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PUBLICATION NUMBER 213 Joints in Steel Construction Composite Connections Published by: The Steel Construction Institute Silwood Park Ascot Berks 5L5 7QN Tel: 01344623345 Fax: 01344622944 In association with: The British Constructional Steelwork Association Limited 4 Whitehall Court, Westminster, London SW1A 2E5

Joints in Steel Construction Composite Connections · specified in either BS 4449 or BS EN 10080. Detailing rules are therefore given for two cases; bars that just meet the code requirements

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Page 1: Joints in Steel Construction Composite Connections · specified in either BS 4449 or BS EN 10080. Detailing rules are therefore given for two cases; bars that just meet the code requirements

PUBLICATION NUMBER 213

Joints in Steel ConstructionComposite Connections

Published by:

The Steel Construction InstituteSilwood ParkAscotBerks 5L5 7QN

Tel: 01344623345Fax: 01344622944

In association with:

The British Constructional Steelwork Association Limited4 Whitehall Court, Westminster, London SW1A 2E5

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1 998 The Steel Construction Institute

Apart from any fair dealing for the purposes of research or private study or criticism or review, aspermitted under the Copyright Designs and Patents Act, 1 988, this publication may not be

reproduced, stored or transmitted, in any form or by any means, without the prior permission inwriting of the publishers, or in the case of reprographic reproduction only in accordance with theterms of the licences issued by the UK Copyright Licensing Agency, or in accordance with the termsof 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, TheSteel Construction Institute, at the address given on the title page.

Although care has been taken to ensure, to the best of our knowledge, that all data and informationcontained herein are accurate to the extent that they relate to either matters of fact or acceptedpractice or matters of opinion at the time of publication, The Steel Construction Institute, the authorsand the reviewers assume no responsibility for any errors in or misinterpretations of such data and/orinformation or any loss or damage arising from or related to their use.

Publications supplied to the Members of the Institute at a discount are not for resale by them.

Publication Number: SCl-P-213

ISBN 185942 085 0

British Library Cataloguing-in-Publication Data.A catalogue record for this book is available from the British Library.

II

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FOREWORD

This publication is one in a series of books that cover a range of structural steelwork connections. Itprovides a guide to the design of Composite Connections in Steelwork. Other books in the series areJoints in simple construction, Volumes 1 and 2 (shortly to be replaced by Joints in steel construction -Simple Connections), and Joints in steel construction - Moment Connections.

This guide includes composite end plate connections suitable for use in semi-continuous braced frames.Both beam-to-column and beam-to-beam details are considered. Guidance on frame design proceduresis also given.

The publication begins with a list of 'Fundamentals' . These points should be clearly understood byanyone wishing to design a frame incorporating composite connections.

This publication is produced by the SCI/BCSA Connections Group, which was established in 1987 tobring together academics, consultants and steelwork contractors to work on the development ofauthoritative design guides for structural steelwork connections.

III

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AC KNOWLEDGEMENTS

This publication has been prepared with guidance from the SCI/BCSA Connections Group consistingof the following members:

Dr Bishwanath Bose University ofAbertay, DundeeDavid Brown The Steel Construction InstituteMike Fewster Caunton EngineeringPeter Gannon Bolton StructuresDr Craig Gibbons Ove Arup & PartnersEddie Hole British Steel Tubes & PipesAlastair Hughes Arup AssociatesAbdul Malik The Steel Construction InstituteDr David Moore* Building Research EstablishmentProf David Nethercot University of NottinghamDr Graham Owens The Steel Construction Institute (Chairman)Alan Pillinger* Bison StructuresAlan Rathbone* CSC (UK) LtdJohn Rushton* Peter Brett AssociatesCohn Smart British Steel Sections, Plates & Commercial SteelsPhil Williams The British Constructional Steelwork Association Ltd

* Editorial committee, in association with:

Prof David Anderson University of WarwickDr Graham Couchman The Steel Construction InstituteDr Mark Lawson The Steel Construction InstituteJim Mathys Waterman PartnershipAndrew Way The Steel Construction Institute

Valuable comments were also received from:

Alasdair Beal Thomason PartnershipDavid Cunliffe Rowen Structures LtdVictor Girardier The Steel Construction InstituteJason Hensman University of NottinghamDr Thomas Li Ove Arup & PartnersJohn Morrison Buro Happold

The book was compiled by Graham Couchman and Andrew Way.

Sponsorship was received from the Department of the Environment, Transport and the Regions,British Steel plc and the Steel Construction Industry Federation (SCIF).

iv

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CONTENTSPage No.

ACKNOWLEDGEMENTS iii

FOREWORD iv

FUNDAMENTALS 1

1 INTRODUCTION 31 .1 ABOUT THIS DESIGN GUIDE 31.2 SCOPE 31 .3 BENEFITS 41 .4 FRAME LAYOUT 41 .5 FRAME DESIGN METHODS 71 .6 CONNECTION CHARACTERISTICS 81.7 EXCHANGE OF INFORMATION 91.8 MAJORSYMBOLS 11

2 CONNECTION DESIGN 132.1 DESIGN PHILOSOPHY 132.2 TENSION COMPONENTS 142.3 COMPRESSION COMPONENTS 152.4 COLUMN WEB PANEL 162.5 VERTICAL SHEAR COMPONENTS 162.6 STRUCTURALINTEGRITY 16

3 FRAMEDESIGN 173.1 INTRODUCTION 173.2 ULTIMATELIMITSTATE 173.3 SERVICEABILITY LIMIT STATE 22

4 "STEP BY STEP" DESIGN PROCEDURES 234.1 INTRODUCTION 234.2 BEAM-TO-COLUMN CONNECTIONS 234.3 BEAM-TO-BEAM CONNECTIONS 60

5 CONNECTION DETAILING 655.1 BEAM-TO-COLUMN CONNECTIONS 655.2 BEAM-TO-BEAM CONNECTIONS 66

REFERENCES 69

APPENDIX A Worked Example 71

APPENDIX B Design Tables for Standard Composite 'Plastic' Connections 83B.1 INTRODUCTION 83B.2 CAPACITY TABLES 85B.3 DETAILING TABLES 98

V

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FUNDAMENTALS

Designers should ensure that they have a goodunderstanding of the following 'Fundamentals' beforestarting to design composite connections using thisguide.

In order to keep design procedures simple, a numberof issues (e.g. connection rotation capacity) are notchecked explicitly. In some cases detailing limitationsare given in preference to complicated checks in orderto ensure that connection behaviour is appropriate.A good understanding of these 'Fundamentals' willhelp a practising engineer to appreciate some of thebackground to these requirements, without a need toemploy overly complicated checks.

Mechanics of composite connections

Composite connections resist moment by generatinga couple between their tension and compressioncomponents. The mechanics are essentially the sameas those for bare steel moment connections, with theslab reinforcement acting like an additional row ofbolts in an extended end plate. In order to achievetheir full potential, the reinforcing bars must beproperly anchored, and be capable of accommodatingsignificant strain before fracture.

It may be assumed that the lower beam flange cansustain a stress of 1 .4p in compression when it isassumed to act alone. When part of the beam webis also assumed to be subject to compression, thelimiting stress should be reduced to 1 .2p.Compression often extends into the beam web incomposite connections as a result of high tensileforces in the reinforcement. A further consequenceof these high forces is that column compressionstiffeners are often required.

DetailingConsiderable care is needed when detailing compositeconnections to ensure that components are subjectedto sufficient deformation to allow them to generatetheir full potential resistance, whilst at the same timeensuring that they are not over-strained to the pointof premature failure.

Detailing rules given in this guide ensure that the fullpotential resitance of bolt rows that are too near theneutral axis is not considered in the calculation ofmoment capacity. Similarly, to ensure that sufficientstrain takes place to yield the reinforcement,

compression must be limited to the lower half ofthe steel beam. To prevent premature failure ofthe reinforcement (due to excessive strain)adversely affecting the connection's rotationcapacity, it is also essential that reinforcing barsare not located too far from the neutral axis.

