcing steel - transverse and

longitudinal. 2. FC Concrete grade 3. CLEAR Distance from the outer surface of the element to

the edge of the bar. This is considered the same on both top and bottom surfaces of the element.

4. MINMAIN Minimum required size of longitudinal/transverse reinforcing bar

The other parameters shown in Table 9A.1 are not applicable to slab or wall design.

LONG.

TRANS.

X

Y

Z

M

MM

M x

y

x

y


The program contains a number of parameters which are needed to perform the design. Default parameter values have been selected such that they are frequently used numbers for conventional design requirements. These values may be changed to suit the particular design being performed. Table 9A.1 contains a complete list of the available parameters and their default values. It is necessary to declare length and force units as centimeters and Kilograms before performing the concrete design.

Section 9A

9-9

Table 9A.1 Japanese Concrete Design Parameters

Parameter Name


FYMAIN 2200 Kg/cm2 Yield Stress for main reinforcing steel, but user should input this value as steel grade, like SD345, SD295A, etc. program automatically calculates yield stress value depending on design load type (permanent or temporary).

FYSEC 2000 Kg/cm2 Same as FYMAIN except this is for secondary steel.

FC 210 Kg/cm2 Compressive Strength of Concrete.

CL 3.0 cm Clear cover for Beam.

CLS 4.0 cm Clear side cover for Column.



MAXMAIN 41.0 cm Maximum main reinforcement bar size

MAXSEC 41.0 cm Maximum secondary reinforcement bar size.

SFACE 0.0 Face of support location at start of beam.

EFACE 0.0 Face of support location at end of beam. (Note: Both SFACE & EFACE are input as positive numbers).

REINF 0.0 Tied Column. A value of 1.0 will mean spiral.

MMAG 1.0 Design moment magnification factor

SMAG 1.0 Design shear magnification factor

LONG 0.0 Value to define design load type 0 = Permanent Loading 1 = Temporary Loading

BIAXIAL 0.0 Value to define biaxial or uniaxial design type for Column 0 = uniaxial design only 1 = design for biaxial moments

TORSION 0.0 Value to request for torsion design for beam 0 = torsion design not needed 1 = torsion design needed


9-10

Table 9A.1 Japanese Concrete Design Parameters

Parameter Name


WIDTH ZD Width of concrete member. This value defaults to ZD as provided under MEMBER PROPERTIES.

DEPTH YD Depth of concrete member. This value defaults to YD as provided under MEMBER PROPERTIES.


TRACK 0.0 BEAM DESIGN: 0.0 = Critical section design results. 1.0 = Five section design results & design

forces. 2.0 = 12 section design results & design forces. COLUMN DESIGN: 1.0 = Detail design results for critical load case

only.

2.0 = Design results for minimum P, maximum P, maximum MZ and maximum MY among all load cases for both ends.

9-11

Steel Design Per AIJ

9B.1 General

This section presents some general statements regarding the implementation of the “Architectural Institute of Japan” (AIJ) specifications for structural steel design (1986 edition) in STAAD. The design philosophy and procedural logistics are based on the principles of elastic analysis and allowable stress design. Facilities are available for member selection as well as code checking. Two major failure modes are recognized: failure by overstressing and failure by stability considerations. The following sections describe the salient features of the design approach. Members are proportioned to resist the design loads without exceedance of the allowable stresses or capacities and the most economical section is selected on the basis of the least weight criteria. The code checking part of the program also checks the slenderness requirements and the stability criteria. Users are recommended to adopt the following steps in performing the steel design: • Specify the geometry and loads and perform the analysis. • Specify the design parameter values if different from the

default values. • Specify whether to perform code checking or member

selection.

Section 9B

Steel Design Per AIJ Section 9B

9-12


Elastic analysis method is used to obtain the forces and moments for design. Analysis is done for the primary and combination loading conditions provided by the user. The user is allowed complete flexibility in providing loading specifications and in using appropriate load factors to create necessary loading situations. Depending upon the analysis requirements, regular stiffness analysis or P-Delta analysis may be specified. Dynamic analysis may also be performed and the results combined with static analysis results.


For specification of member properties of standard Japanese steel shapes, the steel section library available in STAAD may be used. The next section describes the syntax of commands used to assign properties from the built-in steel table. Members properties may also be specified using the User Table facility. For more information on these facilities, refer to the STAAD Technical Reference Manual.

9B.4 Built-in Japanese Steel Section Library

The following information is provided for use when the built-in steel tables are to be referenced for member property specification. These properties are stored in a database file. If called for, these properties are also used for member design. Since the shear areas are built into these tables, shear deformation is always considered for these members during the analysis. An example of member property specification in an input file is provided at the end of this section.

Section 9B

9-13

A complete listing of the sections available in the built-in steel section library may be obtained using the tools of the graphical user interface. Following are the descriptions of different types of sections. I shapes I shapes are specified in the following way:

Note : While specifying the web thickness, the portion after the decimal point should be excluded.

Example : 1 TO 9 TA ST I300X150X11 12 TO 15 TA ST I350X150X9

H shapes H shapes are specified as follows:

Note : While specifying the web thickness, the portion after the decimal point should be excluded.

Example: 1 TO 8 TA ST H200X100X4 13 TO 17 TA ST H350X350X12

I 250 X 125 X 10

Web thickness (mm)

Nominal width of flange (mm)

Section-type (I)

Nominal height (mm)

H 600 X 200 X 11

Web thickness (mm)


Section-type (H)

Nominal height (mm)


9-14

T shapes T shapes are specified as follows:

Note : While specifying the web thickness, the portion after the decimal point should be excluded

Example: 20 TO 25 TA ST T250X19

Channels Channel sections are specified as follows.

Example: 25 TO 34 TA ST C125X65X6 46 TO 49 TA ST C200X90X8

Double Channels Back to back double channels, with or without a spacing in between them, are available. The letter D in front of the section name is used to specify a double channel.

17 TO 27 TA D C300X90X10 45 TO 76 TA D C250X90X11 SP 2.0

In the above commands, members 17 to 27 are a back to back double channel C300X90X10 with no spacing in between.

T 250 X 16

Flange thickness (mm)

Section-type (T)


C 300 X 90 X 10

Web thickness (mm)


Section-type (C)

Nominal height (mm)

Section 9B

9-15

Members 45 to 76 are a double channel C250X90X11 with a spacing of 2 length units. Angles Two types of specification may be used to describe an angle. The standard angle specification is as follows.

The letter L (signifying that the section is an angle) is followed by the length of the legs and then the thickness of the leg, all in millimetres. The word ST signifies that the section is a STandard angle meaning that the major principal axis coincides with the local YY axis specified in Chapter 1 of Section 1.5.2 of the User's Manual.

