Steel Structures: Practical Design Studies, Second Edition

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Steel Structures

Steel StructuresPractical design studiesSecond editionT.J.MacGinleyFormerly Associate ProfessorNanyang Technological UniversitySingaporeE & FN SPONLondon and New York

Published by E & FN Spon, an imprint of Thomson Professional, 2–6Boundary Row, London SE1 8HN, UKThomson Science Professional, 2–6 Boundary Row, London SE1 8HN, UKThomson Science Professional, Pappelallee 3, 69469 Weinheim, GermanyThomson Science Professional, 115 Fifth Avenue, New York, NY 10003,USAThomson Science Professional, ITP-Japan, Kyowa Building, 3F, 2–2–1Hirakawacho, Chiyoda-ku, Tokyo 102, JapanThomson Science Professional, 102 Dodds Street, South Melbourne,Victoria 3205, AustraliaThomson Science Professional, R.Seshadri, 32 Second Main Road, CITEast, Madras 600 035, IndiaFirst edition 1981This edition published in the Taylor & Francis e-Library, 2005.“To purchase your own copy of this or any of Taylor & Francis or Routledge’s collection of thousands of eBooks please go to www.eBookstore.tandf.co.uk.”Second edition 1998 1998 G.MacGinleyISBN 0-203-47428-7 Master e-book ISBNISBN 0-203-78252-6 (Adobe eReader Format)ISBN 0 419 17930 5 (Print Edition)Apart from any fair dealing for the purposes of research or private study,or criticism or review, as permitted under the UK Copyright Designs andPatents Act, 1988, this publication may not be reproduced, stored, ortransmitted, in any form or by any means, without the prior permission inwriting of the publishers, or in the case of reprographic reproduction onlyin accordance with the terms of the licences issued by the CopyrightLicensing Agency in the UK, or in accordance with the terms of licencesissued by the appropriate Reproduction Rights Organization outside theUK. Enquiries concerning reproduction outside the terms stated hereshould be sent to the publishers at the London address printed on thispage.The publisher makes no representation, express or implied, with regardto the accuracy of the information contained in this book and cannot acceptany legal responsibility or liability for any errors or omissions that may bemade.A catalogue record for this book is available from the British Library

Contents1PrefacexiPreface to First EditionxiiAcknowledgementsxiiiSteel structures—structural engineering11.1Need for and use of structures11.2Structural materials—types and uses11.3Types of structures21.3.1General types of structures21.3.2Steel structures31.4Foundations41.5Structural engineering41.5.1Scope of structural engineering41.5.2Structural designer’s work51.6Conceptual design, innovation and planning71.7Comparative design and optimization81.7.1General considerations81.7.2Aims and factors considered in design comparison81.7.3Specific basis of comparisons for common structures91.8Load paths, structural idealization and modelling111.8.1Load paths111.8.2Structural idealization121.8.3Modelling121.9Drawings, specifications and quantities121.9.1Steelwork 0Fabrication151.11Transport and erection162Structural steel design17Design theories172.12.1.1Development of design17

v2.1.2Design from experience172.1.3Elastic theory172.1.4Plastic theory182.1.5Limit state theory and design codes192.2Limit states and design basis202.3Loads, actions and partial safety factors202.3.1Loads202.3.2Load factors/partial safety factors and design loads212.4Structural steels—partial safety factors for materials212.5Design methods from codes—ultimate limit state212.5.1Design methods from BS 5950212.5.2Analysis of structures—Eurocode 3232.5.3Member and joint design232.6Stability limit state242.7Design for accidental damage242.7.1Progressive collapse and robustness242.7.2Building Regulations 1991252.7.3BS 5950 requirements for structural integrity252.8Serviceability limit states262.8.1Deflection limits262.8.2Vibration262.9Design considerations262.9.1Fatigue262.9.2Brittle fracture272.9.3Corrosion protection282.9.4Fire protection28Preliminary design313.1General considerations313.2Need for and scope of preliminary design methods313.3Design concept, modelling and load estimation3133.3.1Design concept313.3.2Modelling323.3.3Load estimation323.4Analysis323.4.1Statically determinate structures323.4.2Statically indeterminate structures353.5Element design38

vi3.5.1General comments383.5.2Ties and struts393.5.3Beams and girders403.5.4Beam-columns413.5.5Members in portal frames423.6Examples433.6.1Ribbed dome structure433.6.2Two pinned portal—plastic design454Single-storey, one-way-spanning buildings484.1Types of structures484.2Pinned-base portal—plastic design484.2.1Specification and framing plans484.2.2Dead and imposed loads494.2.3Wind loads504.2.4Design load cases524.2.5Plastic analysis and design524.2.6Dead and wind loads544.2.7Plastic design checks554.2.8Rafter under wind uplift594.2.9Portal joints60Serviceability check624.2.104.3Built-up tapered member portal634.3.1General comments634.3.2Design process634.4Two-pinned arch634.4.1General .7Lattice arch6755.1Multistorey buildings72Outline of designs covered725.1.1Aims of study725.1.2Design to BS 5950725.2Building and loads72

