Table of Contents

Cover

Series

Title

FOREWORD

PREFACE

U.K. FOREWORD

Chapter 1: INTRODUCTION

1.1. General Observations
1.2. Codes of Practice and Normalization
1.3. Basis of Design
1.4. Materials
1.5. Geometric Characteristics and Tolerances

Chapter 2: STRUCTURAL ANALYSIS

2.1. Introduction
2.2. Structural Modelling
2.3. Global Analysis of Steel Structures
2.4. Classification of Cross Sections

Chapter 3: DESIGN OF MEMBERS

3.1. Introduction
3.2. Tension
3.3. Laterally Restrained Beams
3.4. Torsion
3.5. Compression
3.6. Laterally Unrestrained Beams
3.7. Beam-Columns

Chapter 4: ELASTIC DESIGN OF STEEL STRUCTURES

4.1. Introduction
4.2. Simplified Methods of Analysis
4.3. Member Stability of Non-prismatic Members and Components
4.4. Design Example 1: Elastic Design of Braced Steel-Framed Building

Chapter 5: PLASTIC DESIGN OF STEEL STRUCTURES

5.1. General Principles for Plastic Design
5.2. Methods of Analysis
5.3. Member Stability and Buckling Resistance
5.4. Design Example 2: Plastic Design of Industrial Building

REFERENCES

Annex A: ABACUS TO CALCULATE THE COEFFICIENTS C₁, C₂ AND

A.1. Elastic critical moment in beams submitted to end moments simultaneously with transverse loads
A.2. Elastic critical moment of unbraced cantilevers

End User License Agreement

List of Tables

Chapter 1: INTRODUCTION

Table 1.1 – Definition of consequence classes
Table 1.2 – Design supervision levels
Table 1.3 – Inspection levels
Table 1.4 – Determination of execution classes in steel structures
Table 1.5 – Limiting values for the vertical displacements in beams (span L)
Table 1.6 – Hot-rolled steel grades and qualities according to EN 10025-2
Table 1.7 – Choice of quality class according EN 10164
Table 1.8 – Dimensional tolerances for structural steel I and H sections (EN 10034)
Table 1.9 – Tolerances on out-of-square and web off-centre of structural steel I and H sections (EN 10034)
Table 1.10 – Tolerances on straightness of structural steel I and H sections (EN 10034)
Table 1.11 – Essential manufacturing tolerances – welded sections (EN 1090-2)

Chapter 2: STRUCTURAL ANALYSIS

Table 2.1 – Comparison of results for c/h₀ = 1
Table 2.2 – Comparison of results for c/h₀ = 2
Table 2.3 – Moments in curved beam
Table 2.4 – Stiffness modification coefficient η
Table 2.5 – Transformation parameter β
Table 2.6 – Results at the critical cross sections
Table 2.7 – Results at the critical cross sections with eccentricities
Table 2.8 – Results for full-strength joints, evaluated using the secant stiffness
Table 2.9 – Results for partial-strength joints and secant stiffness
Table 2.10 – Results for partial-strength joints and real behaviour
Table 2.11 – Comparative summary of results
Table 2.12 – Iterative process
Table 2.13 – Synthesis of results
Table 2.14 – Bending moments and axial forces at the critical cross sections (beam elements)
Table 2.15 – Displacements δ (mm), at the critical cross sections
Table 2.16 – Moments at the critical cross sections (slab elements)
Table 2.17 – Bending moments in the critical sections (beam and shell elements)
Table 2.18 – Critical buckling loads and buckling modes
Table 2.19 – K_ij stiffness coefficients in beams
Table 2.20 – Initial local bow imperfections
Table 2.21 – Maximum width-to-thickness ratios for internal compression parts
Table 2.22 – Maximum width-to-thickness ratios of outstand flanges
Table 2.23 – Maximum width-to-thickness ratios of angles and tubular sections

Chapter 3: DESIGN OF MEMBERS

Table 3.1 – Reduction factors β₂ and β₃
Table 3.2 – Shear stresses and torsion constant for typical steel cross section shapes
Table 3.3 – Warping constant for typical cross sections
Table 3.4 – Selection of the buckling curve
Table 3.5 – Factors for the calculation of the critical moment in spans of beams with length L and doubly symmetric section
Table 3.6 – Coefficients C₁ and C₃ for beams with end moments
Table 3.7 – Coefficients C₁, C₂ and C₃ for beams with transverse loads
Table 3.8 – Buckling curves for lateral-torsional buckling (General method)
Table 3.9 – Buckling curves for lateral-torsional buckling (Alternative method)
Table 3.10 – kc correction factors
Table 3.11 – Summary table
Table 3.12 – Values for the calculation of NRk, Mi,Rk and ΔMi,Ed
Table 3.13 – Interaction factors k_ij according to Method 1
Table 3.14 – Auxiliary terms for the calculation of the interaction factors k_ij of the previous table
Table 3.15 – Equivalent factors of uniform moment Cm_i,0
Table 3.16 – Interaction factors k_ij in members not susceptible to torsional deformations according to Method 2
Table 3.17 – Interaction factors k_ij in members susceptible to torsional deformations according to Method 2
Table 3.18 – Equivalent factors of uniform moment C_m_i