Example: 1 4 TA ST L150X90X9

If the minor principal axis coincides with the local YY axis specified in Chapter 2 of the User's Manual, the word RA (Reverse Angle) should be used instead of ST as shown below.

7 TO 23 TA RA L90X75X9

Double angles Short leg back to back and long leg back to back double angles may be specified by using the words SD or LD in front of the angle size. In the case of an equal angle, either SD or LD will serve the purpose. The spacing between the angles may be specified by using the word SP after the angle size followed by the value of the spacing.

L 125 X 90 X 10

Thickness (mm)

Length of shorter side (mm)

Section-type (L)

Length of longer side (mm)


9-16

8 TO 25 TA SD L100X65X7 SP 2.0 36 TO 45 TA LD L300X90X11 SP 3.0

The first example indicates a short legs back to back double angle comprised of 100X65X7 angles separated by 2 length units. The latter is a long legs back to back double angle comprised of 300X90X11 angles separated by 3 length units. Tubes Tube names are input by their dimensions. For example,


is a tube that has a height of 8 length units, width of 6 length units and a wall thickness of 0.5 length units. Only code checking, no member selection can be performed on TUBE sections. Pipes (Circular Hollow sections) Circular hollow sections may be provided by specifying the word PIPE followed by the outside and inside diameters of the section. For example,


specifies a pipe with outside diameter of 25 length units and an inside diameter of 20 length units. Only code checking, no member selection, can be performed on PIPE sections.

Section 9B

9-17

Sample Input file containing Japanese shapes STAAD SPACE UNIT KIP FEET JOINT COORD 1 0 0 0 12 11 0 0 MEMB INCIDENCE 1 1 2 11 UNIT INCH MEMBER PROPERTY JAPANESE * H-SHAPE 1 TA ST H200X100X4 * I SHAPE 2 TA ST I250X125X10 * T SHAPE 3 TA ST T200X19 * CHANNEL 4 TA ST C125X65X6 * DOUBLE CHANNEL 5 TA D C200X90X8 * REGULAR ANGLE 6 TA ST L100X75X7 * REVERSE ANGLE 7 TA RA L90X75X9 * DOUBLE ANGLE - LONG LEG BACK TO BACK 8 TA LD L125X75X7 SP 2.0 * DOUBLE ANGLE - SHORT LEG BACK TO BACK 9 TA SD L300X90X11 SP 1.5 * TUBE 10 TA ST TUBE DT 3.0 WT 2.5 TH 0.25 * PIPE 11 TA ST PIPE OD 3.0 ID 2.5 PRINT MEMBER PROPERTIES FINISH


9-18


As mentioned before, member design and code checking in STAAD are based upon the allowable stress design method. It is a method for proportioning structural members using design loads and forces, allowable stresses, and design limitations for the appropriate material under service conditions. The basic measure of member capacities are the allowable stresses on the member under various conditions of applied loading such as allowable tensile stress, allowable compressive stress etc. These depend on several factors such as cross sectional properties, slenderness factors, unsupported width to thickness ratios and so on. Explained here is the procedure adopted in STAAD for calculating such capacities. Design Capabilities

All types of available shapes like H-Shape, I-Shape, L-Shapes, CHANNEL, PIPE, TUBE, Prismatic section etc. can be used as member property and STAAD will automatically adopt the design procedure for that particular shape if Steel Design is requested. STEEL TABLE available within STAAD or UPTABLE facility can be used for member property. Methodology

For steel design, STAAD compares the actual stresses with the allowable stresses as required by AIJ specifications. The design procedure consist of following three steps. 1) Calculation of sectional properties

Program extract sectional properties like sectional area ( A ), Moment of Inertia about Y axis and Z axis ( Iyy, Izz) from in-built Japanese Steel Table and calculates Zz, Zy, iy, iz using appropriate formula. For calculation of i ( radius of gyration needed for bending ), program calculates moment of inertia ( Ii )and sectional area ( Ai ) for 1/6th section and then uses following formula:

Section 9B

9-19

AiIii =

Please note, that the above mentioned procedure for calculation of i is applicable for I shape, H shape and Channel sections.

2) Calculation of actual and allowable stresses

Program calculates actual and allowable stresses by following methods: i) Axial Stress :

Actual tensile stresses ( FT ) = Force / ( A × NSF ), NSF = Net Section Factor for tension Actual compressive stress ( FC ) = Force / A Allowable tensile stress ( ft ) = F / 1.5 (For Permanent Case) = F ( For Temporary Case ) Allowable compressive stress

( ){ } ∆≤λν∆λ−= when /F x / x4.1 )fc( 2

( ) ∆>λ∆λ= when / /F x 77.2 2 = fc × 1.5 (For Temporary Case )

where, )xF6/(.E2π=∆ ∆ =F) , ν =3 / 2 + 2 / 3 × (λ / ∆)2

ii) Bending Stress :

Actual bending stress for My for compression ( Fbcy) = My / Zcy Actual bending stress for Mz for compression ( Fbcz) = Mz / Zcz Actual bending stress for My for tension ( Fbty) = My / Zcy Actual bending stress for Mz for tension ( Fbtz) = Mz / Zcz


9-20

where, Zcy , Zcz are section modulus for compression and Zty, Ztz are section modulus for tension Allowable bending stress for My ( fbcy) = ft Allowable bending stress for Mz ( fbcz) = { 1-.4 × (lb / i )2 / (C λ2)}ft max = 900/ ( lb × h / Af ) For Temporary case, fbcz = 1.5 × (fbcz for Permanent Case) where, C = 1.75 -1.05(M2/M1)+0.3(M2/M1)2

Allowable bending stress for My ( fbty) = ft Allowable bending stress for Mz ( fbtz) = fbcz

iii) Shear Stress Actual shear stresses are calculated by following formula : qy = Qy / Aww, Where, Aww = web shear area = product of depth and web thickness qz = Qz / Aff , Where, Aff = flange shear area = 2/3 times total flange areas Allowable shear stress ( fs ) = Fs / 1.5 , Fs = F / 3

3) Checking design requirements : User provided RATIO value ( default 1.0 ) is used for checking design requirements

The following conditions are checked to meet the AIJ specifications. For all the conditions calculated value should not be more than the value of RATIO. If for any condition value exceeds RATIO , program gives the message that the section fails. Conditions: i) Axial tensile stress ratio = FT / ft ii) Axial compressive stress ratio = FC / fc iii) Combined compression &

bending ratio = FC/fc+Fbz/fbz+Fby/fby

Section 9B

9-21

iv) Combined compression & bending ratio = (Fbtz+Fbty-FC) / ft

v) Combined tension & bending ratio = FT/ft +Fbz/fbz+Fby/fby vi) Combined tension & bending ratio = (Fbcz+Fbcy-FT) / fbcz vii) Shear stress ratio for qy = qy / fs viii) Shear stress ratio for qz = qz / fs New Output Format ( TRACK -- 3 )

One new output format has been introduced which provides details step by step information of Steel Design for guiding load case only. If Section command is used before Parameter command this output will provide details information for all the sections specified by Section Command. Please note, that this output format is available only when Beam parameter value is 0 and Track parameter value is 3. If section command is not used design information will be printed for two ends only. If Member Truss option is used no Shear Design information will be printed.