Detailing rules are given for two basic types ofconnection. Less onerous rules, in terms of theminimum area of reinforcement required, lead towhat may be described as 'compact' connections.Like 'compact' beams, these connections candevelop a moment capacity that is based on astress block model (analogous to M for a beam),but have insufficient rotation capacity to form aplastic hinge. More onerous limitations are neededfor 'plastic' connections, which are capable offorming a plastic hinge.

Non-ductile failure modes must not govern themoment capacity of 'plastic' connections. Theseinclude:

. column and beam web tension failure

. column web buckling or bearing failure incompression.

Non-ductile failure modes must be avoided eitherby local stiffening/strengthening, or bymodification of component choice.

All composite connections detailed in accordancewith this guide will be 'partial strength', i.e. theirmoment capacity will be less than that in hoggingof the beam to which they are attached.

All connections detailed in accordance with thisguide will be 'rigid' in their composite state.

MaterialsThe properties of the reinforcement used in acomposite connection, in particular the elongationthat the reinforcement can undergo before failure,are of vital importance because they have anoverriding influence on the rotation capacity of theconnection. Designers should note the followingpoints in relation to reinforcement ductility:

The contribution of any mesh to the momentcapacity of the connection should beignored, as mesh may fracture before the

1

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Composite Connections

connection has undergone sufficient rotation atthe ultimate limit state. Structural reinforcementshould comprise 1 6 mm or 20 mm diametrs.

. Reinforcing bars currently produced in the UK areoften considerably more ductile than thosespecified in either BS 4449 or BS EN 10080.Detailing rules are therefore given for two cases;bars that just meet the code requirements(identified as bars that are capable of 5% totalelongation at maximum force - see Section 4.2Step 1 A for exact definitions of coderequirements), and bars that have twice thiselongation capacity (10%). When the designerhas assumed that bars can achieve 10%elongation, he must make this non-standardcondition clear in the contract documents. Barswith non-standa rd performance requirementsshould be identified with an X (i.e. Xl 6 or X20)to indicate that specific requirements are given inthe contract documents.

Steelwork detailing must also ensure that adequaterotation can take place. To achieve this, rotationshould be primarily the result of end plate or columnflange bending, rather than by elongation of the boltsor deformation of the welds, as these componentsgenerally fail in a brittle manner. End plates shouldalways be grade 5275, regardless of the beam grade.

Frame design

Recommended frame design procedures, consideringboth the ultimate (ULS) and serviceability (SLS) limitstates, are given in this publication. Beam design atthe ULS assumes that plastic hinges form in theconnections at the beam ends. The method istherefore only applicable when 'plastic' connectionsare used. In addition, the following limitations mustbe imposed to ensure that the required beam endrotations are not excessive:

. a minimum required connection strength (30%relative to the beam in sagging),

. a lower bound on the beam span to depth ratio,

. a reduction factor on the sagging momentcapacity of the composite beam. Although intheory this reduction factor varies as a functionof several parameters, including the beam gradeand load arrangement, a value of 0.85 may beused for all cases. The reduction factor isnecessary to limit the amount of plastificationthat takes place in the beam, and therebysubstantially reduce the end rotationrequirements.

2

Implications of propping the beams duringconstruction are far reaching, and considered atsome length. Not only will dead load deflectionsclearly be affected, but there will also be aninfluence on the moments that are applied to thecolumns, and the levels of rotation required fromthe connections. The implications of propping caneven affect the basic choice of frame layout andconnection types. The designer must thereforeclearly communicate his requirements for proppingto all parties concerned.

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1 INTRODUCTION

1.1 ABOUT THIS DESIGN GUIDE

Composite construction has achieved dominance inthe UK because of its overall economy of use ofmaterials, and ease of construction relative toalternative reinforced concrete and steel options.Attention has now turned to further improving theeconomy of composite construction by takingadvantage of the performance of the connections inthe analysis and design of the frame. Even relativelysimple non-composite details can achieve areasonable degree of stiffness and strength whencomposite action is present. This is not only due tothe continuity of reinforcement in the slab, but is alsothe result of other less quantifiable effects, such asmembrane action in the floor plate.

This publication considers connections in frameswhere the steel beams act compositely with concretefloor slabs, and where some of the connections arealso designed to act compositely. The structuralinteraction of the beams and slabs allows smallerbeams to be used in a frame of given stiffness andstrength. Shear connectors provide the means ofenhancing moment capacity and stiffness bytransferring longitudinal shear between the steelbeams and concrete. In addition to the beams, thefloor slabs themselves are often composite,comprising profiled steel decking and in-situ concrete.However, most of the beam-to-column and beam-to-beam connections in composite frames are currentlynon-composite and treated as 'simple'. Their abilityto resist moment is not exploited, mainly because ofa lack of appropriate design guidance for compositeconnections.

Procedures for the design of moment resistingcomposite connections, and guidance on the layoutand design of braced semi-continuous framesincorporating composite connections, are given in thispublication. Typical composite connection details areshown in Figure 1 . 1 . Reinforcement comprises 1 6 or20 mm bars local to the column. Compositeinteraction between the steel components and thereinforcement, via the concrete slab, enables theconnection to resist moment by forming a couplebetween the reinforcement in tension and steel beamin compression.

The most cost effective composite construction willoften arise when composite connections are used inconjunction with moment resisting non-compositeconnections in appropriate locations. For maximumeconomy, the designer should also consider the use

of some 'simple' steel details, for exampleconnections to perimeter columns in order to preventthe transfer of substantial moments.

Design procedures for bare steel connections are notincluded in this publication. The designer should referto other books in the BCSA/SCI 'Green Book' seriesfor information concerning bare steel detail&1'2'3'4.

1.2 SCOPE

This publication covers the following types ofconnections:

S composite, using flush end plates for beam-to-column connections

. composite, using partial depth end plates forbeam-to-beam connections

. suitable for use in braced frames only

. rigid

3

(a) beam-to-column

(b) beam-to-beam

Figure 1 . 1 Typical composite connection

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Composite Connections

. either 'compact' - so that their moment capacitycan be calculated using plastic stress blocks

. or 'plastic' - in addition, they have sufficientrotation capacity to be justifiably modelled asplastic hinges.

A range of standard connections is included, all ofwhich are 'plastic', and which are therefore suitablefor inclusion in a frame that is analysed using plasticmethods. Steelwork detailing for these connectionsis based on the standard wind-moment connectionspresented in Reference 4.

The standard composite connections have all beendetailed so that the connection moment capacity isless than that of the beam (in hogging). This makesall the standard connections partial strength. This isa necessary requirement when plastic frame analysisis adopted and the beams are anything other thanClass 1 (plastic) in hogging, because the plastichinges form in the weaker connections rather thanthe adjacent beams.

Because plastic models are used to calculate themoment capacity, beam flanges must be either Class1 or 2, and webs Class 1 , 2 or 3. Class 3 webs maybe treated as effective Class

Although the publication is essentially a compositeconnection design guide, it includes guidance onchoice of frame topology and frame designprocedures.

1.3 BENEFITS

The use of composite connections in braced framescan result in:

• reduced beam depths, which may be importantfor the integration of building services, reductionin overall building height, reduction in claddingcosts etc.

• reduced beam weights

• improved serviceability performance

greater robustness, as a result of improvedcontinuity between frame members (seeSection 2.6)

• control of cracking in floor slabs on column lines(due to the, presence of substantialreinforcement).

For a semi-continuous composite frame, that is onein which the connections are partial strength, the

4

weight and depth savings on individual beams may beup to 25%. Overall frame savings in weight anddepth will vary considerably depending on the extentto which an optimal framing arrangement can beadopted. Guidance on framing arrangements whichexploit the benefits of composite connections is givenin Section 1 .4.

For maximum cost savings it is essential to base thecomposite connections on steel details that are notsignificantly more complicated than those traditionallyconsidered to be 'simple'. Column tension stiffenersnot only increase fabrication costs, but may alsocomplicate the positioning of other incoming beams.They should therefore be avoided where possible.Although column compression stiffeners also increasefabrication costs and should preferably be avoided,they are less of a problem if the orthogonal beamsare sufficiently shallow to avoid a clash.Compression stiffeners are often unavoidable incomposite connections that adopt a substantial areaof reinforcement. In some situations increasing thecolumn size may be more cost effective than localstiffening.