Chapter 4: ELASTIC DESIGN OF STEEL STRUCTURES

Table 4.1 – Bending moments and axial forces at the critical cross sections (ASM)
Table 4.2 – Bending moments and axial forces at the critical cross sections
Table 4.3 – Comparative synthesis of results
Table 4.4 – Elastic critical loads
Table 4.5 – Buckling resistance
Table 4.6 – Equivalent uniform moment factor m_t
Table 4.7 – Equivalent section factor, c₀
Table 4.8 – Comparison of results
Table 4.9 – Geometric characteristics of the beams (1^st floor)
Table 4.10 – Geometric characteristics of the beams (2^nd floor)
Table 4.11 – Geometric characteristics of the beams (3^rd to 8^th floors)
Table 4.12 – Geometric characteristics of the columns
Table 4.13 – External pressure coefficients c_pe
Table 4.14 – External and internal pressures
Table 4.15 – Summary of actions
Table 4.16 – Initial imperfections
Table 4.17 – Equivalent horizontal forces in transversal frames
Table 4.18 – Equivalent horizontal forces in longitudinal frames
Table 4.19 – Reduction factors ψ
Table 4.20 – Elastic critical load factors
Table 4.21 – Comparative results for column E1 (combination 1)
Table 4.22 – Comparative results for beam E1 to E4 (combination 1)
Table 4.23 – Utilization levels for column E1
Table 4.24 – Utilization levels for beam E1-E4
Table 4.25 – Beam E1-E4 LTB ratios
Table 4.26 – Column E1 buckling ratios

Annex A: ABACUS TO CALCULATE THE COEFFICIENTS C₁, C₂ AND C₃

Table A.1 – Values of C₁ and C₂ for cantilevers with warping prevented at the fixed end
Table A.2 – Values of C₃ for cantilevers with warping prevented at the fixed end
Table A.3 – Values of C₁ and C₂ for cantilevers with warping free at the fixed end

Table A.4 – Values of C₃ for cantilevers with warping free at the fixed end.

List of Illustrations

Chapter 1: INTRODUCTION

Figure 1.1 – European normative structure for the construction sector
Figure 1.2 – Vertical deformations in beams
Figure 1.3 – Limiting values for horizontal displacements in frames
Figure 1.4 – Anti-corrosion details
Figure 1.5 – Location and orientation of samples and pieces for tests
Figure 1.6 – Geometry of proportional flat test samples
Figure 1.7 – Schematic stress-strain curve
Figure 1.8 – Relationship between impact energy and temperature
Figure 1.9 – Lamellar tearing
Figure 1.10 – Rolled sections
Figure 1.11 – Cold formed sections
Figure 1.12 – Conventions for dimensions and axes of steel cross sections