Example: SECTION 0.0 0.25 0.5 0.75 1.0 ALL PARAMETER CODE JAPAN BEAM 0.0 ALL TMP 0.0 MEMB 1 to 4 TMP 1.0 MEMB 5 to 8 TRACK 3 ALL CHECK CODE ALL FINISH

Allowable stress for Axial Tension

Allowable axial stress in tension is calculated per section 5.1 (1) of the AIJ code. In members with axial tension, the tensile load must not exceed the tension capacity of the member. The tension capacity of the member is calculated on the basis of the member


9-22

area. STAAD calculates the tension capacity of a given member based on a user supplied net section factor (NSF-a default value of 1.0 is present but may be altered by changing the input value, see Table 8B.1) and proceeds with member selection or code checking. Allowable stress for Axial Compression

The allowable stress for members in compression is determined according to the procedure of section 5.1 (3). Compressive resistance is a function of the slenderness of the cross-section (Kl/r ratio) and the user may control the slenderness value by modifying parameters such as KY, LY, KZ and LZ. In the absence of user provided values for effective length, the actual member length will be used. The slenderness ratios are checked against the permissible values specified in Chapter 11 of the AIJ code. Allowable stress for Bending

The permissible bending compressive and tensile stresses are dependent on such factors as length of outstanding legs, thickness of flanges, unsupported length of the compression flange (UNL, defaults to member length) etc. The allowable stresses in bending (compressive and tensile) are calculated as per the criteria of Clause 5.1 (4) of the code. Allowable stress for Shear

Shear capacities are a function of web depth, web thickness etc. The allowable stresses in shear are computed according to Clause 5.1 (2) of the code.


For members experiencing combined loading (axial force, bending and shear), applicable interaction formulas are checked at different locations of the member for all modelled loading situations. Members subjected to axial tension and bending are checked using the criteria of clause 6.2. For members with axial compression and bending, the criteria of clause 6.1 is used.

Section 9B

9-23


The user is allowed complete control over the design process through the use of parameters mentioned in Table 9B.1 of this chapter. These parameters communicate design decisions from the engineer to the program. The default parameter values have been selected such that they are frequently used numbers for conventional design. Depending on the particular design requirements of the situation, some or all of these parameter values may have to be changed to exactly model the physical structure.

Table 9B.1 - Japanese Steel Design Parameters

Parameter Name




LY Member Length

Length in local y-axis to calculate slenderness ratio.

LZ Member Length

Same as above except in z-axis

FYLD 235 MPA Yield strength of steel in Megapascal.


UNL Member Length

Unsupported length for calculating allowable bending stress.

UNF 1.0 Same as above provided as a fraction of actual member length.

SSY 0.0 0.0 = Sidesway in local y-axis. 1.0 = No sidesway

SSZ 0.0 Same as above except in local z-axis.

MAIN 0.0 0.0 = check for slenderness 1.0 = suppress slenderness check


9-24

Table 9B.1 - Japanese Steel Design Parameters

Parameter Name


TRACK 0.0 0.0 = Suppress critical member stresses 1.0 = Print all critical member stresses 2.0 = Print expanded output

DMAX 100 cm Maximum allowable depth for member.

DMIN 0.0 cm Minimum allowable depth for member.

TMP 0 (Permanent

Load)

0 = Permanent Loading 1 = Temporary Loading


BEAM 0.0 0.0 = design only for end moments or those at locations specified by the SECTION command.

1.0 = calculate moments at twelfth points along the beam, and use the maximum Mz location for design.


deflection check)






NOTE: 1) "Deflection Length" is defined as the length that is used for

calculation of local deflections within a member. It may be noted that for most cases the "Deflection Length" will be equal to the length of the member. However, in some situations, the "Deflection Length" may be different. For example, refer to the figure below where a beam has been modeled using four joints and three members. Note that the "Deflection Length" for all three members will be equal to the total length of the beam in this case. The parameters DJ1 and DJ2 should be used to model this situation. Also the straight line joining DJ1 and

Section 9B

9-25

DJ2 is used as the reference line from which local deflections are measured. Thus, for all three members here, DJ1 should be "1" and DJ2 should be "4".


D

1

2 3

4

1

2 3




3) The above parameters may be used in conjunction with other available parameters for steel design.

9B.8 Code Checking

The purpose of code checking is to check whether the provided section properties of the members are adequate to carry the forces transmitted to it by the loads on the structure. The adequacy is checked per the AIJ requirements. Code checking is done using forces and moments at specified sections of the members. If the BEAM parameter for a member is set to 1, moments are calculated at every twelfth point along the beam, and the maximum moment about the major axis is used. When no sections are specified and the BEAM parameter is set to zero (default), design will be based on the forces at the start and end joints of the member. The code checking output labels the members as PASSed or FAILed. In addition, the critical condition, governing load case, location (distance from start joint) and magnitudes of the governing forces and moments are also printed.


9-26


The member selection process basically involves determination of the least weight member that PASSes the code checking procedure based on the forces and moments obtained from the most recent analysis. The section selected will be of the same type as that specified initially. For example, a member specified initially as a channel will have a channel selected for it. Selection of members whose properties are originally provided from a user table will be limited to sections in the user table. Member selection cannot be performed on TUBES, PIPES or members listed as PRISMATIC.

Sample Input data for Steel Design UNIT METER PARAMETER CODE JAPAN NSF 0.85 ALL UNL 10.0 MEMBER 7 KY 1.2 MEMBER 3 4 RATIO 0.9 ALL TRACK 1.0 ALL CHECK CODE ALL SELECT ALL

Section 10 American Aluminum

Code

10-1

Design Per American Aluminum Code

10.1 General

STAAD is currently equipped with the facilities to perform design based on the specifications for Aluminum Structures. The requirements of the Allowable Stress Design, Sixth edition, October 1994, have been implemented. The various issues related to the implementation of this code in STAAD are explained below.