1.4 FRAME LAYOUT

The extent to which a beneficial framing layout canbe adopted will have a major influence on whetherthe use of composite connections is economical.General principles that should be considered whenplanning the layout of beams and orientation ofcolumns are given in this Section.

1.4.1 Unpropped construction

Beam design criteria

Beam size may be governed by any of the followingfactors:

• the strength of the bare steel beam duringconstruction

• the stiffness of the bare steel beam duringconstruction

• the strength of the composite beam in its finalstate

• the stiffness of the composite beam in its finalstate.

The second of these is only relevant if dead loaddeflections need to be controlled (for example toprevent excess ponding of the concrete duringcasting) and pre-cambering of the steel beam is nota viable option.

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Introduction

Stiffness considerations are most likely to be criticalfor beams that are made from higher grade steel(5355) and that are subject to UDL or multiple pointloads. Stiffness influences both deflections andresponse to dynamic loading.

Choice of connectionsBeams that are governed by strength considerationsneed strong (moment resisting) connections to reducethe sagging moment that must be resisted by thebeam. This applies to either the bare steel beam(with steel connections) during construction, or thecomposite beam (with composite connections) in itsfinal state.

Beams that are governed by stiffness considerationsneed stiff connections to provide rotational restraintat the beam ends. This could be in either the initialbare steel or final composite state. In the absence ofstiff bare steel connections, pre-cambering can beused to reduce dead load deflections of unproppedbeams during construction.

The following guidelines should also be consideredwhen choosing the connections:

. The use of both major and minor axis compositeconnections to a given column may result inproblems accommodating the necessaryreinforcement in a limited thickness of slab. It isgenerally recommended that the connections toone of the axes should be non-composite.

. It is recommended that connections to perimetercolumns should be non-composite, to avoidproblems anchoringor locating the reinforcement.

S Beam-to-beam connections based on partialdepth end plate steel details offer limitedstiffness at the construction stage. If dead loaddeflections of secondary beams are to becontrolled, pie-cambering may be the onlypossible option (in the absence of propping).

sided' composite connections,the steelwork to the column webcommon need for local column

Typical framing solutionsTwo framing solutions that capitalise on theprinciples outlined above, and avoid the need forpropping, are shown in Figures 1 .2 and 1 .3.Schematic connection details, and references towhere appropriate design guidance may be found, areshown on each Figure. These details are included toillustrate the required connection characteristics at

various frame locations, for example non-compositeand 'simple', or composite and moment resisting.The types of detail shown will not be appropriate inall situations, for example flexible end plates mayneed to be used for 'simple' connections, rather thanfin plates, when beams have a limited web area.

The following points explain the choice of layoutshown in Figure 1 .2.

. The use of moment resisting compositeconnections (type 2) on the beams C (which aregoverned by strength considerations) allows thesagging moment requirements on the compositebeams in the final state to be reduced.

. The use of moment resisting non-compositeconnections (type 1 ) on the beams A (which aregoverned by stiffness considerations) allows thedead load deflections to be reduced, without theneed for pre-cambering. It also avoids a clashwith the orthogonal composite connections atthe internal columns.

. The type 3 non-composite connection detailshave been chosen at the perimeter ends ofbeams C to facilitate erection, and to avoid thecomplexities of producing moment resisting non-composite details to the webs of perimetercolumns.

. The type 4 non-composite connection at theperimeter end of beam B is chosen for ease oferection, and because the torsionally weakperimeter beam offers no moment resistancecapability.

. The type 5 composite connections can be usedat one end of beams B to reduce saggingmoments and imposed load deflections in thefinal state. Dead load deflection of these beamswill normally only be reduced if pre-cambering isadopted, because of difficulties in achieving stiffbare steel beam-to-beam connections duringconstruction. Type 5 composite connections willbe difficult to achieve should the secondarybeams (B) not be shallower than the primaries(C). This will depend on the relative spans. Pre-cambering would therefore become moreattractive as the span of the mark B beamsincreased.

Figure 1 .3 shows another potential framing solution,for which the long span beams will be deeper/heavierthan would be the case for an arrangement as shownin Figure 1.2.

For 'twoconnectingavoids thestiffening.

5

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Composite Connections

C

(3

____-@ Non-composite

Moment resistingReference 4, Section 2.8

CompositeMoment resistingSection 4.2

Non-compositeNominal pinReference 1, Section 3.5

® Non-compositeNominal pinReference 1, Section 4.5

® CompositeMoment resistingSection 4.3

Figure 1 .2 Typical floor beam layout - for spans up to approximately 1 2 mit may be possible to achieve beams of similar depth. (Numbersrepresent connection types. A, B and C are beams)

® ® ®

B C - -

I- A® ® ® (2p

Figure 1 .3 Alternative floor beam layout - services may be located beneathshort span beams. (Numbers represent connection types. A, Band C are beams).

6

rn! rn.r 1--

'L

(3

B

1A

(3

. ®I ®I rn

:D Non-composite CompositeMoment resisting Moment resistingReference 4, Section 2. 8 Section 4.2

Non-composite ® Non-compositeNominal pin Nominal pinReference 1, Section 3. 5 Reference 1, Section 4.5

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Introduction

. The use of moment resisting connections, eithercomposite (type 3) or non-composite (type 1)allows the size of the long span beams A to bereduced.

. The depth of the short span beams B and C willbe significantly less than that of the long spanmembers, so there will be no penalty in terms ofoverall depth of the steel members if thedesigner adopts inexpensive 'simple' connectionsfor these beams.

. It may be possible to run services beneath thesecondary beams, within the depth of the longspan primaries.

The economics of this type of solution will depend onthe relative spans, but it will normally be lessefficient than a layout of the type shown inFigure 1.2.

1 .4.2 Propped construction

If propping is acceptable (recognising that there maybe implications in terms of both the work programmeand costs), or there is no need to control dead loaddeflections, the most economic frame layouts maydiffer from those shown in Figures 1 .2 and 1 .3.Composite connections should be used in the mostbeneficial locations, either to reduce saggingmoments, or to reduce imposed load deflections.These improvements are possible because of thestrength and stiffness of the connectionsrespectively. The most appropriate connectionchoices will depend on the relative spans, and thecolumn orientations will be influenced by theconnection choice.

1.5 FRAME DESIGN METHODS

It is essential, and indeed a requirement of BS 5950:Part 1 (6)), that connection behaviour is compatiblewith the assumptions made in the design of a frame.The connection characteristics determine whether theframe is:

S Simple - the small moment capacity and stiffnessthat the connections possess are neglected inthe frame analysis, and the connections aretreated as 'pinned'.

Semi-continuous - the moment capacity of theconnections is allowed for in a plastic globalanalysi of the frame. Alternatively, theirstiffness is allowed for in an elastic analysis.Both connection stiffness and strength are

considered in an elastic-plastic analysis of asemi-continuous frame.

. Continuous - the connections are designed toresist moments and forces predicted by anelastic or plastic global analysis, assuming thatthey either behave rigidly (elastic analysis) or are'full strength' (plastic analysis), to provide fullcontinuity between the frame members. Rigid,full strength behaviour is assumed in an elastic-plastic analysis of a continuous frame.

Global analysis - ULSIn a semi-continuous frame the moments and forcesat the ULS may be determined by either elastic orplastic global analysis. Factors that influence thechoice of analysis method are:

. the type of connections used

. the classification of the beam cross-sections(noting differences between hogging andsagging).

Elastic frame analysis relies on the assumption thateach material being modelled behaves in a linear-elastic manner. An appropriate value of elasticmodulus must be used, so that member stiffness canbe calculated. When connections are semi-rigid, theirstiffness must also be incorporated in the analysis.Procedures are given in EC3 Annex j(7) for bare steelconnections, and the COST Cl document8 that willform the basis for the EC4 Annex for compositeconnections, for calculating stiffness.

Rigid-plastic analysis considers the resistance ofmembers and connections rather than their stiffness.This avoids the need to predict connection stiffness.Connection strength, i.e. moment resistance, can bepredicted more accurately than stiffness using currentmethods. A rigid-plastic analysis assumes thatplastic hinges form at certain points in the frame.This assumption is only valid when the points atwhich hinges may form, including the connections,have sufficient capacity to rotate without loss ofstrength.