Chapter 2: STRUCTURAL ANALYSIS

Figure 2.1 – Nonlinear analysis
Figure 2.2 – Industrial building
Figure 2.3 – Multi-storey building
Figure 2.4 – Structural model with two-dimensional elements
Figure 2.5 – Influence of the choice of member axis
Figure 2.6 – Influence of load eccentricity in relation to the shear centre
Figure 2.7 – Influence of eccentricities
Figure 2.8 – Influence of discontinuities at intermediate sections
Figure 2.9 – Examples of elements with variable cross section
Figure 2.10 – Alternative discretizations for a beam with parabolic variation of the depth of the cross section
Figure 2.11 – Bending moment diagram and vertical displacements of the beam
Figure 2.12 – Influence of the elements’ curvature
Figure 2.13 – Typical 3D behaviour of bolted end-plate beam-to-column steel joint
Figure 2.14 – Bending-rotation moment curve of a joint
Figure 2.15 – Modelling of joints in structural analysis
Figure 2.16 – Definition of the secant stiffness of a joint
Figure 2.17 – Modelling of joints in the internal node of a frame
Figure 2.18 – Internal node steel beam-to-column joint
Figure 2.19 – Alternative models for the representation of the column web panel in shear
Figure 2.20 – Beam and shell structural model
Figure 2.21 – Modelling of in-plane rigid slab behaviour
Figure 2.22 – Steel frame
Figure 2.23 – Calculation model without eccentricities
Figure 2.24 – Bending moment diagram
Figure 2.25 – Transverse shear diagram
Figure 2.26 – Axial force diagram
Figure 2.27 – Definition of the frame’s eccentricities
Figure 2.28 – Calculation model with eccentricities
Figure 2.29 – Full-strength joint at intermediate beam level
Figure 2.30 – Full-strength joint at top beam level
Figure 2.31 – Steel frame with semi-rigid joints
Figure 2.32 – Partial-strength joint at the intermediate beam level
Figure 2.33 – Partial-strength joint at top beam level
Figure 2.35 – Steel frame
Figure 2.36 – Detail of the internal node joint
Figure 2.37 – Modelling of the internal node joint
Figure 2.38 – Bending moment diagram
Figure 2.39 – Two-storey steel framed building
Figure 2.40 – Loads on secondary beams
Figure 2.41 – Critical cross sections in the middle frame
Figure 2.42 – Structural steel model (neglecting the slab)
Figure 2.43 – Structural steel model with horizontal bracing
Figure 2.44 – Bending moment diagram
Figure 2.45 – Shear force diagram
Figure 2.46 – Axial force diagram
Figure 2.47 – Typical displacements Δ and δ
Figure 2.48 – Recommended discretization for the evaluation of critical loads
Figure 2.49 – Definition of the axial loading for the determination of critical load
Figure 2.50 – “Sway mode” (a)) and “Non-sway mode” (b))
Figure 2.51 – Lateral displacements in an unbraced frame
Figure 2.52 – Wood’s equivalent frame
Figure 2.53 – “Equivalent geometric imperfection” in framework structures
Figure 2.54 – Imperfections and corresponding equivalent horizontal forces
Figure 2.55 – Plan view of translational and torsional effects
Figure 2.56 – Imperfections for bracing systems
Figure 2.57 – Bracing forces at splices in compression elements
Figure 2.58 – Steel frame
Figure 2.59 – Loadcase arrangement for combination 1
Figure 2.60 – Loadcase arrangement for combination 2
Figure 2.61 – Bending moment due to vertical loads (comb. 1)
Figure 2.62 – Shear force due to vertical loads (comb. 1)
Figure 2.63 – Axial force due to vertical loads (comb. 1)
Figure 2.64 – Bending moment due to horizontal loads (comb. 1)
Figure 2.65 – Shear force due to horizontal loads (comb. 1)
Figure 2.66 – Axial force due to horizontal loads (comb. 1)
Figure 2.67 – Structural displacements for combination 1 (horizontal loads)
Figure 2.68 – Elastic 2^nd order bending moment diagram
Figure 2.69 – Elastic 2^nd order shear force diagram
Figure 2.70 – Elastic 2^nd order axial force diagram
Figure 2.71 – Bending moments due to vertical loads (comb. 2)
Figure 2.72 – Shear forces due to vertical loads (comb. 2)
Figure 2.73 – Axial forces due to vertical loads (comb. 2)
Figure 2.74 – Bending moments due to horizontal loads (comb. 2)
Figure 2.75 – Shear forces due to horizontal loads (comb. 2)
Figure 2.76 – Axial forces due to horizontal loads (comb. 2)
Figure 2.77 – Structural displacements due to combination 2 (horizontal loads)
Figure 2.78 – Design bending moments
Figure 2.79 – Design shear forces
Figure 2.80 – Design axial forces
Figure 2.81 – Structural displacements for combination 1 (SLS)
Figure 2.82 – Structural displacements for combination 2 (SLS)
Figure 2.83 – Cross section behaviour in bending
Figure 2.84 – Classification of cross sections