10.2 Member Properties

In order to do this design in STAAD, the members in the structure must have their properties specified from Section VI of the above-mentioned manual. The section names are mentioned in Tables 5 through 28 of that manual. All of those tables except Table 10 (Wing Channels) and Table 20 (Bulb Angles) are available in STAAD. Described below is the command specification for various sections: Standard single section

memb-list TA ST section-name

Section 10

Design Per American Aluminum Code Section 10

10-2

Example 1 TO 5 TA ST CS12X11.8 9 TA ST I8.00X13.1 11 33 45 67 TA ST LS8.00X8.00X0.625 18 TA ST 1.50PipeX160 15 TA ST T(A-N)6.00X8.00X11.2 23 25 29 TA ST 20X12RectX.500Wall

Double channel back-to-back

memb-list TA BACK section-name SPACING value

Example 3 TA BACK C(A-N)7X3.61 SPACING 1.5 5 TA BACK C15X17.33 SP 0.75

Double channel front-to-front

memb-list TA FRONT section-name SPACING value

Example 2 TA FRONT CS12X10.3 SP 1.0 4 TA FR CS10X10.1 SP 0.5

Section 10

10-3

Double angle long leg back-to-back

memb-list TA LD section-name SPACING value

Example 14 TA LD LS4.00X3.00X0.375 SP 1.5

Double angle short leg back-to-back

memb-list TA SD section-name SPACING value

Example 12 TA SD L3.5X3X0.5 SP 0.25 13 TA SD L8X6X0.75 SP 1.0

10.3 Design Procedure

The design is done according to the rules specified in Sections 4.1, 4.2 and 4.4 on pages I-A-41 and I-A-42 of the Aluminum code. The allowable stresses for the various sections are computed according to the equations shown in Section 3.4.1 through 3.4.21 on pages I-A-27 through I-A-40. The adequacy of the member is checked by calculating the value of the left-hand side of equations 4.1.1-1, 4.1.1-2, 4.1.1-3, 4.1.2-1, 4.4-1 and 4.4-2. This left-hand side value is termed as RATIO. If the highest RATIO among these equations turns out to be less than or equal to 1.0, the member is declared as having PASSed. If it exceeds 1.0, the member has FAILed the design requirements.


10-4

The check for torsion per Clause 4.3 for open sections is currently not done.

10.4 Design Parameters

The following are the parameters for specifying the values for variables associated with the design.

Table 10.1 Aluminum Design Parameters

Parameter Default Description Name Value ALLOY 34 This variable can take on a value from 1 through 40.

The default value represents the alloy 6061-T6. See Table 10A.2 in the following pages for a list of values for this parameter and the alloy they represent. Table 3.3-1 in Section I-B of the Aluminum specifications provides information on the properties of the various alloys.

PRODUCT 1 This variable can take on a value from 1 through 4. They represent: 1 - All 2 - Extrusions 3 - Drawn Tube 4 - Pipe The default value stands for All. The PRODUCT parameter finds mention in Table 3.3-1 in Section I-B of the Aluminum specifications.

ALCLAD 0 This variable can take on a value of either 0 or 1. 0 - Material used in the section is not an Alclad. 1 - Material used in the section is an Alclad.

WELD 0 In Table 3.4-2 in Section I-A of the Aluminum specifications, it is mentioned that the value of coefficients Kt and Kc are dependent upon whether or not, the location of the section where design is done is within 1.0 inch of a weld. The WELD parameter is used in STAAD for this purpose. The values that can be assigned to this parameter are: 0 - Region is farther than 1.0in from a weld 1 - Region is within 1.0in from a weld

Section 10

10-5


Parameter Default Description Name Value STRUCTURE 1 In Table 3.4-1 in Section I-A of the Aluminum

specifications, it is mentioned that the value of coefficients nu, ny and na are dependent upon whether the structure being designed is a building or a bridge. Users may convey this information to STAAD using the parameter STRUCTURE. The values that can be assigned to this parameter are: 1 - Buildings and similar type structures 2 - Bridges and similar type structures

DMAX 1000 in. Maximum depth permissible for the section during member selection. This value must be provided in the current units.

DMIN 0.0 in Minimum depth required for the section during member selection. This value must be provided in the current units.

UNL Member length

Distance between points where the compression flange is braced against buckling or twisting. This value must be provided in the current units. This value is used to compute the allowable stress in bending compression.

KY 1.0 Effective length factor for overall column buckling in the local Y-axis. It is a fraction and is unit-less. Values can range from 0.01 (for a column completely prevented from buckling) to any user specified large value. It is used to compute the KL/R ratio for determining the allowable stress in axial compression.

LY Member length

Effective length for overall column buckling in the local Y-axis. It is input in the current units of length. Values can range from 0.01 (for a column completely prevented from buckling) to any user specified large value. It is used to compute the KL/R ratio for determining the allowable stress in axial compression.


10-6


Parameter Default Description Name Value KZ 1.0 Effective length factor for overall column buckling in

the local Z-axis. It is a fraction and is unit-less. Values can range from 0.01 (for a column completely prevented from buckling) to any user specified large value. It is used to compute the KL/R ratio for determining the allowable stress in axial compression.

LZ Member length

Effective length for overall column buckling in the local Z-axis. It is input in the current units of length. Values can range from 0.01 (for a column completely prevented from buckling) to any user specified large value. It is used to compute the KL/R ratio for determining the allowable stress in axial compression.

KT 1.0 Effective length factor for torsional buckling. It is a fraction and is unit-less. Values can range from 0.01 (for a column completely prevented from torsional buckling) to any user specified large value. It is used to compute the KL/R ratio for twisting for determining the allowable stress in axial compression. See Equation 3.4.7.2-6 on page I-A-28 of the Aluminum specifications for details.

LT Member length

Unbraced length for twisting. It is input in the current units of length. Values can range from 0.01 (for a column completely prevented from torsional buckling) to any user specified large value. It is used to compute the KL/R ratio for twisting for determining the allowable stress in axial compression. See Equation 3.4.7.2-6 on page I-A-28 of the Aluminum specifications for details.

STIFF Member length

Spacing in the longitudinal direction of shear stiffeners for stiffened flat webs. It is input in the current units of length. See section 3.4.21 on page I-A-40 of the Aluminum specifications for information regarding this parameter.

Section 10

10-7


Parameter Default Description Name Value SSY 0.0 Factor that indicates whether or not the structure is

subjected to sidesway along the local Y axis of the member. The values are: 0 - Sidesway is present along the local Y-axis of the member 1 - There is no sidesway along the local Y-axis of the member. The sidesway condition is used to determine the value of Cm explained in Section 4.1.1, page I-A-41 of the Aluminum specifications.

SSZ 0.0 Factor that indicates whether or not the structure is subjected to sidesway along the local Z axis of the member. The values are: 0 - Sidesway is present along the local Z-axis of the member 1 - There is no sidesway along the local Z-axis of the member. The sidesway condition is used to determine the value of Cm explained in Section 4.1.1, page I-A-41 of the Aluminum specifications.

