DESIGN OF COLD-FORMED STEEL STRUCTURES

Transcription

1 DESIGN OF COLD-FORMED STEEL STRUCTURES

2 ECCS EUROCODE DESIGN MANUALS ECCS EUROCODE DESIGN MANUALS ECCS EDITORIAL BOARD Luís Simões da Silva (ECCS) António Lamas (Portugal) Jean-Pierre Jaspart (Belgium) Reidar Bjorhovde (USA) Ulrike Kuhlmann (Germany) DESIGN OF STEEL STRUCTURES Luís Simões da Silva, Rui Simões and Helena Gervásio FIRE DESIGN OF STEEL STRUCTURES Jean-Marc Franssen and Paulo Vila Real DESIGN OF PLATED STRUCTURES Darko Beg, Ulrike Kuhlmann, Laurence Davaine and Benjamin Braun FATIGUE DESIGN OF STEEL AND COMPOSITE STRUCTURES Alain Nussbaumer, Luís Borges and Laurence Davaine DESIGN OF COLD-FORMED STEEL STRUCTURES Dan Dubina, Viorel Ungureanu and Raffaele Landolfo AVAILABLE SOON DESIGN OF COMPOSITE STRUCTURES Markus Feldman and Benno Hoffmeister DESIGN OF JOINTS IN STEEL AND COMPOSITE STRUCTURES Jean-Pierre Jaspart, Klaus Weynand DESIGN OF STEEL STRUCTURES FOR BUILDINGS IN SEISMIC AREAS Raffaele Landolfo, Federico Mazzolani, Dan Dubina and Luís Simões da Silva INFORMATION AND ORDERING DETAILS For price, availability, and ordering visit our website For more information about books and journals visit

3 DESIGN OF COLD-FORMED STEEL STRUCTURES Eurocode 3: Design of Steel Structures Part 1-3 Design of Cold-formed Steel Structures Dan Dubina Viorel Ungureanu Raffaele Landolfo

4 Design of Cold-formed Steel Structures 1 st Edition, 2012 Published by: ECCS European Convention for Constructional Steelwork publications@steelconstruct.com Sales: Wilhelm Ernst & Sohn Verlag für Architektur und technische Wissenschaften GmbH & Co. KG, Berlin All rights reserved. No parts of this publication may be reproduced, stored in a retrieval system, or transmitted in any form or by any means, electronic, mechanical, photocopying, recording or otherwise, without the prior permission of the copyright owner. ECCS assumes no liability with respect to the use for any application of the material and information contained in this publication. Copyright 2012 ECCS European Convention for Constructional Steelwork ISBN (ECCS): ISBN (Ernst & Sohn): Legal dep.: - Printed in Multicomp Lda, Mem Martins, Portugal Photo cover credits: BRITT Ltd., Timisoara, Romania.

5 TABLE OF CONTENTS TABLE OF CONTENTS FOREWORD PREFACE xi xiii Chapter 1 INTRODUCTION TO COLD-FORMED STEEL DESIGN General Cold-formed steel sections Types of cold-formed steel sections Manufacturing Some peculiar characteristics of cold-formed steel sections Peculiar problems of cold-formed steel design Buckling strength of cold-formed steel members Torsional rigidity Web crippling Ductility and plastic design Connections Design assisted by testing Design standards North American Cold-formed Steel Specification, 2001 Edition (AISI, 2001) and 2007 Edition (AISI, 2007) Australian/New Zealand Standard AS/NZS 4600, 2005 Edition (AS/NZS, 2005) Eurocode 3 Design of Steel Structures, Part 1.3 General Rules, Supplementary Rules for Cold-formed Thin Gauge Members and Sheeting Fire resistance Corrosion 28 i

6 TABLE OF CONTENTS Sustainability of cold-formed steel construction Main applications of cold-formed steel Advantages of cold-formed steel in building construction Advantages during construction Advantages in service Applications 34 ii Chapter 2 BASIS OF DESIGN General Limit state design Actions on structures. Combinations of actions Verification at the Ultimate Limit State Verification at the Serviceability Limit State Deflections Dynamic effects Materials General Structural steel Material properties of base material Material properties of cold-formed sections and sheeting Thickness and thickness tolerances Methods of analysis and design Methods of analysis Global frame analysis Finite Element Methods (FEM) for analysis and design Design assited by testing Imperfections Imperfections for global analysis of frames Imperfections for analysis of bracing systems Role of imperfections in advanced numerical simulation Section imperfections Residual stresses 94