A third possibility is to combine stiffness andstrength considerations in an elastic-plastic analysis.Software may be used to perform this type ofanalysis, allowing for the connection characteristics.Although such software is not common in designoffices, it is used for certain types of structure, suchas portal frames.

The authors recommend the use of rigid-plasticanalysis for hand calculations, using connections that

7

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Composite Connections

have a configuration which is known to besufficiently ductile. Because the plastic hinges formin the partial strength connections, the beam analysis.is divorced from column considerations.

Table 1 . 1 summarises the characteristics that areneeded for connections in frames designed using thevarious methods currently available. The methodrecommended in this publication (and explained indetail in Section 3) is shaded in the table.

Global analysis - SLS

Elastic analysis should be used to predict framebehaviour under serviceability loading. Because allcomposite connections complying with this guidemay be assumed to be 'rigid', they may be modelledas fully continuous joints between frame membersonce composite action is achieved.

Connections will be considerably more flexible duringconstruction, and this may influence some aspects offrame behaviour.

Table I . I General methods of ULS design

DESIGN CONNECTIONS

COMMENTS.Type of Framing

Global.

Analysis.

Properties

Simple Pin Joints Nominally PinnedEconomic method for braced multi-storey frames.Connection design is for shear strength only (plus robustnessrequirements).

.Continuous(Note 1)

Elastic Rigid Conventional elastic analysis.

Plastic Full StrengthPlastic hinges form in the adjacent member, not in theconnections. Popular for portal frame designs.Elastic-

PlasticFull Strength andRigid

. . . . Connections are modelled as rotational springs. Prediction of1 Elastic Semi-Rigid . . . .

H connection stiffness may present difficulties.

P1 1 Partial Strength Wind-moment design is a variant of this method (forSemi-Continuous

as ic and Ductile unbraced frames).(Note 2)

. . . . .

. . Full connection properties are modelled in the analysis.Elastic- Partial Strength .

. . . . Currently more of a research tool than a practical designPlastic and/or Semi-Rigid method for most frames.

Note 1 BS 5950: Part 1 refers to these design methods as 'Rigid' and 'Semi-Rigid' respectively.Note 2 Shading indicates the design method considered in Section 3 of this document.

1 .6 CONNECTION CHARACTERISTICS

It should not be assumed that a moment connection,be it composite or not, is adequate simply because itis capable of resisting the bending moment, shearand axial forces predicted by a frame analysis. It isalso necessary to consider either the rotationalstiffness or the rotation capacity (ductility) of theconnection, depending on the type of analysisadopted.

The characteristics of a connection can best beunderstood by considering its rotation under load.Rotation is the change in angle () that takes place atthe connection, as shown in Figure 1 .4. The three

8

important connection characteristics are illustrated inFigure 1 .5. These three characteristics are:

. Moment CapacityThe connection may be either full strength orpartial strength (relative to the resistance of thecomposite beam in hogging), or nominally pinned(having negligible moment resistance).

S Rotational StiffnessThe connection may be rigid, semi-rigid ornominally pinned (having negligible rotationalstiffness).

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Intro duct/on

Rotation CapacityConnections may need to be ductile. Thischaracteristic is less familiar than strength orstiffness to most designers, and is necessarywhen a connection needs to rotate plasticallyduring the loading cycle. Considerable connectionductility may be needed if a frame is to beanalysed plastically.

jFull strength

Partial strength

Rigid, partial strength,ductile connectionresponse

arrangement and whether the frame is braced orunbraced.

In this guide a set of simple rule-of-thumb guidelinesis presented to ensure that the frame designassumptions are not invalidated by the use ofinappropriate connections. The designer has no needto consider explicitly either connection stiffness orconnection ductility.

Any composite connection satisfying the detailingrules given in this guide (see Sections 4 and 5) maybe assumed to be rigid once concreted. Elasticmethods may therefore be used for frame analysis inthe final state, with no need for the designer todetermine the exact value of composite connectionstiffness.

The rotation capacity of a composite connection maybe less than that of the steel detail alone. Onereason for this is that reinforcing steel is generallyable to undergo less elongation before fracture thantypical structural steel. The detailing requirementsgiven in this guide ensure that, in terms of ductility,all composite connections will fall into one of twocategories:S 'compact' connections are sufficiently ductile to

ensure that a stress block model can be used topredict the moment resistance

. 'plastic' connections have sufficient additionalductility to ensure that they can behave as aplastic hinge.

Detailing requirements (particularly concerning aminimum area of reinforcement) are more onerous for'plastic' connections.

The standard connections presented in Section 6 are'plastic', and may be used as such in either proppedor unpropped braced frames analysed using plasticmethods.

Figure 1.5 Classification of connections

Figure 1 .5 shows boundaries between rigid/semi-rigid, full strength/partial strength, andnon-ductile/ductile, in addition to a typical compositeconnection response. The typical curve indicates thatcomposite connections are normally ductile, rigid, andpartial strength.

Although Eurocode 4 (EC4) will present a method forcalculating the stiffness of a composite end plateconnection based on the approach of EC3, this canbe a tortuous process. Assessing a connection'srotation capacity is also difficult, and the rotationrequired depends on parameters such as the loading

1 .7 EXCHANGE OF INFORMATION

The design of a steel frame is often undertaken intwo distinct stages, with the frame membersdesigned by one engineer/organisation, and theconnections designed by another. This method ofworking may be inappropriate when compositeconnections are used, because of interdependence ofmember and connection resistances, and because ofthe interaction between steel and concretecomponents.

9

Figure 1 .4 Rotation of a composite connection

M Non ductile Ductile

MRigid

/" Semi-rigid

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Composite Connections

It will often be prudent for the designer of themembers in a semi-continuous frame to undertake thecomposite connection design, or at least to specify'industry standard' details. Integrating member andconnection design is particularly important forcomposite connections, because of the interactionbetween the steelwork components and the local slabreinforcement.

Care must be taken to ensure that requirements forany connections not designed by the memberdesigner are clearly defined in the contractdocuments and on the design drawings. Connectionsthat have been chosen to be composite should beclearly identified. The National Structural SteelworkSpecification for Building Construction9 givesappropriate guidance on the transfer of information.

In addition to the exchange of information at thedesign stage, the use of composite connectionsshould be noted in the building owner's manual forfuture reference. Their presence may influence futuremodifications and demolition of the building.

10

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Intro duct/on

1.8 MAJOR SYMBOLS

Note: Other symbols employed in particular Sections are described where used.

B Width of section (subscript b or c refers to beam or column)

b Width of plate

C Compression force

D Depth of section (subscript b or c refers to beam or column)

d Depth of web between fillets or diameter of bolt

d Depth of slab above decking

e End distance

F Force (subscript indicates whether in reinforcement, bolt etc)f Cube strength of concrete

f Yield strength of reinforcement

g Gauge (transverse distance between bolt centrelines)

M Bending moment

N Axial force

PC Capacity in compression

Pt, Enhanced tension capacity of a bolt when prying is considered

p Bolt spacing ('pitch')

py Design strength of steel

0 Prying force associated with a bolt

Fillet weld leg length

S Plastic modulus

T Thickness of flange (subscript b or c refers to beam or column) or tension force

Thickness of plate

t Thickness of web (subscript b or c refers to beam or column)

r Root radius of section

V Shear force

Z Elastic modulus

Ym Material strength factor

Lengths and thicknesses stated without units are in millimetres

11

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12

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2 CONNECTION DESIGN

2.1 DESIGN PHILOSOPHY

The design model presented here uses the'component approach' adopted in Eurocodes 3 and4(71O) Using this approach, the moment capacity ofthe connection is determined by considering thestrength of each relevant component, e.g. the tensilecapacity of the slab reinforcement. Adopting a'component approach' means that the designer canapply different aspects as appropriate to a particularsituation. For example, the model can be applied toboth composite and non-composite end plateconnections. In the case of a non-compositeconnection, checks relating to the reinforcement areignored. The Eurocode model has been validated bycomparison with extensive test results.