45.3Simple design centre frame755.3.1Slabs755.3.2Roof beam755.3.3Floor beam755.3.4Outer column—upper length 7–10–13755.3.5Outer column—lower length 1–4–7755.3.6Centre column—upper length 8–11–14765.3.7Centre column—lower length 2–5–8765.3.8Joint design775.3.9Baseplate—centre column775.4Braced rigid elastic design785.4.1Computer analysis785.4.2Beam design785.4.3Column design815.4.4Joint design825.5Braced rigid plastic design835.5.1Design procedure835.5.2Design loads and moments845.5.3Frame design85Semirigid design905.65.6.1Code requirements905.6.2Joint types and performance915.6.3Frame analysis915.6.4Frame design945.7Summary of designs100Floor systems1016.1Functions of floor systems1016.2Layouts and framing systems1016.3Types of floor construction1026.4Composite floor slabs1036.4.1General comments1036.4.2Design procedure10366.56.5.1Composite beam designDesign basis104104

viii6.5.2Effective section1056.5.3Plastic moment capacity1056.5.4Construction1066.5.5Continuous beam analysis1066.5.6Design of members1066.5.7Shear connectors1076.5.8Longitudinal shear1086.5.9Deflection1096.6Simply supported composite beam1096.6.1Specification1096.6.2Moment capacity1106.6.3Shear1106.6.4Shear connectors1106.6.5Longitudinal shear1106.6.6Deflection1106.7Continuous composite beam1116.7.1Specification1116.7.2Floor loads1126.7.3Elastic analysis and redistribution1136.7.4Section design checks1166.7.5Shear connectors1186.7.6Longitudinal shear1196.7.7Deflection120Tall buildings1227.1General considerations1227.2Structural design considerations1237.3Structural systems12377.3.1All-steel braced structure1237.3.2Rigid frame and mixed systems1247.3.3All-steel outrigger and belt truss system1257.3.4Composite structures1267.3.5Suspended structures1277.3.6Tube structures1287.3.7SWMB structures1297.4Construction details1297.4.1Roofs and floors1297.4.2Walls131

ix7.4.37.5Steel membersMultistorey building—preliminary design1311317.5.1Specification1317.5.2Dead and imposed loads1327.5.3Beam loads and design1337.5.4Design of perimeter column PC11367.5.5Braced core wall—vertical loads1397.5.6Wind loads1407.5.7Stability, foundations and bracing1448Wide-span buildings1468.1Types and characteristics1468.2Tie-stayed roof—preliminary design1478.2.1Specification1478.2.2Preliminary design1498.2.3Stability and wind load1538.3Space decks1558.3.1Two-way spanning roofs1558.3.2Space decks1578.3.3Space deck analysis and design157Preliminary design for a space deck1588.48.4.1Specification1588.4.2Arrangement of space deck1588.4.3Approximate analysis and design1588.4.4Computer analysis1598.4.5Computer results1628.4.6Member design1628.5Framed domes1638.5.1Types1638.5.2Dome 5Stability1668.6Schwedler dome1668.6.1Specification1668.6.2Loading for statical analysis1678.6.3Statical analysis1678.6.4Member design171

x8.6.58.7Membrane analysisRetractable roof stadium1721728.7.1Introduction1728.7.2Proposed structure1738.7.3Preliminary section sizes1748.7.4Problems in design and operation175Bibliography177Index179

PrefaceThe main purpose of the second edition is again to present principles, relevant considerations and sample designs for some ofthe major types of steel-framed buildings. All buildings can be framed in different ways with different types of joints andanalysed using different methods. Member design for ultimate conditions is specified. Projects are selected to showalternative designs for the same structure.Designs are now to conform to limit state theory—the British steel code and the new Eurocode. Design principles are setout briefly and designs made to the British code only. Reference is made to the Eurocode in one special case. Many moredesign calculations and checks are required for the limit state code than for the previous elastic code and thus not all load casesor detailed checks can be carried out for every design project. However, further necessary design work is indicated in thesecases.Though computer methods, mainly for analysis, but also increasingly used for member and connection design are now thedesign office procedural norm, approximate, manual methods are still of great importance. These are required mainly toobtain sections for computer analysis and to check final designs.The book, as in the case of the first edition, is aimed at final year students, candidates on master’s degree courses instructural engineering and young engineers in industry. Fundamental knowledge of the methods of structural analysis anddesign from a basic design course is assumed.