TRACK 2 This parameter is used to control the level of detail in which the design output is reported in the output file. The allowable values are: 1 - Prints only the member number, section name,

ratio, and PASS/FAIL status. 2 - Prints the design summary in addition to that

printed by TRACK 1 3 - Prints the member properties and alloy properties in addition to that printed by TRACK 2. 4 - Prints the values of variables used in design in

addition to that printed by TRACK 3.


10-8


Parameter Default Description Name Value BEAM 0.0 If this parameter is set to 1.0, the adequacy of the

member is determined by checking a total of 13 equally spaced locations along the length of the member. If the BEAM value is 0.0, the 13 location check is not conducted, and instead, checking is done only at the locations specified by the SECTION command (See STAAD manual for details). If neither the BEAM parameter nor any SECTION command is specified, STAAD will terminate the run and ask the user to provide one of those 2 commands. This rule is not enforced for TRUSS members.

10.5 Code Checking

The purpose of code checking is to determine whether the initially specified member properties are adequate to carry the forces transmitted to the member due to the loads on the structure. Code checking is done at the locations specified by either the SECTION command or the BEAM parameter described above. It is done with the aid of the command “CHECK CODE” described in the main STAAD Technical Reference Manual. Example Problem 1 in the Getting Started and Examples Manual for STAAD provides an example on the usage of the CHECK CODE command.

10.6 Member Selection

The member selection process involves the determination of the least weight member that PASSes the code checking procedure based on the forces and moments of the most recent analysis. The section selected will be of the same type as that specified initially. For example, a member specified initially as a channel will have a channel selected for it. It is done with the aid of the command “SELECT MEMBER” described in the main STAAD Technical

Section 10

10-9

Reference Manual. Example Problem 1 in the Getting Started and Examples Manual for STAAD provides an example on the usage of the SELECT MEMBER command.

Sample input data for Aluminum Design PARAMETER CODE ALUMIMUM BEAM 1 ALL KY 1.2 MEMB 3 4 ALLOY 35 ALL PRODUCT 2 ALL TRACK 3 ALL SELECT ALL ALCLAD 1 ALL STRUCT 1 ALL CHECK CODE ALL


10-10

Table 10.2 - ALLOY PARAMETER :

Values and Corresponding Names 1 1100-H12 2 1100-H14 3 2014-T6 4 2014-T6510 5 2014-T6511 6 2014-T651 7 3003-H12 8 3003-H14 9 3003-H16 10 3003-H18 11 3004-H32 12 3004-H34 13 3004-H36 14 3004-H38 15 5005-H12 16 5005-H14 17 5005-H32 18 5005-H34 19 5050-H32 20 5050-H34 21 5052-H32 22 5052-H34 23 5083-H111 24 5086-H111 25 5086-H116 26 5086-H32 27 5086-H34 28 5454-H111 29 5454-H112 30 5456-H111 31 5456-H112 32 6005-T5 33 6105-T5

Section 10

10-11

34 6061-T6 35 6061-T6510 36 6061-T6511 37 6061-T651 38 6063-T5 39 6063-T6 40 6351-T5


10-12

Section 11 American Transmission

Tower Code

11-1

Steel Design per ASCE Manuals and Reports

11.1 General Comments

This document presents some general statements regarding the implementation of the Steel Design per ASCE Manuals and Reports on Engineering Practice No. 52 – Guide for Design of Steel Transmission Towers, Second Edition. The design philosophy and procedural logistics for member selection and code checking is based upon the principles of allowable stress design. Two major failure modes are recognized: failure by overstressing and failure by stability considerations.

The following sections describe the salient features regarding the process of calculation of the relevant allowable stresses and the stability criteria being used. Members are proportioned to resist the design loads without exceeding the allowable stresses and the most economical section is selected based on the least weight criteria. The code checking part of the program also checks the slenderness requirements, the minimum metal thickness requirements and the width-thickness requirements. It is generally assumed that the user will take care of the detailing requirements like provision of stiffeners and check the local effects like flange buckling, web crippling, etc. It general, it may be noted that the concepts followed in MEMBER SELECTION and CODE CHECKING procedures are similar to that of the AISC based design. It is assumed that the user is familiar with the basic concepts of Steel Design facilities available in STAAD. Please refer to Section 3 of the STAAD Technical Reference Manual for detailed information on this topic. This document specifically addresses the implementation of steel design based on ASCE Pub. 52.

Section 11

Steel Design Per ASCE Manuals And Reports Section 11

11-2

11.2 Allowable Stresses per ASCE (Pub. 52)

The member design and code checking in the STAAD implementation of ASCE (Pub. 52) is based upon the allowable stress design method. Appropriate sections of this publication are referenced below. Allowable Axial Tensile Stress

Allowable tensile stresses are calculated on the basis of the procedure described in section 4.10. The NSF parameter (Table 1.1) may be used if the net section area needs to be used.

Allowable Axial Compressive Stress

Allowable compressive stress calculation is based on the procedures of section 4.6 through 4.9. For angle members under compression, the procedure of sections 4.7 and 4.8 have been implemented. Capacity of the section is computed for column buckling and wherever applicable, torsional buckling. The user may control the effective lengths for buckling using the LX, LY, LZ and/or KX, KY, KZ parameters (Table 1.1). Allowable Bending Compressive Stress

Calculations for allowable bending compressive stress about the major axis and minor axis are based on the procedures of section 4.14. Procedures outlined in sections 4.14.1 through 4.14.6 have been implemented. Allowable Bending Tensile Stress

Calculations for allowable bending tensile stress about the major and minor axis are based on the procedures of section 4.14.2. Allowable Shear Stress

Calculation of the allowable shear stress is based on the procedure outlined in section 4.15 of the ASCE Pub. 52. The procedure of

Section 11

11-3

section 4.15.2 is followed for angles and the procedure of section 4.15.1 is followed for all other sections.

Critical Conditions used as criteria to determine Pass/Fail status

These are Clause 4.4 for slenderness limits, Equation 4.12-1 for Axial Compression and Bending, Equation 4.13-1 for Axial Tension and Bending, Clause 4.9.2 for Maximum w/t ratios and Clause 4.15 for Shear.


Design per ASCE (Pub. 52) must be initiated by using the command CODE ASCE. This command should be the first command after the PARAMETER statement. Other applicable parameters are summarized in Table 1.1. These parameters may be used to control the design process to suit specific modeling needs. The default parameter values have been selected such that they are frequently used numbers for conventional design.

11.4 Code Checking and Member Selection

Both code checking and member selection options are available in the ASCE Pub. 52 implementation. For general information on these options, refer to section 3 of the STAAD Technical Reference Manual. For information on specification of these commands, refer to section 6.