Chapter 3: DESIGN OF MEMBERS

Figure 3.1 – Definition of the net area of a cross section
Figure 3.2 – Angle with holes in both legs
Figure 3.3 – Effective class 2 web
Figure 3.4 – Class 4 cross section submitted to a compressive axial force
Figure 3.5 – Class 4 cross section submitted to bending moment
Figure 3.6 – Structures with some members in tension
Figure 3.7 – Typical cross sections of members in tension
Figure 3.8 – Concentration of tension next to a hole
Figure 3.9 – Eccentric connections
Figure 3.10 – Welded connections between hollow sections
Figure 3.11 – Angles connected by one leg
Figure 3.12 – Net area of a plate
Figure 3.13 – Steel truss
Figure 3.14 – A_net in the bolted connection
Figure 3.15 – Lattice girder
Figure 3.16 – Actions and internal forces on the structure
Figure 3.17 – Connection of the diagonal bars of the truss
Figure 3.18 – Elastic distributions of normal stresses and shear stresses
Figure 3.19 – Elastic and plastic bending moment cross sectional resistance
Figure 3.20 – Shear area for a I cross section
Figure 3.21 – Model for bending moment - shear force interaction in a I or H section
Figure 3.22 – Bending moment – shear force interaction diagrams for I or H sections
Figure 3.23 – Simply supported steel beam
Figure 3.24 – Diagrams of internal forces
Figure 3.25 – Continuous beam
Figure 3.26 – Load combination 1
Figure 3.27 – Load combination 2
Figure 3.28 – Load combination 3
Figure 3.29 – Diagrams of elastic internal forces for load combination 1
Figure 3.30 – Redistribution of bending moments
Figure 3.31 – Design internal forces after redistribution
Figure 3.32 – Cantilever beam
Figure 3.33 – Member under uniform torsion
Figure 3.34 – Member with I section under non-uniform torsion
Figure 3.35 – Shear stresses due to uniform torsion for typical steel cross section shapes
Figure 3.36 – Deformation in an I section under non-uniform torsion
Figure 3.37 – Stresses due to warping torsion T_w
Figure 3.38 – Thin-walled closed rectangular section
Figure 3.39 – Thin-walled steel cross sections
Figure 3.40 – Cantilever beam
Figure 3.41 – Distributions of stresses at section A
Figure 3.42 – Buckling in a pinned member (Euler’s column)
Figure 3.43 – Buckling length L_E as a function of the real length L of the column
Figure 3.44 – σ - λ relationship of a compressed member
Figure 3.45 – Torsional buckling and flexural-torsional buckling
Figure 3.46 – Column with initial geometrical imperfection
Figure 3.47 – Typical residual stresses in a rolled member with a I cross section
Figure 3.48 – Results of experimental tests in real members
Figure 3.49 – Behaviour of metals
Figure 3.50 – Buckling curves according to EC3-1-1
Figure 3.51 – Closely spaced built-up members
Figure 3.52 – Design of a column
Figure 3.53 – Actions and internal forces on the lattice girder of example 3.3
Figure 3.54 – Detail in the diagonals of the truss
Figure 3.55 – Lateral-torsional buckling of a cantilever beam
Figure 3.56 – Lateral-torsional buckling in a doubly symmetric I section under constant bending moment
Figure 3.57 – Effect of the point of load’s application
Figure 3.58 – Cantilever beam at the end of a continuous beam
Figure 3.59 – Sections mono-symmetric about the weak axis
Figure 3.60 – Beams with end moments and transverse loads
Figure 3.61 – Simply supported beam with two concentrated loads
Figure 3.62 – Diagrams of internal forces
Figure 3.63 – Laterally braced beam
Figure 3.64 – Continuous beam with a cantilever span
Figure 3.65 – Diagrams of internal forces
Figure 3.66 – Steel members subjected to bending and axial force
Figure 3.67 – Bending moment-axial force plastic interaction
Figure 3.68 – M + N interaction diagram in a rectangular solid section
Figure 3.69 – Behaviour of a member subjected to bending and compression
Figure 3.70 – Hot-finished rectangular hollow section structure
Figure 3.71 – Internal force diagrams
Figure 3.72 – Column subjected to major-axis bending and compression
Figure 3.73 – Member under bi-axial bending and compression
Figure 3.74 – Diagrams of internal forces
Figure 3.75 – Variation of utilization factor along the member