The strength checks given in this document havebeen modified to conform with British standardseventhough the design philosophy is taken directlyfrom the Eurocodes.

The connection resists moment by coupling tensionin the reinforcement and upper bolts withcompression in the lower part of the beam. Themoment capacity is calculated by consideringappropriate lever arms between the components.The force transfer mechanism is shown schematicallyin Figure 2.1. Evaluation of the

I

\/

tension and compression components that form acomposite end plate connection are discussed inSections 2.2 and 2.3.

The moment capacity of the connection may beevaluated by plastic analysis, using 'stress block'principles, provided that:

There is an effective compression transfer to andthrough the column.

. The connection is detailed such that themaximum possible reinforcement and tensionbolt capacities are generated. The reinforcementforce is governed by yielding of the bars,whereas the bolt forces are governed by yieldingof the end plate and/or column flange. Thisrequires appropriate levels of strain to develop inthe different tensile components (see Section 4).

. There are sufficient shear connectors to developthe tensile resistance of the reinforcement, withforce being transferred through the concrete.

. The reinforcement is effectively anchored onboth sides of the connection.

. Premature buckling failure, for example of thecolumn web, is avoided.

Compositeslab

Figure 2. 1 Typical composite connection at internal column, showing force transfer by the variouselements

13

Shear connector

/Reinforcing bar

Bolt

I11

U

Beam/Column

Welded end plate

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Composite Connections

Tests show that, by the ultimate limit state, rotationhas taken place with the centre of rotation in thelower part of the beam. For relatively small areas ofreinforcement, compression is concentrated at thelevel of the centre of the lower beam flange. Whenthe reinforcement area is greater and thecompressive force is such that it exceeds thecapacity of the beam flange, compression extendsup into the beam web, and the centre of rotationchanges accordingly.

2.2 TENSION COMPONENTS

Three of the connection components govern themagnitude of tensile force that can be generated.They are:

the reinforcement

the upper row(s) of bolts

• the interface shear connection in the hoggingmoment region of the beam.

2.2.1 Tensile force in thereinforcement

To effectively contribute to the connectionbehaviour, the reinforcement must be located withina certain distance of the centre line of the column(detailing rules are given in Section 5). Thisdistance is not the same as the effective breadth ofslab in the negative (hogging) moment region of thebeam (as defined in Clause 4.6 of BS 5950:Part 3: Section

Tests and models8 have shown that connectionrotation capacity increases as the area ofreinforcement increases. Minimum values ofreinforcement area for 'compact' and 'plastic'connections are given in Section 4.

The maximum area of reinforcement in theconnection is governed by:

• the ability of the shear connectors in thenegative moment region to transfer the requiredforce to the reinforcement (any excessreinforcement would simply be redundant)

• the compression resistance of the beam (anyexcess reinforcement would be redundant)

• the resistance of the column web, with dueconsideration of any stiffeners (any excessreinforcement could provoke a non-ductilefailure)

• the strength of the concrete that bears againstthe column under unbalanced moment (any

14

excess reinforcement could provoke non-ductilefailure).

Connection moment capacity is calculatedassuming that bar reinforcement yields. Adoptionof the detailing rules given in Sections 4 and 5 willensure that the steelwork components do not failbefore the reinforcement has undergone sufficientstrain to achieve this. This allows the contributionof the upper bolts to the connection momentcapacity to be considered. The contribution tomoment capacity of any mesh reinforcement thatmay be present in the slab should be ignored,because it fails at lower values of elongation thando larger bars.

2.2.2 Tensile force in the boltsAlthough tension in the upper rows of bolts can beignored to make a simple estimate of theconnection resistance, the final connection designshould consider their contribution. Ignoring the boltforces underestimates the compression acting onthe column, and could be unsafe if it led to a non-ductile compression failure. The design proceduresgiven in Section 4 explain how to calculate themagnitude of the bolt forces.

The bolt row furthest from the beam compressionflange tends to attract more tension than the lowerbolts. Traditional practice in steelwork design hasbeen to assume a triangular distribution of bolt rowforces, based on a limit imposed by the furthestbolts. Although the method presented in Section 4also gives greater priority to the upper bolts, itallows a plastic distribution of bolt forces. Theforce permitted in any bolt row is based on itspotential resistance, and not just on its lever arm(as in a triangular distribution). Bolts near a pointof stiffness, such as the beam flange or a stiffener,attract more load. Surplus force in one row of boltscan be transferred to an adjacent row that has areserve of capacity. This principle is closer to theway connections perform in practice.

Bolt rows may only contribute their full capacity tothe tensile resistance of a composite connectionwhen the connection detailing is appropriate. Insome situations, primarily when considerablereinforcement is present, a large compressive forcein the beam means that the neutral axis is relativelyhigh in the beam web. Deformations of the endplate and/or column web in the locality of bolt rowsthat are too close to the neutral axis will not besufficient to develop the full bolt row forces thatare associated with plate yielding. A simple linearreduction of bolt row forces is suggested in

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Connection Design

Section 4.2 Step 1 D for rows that are less than200 mm from the neutral axis.

When plastic frame analysis is adopted, as isrecommended in this guide, the connections musthave a substantial rotation capacity. A compositeconnection with a steel detail that allows substantialdeformation of the end plate to take place withoutbolt failure, and which has appropriate reinforcementdetailing (see Sections 4 and 5), may be assumed tobe 'plastic'; its rotation capacity will be sufficient fora plastic hinge to form at the connection. Ifdeformation of the steelwork detail is not primarilylimited to the end plate or column flange (known as'mode 1 ' according to Reference 7), ductility cannotbe assumed unless it has been demonstrated bytesting.

2.2.3 Longitudinal shear forceThe development of the full tensile force in thereinforcement depends on longitudinal shear forcebeing transferred from the beam to the slab via theshear connectors and concrete, as shown inFigure 2.2. BS 5950: Part 3(5) requires that fullshear connection is provided in the negative momentregion. The need for full shear connection has beenconfirmed by tests on composite connections. Thereinforcement should extend over the negativemoment region of the span and be anchored asufficient distance into the compression region ofthe slab to satisfy the requirements of BS 8110(11)(for example 40 times the bar diameter for a 'Type2 deformed' bar in concrete with a cube strength of30 N/mm2).

Point of

N /Negativemoment

k regionBending moment

T TT TT TT TTTTT TT TTTTTTF

Longitudinal shear forcein shear connectors

Figure 2.2 Transfer of longitudinal shear forcesin a composite beam

2.3 COMPRESSION COMPONENTS

Two of the connection components govern themagnitude of compression force that can beaccommodated. They are:

. the beam lower flange and adjacent web

. the column web.

2.3.1 Beam lower flange and webTransfer of the compression force through theconnection relies on direct bearing of the lower partof the beam on the column. To establish the depthof beam in compression, the designer shouldinitially compare the applied compressive force withthe resistance of the lower flange alone, assuminga design stress of 1 .4p. The factor of 1 .4 allowsfor strain hardening and some dispersion into theweb at the root of the section4. If the magnitudeof applied compression does not exceed this flangeresistance, the centre of compression should betaken as the mid-depth of the flange.

However, most composite connections will havesubstantial reinforcement, and the compressionresistance required is likely to exceed the flangelimit. In such cases compression is assumed toextend into the beam web, and then the resistanceshould be based on 1 .2 ps,,. An appropriate centreof compression must be adopted when calculatingthe moment capacity.

Because a plastic stress block model is considered,with design stresses in excess of yield, the designprocedures are only appropriate for beams withflanges that are either Class 1 (plastic) or 2(compact), and webs that are Class 1 , 2 or 3 (semi-compact).

2.3.2 Column web

In addition to considering the resistance of thebeam flange in compression, checks should bemade on the local resistance of the column incompression. The buckling or crushing (bearing)resistance of the column web may limit themaximum compression force that can betransferred. This may be a particular problem forcomposite connections with a substantial area ofreinforcement.

Because both crushing and buckling failure of thecolumn web are non-ductile, they cannot beallowed to govern the moment capacity of a'plastic' connection. Stiffeners must be added, ora heavier column section used, to avoid prematurefailure. Stiffener design is covered in Section 4.