11-4

11.5 Parameter Definition Table

Table 11.1 - Steel Design Parameters for ASCE (PUB. 52) Based Design

Parameter Name

Default Value

Description

KY 1.0 Effective length factor (K) for compression buckling about the Y-axis (minor axis)

KZ 1.0 Effective length factor (K) for compression buckling about the Z-axis (major axis)

KT 1.0 Effective length coefficient for warping restraint (clause 4.14.4, pg 36)

LY Member Length

Length to calculate slenderness ratio for buckling about the Y-axis (minor axis)

LZ Member Length

Length to calculate slenderness ratio for buckling about the Z-axis (major axis)

LT Member Length

Effective length for warping.

FYLD 36.0 KSI Yield Strength of steel

NSF 1.0 Net section factor for tension members

UNL Member Length

Unsupported length of member for calculation of allowable bending stress

UNF 1.0 Same as UNL, but provided as a fraction of the member length

TRACK 0.0 0.0 = Suppresses printing of allowable stresses 1.0 = Prints all allowable stresses

DMAX 45.0 in. Maximum allowable depth for member selection

DMIN 0.0 in. Minimum allowable depth for member selection

RATIO 1.0 Permissible ratio that determines the cut off point for pass/fail status. A value below this quantity indicates PASS while a value greater than this quantity indicates FAILURE.

BEAM 0.0 0.0 = Perform design using the section locations specified according to the SECTION command 1.0 = Perform design at the ends and eleven intermediate sections of the beam

Section 11

11-5


Parameter Name

Default Value

Description

MAIN 2 Parameter that indicates the member type for the purpof calculating the KL/R ratio (SEE CLAUSE 4.4, PAGE 25) = 10 : DO NOT PERFORM THE KL/R CHECK = 1 : LEG MEMBER KL/R <= 150 = 2 : COMPRESSION MEMBER KL/R <= 200 = 3 : TENSION MEMBER KL/R <= 500 = 4 : HANGAR MEMBERS KL/R <= 375 (Clause 4C.4, page 43) = 5 : REDUNDANT MEMBERS KL/R <= 250

ELA 4 Indicates what type of end conditions are to be used From among Equations 4.7-4 thru 4.7-7 to determine tthe KL/R ratio. ELA=1 : EQN.4.7-4, Page 26

(VALID FOR LEG MEMBERS ONLY) ELA=2 : EQN.4.7-5, Page 27 ELA=3 : EQN.4.7-6, Page 27 ELA=4 : EQN.4.7-7, Page 27

ELB 1 Indicates what type of end conditions are to be used From among Equations. 4.7-8 thru 4.7-10 to determine the KL/R ratio. ELB=1 : EQN.4.7-8, Page 27, EQN.4.7-12, Page 28 ELB=2 : EQN.4.7-9, Page 27, EQN.4.7-13, Page 28 ELB=3 : EQN.4.7-10, Page 27, EQN.4.7-14,Page28

LEG 0.0 This parameter is meant for plain angles. 0.0 = indicates that the angle is connected by both legs and allowable stress in axial tension is 1.0FYLD. 1.0 = indicates that the angle is connected only by the shorter leg and allowable tensile stress is computed per clause 4.10.2 as 0.9FYLD. 2.0 = indicates that the angle is connected by the longer leg.

DBL 0.75 in. Diameter of bolt for calculation of number of bolts required and the net section factor.

FYB 36 KSI Yield strength of bolt.

FVB 30 KSI Shear strength of bolt.


11-6


Parameter Name

Default Value

Description

NHL

0 Number of bolt holes on the cross section that should be used to determine the net section factor fortension capacity.

Notes: All values must be provided in the current unit system.

Section 12 American Steel Design

Per A.P.I. Code

12-1

Steel Design Per A.P.I.

12.1 Design Operations

STAAD contains a broad set of facilities for the design of structural members as individual components of an analyzed structure. The member design facilities provide the user with the ability to carry out a number of different design operations. These facilities may be used selectively in accordance with the requirements of the design problem. The operations to perform a design are: • Specify the members and the load cases to be considered in the

design; • Specify whether to perform code checking or member

selection; • Specify design parameter values, if different from the default

values; and • Specify design parameters to carry out punching shear checks.

These operations may be repeated by the user any number of times depending upon the design requirements, but care should be taken when coupled with manipulation of the punching shear LEG parameter. The basic process is:-

a. Define the STAAD model geometry, loading and analysis.

b. Define the API code parameters with LEG 1.0.

c. Run the analysis and API design which creates the Geometry file and give preliminary design results.

d. Check and modify the Geometry file as necessary.

Section 12


Section 12

12-2 e. Reset the LEG parameter to 2.0 and re-run the analysis to read

the modified Geometry file for the final design results.

12.2 Allowables per API Code

For steel design, STAAD compares the actual stresses with the allowable stresses as defined by the American Petroleum Institute (API-RP2A) Code. The 20th edition of API Code, as published in 1993, is used as the basis of this design (except for tension stress).

12.2.1 Tension Stress

Allowable tension stresses, as calculated in STAAD, are based on the API Code, clause (3.2.1-1). Allowable tension stress on the net section

Ft = 0.60Fy

12.2.2 Shear Stress

Beam Shear Stress

Allowable beam shear stress on the gross section must conform to (3.2.4-2):

Fv = 0.4 Fy The maximum applied beam shear stress is:

fv = V / 0.5 A (3.2.4-1)

Torsional Shear Stress

Allowable torsional shear stress

Fvt = 0.4 Fy (3.2.4-4)

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12-3

Fvt is the maximum torsional shear stress per (3.2.4-3).

12.3 Stress due to Compression

The allowable compressive stress on the gross section of axially loaded compression members is calculated based on the formula 3.2.2-1 in the API Code, when the largest effective slenderness

ratio

rKl

is less than Cc =yF

E22π . If r

Kl exceeds Cc the

allowable compressive stress is increased as per formula (3.2.2-2) of the Code.

For tD

> 60 the lesser of Fxe or Fxc are substituted for Fxy .

Fxe = the elastic local buckling stress calculated with C, the critical elastic buckling coefficient = 0.3 (3.2.2-3) Fxc = the inelastic local buckling stress, (3.2.2-4)

12.4 Bending Stress

The allowable bending stress for tension and compression for a symmetrical member loaded in the plane of its minor axis, as given in Section 3.2.3 is:

a) Fb = 0.75 Fy

provided tD

≤ yF

1500 (Imperial Units)

b) Fb =

−

EtDFy74.184.0 Fy


Section 12

12-4

where yF

1500 <

tD

< yF

3000 (Imperial Units)

c) Fb =

−

EtDFy58.072.0 Fy

where yF

3000 <

tD

≤ 300 (Imperial Units)

12.5 Combined Compression and Bending

Members subjected to both axial compression and bending stresses are proportioned to satisfy API formula 3.3.1-1 and 3.3.1-2 when

a

a

Ff

is greater than 0.15, otherwise formula 3.3.1-3 applies. It

should be noted that during code checking or member selection, if

a

a

Ff

exceeds unity, the program does not compute the second

3.3.1-1/2.