Chapter 4: ELASTIC DESIGN OF STEEL STRUCTURES

Figure 4.1 – Braced and unbraced frames
Figure 4.2 – Amplified sway moment method
Figure 4.3 – Steel frame
Figure 4.4 – Critical cross sections
Figure 4.5 – Modified no-sway frame and load arrangement for load combination 1
Figure 4.6 – Original sway frame subjected to the horizontal reactions (load comb. 1)
Figure 4.7 – Design bending moment diagram (ASM)
Figure 4.8 – Design shear forces (ASM)
Figure 4.9 – Design axial forces (ASM)
Figure 4.10 – Load arrangement for load combination 1
Figure 4.11 – Original frame subjected to the horizontal reactions (load comb. 1)
Figure 4.12 – Design bending moment diagram for load combination 1 (SMBL)
Figure 4.13 – Design shear diagrams for load combination 1 (SMBL)
Figure 4.14 – Design axial force diagrams for load combination 1 (SMBL)
Figure 4.15 – Lowest sway buckling mode
Figure 4.16 – Double-symmetric tapered I section beam
Figure 4.17 – Variation of the elastic critical loads with reference cross section
Figure 4.18 – Utilization ratio α (%) for the relevant modes
Figure 4.19 – Non-prismatic I-section columns (b, t_f and t_w are all constant)
Figure 4.20 – Partial and total bracing
Figure 4.21 – Reference and bracing axes
Figure 4.22 – Value of β_t
Figure 4.23 – Definition of the cross sections for non linear moment variation
Figure 4.24 – Flowchart for the application of the General Method
Figure 4.25 – Double-symmetric tapered I section beam
Figure 4.26 – Design internal force diagrams
Figure 4.27 – Cross section classification
Figure 4.28 – Cross section plastic interaction diagram
Figure 4.29 – Variation of the utilization ratio along the length of the member
Figure 4.30 – Elastic critical load multiplier
Figure 4.31 – Side elevation view
Figure 4.32 – Plan of the 3^rd to 7^th floor
Figure 4.33 – Plan of the 1^st floor
Figure 4.34 – Plan of the 2^nd floor
Figure 4.35 – Plan of the 8^th floor
Figure 4.36 – Velocity pressure distribution on face D (θ = 0°)
Figure 4.37 – Velocity pressure distribution on face D (θ = 90°)
Figure 4.38 – Pressure zones for wind direction θ = 0°
Figure 4.39 – Pressure zones for wind direction θ = 90°
Figure 4.40 – External and internal coefficients
Figure 4.41 – Wind pressures (kN/m²) on walls, θ = 0°
Figure 4.42 – Wind pressures (kN/m²) on walls, θ = 90°
Figure 4.43 – Load arrangement for the analysis of the shadow areas
Figure 4.44 – Load distribution in the secondary beams
Figure 4.45 – 3D structural model
Figure 4.46 – 1^st buckling mode for combination 1 – frontal view
Figure 4.47 – Internal forces on column E1 for load combination 1 (local axes)
Figure 4.48 – Internal forces on beam E1-E4 in the 4^th floor for load combination 1

Annex A: ABACUS TO CALCULATE THE COEFFICIENTS C₁, C₂ AND C₃

Figure A1 – C₁ coefficient for end moment and uniform load, with μ > 0
Figure A2 – C₁ coefficient for end moment and uniform load, with μ < 0
Figure A3 –C₂ coefficient for end moment and uniform load, with μ > 0
Figure A4 – C₂ coefficient for end moment and uniform load, with μ < 0

Figure A5 – C₁ coefficient for end moment and point load at mid span, with μ > 0

Figure A6 – C₁ coefficient for end moment and point load at mid span, with μ < 0

Figure A7 – C₂ coefficient for end moment and point load at mid span, with μ > 0

Figure A8 – C₂ coefficient for end moment and point load at mid span, with μ < 0

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 OD STEEL AND COMPOSITE STRUCTURES

Alain Nussbaumer, Luís Borges and Laurence Davaine

DESIGN OF COLD-FORMED STEEL STRUCTURES

Dan Dubina, Viorel Ungureanu and Raffaele Landolfo

ECCS – SCI EUROCODE DESIGN MANUALS

DESIGN OF STEEL STRUCTURES, U. K. EDITION

Luís Simões da Silva, Rui Simões, Helena Gervásio and Graham Couchman

AVAILABLE SOON

DESIGN OF JOINTS IN STEEL AND COMPOSITE STRUCTURES

Jean-Pierre Jaspart, Klaus Weynand

DESIGN OF COMPOSITE STRUCTURES

Markus Feldman and Benno Hoffmeister

DESIGN OF STEEL STRUCTURES FOR BUILDINGS IN SEISMIC AREAS

Raffaele Landolfo, Federico Mazzolani, Dan Dubina and Luís Simões da Silva

INFORMATION AND ORDERING DETAILS

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DESIGN OF STEEL STRUCTURES

Eurocode 3: Design of steel structures Part 1-1 – General rules and rules for buildings

U.K. Edition

Luís Simões da Silva

Rui Simões

Helena Gervásio

Graham Couchman

Design of Steel Structures

U.K. Edition

2014

Published by:

ECCS – European Convention for Constructional Steelwork

publications@steelconstruct.com

www.steelconstruct.com

Sales:

Wilhelm Ernst & Sohn Verlag für Architektur und technische Wissenschaften GmbH & Co. KG, Berlin Sales:

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.

ISBN (ECCS): 978-92-9147-123-2

ISBN (Ernst & Sohn): 978-3-433-0313-53

FOREWORD

The development program for the design manuals of the European Convention for Constructional Steelwork (ECCS) represents a major effort for the steel construction industry and the engineering profession in Europe. Conceived by the ECCS Technical Activities Board under the leadership of its chairman, Professor Luis Simões da Silva, the manuals are being prepared in close agreement with the final stages of Eurocode 3 and its national Annexes. The scope of the development effort is vast, and reflects a unique undertaking in the world.