7 TABLE OF CONTENTS Chapter 3 BEHAVIOUR AND RESISTANCE OF CROSS SECTION General Properties of gross cross section Nominal dimensions and idealisation of cross section Net geometric properties of perforated sections Dimensional limits of component walls of cold-formed steel sections Modelling of cross section component walls for analysis Flange curling Shear lag Local buckling Sectional buckling modes in thin-walled sections Elastic buckling of thin plates Distortional buckling: analytical methods for predicting elastic distortional buckling stresses The method given in EN : Design against local and distortional buckling according to EN General Plane elements without stiffeners Plane elements with edge or intermediate stiffeners General Plane elements with edge stiffeners Conditions General procedure Plane elements with intermediate stiffeners Conditions General procedure Trapezoidal sheeting profiles with intermediate stiffeners General 165 iii

8 TABLE OF CONTENTS iv Flanges with intermediate stiffeners Webs with up to two intermediate stiffeners Sheeting with flange stiffeners and web stiffeners Resistance of cross sections General Axial tension Axial compression Bending moment Elastic and elastoplastic resistance with yielding at the compressed flange Elastic and elastoplastic resistance with yielding at the tension flange only Effects of shear lag Shear force Torsional moment Local transverse forces General Cross sections with a single unstiffened web Cross sections with two or more unstiffened webs Stiffened webs Combined tension and bending Combined compression and bending Combined shear force, axial force and bending moment Combined bending moment and local load or support reaction 231 Chapter 4 BEHAVIOUR AND DESIGN RESISTANCE OF BAR MEMBERS General Compression members Theoretical background Ideal elastic members 241

9 TABLE OF CONTENTS Imperfect member Class 4 sections: local-global interactive buckling Buckling resistance of uniform members in compression. Design according to EN Flexural buckling Torsional buckling and flexural-torsional buckling Buckling strength of bending members Theoretical background Design according to EN Lateral-torsional buckling of members subject to bending Simplified assessment methods for beams with restraints in building Buckling of members in bending and axial compression Theoretical background Design of beam-columns according to EN and EN General method for lateral and lateral-torsional buckling of structural components Beams restrained by sheeting General. Constructional detailing and static system Modelling of beam-sheeting interaction Design of beams restrained by sheeting according to EN Design criteria Design resistance Rotational restraint given by the sheeting Simplified design of purlins Design of beams at serviceability limit states 363 v Chapter 5 SHEETING ACTING AS DIAPHRAGM Introduction 367

10 TABLE OF CONTENTS vi 5.2 General design considerations for diaphragm action Conditions and restrictions for the use of stressed skin design Types of diaphragms Irregular roof chape Design criteria Diaphragm flexibility Diaphragm strength Interaction of diaphragm action and rigid-jointed frames The danger of ignoring stressed skin action in conventional construction Design procedures for sheeting acting as diaphragm Design expressions for shear flexibility of diaphragm Sheeting spanning perpendicular to length of diaphragm Sheeting spanning parallel to length of diaphragm Design expression for shear strength of diaphragms Sheeting spanning perpendicular to length of diaphragms Sheeting spanning parallel to length of diaphragm Buckling strength of sheeting in shear General Global shear buckling Local shear buckling Effect of combined loads Diaphragms with openings Discrete openings Requirements for discrete openings Flexibility of diaphragms with discrete openings 409

11 TABLE OF CONTENTS Strength of diaphragms with discrete openings Strip openings Two skin envelopes Interaction of the shear diaphragms with supporting framing General Elastic design of framing Rectangular frames: all frames loaded Pitched roof frames: all frames loaded One frame loaded Plastic design of framing Rectangular frames Pitched roof frames Modelling of diaphragm effect for frame analysis Diaphragm action of sandwich panels 422 Chapter 6 STRUCTURAL LINER TRAYS Introduction Design procedures for cassette sections General Axial compression Moment resistance Bending with the narrow flange in compression (wide flange in tension) Bending with the wide flange in compression Behaviour in shear Design procedures for cassette panels acting as diaphragm Cassettes spanning horizontal to the length of diaphragm (liner tray shear panels) Some peculiar problems for design of wall panels of cassettes spanning vertically to the length of diaphragm Combined effects 457 vii