Preface to the First EditionThe purpose of the book is to present the principles and practice of design for some of the main modern structures. It isintended for final year degree students to show the application of structural engineering theory and so assist them to gain anappreciation of the problems involved in the design process in the limited time available in college. In such a presentationmany topics cannot be covered in any great detail.Design is a decision-making process where engineering judgement based on experience, theoretical knowledge,comparative design studies etc., is used to arrive at the best solution for a given situation. The material in the book covers thefollowing:(a) discussion of conceptual design and planning;(b) presentation of the principles and procedures for the various methods of analysis and design;(c) detailed analysis and design for selected structures. Preliminary design studies are made in other cases where the fulltreatment of the problem is beyond the scope of this book.In detailed design, the results are presented in the form of sketches showing framing plans, member sizes and constructionaldetails.Although the book is primarily concerned with the design of steel structures, important factors affecting both the overalldesign and detai required are discussed briefly. These include the choice of materials, type of foundations used, methods ofjointing, the fabrication process and erection methods, Other design considerations such as fatigue, brittle fracture, fireresistance and corrosion protection are also noted.The use of computers in design is now of increasing importance. Where required, computer programs are used in the bookfor analysis. While examples of computer-aided design have not been included, a project on this topic is listed at the end ofthe book. It is felt that the student must thoroughly understand design principles before using design programs.In college, the student is instructed through formal lectures backed by reading from textbooks and journals and byconsultation with staff and fellow students. The acquisition of knowledge and the exchange of ideas help him to develop hisexpertise and judgement and to make sound decisions. However, the most important part of the learning process is thecarrying out of practical design work where the students are given selected coursework exercises which cover the stages in thedesign process. Such exercises have been included at the end of most chapters. These, generally, consist of making designsfor given structures including framing plans, computer analysis, design and details drawings.In many first degree courses, the student is also required to undertake a project for which he may choose a topic from thestructural engineering field. This gives him the opportunity to make a study in a particular area of interest in greater depththan would be possible through the normal lectures. Some suggestions for projects are given at the end of the book. Thesemay be classified as follows:(a) comparative design studies;(b) computer-aided design projects;(c) construction and testing of structural models and presentation of results in report form.The intention of the book is to help equip the young engineer for his role in structural engineering in industry. It is importantto foster interest in structural engineering in industry. It is important to foster interest in structural design where this is shownby a student. It is hoped that this book will go some way towards this goal.

AcknowledgementsExtracts from British Standard BS 5950: Parts 1, 3 and 4 are reproduced by permission of the British Standards Institution, 2Park Street, London W1A 2BS, from whom copies can be obtained.

CHAPTER 1Steel structures—structural engineering1.1NEED FOR AND USE OF STRUCTURESStructures are one of mankind’s basic needs next to food and clothing, and are a hallmark of civilization. Man’s structuralendeavours to protect himself from the elements and from his own kind, to bridge streams, to enhance a ruling class and forreligious purposes go back to the dawn of mankind. Fundamentally, structures are needed for the following purposes: to enclose space for environmental control;to support people, equipment, materials etc. at required locations in space;to contain and retain materials;to span land gaps for transport of people, equipment etc.The prime purpose of structures is to carry loads and transfer them to the ground.Structures may be classified according to use and need. A general classification is: residential—houses, apartments, hotels;commercial—offices, banks, department stores, shopping centres;institutional—schools, universities, hospitals, gaols;exhibition—churches, theatres, museums, art galleries, leisure centres, sports stadia, etc.;industrial—factories, warehouses, power stations, steelworks, aircraft hangers etc.Other important engineering structures are: bridges—truss, girder, arch, cable suspended, suspension; towers—water towers, pylons, lighting towers etc.; special structures—offshore structures, carparks, radio telescopes, mine headframes etc.Each of the structures listed above can be constructed using a variety of materials, structural forms or systems. Materials arediscussed first and then a general classification of structures is set out, followed by one of steel structures. Though the subjectis steel structures, steel is not used in isolation from other materials. All steel structures must rest on concrete foundations andconcrete shear walls are commonly used to stabilize multistorey buildings.1.2STRUCTURAL MATERIALS—TYPES AND USESFrom earliest times, naturally occurring materials such as timber, stone and fibres were used structurally. Then followedbrickmaking, rope-making, glass and metalwork. From these early beginnings the modern materials manufacturing industriesdeveloped.The principal modern building materials are masonry, concrete (mass, reinforced and prestressed), structural steel in rolledand fabricated sections and timber. All materials listed have particular advantages in given situations, and construction of aparticular building type can be in various materials, e.g. a multistorey building can be loadbearing masonry, concrete shearwall or frame or steel frame. One duty of the designer is to find the best solution which takes account of all requirements —economic, aesthetic and utilitarian.