The program contains a large number of parameter names which are required to perform design and code checks. These parameter names, with their default values, are listed in Table 12.1. These parameters communicate design decisions from the engineer to the program. (Also see section 5.44.1). The default parameter values have been selected such that they are frequently used numbers for conventional design. Depending on the particular design requirements for an analysis, some or all of these parameter values may have to be changed to exactly model the physical structure. For example, by default the KZ value (k value in local z-axis) of a member is set to 1.0, wile in the real

Section 12

12-5

structure it may be 1.5. In that case, the KZ value in the program can be changed to 1.5, as shown in the input instruction (Section 5). Similarly, the TRACK value of a member is set to 0.0, which means no allowable stresses of the member will be printed. If the allowable stresses are to be printed, the TRACK value must be set to 1.0. Note: The parameter names DMAX and DMIN are only used for member selection.

Table 12.1- American (API) Steel Design Parameters

Parameter Name

Default Value

Description

KY 1.0 K value in local y-axis.

Usually, this is minor axis.

KZ 1.0 K value in local z-axis.

Usually, this is major axis.

LY Member Length

Length in local Y-axis to calculate slenderness ratio.

LZ Member Length

Length in local Z-axis to calculate slenderness ratio.

FYLD 36 KSI Yield strength of steel.


UNL Member Length

Unsupported length for calculating allowable bending stress

UNF 1.0 Same as above provided as a fraction of actual member length

CB 1.0 Cb value as used in Section 1.5 of AISC 0.0 = Cb value to be calculated Any other value will mean the value to be used in design

MAIN 0.0 1.0 = Main member

2.0 = Secondary member

SSY 0.0 0.0 = Sidesway in local y-axis

1.0 = No sidesway


Section 12

12-6

Table 12.1- American (API) Steel Design Parameters

Parameter Name

Default Value

Description

SSZ 0.0 Same as above except in local z-axis

CMY

CMZ

0.85 for sidesway*

and calculated for no sidesway

Cm value in local y & z axes

TRACK 0.0 1.0 = Print all critical member stresses

100.0 = Suppress all checks except punching shear

DMAX 0.0 Maximum allowable depth

DMIN 0.0 Minimum allowable depth

RATIO Permissible ratio of the actual to allowable stresses

WELD 1 for closed sections

2 for open sections

Weld type, as explained in section 3.1.1.

1 = Welding is one side only except for wide flange or tee sections, where the web is always assumed to be welded on both sides.

2 = Welding is both sides. For closed sections like pipe or tube, the welding will be only on one side.

BEAM 1.0 0.0 = design only for end moments or those at locations specified by the SECTION command.

= calculate moments at twelfth points along the beam, and use the maximum Mz location for design.

WMIN 1.16 in. Minimum thickness

WSTR 0.4 X FLYD Allowable welding stress

LEG 1.0

2.0

To write out external parameters file.

To read in the external parameters file.

Section 12

12-7

12.7 Code Checking

The purpose of code checking is to ascertain whether the provided section properties of the members are adequate as per API. Code checking is done using the forces and moments at specific sections of the members. If no sections are specified, the program uses the start and end forces for code checking. When code checking is selected, the program calculates and prints whether the members have passed or failed the checks, the critical condition of API code (like any of the API specifications for compression, tension, shear, etc.), the value of the ratio of the critical condition (overstressed for value more than 1.0 or any other specified RATIO value), the governing load case, and the location (distance from the start of the number of forces in the member) where the critical condition occurs. Code checking can be done with any type of steel section listed in Section 2.2, American Steel Design, of the Technical Reference manual.

12.8 Member Selection

STAAD is capable of performing design operations on specified members. Once an analysis has been performed, the program can select the most economical section, i.e. the lightest section which fulfills the code requirements for the specified member. The section selected will be of the same type section as originally designated for the member being designed. Member selection can also be constrained by the parameters DMAX and DMIN which limits the maximum and minimum depth of the members. Member selection can be performed with all types of hollow steel sections.


Section 12

12-8 Selection of members whose properties are originally input from a user created table will be limited to sections in the user table. Member selection cannot be performed on members whose section properties are input as prismatic.

12.9 Truss Members

As mentioned earlier, a truss member is capable of carrying only axial force. So in design, no time is wasted calculating the allowable bending or shear stresses, thus reducing design time considerably. Therefore, if there is any truss member in an analysis (like bracing or strut, etc.), it is wise to declare it as a truss member rather than as a regular frame member with both ends pinned.

12.10 Punching Shear

For tubular members, punching shear may be checked in accordance with the American Petroleum Institute (API) RP 2A – 20th Edition Section 4. The parameter PUNCH is used to identify joint types for each end of the member where the punching shear check is required. The PUNCH parameter is only read in from the external geometry file. The external geometry file is described in section 12.13. The PUNCH parameter is not specified within the STAAD input file (the file with the .std extension).

Type of Joint and Geometry Req. Value of Parameter PUNCH

K (overlap) 1.0 K (gap) 2.0 T & Y 3.0 CROSS 4.0 CROSS (with/diaphragms) 5.0

Section 12

12-9

Note: A value representing joint type and geometry must be provided for parameter PUNCH, in the external file. On the first run where no external table is present, LEG must equal 1.0.

12.11 Generation of the Geometry File

Automatic selection of the chord and brace members are performed with the parameter LEG 1.0. Two tubular members are used by the program to identify the chord member. The chord members must be collinear (5 degree tolerance). The chord member must have a greater diameter and thickness than the brace member being considered. The punching shear check is performed on the joint treating it as a T/Y joint. The yield stress of the brace is used. In the 50% strength check the brace and chord yield are assumed to be the same. The major moment axis Mz is taken as In Plane Bending (IPB). To change this, the parameter SWAP 1 should be used in the external geometry file. Note: The in-plane/out-of-plane correspondence can be set by using the BETA angle. If the punching shear cannot be performed at the joint for the member being considered, a message is written to the output file <filename>.ANL. If a punching shear check is performed with the parameter LEG 1.0 used, then the geometry data used to perform the check is written to the default external output file APIPUN. The default external output/input file name can be changed by using the command line:-


Section 12

12-10 CODE API <filename>. This external output data file can be edited and used as an external input file to re-perform the check using the parameter PUNCH 1.0 to 5.0. This external input file allows can/stub geometry data to be specified and chords to be assigned geometry where they could not be identified in the Automatic selection. The parameter LEG 2.0 must be used to read an external input file where the default name is APIPUN. The yield strength of the brace is used in the punching shear check. This can be changed in the external geometry file. The user should ensure that the correct cord member has been selected for the check.