The publication of the first of the manuals, Design of Steel Structures, is a signal achievement which heralds the successful completion of the Eurocode 3 work and brings it directly to the designers who will implement the actual use of the code. As such, the book is more than a manual – it is a major textbook that details the fundamental concepts of the code and their practical application. It is a unique publication for a major construction market.

Following a discussion of the Eurocode 3 basis of design, including the principles of reliability management and the limit state approach, the steel material standards and their use under Eurocode 3 are detailed. Structural analysis and modeling are presented in a chapter that will assist the design engineer in the first stages of a design project. This is followed by a major chapter that provides the design criteria and approaches for the various types of structural members. The theories of behavior and strength are closely tied to the Eurocode requirements, making for a unique presentation of theory into practice. The following chapters expand on the principles and applications of elastic and plastic design of steel structures.

The many design examples that are presented throughout the book represent a significant part of the manual. These will be especially well received by the design profession. Without a doubt, the examples will facilitate the acceptance of the code and provide for a smooth transition from earlier national codes to the Eurocode.

Reidar Bjorhovde
Member, ECCS Editorial Board

PREFACE

This book is the first of a series of joint SCI-ECCS publications, a series that will be extremely helpful to U.K. designers helping them through the change that Eurocodes represent. This joint publication is the 1^st Edition, revised second impression of the ECCS Eurocode Design Manual to EN 1993-1-1, supplemented by a U.K. Foreword. In this edition, the reader will find information that is either of a general nature, or relevant to specific sections of the publication, to facilitate its application in a U.K. context.

The General rules and rules for buildings of part 1-1 of Eurocode 3 constitute the core of the code procedures for the design of steel structures. They contain the basic guidance for structural modeling and analysis of steel frameworks and the rules for the evaluation of the resistance of structural members and components subject to different loading conditions.

According to the objectives of the ECCS Eurocode Design Manuals, it is the objective of this book to provide mix of “light” theoretical background, explanation of the code prescriptions and detailed design examples. Consequently, this book is more than a manual: it provides an all-in-one source for an explanation of the theoretical concepts behind the code and detailed design examples that try to reproduce real design situations instead of the usually simplified examples that are found in most textbooks.

This book evolved from the experience of teaching Steel Structures according to ENV 1993-1-1 since 1993. It further benefited from the participation in Technical Committees TC8 and TC10 of ECCS where the background and the applicability of the various clauses of EN 1993-1-1 was continuously questioned. This book covers exclusively part 1-1 of Eurocode 3 because of the required level of detail. Forthcoming volumes discuss and apply most of the additional parts of Eurocode 3 using a consistent format.

Chapter 1 introduces general aspects such as the basis of design, material properties and geometric characteristics and tolerances, corresponding to chapters 1 to 4 and chapter 7 of EN 1993-1-1. It highlights the important topics that are required in the design of steel structures. Structural analysis is discussed in chapter 2, including structural modelling, global analysis and classification of cross sections, covering chapter 5 of EN 1993-1-1. The design of steel members subjected to various types of internal force (tension, bending and shear, compression and torsion) and their combinations is described in chapter 3, corresponding to chapter 6 of EN 1993-1-1. Chapter 4 presents the design of steel structures using 3D elastic analysis based on the case study of a real building. Finally, chapter 5 discusses plastic design, using a pitched-roof industrial building to exemplify all relevant aspects.

Furthermore, the design examples provided in this book are chosen from real design cases. Two complete design examples are presented: i) a braced steel-framed building; and ii) a pitched-roof industrial building. The chosen design approach tries to reproduce, as much as possible, real design practice instead of more academic approaches that often only deal with parts of the design process. This means that the design examples start by quantifying the actions. They then progress in a detailed step-by-step manner to global analysis and individual member verifications. The design tools currently available and adopted in most design offices are based on software for 3D analysis. Consequently, the design example for multi-storey buildings is analysed as a 3D structure, all subsequent checks being consistent with this approach. This is by no means a straightforward implementation, since most global stability verifications were developed and validated for 2D structures.

The authors are indebted to Prof. Reidar Bjorhovde who carried out a detailed technical review of the manuscript and provided many valuable comments and suggestions. Warm thanks to Prof. David Anderson who carried out an additional detailed revision of the book and also made sure that the English language was properly used. Further thanks to Liliana Marques and José Alexandre Henriques, PhD students at the University of Coimbra, for the help with the design examples of chapter 4. Additional thanks to Prof. Tiago Abecasis who spotted innumerous “bugs” in the text. Finally, thanks to Joana Albuquerque and the staff of cmm and ECCS for all the editorial and typesetting work, making it possible to bring to finalize this project.