15

/ Point of maximumsagging moment

Tension inreinforcement1

Compressionin concete

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Composite Connections

Whilst column web compression stiffeners mayoften be hard to avoid in composite connections,their addition increases fabrication costs, and maycomplicate the positioning of orthogonal beams. Amore economic solution might be to use a heaviercolumn section that requires no stiffening. Thepresence of end plate connections on orthogonalbeams connecting into the column web may preventweb buckling4, but will not increase the columnweb crushing resistance. Supplementary web platesare an alternative form of web reinforcement thatavoids clashes with other beams.

2.4 COLUMN WEB PANEL

For major axis connections, the column web panelmust resist the horizontal shear forces. Whenchecking panel shear, any connection to theopposite column flange must be taken into account,since the web must resist the resultant of theshears. In a one-sided connection with no axialforce, the web panel shear F is equal to thecompressive force in the lower part of the beam.For the case of a two-sided connection withbalanced moments, the web panel shear is zero.

FII..T..

(I'IL It'lit tfl --'

F C2C1Figure 2.3 Column web panel shear

2.5 VERTICAL SHEAR COMPONENTS

The vertical shear resistance of a connection relieson the steel components. Any shear resistance ofthe concrete or reinforcement should be ignoredbecause of cracking in the slab. Traditionally, thelower bolts in a steel connection are assumed toresist the total applied shear force. However,although loaded in tension, the upper bolts may alsoresist a proportion of their design shear resistance(according to BS 5950: Part 1 , Clause 6.3.6.3, thecombined utilisation for shear and tension may beup to 1 .4, so a bolt that is fully loaded in tensioncan still achieve 40% of its shear capacity).

16

Limited researc&12 has suggested that thepresence of high vertical shear force, or high axialload in the column, may reduce the momentcapacity of a composite connection. However, inthe absence of further information the authors donot feel it appropriate to include suchconsiderations for composite connections used inorthodox frames with typical loading. For othercases, e.g. beams subject to heavy concentratedpoint loads near their supports, alternativeconsiderations may be appropriate (seeReference 12).

2.6 STRUCTURAL INTEGRITY

It is a requirement of both the BuildingRegulation&13 and BS 5950: Part 1 (6) (Clause2.4.5.2) that all building frames be effectively heldtogether at each principal floor and roof level7.Steelwork details in accordance with thispublication will generally be capable of carrying thebasic 75 kN tying forc&1 required by the BritishStandard (see Reference 1 ). However, larger tyingforces may be required for tall, multi-storeybuildings. The tensile capacity of the reinforcement(when properly anchored) may be added to thecapacity of the bare steel connection in suchsituations. For the standard connection details, theresistance of the reinforcement and bolts may beextracted directly from the capacity tables inAppendix B.

The designer is advised that current rethinking ofrobustness requfrements may lead to revised designcriteria for structural integrity in the near future.

M(c1+i

-

}T2

)M2

- C2

- F-

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3 FRAME DESIGN

3.1 INTRODUCTION

This Section gives an overview of recommendedanalysis and design procedures for composite semi-continuous braced frames. Guidance is not given onchecking of the bare steel frame under constructionloading, which must however be considered as partof the frame design process.

3.2 ULTIMATE LIMIT STATE

The following recommended frame design proceduresmay only be adopted when 'plastic' connections areused. Plastic frame analysis and design isrecommended because of its economy and simplicity.

Because plastic hinges are assumed to form in theconnections rather than the adjacent beams, thecomposite connections must be partial strength (i.e.have a lower moment capacity than the beam inhogging). The standard connections presented inSection 6 are all partial strength. Connections mustalso be 'plastic' because the hinges are assumed torotate. The standard connections presented inSection 6 are all 'plastic'. Despite the assumption ofplastic hinge formation in the connections, it is notnecessary to consider alternating plasticity in theconnections, or incremental collapse of the fram&14.

The assumption that hinges form in the connectionsbetween the members allows the beams and columnsto be considered separately, as discussed in Sections3. 2 . 1 and 3 .2 . 2 respectively.

3.2.1 BeamsIn a semi-continuous braced frame, beams aredesigned for a lower sagging moment than in anequivalent simple frame. This is possible because theconnections allow hogging moments to be generatedat the beam supports. The weight and/or depth ofthe beams can therefore be reduced. The influenceof support moments on the required beam saggingmoment capacity is illustrated in Figure 3.1, whichshows moments for a beam that is:

(a) simply supported at both ends

(b) simply supported at one end and. . . Figure 3. 1 Applied moments and momentsemi-continuous at the other . .capacities for beams with different. . support conditions (UDL, a = 0.85)(c) semi-continuous at both ends.

- Simple\Column connection

Appliedmoment

M� jLa) Simply supported beam

SimpleconnectionI

Partial strengthconnection

M

Criticalsection (at mid span)

cx M 1L2 O.45MJ (approx)

b) Partial strength connectionat one end

Partial strengthconnection

aMc) Partial strength connection

at both ends

17

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Composite Connections

Figure 3.1 shows schematically how the free bendingmoment (w/2/8) is related to the moment capacitiesof the beam and connections for design. The benefitof semi-continuous construction in reducing thesagging moment that the beam must resist in a semi-continuous braced frame is evident. Despite thepresence of the reduction factor a, the saggingmoment is considerably reduced by the presence ofmoment resisting connections.

The beam sagging moment capacity should bedetermined using rules given in BS 5950: Part 3(5)However, a reduction factor a must be applied to themoment capacity of the beam in sagging whenconnections detailed in accordance with this guideare used. The reduction factor is needed in order tolimit the amount of plastic deformation that takesplace in the beam in sagging, and thereby limit therequired connection rotation1 . Although therequired reduction factor is a function of the loadarrangement, the grade of steel, and whether or notthe beam is propped during construction, a value of0.85 may be used for all cases. A less conservativevalue could be used in some cases, but a single valueis proposed for simplicity.

In addition to using a reduced effective beam momentcapacity, to further limit support rotationrequirements the connection moment capacity mustexceed 30% of the beam moment capacity insagging (this is achieved by all the standardconnections given in Section 6). A lower. limit onconnection strength is necessary because connectionrotation requirements decrease as the relativestrength of the connection increases, tendingtowards zero for a beam with ends that are fullybuilt-in.

A third requirement in order to ensure that requiredconnection rotations are not excessive is that thespan to depth ratios of beams must satisfy thefollowing limits15 (where D is the total depth of steelbeam plus slab):

. LID � 25 for beams subject to UDL, multiplepoint loads or a central point load

. LID � 20 for beams subject to two point loads(at third span points).

Combined connection and beam strengths that canbe achieved using the standard connection details arepresented in Table 3.1 . This table can be used at thescheme design stage to identify possible beam sizes,as illustrated by the following example. For a beamsubject to UDL, the free bending moment w12/8should be compared with values of MTMIN or MTMAX.As an example, consider the following parameters:

18

Total factored load = 45.6 kN/mFree bending moment is w1218 = 570 kNm

From Table 3.1, possible beams would include:356 x 1 7 1 x 45, 5275 (which can support amoment in the range 558 to 583 kNm)305 x 1 27 x 48, 5275 (531 to 595 kNm)254x 146x43, 5355 (558 to 606 kNm)

If the beam were simply supported, the free bendingmoment would be compared with M. Theshallowest simply supported composite beam thatcould satisfy the input parameters given above wouldbe a 356 x 1 71 x 67 (5275). Comparison of thisbeam size with the possible semi-continuoussolutions listed above clearly shows the benefits ofusing composite connections.

A recommended procedure for beam design issummarised in Figure 3.2. This flow chart is basedon the following assumptions:

preliminary studies have been carried out thatshow that composite connections are worthwhilefor the beam in question

• column orientations have been identified

preliminary column sizes are known

• the final choice of column size will depend on theconnection details that will be chosen.