2STEEL STRUCTURES—STRUCTURAL ENGINEERINGThe principal uses, types of construction and advantages of the main structural materials are as follows. Masonry—loadbearing walls or columns in compression and walls taking in-plane or transverse loads. Construction is verydurable, fire resistant and aesthetically pleasing. Building height is moderate, say to 20 storeys. Concrete—framed or shear wall construction in reinforced concrete is very durable and fire resistant and is used for thetallest buildings. Concrete, reinforced or prestressed, is used for floor construction in all buildings, and concretefoundations are required for all buildings. Structural steel—loadbearing frames in buildings, where the main advantages are strength and speed of erection. Steelrequires protection from corrosion and fire. Claddins and division walls of other materials and concrete foundations arerequired. Steel is used in conjunction with concrete in composite and combined frame and shear wall construction.Structural steels are alloys of iron, with carefully controlled amounts of carbon and various other metals such as manganese,chromium, aluminium, vanadium, molybdenum, neobium and copper. The carbon content is less than 0.25%, manganese lessthan 1.5% and the other elements are in trace amounts. The alloying elements control grain size and hence steel properties,giving high strengths, increased ductility andTable 1.1 Strengths of steels used in structuresSteel type and useYield stress (N/mm2)Grade 43—structural shapesGrade 50—structural shapesQuenched and self-temperingQuenched tempered-platesAlloy bars—tension membersHigh carbon hard-drawn wire for cables27535550069010301700fracture toughness. The inclusion of copper gives the corrosion resistant steel Cor-ten. High-carbon steel is used tomanufacture hard drawn wires for cables and tendons.The production processes such as cooling rates, quenching and tempering, rolling and forming also have an importanteffect on the micro structure, giving small grain size which improves steel properties. The modern steels have much improvedweldability. Sound full-strength welds free from defects in the thickest sections can be guaranteed.A comparison of the steels used in various forms in structures is given in Table 1.1. The properties of hot-rolled structural steelsare given Chapter 2 (Table 2.3).Structural steels are hot-rolled into shapes such as universal beams and columns. The maximum size of universal column inthe UK is 356 406 UC, 634 kg/m, with 77 mm-thick flanges. Trade-ARBED in Luxembourg roll a section 360 401 WTM,1299 kg/m, with 140 mm-thick flanges. The heavy rolled columns are useful in high-rise buildings where large loads must becarried. Heavy built-up H, I and box sections made from plates and lattice members are needed for columns, transfer girders,crane and bridge girders, etc. At the other end of the scale, light weight cold-rolled purdins are used for roofing industrialbuildings. Finally, wire, rope and high-strength alloy steel bars are required for cable-suspended and cable-girder roofs andsuspended floors in multistorey buildings.1.3TYPES OF STRUCTURES1.3.1General types of structuresThe structural engineer adopts a classification for structures based on the way the structure resists loads, as follows.1. Gravity masonry structures—loadbearing walls resist loads transmitted to them by floor slabs. Stability depends ongravity loads.2. Framed structures—a steel or concrete skeleton collects loads from plate elements and delivers them to the foundations.3. Shell structures—a curved surface covers space and carries loads.4. Tension structures—cables span between anchor structures carrying membranes.5. Pneumatic

3.4.2 Statically indeterminate structures 35 3.5 Element design 38 v. 3.5.1 General comments 38 3.5.2 Ties and struts 39 3.5.3 Beams and girders 40 3.5.4 Beam-columns 41 3.5.5 Members in portal frames 42 3.6 Examples 43 3.6.1 Ribbed dome structure 43 3.6.2 Two pinned portal—plastic design 45 .

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