Luís Simões da Silva
Rui Simões
Helena Gervásio
Graham Couchman
Coimbra, 2014

U.K. FOREWORD

INTRODUCTION

SCI has a history going back over 25 years of producing design guides aimed at structural engineers. These have typically been of a ‘how to do’ nature, aimed at designers with a certain level of experience and within the context of a given design standard.

This publication represents a departure from that tradition. It is the first in an envisaged series of joint ECCS-SCI publications, a series we hope will be extremely helpful to U.K. designers given the step change that the move to Eurocodes represents. We believe its format complements other SCI guidance. This joint publication is the 1^st Edition, revised second impression of the ECCS Eurocode Design Manual to EN 1993-1-1, which was published in 2013, supplemented by a U.K. Foreword.

The content includes much useful background to the code rules (pointers to reasoning and research work that should help ensure correct application of the rules), and a reminder of some engineering principles. Helpfully, this information is presented in the context of Eurocode terminology and notation, and with reference to clause numbers etc, to aid the reader’s familiarity with EN 1993-1-1. A significant number of SCI publications and other work are cited in the references.

Within this so-called U.K. Foreword the reader will find information that is either of a general nature, or relevant to specific sections of the publication. In both cases this information is presented to facilitate application of the rest of the publication in a U.K. context.

It is noted and should be accepted that there will inevitably be some differences of interpretation between the recommendations of ECCS and those previously published by SCI.

GENERAL COMMENTS

The Eurocodes contain so-called Nationally Determined Parameters (NDPs), which permit specific parts of the codes to be subject to national variations. The base ECCS publication uses either the default (recommended) Eurocode values, or in some cases Portuguese values for these NDPs. For a given design the NDPs must be in accordance with the rules for the country in which the structure is to be constructed. Some uses of specific NDPs in the U.K. are noted below.

The examples are described as being ‘realistic’, but it must be recognised that practice varies between nations so they do not necessarily reflect typical U.K. practice. Some specific exceptions are noted in this U.K. Foreword. Similarly, some references to ‘common practice’ may not reflect common U.K. practice, and these are highlighted.

Some units may be unfamiliar to U.K. designers, in particular 1 GPa = 1 N/mm²

The following comments are also included in the specific sections throughout the book.

SECTION SPECIFIC COMMENTS

Section 1.2

Reference is made to the need for integration between standards, to ensure that design rules are compatible with execution tolerances. When complementary material is used, which it invariably will be because even a set of standards as comprehensive as the Eurocodes cannot cover every need, the designer should take care to ensure it is appropriate.

Section 1.3.2

At the time of writing (Autumn 2014) an amendment is about to be published that moves the decision regarding Execution Class from EN 1090 to EN 1993-1-1.

Section 1.3.3.3

Reference is made to material partial safety factors (γ_m), which are NDPs. Both recommended and U.K. values are based on extensive analysis of European steel production. When steel from other sources is used these values may not be appropriate.

Section 1.3.5

Reference is made to rules of thumb that may be used to assure satisfactory dynamic performance. SCI has produced guidance on this subject (SCI, 2009a) and suggests rules of thumb are only used with care, as they can be misleading.

Section 1.4.1

Its U.K. National Annex states that Table 3.1 of EN 1993-1-1 should not be used, moreover that when a range of ultimate strengths is quoted in a product standard the lowest value should be taken.

Section 1.5

The National Structural Steelwork Specification 5^th edition (CE Marking Version) was configured to complement EN 1090-2 (BCSA, 2010).

Section 2.2.2

The Eurocodes use a different convention for axis notation than has traditionally been used in the U.K. Also, the Eurocodes are not entirely consistent within themselves concerning axis definition. Care is therefore needed!

Section 2.2.3

Common U.K. practice is to determine forces and moments at centreline intersections, not to use rigid links and to determine forces and moments at (for example) the face of a column.

Section 2.2.5

Although non-linear springs may be used to model joint behaviour, it is very difficult to model the complex behaviour of a joint (connection) – its stiffness, strength, rotation capacity, and indeed different behaviour in loading and unloading. This is mentioned in Section 5.2 of the guide. Traditional U.K. practice is to predict joint behaviour on the basis of past experience.

Section 2.2.7 – Example 2.1

It should be noted that European sections are not commonly used in the U.K. (although they are the subject of growing interest). S 235 steel is not used in the U.K., where S 355 is the current (2014) common grade.

Normal U.K. practice is to assume joint classification (generally ‘rigid’ or ‘nominally pinned’) and subsequently to ensure that the joint details satisfy the assumptions made.

Figures 2.29 and 2.30 show a joint with a stiffener that appears to prevent fitting of bolts/nuts. A Morris Stiffener could be used to avoid this problem.