12 PREFACE PREFACE The use of cold-formed steel members in building construction began in the 1850s in both the United States and Great Britain. In the 1920s and 1930s, acceptance of cold-formed steel as a construction material was still limited because there was no adequate design standard and there was limited information on material use in building codes. One of the first documented uses of cold-formed steel as a building material is the Virginia Baptist Hospital, constructed around 1925 in Lynchburg, Virginia, USA. The building structure was composed by masonry and the floors supported by cold-formed steel built-up joists of back- to- back lipped channel sections. Only some 20 years later, only, Lustron Corporation built in Albany, New York, with almost 2500 steel-framed homes, with the framing, finishes, cabinets and furniture made from cold-formed steel. These inexpensive houses were built for the veterans returning from the World War II. This was the beginning of cold-formed steel adventure in building. In recent years, cold formed steel sections are used more and more as primary framing components. Wall stud systems in housing, trusses, building frames or pallet rack structures are some examples. As secondary structural systems they are used as purlins and side rails or floor joists, as well as in building envelops. Cassette sections in modern housing systems play simultaneously the role of primary structure and envelope. Profiled decking is widely used as basic components in composite steel-concrete slabs. xiii Cold-formed steel members are efficient in terms of both their stiffness and strength. Additionally, because the base steel is thin, even less than 1mm thick when high strength steel is used, the members are lightweight. The use of thinner sections and high strength steel leads to design problems for structural engineers which may not normally be encountered in routine structural steel design. Further, the shapes which can be cold-formed are often considerably more complex than hot-rolled steel shapes such as I-

13 PREFACE sections and plain channel sections. The cold-formed sections commonly have mono-symmetric or point symmetric shapes, and normally have stiffening lips on flanges and intermediate stiffeners in wide flanges and webs. Both simple and complex shapes can be formed for structural and nonstructural applications. Cold-formed steel design is dominated by two specific problems, i.e. (1) stability behaviour, which is dominant for design criteria of thin sections, and (2) connecting technology, which is specific and influences significantly the structural performance and design detailing. Special design standards have been developed to cover the specific problems of cold-formed steel structures. In the USA, the Specification for the design of cold-formed steel structural members of the American Iron and Steel Institute was first produced in 1946 and has been regularly updated based on research to the most recent 2007 edition, AISI S100-07, entitled North American Specification for Design of Cold-Formed Steel Structural Members. xiv In Europe, the ECCS Committee TC7 originally produced the European Recommendations for the design of light gauge steel members in 1987 (ECCS, 1987). This European document has been further developed and published in 2006 as the European Standard Eurocode 3: Design of steel structures. Part 1-3: General Rules. Supplementary rules for cold-formed thin gauge members and sheeting (EN , 2006). In Australia and New Zeeland, the last version of specification for the design of cold-formed steel structures, AS/NZS 4600, was published in December 2005, and the review of cold-formed steel design specification could be continued around the world. The market share of cold-formed structural steelwork continues to increase in the developed world. The main reasons can be found in the improving technology of manufacture and corrosion protection which leads, in turn, to an increased competitiveness of resulting products as well as new applications. Recent studies have shown that the coating loss for galvanised

14 PREFACE steel members is sufficiently slow, and indeed slows down to effectively zero, than a design life in excess of 60 years can be guaranteed. The range of use of cold-formed steel sections specifically as load-bearing structural components is very wide. Besides building applications, coldformed steel elements can be met in the Automotive industry, Shipbuilding, Rail transport, in Aircraft industry, Highway engineering, Agricultural and Industry equipment, Office equipment, Chemical, Mining, Petroleum, Nuclear and Space industries. This book is primarily concerned with the design of cold-formed steel members and structures in building construction in Europe. For this reason it is mainly focused on the EN , and the related parts of EN 1993 (e.g. EN , EN , EN , etc.). Generally, the book contains the theoretical background and design rules for cold-formed members and connections, accompanied by design oriented flow charts and worked examples for common building application. The book was conceived primarily as a technical support for structural engineers in design and consulting offices, but it is expected to be of interest and useful for students and staff members of structural engineering faculties, as well as, for engineers working in steelwork industry. xv Dan Dubina Viorel Ungureanu Raffaele Landolfo