Joints in Steel Construction. Moment Connections


Joints in Steel Construction
Moment Connections
Published by:
The Steel Construction Institute
Silwood Park
Ascot
Berks SL5 7QN
Tel: 01344 623345
Fax: 01344 622944
In association witli:
The British Constructional Steelwork Association Limited
4 Whitehall Court, Westminster, London SW1A2ES
© Crown Copyright 1995. Published by permission of the Controller of HMSO
Apart from any fair dealing for the purposes of research or private study or criticism or review,
as permitted under the Copyright Designs and Patents Act, 1988, this publication may not be
reproduced, stored, or transmitted, in any form or by any means, without the prior permission
in writing of the publishers, or in the case of reprographic reproduction only in accordance with
terms of the licences issued by the UK Copyright Licensing Agency, or in accordance with the
terms of licences issued by the appropriate Reproduction Rights Organisation outside the UK.
Enquiries concerning reproduction outside the terms stated here should be sent to the publishers.
The Steel Construction Institute, at the address given on the title page.
Although care has been to ensure, to the best of our knowledge, that all data and information
contained herein are accurate to the extent that they relate to either matters of fact or accepted
practice or matters of opinion at the time of publication, The Steel Construction Institute, The
British Constructional Steelwork Association Limited, The Building Research Establishment, the
authors and the reviewers assume no responsibility for any errors in or misinterpretations of such data
and/or information or any loss or damage arising from or related to their use.
Publications supplied to Members of the Institute at a discount are not for resale by them.
Publication Number: 207/95
ISBN1 85942 018 4
British Library Cataloguing-in-Publication Data.
A catalogue record for this book is available from the British Library.
Reprinted October 1996, January 1997, March 1997 (with amendments)
(Hi)
ACKNOWLEDG EM ENTS
This publication has been prepared with guidance from the SCI/BCSA Connections Group consisting of the
following members:
Peter Allen*
David Brown*
Mike Fewster*
Peter Cannon*
Dr Craig Gibbons*
Eddie Hole
Alastair Hughes*
Abdul Malik
Dr David Moore*
Prof David Nethercot
Alan Pillinger*
Alan Rathbone*
Graham Raven
John Rushton
Bernard Shuttleworth
Richard Stainsby
Colin Smart
Eric Taylor
The British Constructional Steehvork Association Ltd.
The Steel Construction Institute
Caunton Engineering Ltd.
Watson Steel Ltd
Ove Arup & Partners
British Steel Pic.
Ove Arup & Partners
The Steel Construction Institute (Technical Secretary)
Building Research Establishment
University of Nottingham
Bison Structures Ltd.
Computer Services Consultants (UK) Ltd.
The Steel Construction Institute
Peter Brett Associates
Consultant (Chairman)
Neil R Stainsby Ltd.
British Steel Pic.
Ove Arup & Partners
* Editorial committee members
Valuable comments were received from:
Dr D Anderson
A N Beal
В A Brown
D Chapman
В D Cheal
Dr R Cunningham
M J Glover
R С Hairsine
К Leah
Dr R. M. Lawson
I H Mathys
W Mitchell
I О Surtees
J С Taylor
E Treadaway
University of Warwick
Thomason Partnership
Scott Wilson & Kirkpatrick
Wescol
Consultant
Cunningham Associates
Ove Arup & Partners
Graham Garner & Partners
Henry Brook & Co.
The Steel Construction Institute
Waterman Partnership
Billington Structures
University of Leeds
The Steel Construction Institute
Clark Nicholls & Marcel
The capacity tables were developed, and the book compiled
and typeset by Richard Stainsby assisted by Neil Cruickshank.
In addition to sponsorship by the Building Research Establisment, support on technical and commercial
matters was also received from:
E V Girardier Steel Construction Industry Federation (SCIF)
R A С Latter British Steel Pic.
Dr G W Owens The Steel Construction Institute
Dr D Tordoff The British Constructbnal Steelwork Association Ltd.
References to BS 5950: Part 1 and Eurocode 3 have been made with permission of British Standards Institution,
BSI Customer Services, 389 Chiswick High Road, London, W4 4AL.
(iv)
FOREWORD
This publication is the third in a series of books which cover the range
of structural steelwork connections. It provides a guide to the design of
Moment Connections in Steelwork. The other books in the series are
Joints in Simpie Construction, Volumes 1 and 2.
Included in this guide are both bolted and welded connections suitable
for use in continuous frame design, together with bolted wind-moment
connections, which may be used in semi-continuous design.
The publication is produced by the SCI/BCSA Connections Group with
sponsorship from the Building Research Establishment.
The Connections Group was established in 1987 to bring together
academics, consultants and steelwork contractors to work on the
development of authoritative design guides for structural steelwork
connections.