Section 2.3.2.1

Reference is made to amplifying internal forces and displacements to model second order effects. In the U.K. an alternative approach is to reduce resistance rather than increasing forces, by use of effective lengths. However this can be laborious and for that reason is not recommended.

For certain frame geometries the U.K. National Annex to EN 1993-1-1 permits second order effects to be ignored at α_cr > 5 for the so-called gravity load combination.

Section 2.3.3

The definition of m as the ‘number of columns in a row’ is not strictly correct. It should be defined as the ‘number of columns having an effect on the stability system’. An amendment to EN 1993-1-1 is anticipated.

Section 2.4

All UB sections are Class 1 in bending alone.

Section 3.1.1

The U.K. National Annex to EN 1993-1-1 defines values of γ_M₀ = 1.0, γ_M₁ = 1.0, and γ_M₂ = 1.1. Note these values may vary between Eurocodes, and indeed Eurocode Parts.

Section 3.2.2

Since EN 1993 does not cover what is, in the U.K. at least, a common situation of more than one bolt in the width of an angle leg, it is common practice to use complementary guidance from BS5950 when calculating members resistances.

Section 3.3.5 – Example 3.5

The example assumes that the restraint provided by the composite floor is sufficient. SCI has provided guidance on how a designer can ensure it is sufficient (SCI, 2009b), as in practice it should never be simply assumed.

Section 3.6.2.2

The omission of rules on how to calculate M_cr is one of the gaps in EN 1993 that many U.K. designers are aware of. Some useful complementary information is given here.

Section 3.7.2.2

Reference is made to the two alternative methods for beam-column design given in EN 1993-1-1. It is anticipated that only one method will be given in future editions of the code, although this publication highlights that economy of design effort and economy of design result can sometimes vary depending on the method chosen.

Section 4.1

It should not be assumed that most U.K. design offices use 3D analysis. Reference is also made to the so-called wind moment method having been popular in the past in the U.K. – with modern computing power and knowledge it is not recommended, as its use beyond specific (empirical) limits has no justification.

Reference is made to braced and unbraced frames, and it is worth noting that this does not mean the same thing as non-sway sensitive and sway sensitive. It is not uncommon for a frame that is braced to be sway sensitive – it depends how stiff the bracing mechanism is.

Section 4.2.4 – Example 4.1

The example considers column bases that are fully restrained. These should be avoided if possible – more because of the cost and practicalities of the foundations than the steelwork – and in any case correctly modelled.

Section 4.4.3.4

It should be noted that the calculation of wind actions should follow the U.K. National Annex, which differs significantly from the Eurocode.

Section 4.4.3.6

The definition of m as the ‘number of columns in a row’ should be changed to the ‘number of columns having an effect on the stability system’. In U.K. practice it would generally be assumed that the floor diaphragm constrains all columns to have the same imperfection.

Section 4.4.3.7

For economy, U.K. designers are likely to favour the use of expressions 6.10a and 6.10b of EN 1990 to determine ultimate loads. The combination factors should be taken from the U.K. National Annex to EN 1990.

At the Serviceability Limit State (SLS) the U.K. National Annex recommends using the characteristic combination, and that permanent actions should not be included.

Section 4.4.3.8

In a braced frame, typical U.K. practice would be to design all the floor beams as simply supported. Columns would be designed considering only nominal moments (from eccentric beam reactions), and floors would be considered as fully loaded.

Section 5.2.4.1

An alternative approach to calculate α_cr for a portal frame is considered in SCI (2014).

Section 5.2.5 – Example 5.1 (and Section 5.4.6.3)

U.K. practice is that having allowed for second-order effects and frame imperfections, the effects of in-plane member imperfections are small enough to be ignored. Thus, in addition to cross-section checks, only out-of-plane member verifications are needed. This is considered in SCI (2014).

Section 5.4.2

The example is for a portal frame with height to rafters of 7 m, but many modern portal frames in the U.K. are significantly taller, and therefore potentially more flexible, than this.

REFERENCES TO NATIONAL FOREWORD

BCSA (2010). National Structural Steelwork Specification for Building Construction (5^th Edition CE Marking Version), Publication No. 52/10, The British Constructional Steelwork Association.

SCI (2009a). Design of Floors for Vibration. A New Approach, P354, Revised Edition, Steel Construction Institute, United Kingdom.

SCI (2009b). Composite Slabs and Beams using Steel Decking. Best Practice for Design and Construction, P300, Revised Edition, Steel Construction Institute, United Kingdom.

SCI (2014). Design of Steel Portal Frame Buildings to Eurocode 3, P399, The Steel Construction Institute.