Beam spanDead loadImposed loadLoaded width

10 m4 kN/m26 kN/m23m

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Frame Design

Table 3. 1 Combined beam and connection moment capacity ranges

SerialSize

S275 S355

BEAM0.85 M

BEAM + CONNECTION BEAM0.85 M

BEAM + CONNECTION

MTMIN MTMAXMTM,N MTMAX

533x210x122109101

9282

12001063980920822

15631423133812771176

22381939178016361445

15581383127711871036

21331954184617531599

25962438225820711784

457x191x9889827467

883796752677604

115110621017941866

16191444134811871050

11481036969875778

15101395132712311132

20561838167415261330

457x152x8274676052

716642596528449

983908860791

710

131611711047914449

932837769682580

1293119611251037932

1677148513451161984

406x178x74676054

650582519456

889819755690

1162985888780

839752671589

1078989907823

146512851130988

406x140x4639

384313

619313

647313

496405

731

637824660

356x171x6757

5145

550459406352

761668613558

978780697583

710593525453

921802732659

11741002880742

356x127x3933

299246

502246

502246

386319

589521

621319

305x165x544640

417353306

599533485

697599499

537456396

719636575

896734640

305x127x484237

349303265

531

484436

595528436

451390344

633571515

759615582

305x102x332825

236199168

393342168

399199168

306256217

469399217

469424217

254x146x433731

316269219

467418347

515448347

407348253

558497381

606527381

254x102x282522

195170144

316170144

216170144

251219186

372219186

372219186

M values are based on typical composite beam details, assuming a slab depth of 1 20 mm, andfull shear connectio&5

M-1-MIN is the sum of 0.85 M and the connection moment capacity with minimum reinforcementMTMAX is the sum of 0.85 M and the connection moment capacity with maximum reinforcement.

Note that maximum reinforcement limitations for a particular case may prohibit attainment ofthis value (see Section 4.2 Step IA)

minI

19

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(_ Start IIII::—'1 Use Table 3.1 to estimate beam and connectionrequirements

heck that fo.UDL, UD � 25,

2PL, UD � 20 No Revise beam size

PL, LID � 2

¶es

IRevise beam size

Are bare :dequateateam and connectio

Yes'V

ICheck construction loads on bare steel beam

Iand connections

Compare free moment and O.85M. to determineminimum connection moment resistance required

+I Detail suitable plastic connection I

I connectors) F connection using design tables(bolts, reinforcement and shear Choose a suitable standard

Yes

No Increase column size

j..

[lateaoeflectifelbea}J

Figure 3.2

.

Detailed

late imposed load defIecon of compose be6 �agreed limit'? No9________

Revise beam or

I—iconnection

Revise beam or

J_connection

Revise beam

quD0e5natur51Ch&vibration

No

Iculate natural frequency of the beam Yes 4

ency exceed excitation No

acceptable?frequency?

Yes

:iiiiiiiiiiiii: :Z ' , Yes

design procedure for a beam with composite connections in a semi-continuousbraced frame

20

IRevise beam size

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Frame Design

Lateral buckling adjacent to supportsWhen the steelwork connections are required totransfer moment at the construction stage, it may benecessary to check the stability of the bottom flangeunder the worst case loading of the wet weight ofconcrete on one span, which can cause hoggingmoment over a significant portion of the adjacentspan. The lateral stability of the steel beam shouldbe checked in accordance with BS 5950: Part 1 (6D,taking account of moment variation along the beam.The top flange may be assumed to be laterallyrestrained either by transverse beams or by the steeldecking, which must be properly fixed in position.

At the composite stage, lateral torsional buckling ofthe section is prevented in the sagging momentregion by attachment to the slab. In the negativemoment region, the compression flange cannotdisplace laterally without transverse bending of theweb. This is known as lateral distortional buckling.The critical parameter is the D/t ratio of the web; thehigher the ratio the greater the tendency for buckling.

EC410 offers a general design procedure, but forsections up to 550 mm deep (S275) or 400 mm deep(S355), it states that no checks are required on thestability of the lower flange provided certain loadingand detailing requirements are respected (EC4 Clause4.6.2). Additional guidance may be found inReference 1 7. For deeper beams, the designershould refer to procedures given in EC4 Annex E10,and consider an applied negative moment equal to theresistance of the connection.

In practice, for any depth of beam a check of lateralstability in the hogging moment region is only neededwhen connections possess a resistance in excess ofapproximately 80% of the moment capacity of thecomposite beam in hogging. The capacity tables inSection 6 highlight connections that may possess acapacity in excess of this limit. It should be notedhowever that in the interests of simplicity, thehighlighting is based on a comparison of theconnection moment capacity with that of a grade5275 beam. If a grade 5355 beam were used, therelative connection capacity would clearly decrease,below the 80% limit in some cases. The designershould calculate the beam capacity, for comparison,when necessary.

3.2.2 ColumnsThe moment capacity of a composite connection isgenerally low in comparison to that of the compositebeam in sagging. Because of this, when beams arepropped during construction, the composite

connection moment capacity is normally developedunder dead load alone when the props are removed.There is therefore no increase in support moments asimposed load is applied, the connection merelyrotates, and frame moments under pattern loading arethe same as when imposed load is present on allbeams. Column checks therefore need only beperformed for the 'all spans loaded' case. Forpropped construction, this means that internalcolumns need only be designed to resist momentsthat are due to differing connection strengths eitherside of a node. Moments due to eccentric beamreactions (acting at either the column face or the faceplus 1 00 mm nominal eccentricity, as considered insimple design to BS 5950: Part 1 ) need not be addedto the connection moment capacities. Beams shouldtherefore be considered as spanning between thecentrelines of the columns.

When unpropped construction is adopted, theconnections only act compositely under imposedload. Under dead load, only the moment capacity ofthe bare steel connection can be mobilised. Patternloading therefore gives rise to unbalanced momentson the column even when opposing compositeconnections of equal moment capacity are used.

The designer may conservatively assume that themagnitude of the unbalanced moment is equal to thedifference between the composite connectioncapacity on one side of the column and the bare steelcapacity on the other. The unbalanced momentshould be distributed between the column lengthsabove and below the node, in proportion to thestiffness f/IL) of each length. This procedure is as forBS 5950: Part 1 columns in simple construction.

For a less conservative calculation of columnmoments with unpropped construction, the designershould redistribute the unbalanced beam endmoments considering an elastic sub-frame, asproposed in BS 5950: Part 1 Clause 5.6.4. Theelastic beam stiffness is a function of the compositebeam properties in both hogging and sagging. Aglobal value equal to 1 .8 times the second moment ofarea of the bare steel section (which can be obtainedfrom standard section tables) which may beconservatively adopted. Connection stiffness neednot be incorporated into the sub-frame model becausethe connections are 'rigid' in their composite state.The moments that can be distributed to the beamsare, however, limited by the composite connectionmoment capacities. Any excess beam moments thatare predicted by an elastic sub-frame distributionshould be reallocated to the column.

21

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Composite Connections

When choosing column effective lengths, thedesigner must assess the degree of restraint that willbe offered by beams, column continuity, and/or basedetails. Appropriate general procedures are given inAppendix E of BS 5950: Part 1 (6 Althoughcomposite connections satisfying the detailingrequirements given in this guide have an initialstiffness that is at least as great as that ofconventional 'rigid' steel connections, the rotationalrestraint provided by some beams may only becomparable to that of a simply supported beam(because of plastic hinge formation at relatively lowlevels of load). The designer should pay particularattention to minor axis connections, which willnormally be relatively flexible, and minor axisconditions will often dictate column size.

Further guidance on the choice of column effectivelengths may be found in Reference 18.

3.3 SERVICEABILITY LIMIT STATE

Elastic analysis must be used to check framebehaviour under serviceability loading.

For checks on imposed load deflections, which shouldbe based on the initial stiffness of the connections,any composite connection complying with thedetailing rules given in this guide may be assumed tobe 'rigid' when used in a braced frame. Thisassumption is based on experimental evidence. Fullcontinuity between the frame members can thereforebe assumed.

Alternatively, the composite beams may be assumedto be continuous over 'knife-edge' supports;procedures given in BS 5950: Part 3 clause 6.1 •3(5)should then be used to calculate imposed loaddeflections. Support moments must be limited to themoment capacity of the connections. Simplifiedprocedures for modelling the influence of patternloading and shakedown are included in the Code.