12.12 Chord Selection and Qf Parameter

Qf is a factor to account for the presence of nominal longitudinal stress in the chord. When calculating Qf for the joints, the moments used in the chord stress calculation will be from the computer node results and not the representative moments underneath the brace. If the moment varies significantly along the chord, it is more accurate to use the actual chord moment in the middle of the brace foot print. The tests reported in Reference I1 were performed with a constant moment along the chord. Thus for a local joint check, the local chord moment (under the brace) should be used. STAAD calculates Qf based on the moment at the chord member. The chord member can be selected automatically by initial screening by the program (based on geometry and independent of loading) or specified by the user in the External file.

1 Ref I: Boone, TJ, Yura, JA and Hoadley, PW, Ultimate Strength if Tubular Joints – Chord Stress Effects, OTC 4828, 1984

Section 12

12-11

In the automatic selection of the chord two collinear members (5 degree tolerance) are used to identify the chord. The chord is then selected from one of the two members based on the larger diameter then thickness or then by the minimum framing angle; for T joints the first member modeled will be selected as the chord. The user should confirm that the chord either be assigned by the program or the user is representative of the local chord moment for the brace in question.

12.13 External Geometry File

An example of the external geometry file is shown below:

BRACE CHORD PUNCH D T d T GAP FYLD THETAT TW SWAP

209 211 3 17.992 0.984 12.752 0.787 0.000 50.00 0.00 0.000 0

209 210 3 17.992 0.984 12.752 0.787 0.000 50.00 0.00 0.000 0

212 202 3 17.992 0.787 12.752 0.787 0.000 50.00 0.00 0.000 0

The parameters used in the external file are defined as follows: Table 12.2 – External File

Parameter Description

PUNCH Parameter for punching shear (See Section 12.10)

BRACE Member number of brace CHORD Member number of chord D Chord Diameter in inches T Chord Thickness in inches d Brace Diameter in inches T Brace Thickness in inches GAP Gap in inches (must be negative for overlap

K-joint) FYLD Local yield strength used for joint in KIPS THETAT Angle of through brace in overlap K-joint in


Section 12

12-12 Table 12.2 – External File

Parameter Description

Degrees TW Used in overlap K-joint, taken as the lesser of

the weld throat thickness or thickness t of the thinner brace in inches

SWAP If parameter SWAP 0 is used then major moment Mz is taken for In Plane Bending (IPB). SWAP 1 uses the minor moment My as the IPB.

Notes: • For overlap K-joints, the through brace is assumed to be the

same diameter as the brace being checked. • If any of the parameters for diameter and thickness specified

in the external file are less than that for members being checked, then the member properties specified in the STAAD file shall be used.

• The member diameter and thickness should be used in API equation (4.1-1); in this check it has been assumed that the yield strength of the chord and brace members are the same.

• The geometry file name is currently limited to eight characters (4 if an extension as .txt is used).

The overall process of performing punching shear checks consists of two steps. These steps are explained in section 12.16.

12.14 Limitations

The parameter SELECT 1.0 should not be used while carrying out punching shear checks. It can be used in initial runs for member selection. No classification of the joint is performed using the loading. No hydrostatic checks are performed.

Section 12

12-13

12.15 Tabulated Results of Steel Design

For code checking or member selection, the program produces the results in a tabulated fashion. The items in the output table are explained as follows:

a) Member refers to the member number for which the design is performed.

b) TABLE refers to AISC steel section name which has been checked against the steel code or has been selected.

c) RESULTS prints whether the member has PASSed or FAILed. If the RESULT is FAIL, there will be an asterisk (*) mark on front of the member.

d) CRITICAL COND refers to the section of the AISC code which governs the design.

e) RATIO prints the ratio of the actual stresses to allowable stresses for the critical condition. Normally a value of 1.0 or less will mean the member has passed.

f) LOADING provides the load case number which governed the design.

g) FX, MY, and MZ provide the axial force, moment in local Y-axis, and the moment in local Z-axis respectively. Although STAAD does consider all the member forces and moments (except torsion) to perform design, only FX, MY and MZ are printed since they are the ones which are of interest, in most cases.

h) LOCATION specifies the actual distance from the start of the member to the section where design forces govern.

i) If the parameter TRACK is set to 1.0, the program will block out part of the table and will print the allowable bending stressed in compression (FCY & FCZ) and tension (FTY & FTZ), allowable axial stress in compression (FA), and allowable shear stress (FV).


Section 12

12-14

12.16 The Two-Step Process

The overall procedure for performing the code check per the API code is as follows: Step 1 – Creating the geometry data file. This is done by specifying the name of the geometry data file alongside the command line CODE API. If a file name is not specified, STAAD automatically assigns the file name APIPUN to the geometry data file. The parameter instructions in the .std file should contain the LEG parameter and it should be assigned the value 1.0.

Example Reading External Geometry File UNIT INCHES KIPS PARAMETERS * All joint data will be written to external file GEOM1 for punching shear. CODE API GEOM1 LEG 1.0 * Joints to be considered as T and Y, i.e. PUNCH is set to 3.0. FYLD 50.0 ALL TRACK 1.0 ALL RATIO 1.0 ALL BEAM 1.0 ALL CHECK CODE ALL

After ensuring that your STAAD input file contains the above data, run the analysis. Once the analysis is completed, you will find that a file by the name GEOM1 has been created and is located in the same folder as the one where your .std file is located. (In case you did not specify a file name - GEOM1 shown in the earlier example - STAAD will create the file named APIPUN.

Section 12

12-15

Step 2 – The geometry data file (GEOM 1 or otherwise) should be inspected and modified as required such as changing the PUNCH values and local section properties for the punching shear checks. Modify the .std file so it reruns the code check process by reading the instructions of the GEOM file. This message is conveyed by changing the value of the LEG parameter to 2.0. After making this change, a re-analysis will result in the program using the information in the geometry data file (GEOM1, APIPUN, or otherwise) for performing the code check.

Example Reading an existing Joint Geometry Data File, GEOM1 UNIT INCHES KIPS PARAMETERS * All joint data will be read from the external file GEOM1 for punching shear. CODE API GEOM1 LEG 2.0 FYLD 50.0 ALL TRACK 1.0 ALL RATIO 1.0 ALL BEAM 1.0 ALL CHECK CODE ALL


Section 12

12-16

International Codes 2004

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