(V)
PICTORIAL INDEX
BOLTED END PLATE CONNECTIONS
Page
Section 2 7
Beam/Column connection capacity tables 142
Portal connection capacity tables 188
WIND - MOMENT CONNECTIONS
Page
Section 3 50
Wind-moment Connection Tables 202
WELDED BEAM TO COLUMN
CONNECTIONS
Section 4
Page
55
SPLICES
Section 5
Page
73
COLUMN BASE CONNECTIONS
Section 6
Page
86
(vi)
CONTENTS
PACE
1. INTRODUCTION 1
1.1 About this design guide 1
1.2 Classification of connections 1
1.3 Exchange of Information 2
1.4 Costs 3
1.5 Definitions 5
1.6 Major symbols б
2. BOLTED END PLATE CONNECTIONS 7
2.1 Scope 7
2.2 Design philosophy 8
2.3 Capacity checks 10
2.4 Methods of strengthening 12
2.5 Connection rotational stiffness 12
2.6 Standardisation 14
2.7 Using the capacity tables 15
2.8 Design procedures - Rigorous method 1 б
2.9 Abridged method for manual design 42
2.10 Worked example using the abridged method for manual design 44
3. WIND-MOMENT CONNECTIONS 50
3.1 Introduction 50
3.2 Design method 50
3.3 Design rules 51
3.4 Standard details 51
4. WELDED BEAM TO COLUMN CONNECTIONS 55
4.1 Scope 55
4.2 Shop welded connections 56
4.3 Site welded connections 57
4.4 Design philosophy 60
4.5 Design procedures 61
4.6 Site welded worked example 68
5. SPLICES 73
5.1 Scope 73
5.2 Bolted cover plate splices 73
5.3 Design procedures 74
5.4 Bolted splice - worked example 79
5.5 Bolted end plate splices 82
5.6 Beam-through-beam moment connections 83
5.7 Welded splices 84
6. COLUMN BASE CONNECTIONS 86
6.1 Scope 86
6.2 Design philosophy 87
6.3 Capacity checks 88
6.4 Rigidity of column base connections 89
6.5 Standardisation 89
6.6 Bedding space for grout 89
6.7 Preliminary sizing of base plate 89
6.8 Stiffened baseplates 90
6.9 Design procedures 91
6.10 Column base - Worked example 99
REFERENCES 103
APPENDICES 105
Appendix I Worked example - Bolted end plate using the rigorous method 106
Appendix II Bolted end plate connections - Background to the design method 135
Appendix III Mathematical derivation of alpha chart 139
Appendix IV 8.8 Bolts - Enhanced tensile strength 140
CAPACITY TABLES and Dimensions for detailing (Yellow Pages) 141
(vii)
1. INTRODUCTION
1.1 ABOUT THIS DESIGN GUIDE
This publication provides methods for designing
the following types of moment resisting connections in
steel-framed structures:
Beam to column
• Bolted end plates
• Wind-moment connections
• Shop and site-welded connections
Beams
• Bolted splices
• Welded splices
Columns
• Bolted splices
• Welded splices
• Bases
Connections subject to seismic loading are not covered in
this publication.
Although each Section of this publication describes
connections between l-section members bending about
their major axes, the general principles can be adapted for
use with other section types and configurations.
Design procedures
The capacity checks on bolts, welds and sections are all
based on BS 5950: Part 1 ^^\
Other features in the design model are taken from a
variety of sources. They include established methods used
in the UK and overseas. (^ ^° 8)
Historically, moment connections have been designed for
strength only with little regard to other characteristics
i.e. stiffness and ductility. There is growing recognition
that in certain situations this practice is questionable and
so guidance is given to help designers.
Steel grades
Steel grades have been designated with the commonly
used BS 5950: Part 1 notation (Amendment No. 1 1992).
The equivalent designations in other specifications are
given in Table 1.1.
Table 1.1 Steel grades
BS 5950 : Part 1
Design Grade 43
Design Grade 50
BS 4360
Grade 43
Grade 50
BSEN 10 025
1990
Fe430
Fe510
1993
S275
S355
Capacity tables
Without access to suitable software, designing efficient
moment connections can be a long and tedious process.
To help overcome this problem, capacity tables for
standardised bolted beam to column connections are
provided in the yellow pages of this publication.
The capacity tables have been arranged so that the
designer can simply select a beam connection and with
the minimum of calculation check whether the column it
connects to needs to be stiffened.
The tables serve two other useful functions. Firstly, they
can be an aid for frame designers to help with member
selection, and secondly they can be used to provide a
good 'first guess' in those cases where the standard
geometry may not be appropriate.
A key aim during the production of the tables was to
standardise the selection of bolts and fittings.
This process continues the work on connection
standardisation which was introduced in Joints in Simple
Construction (^^ and is widely recognised as being an
important step towards improving the efficiency of the
industry.
Design examples
Worked examples illustrating the design method are
included in most Sections, with a further example of a
bolted end plate connection in Appendix I. Examples
showing use of the capacity tables precede each set of
tables.
1.2 CLASSIFICATION OF CONNECTIONS
BS 5950: Part 1 requires that the connections in a steel
structure should accord with the assumptions made in the
design of the frame. It is not sufficient in all situations to
assume that a moment connection is adequate simply
because it is capable of resisting the design bending
moment, shear and axial forces. It may also be necessary to
consider the rotational stiffness and the rotation capacity.
1
Moment Connections
The characteristics of a joint can be best understood by
considering its rotation under load. Rotation is the actual
change in angle which takes place as shown in Figure 1.1.
Checking for ductility is just as daunting. Assessing the
connection is not an easy process and in principle the
rotation capacity needed will depend on the arrangement
of loading and whether the frame is braced or unbraced.
For these reasons, it is felt that the most realistic approach
isfor the designer to follow simple rule-of-thumbguidelines
which will in most circumstances ensure that the frame
design assumptions have not been invalidated. The use of
8mm and 10mm thick fittings with wide bolt spacing
recommended in Joints in Simple Construction is an
example of this approach.
Guidance to help ensure adequate levels of stiffness and
ductility can be found in Section 2.5.
Figure 1.1 Moment - rotation of a connection
Connections can be classified in three ways as illustrated
in Figure 1.2 on page 4. These are by:
• Moment Resistance;
the connection may be either full strength, partial
strength, or nominally pinned (i.e. not moment resisting),
• Rotational Stiffness;
the connection may be rigid, semi-rigid or nominally
pinned (i.e. no rotational stiffness),
• Rotation Capacity;
connections may need to be ductile. This criterion is
less familiar to most designers and introduces the
concept that a connection may need to rotate plastically
at some stage of the loading cycle without failure.
Joints in simple construction (^^ have to perform this
way, and...


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