If it is necessary to check total load deflections, forexample to avoid excess ponding of the concreteduring construction for an unpropped beam, it shouldbe noted that the dead load deflection will depend onthe stiffness of the connections at the stage whendead load is applied to the beam. This variesaccording to the steelwork detailing and constructionprocedure. When beams are unpropped, dead loaddeflections are a function of the bare steel connectionproperties. Guidance on the calculation of deflectionsin the bare steel state may be found in Reference 19.

22

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4 "STEP BY STEP" DESIGN PROCEDURES

4.1 INTRODUCTION

This Section presents design procedures forcomposite connections subject to hogging moments(with the reinforced slab in tension). Compositeconnections subject to sagging moments, as mayoccur in some unbraced frames when wind loads arerelatively high, behave in a different way. They arenot covered by this publication as there is currentlyinsufficient information available to develop a designmodel. The following design procedures are thereforeonly applicable to composite connections in bracedframes.

The procedures are not advocated for routine handcalculations. They are intended:

. as a source of reference,

. for use in writing software,

. for use in checking output from software,

S for spreadsheet implementation.

The procedures were used to calculate momentcapacities for a range of standard beam-to-columndetails, and these are presented in Design Tables inAppendix B.

The reader who is familiar with Joints in steelconstruction: moment connections4 will note thatthe procedures for the steelwork componentresistances are essentially unchanged. Moreexplanation of some of these procedures may befound in Reference 4.

4.2 BEAM-TO-COLUMN CONNECTIONS

The procedures that follow are suitable for beam-to-column connections using flush end plates. Althoughall the checks are needed for (major axis) connectionsto column flanges, the following steps are notrelevant for (minor axis) connections to column webs:

. Step 1 B - column flange bending

. Step 1 C - column web tension

S Step 2A - column web compression

. Step 3 £ column panel shear

. Step 6 - design of stiffeners

Alternative checks for major and minor axisconnections are given in Step 5.

Opposing beams connecting into a column webshould be treated as semi-continuous over a 'knifeedge' support, with the presence of the column webassumed to have no influence on beam behaviour.However, beams must be of similar depth to achievecontinuity, because the webs of typical columns donot have sufficient stiffness and strength to transfer'eccentric' compression forces. It is recommendedthat opposing beams are of the same serial size.Similar consideration must be given to beam-to-beamconnections.

The sequence of design checks is presented in theform of a flow chart in Figure 4.2, and the zonesconsidered in the steps are illustrated in Figure 4. 1.A worksheet is included in Step 1 so that the processof calculating the reinforcement and bolt row forcescan be set down in tabular form (see page 42).

A worked example illustrating the design of aconnection using these procedures is given inAppendix A.

ShearzoneSTEP 3

Figure 4. 1 Check zones for a composite endplate beam-to-column connection

23

Compression zoneSTEP 2

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Composite Connections

ISTART

ISettrial configuration

1STEP 0 (Optional)

Calculate the moment capacity at theconstruction stage (bare steel)

STEP ICalculate the resistances of the

reinforcement and bolt rows in tension

STEP 2Calculate the resistance in the

compression zone

STEP 3Calculate the resistance of the column Stiffen the connection, add more bolt

web panel in shear rows, add more reinforcement, etc.

STEP 4Adjust the resistances from STEP 1 to

Vensure equilibrium. Calculate the

moment capacity, M

Yes

STEP 5Design for vertical shear forces

STEP 6Design the stiffeners

STEP 7Design the welds

END

Figure 4.2 Flow diagram - connection design checks

24

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Beam-to-Column Connections

CALCULATION OF MOMENT CAPACITY - CONSTRUCTION STAGE

It is important that the designer considers the baresteel performance under construction loading as partof the composite beam design. Indeed, a compositebeam cannot be said to have been properly designedif the construction stage has not been considered.

If the moment capacity of the bare steel connectionis needed for the construction stage checks, itshould be calculated using the procedures given inSection 2 of Reference 4.

F —*

Fr2Fr3

Figure 4.3 Momentconnection

resisting bare steel

25

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Composite Connections

STEP 1 POTENTIAL RESISTANCES OF REINFORCEMENT AND BOLTROWS IN THE TENSION ZONE

The resistances of the tension components that arecalculated first are only potential values. It may benecessary to reduce them in Step 4 in order toachieve equilibrium depending on the resistance ofthe connection compression components.

Reinforcement

The potential resistance of the reinforcement islimited by yielding of the bars, and by limitations onthe minimum and maximum area of reinforcementthat can be used. Details are given in Step I A.

Bolts

The potential resistance of each row of bolts in thetension zone is limited by bending in the end plate orcolumn flange, bolt failure, or tension failure in thebeam or column web.

The values 'cr1' r2' 'r3' etc. are calculated in turnstarting at the top row 1 and working down.Priority for load is given to row 1 and then row 2and so on. At every stage, bolts below the currentrow are ignored.

Each bolt row is checked first in isolation and thenin combination with successive rows above it, i.e.:

'r1 = (resistance of row 1 alone)

= Mm. of:resistance of row 2 alone(resistance of rows 2 + 1 ) -

'r3 = Mm. of:resistance of row 3 alone(resistance of rows 3 + 2) - r2(resistance of rows 3 + 2 + 1 ) - r2 r1

and in a similar manner for subsequent rows.

For each of these checks, the resistance of a boltrow or a group of bolt rows is taken as the least ofthe following four values:

. Column flange bending/bolt yielding (Step 1 B)

. End plate bending/bolt yielding (Step 1 B)

. Column web tension (Step 1 C)

. Beam web tension (Step 1 C)

In addition, the resistance of any bolt row may belimited by the connection's inability to achieve aplastic bolt force distribution without premature boltfailure. This additional check, and the requiredmodification to the distribution, is given in STEP 1 D.

:;; : ;:i.1:

Figure 4.4 Potential resistance of reinforcementand bolt rows

ri

*—Pr2jr3)M

26

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STEP 1A 'REINFORCEMENT YIELDING

Beam-to-Column Connections

Potential resistance

The potential resistance of the reinforcement intension is given by:

einf = j 4einfYm

f = design yield strength of reinforcement

Areinf area of reinforcement within the effectivewidth of slab for the connection (seeFigure 4.6 and Section 5).

Ym partial safety factor for reinforcement(taken as 1 .05)

Detailing rules for the reinforcement are given inSection 5.

Minimum area of reinforcement

In general, the rotation capacity of a connectionincreases as the area of reinforcement increases.This is because the level of strain at which thereinforcement fails, allowing for tension stiffening,increase&15. A minimum area is therefore neededto ensure that 'compact' connections can undergosufficient rotation to strain the reinforcement toyield (as is assumed in the moment capacity model).Minimum areas of reinforcement that should beprovided in a 'compact' or 'plastic' compositeconnection are given in Table 4. 1 as a function of:

. beam size

. beam steel grade

. reinforcement properties

. connection type - 'compact' or 'plastic'

The minimum reinforcement limits in Table 4.1 aremore onerous for 'plastic' connections, because inaddition to the need for yielding of thereinforcement, the connection must have sufficientrotation capacity to behave as a plastic hinge.

In Table 4.1 the minimum values, marked '5%',should normally be used. These values areappropriate for high yield bars complying withcurrent British Standard BS 4449,grade 46OB20.

This grade of reinforcement has a mandatoryrequirement of 1 4% minimum elongation at fracture,and a non-mandatory requirement of 5% minimumelongation at maximum force. Grade B500B barscomplying with BS EN 10080(21) are required to

(1 . 1 ) have similar properties; they must be able to achieve5% total elongation at maximum force. Elongationat fracture and total elongation at maximum forceare illustrated in Figure 4.5.

Minimum reinforcement areas are also given inTable 4. '1 for connections that use reinforcementwhich is capable of achieving 10% minimumelongation at maximum force. The increasedreinforcement ductility offers considerableadvantages in some cases, because it permits theuse of less reinforcement.

It is essential that when a design is based on theuse of 1 0% elongation bars this is made clear in theproject specification. This can be done by giving thebars an 'X' designation, rather than the 'T' generallyused for high tensile bar&22. The 'X' informs thecontractor that the bars need specific, non-standardproperties. It is recommended that, if possible, thereinforcement supplier uses coloured labels to clearlydistinguish the high elongation 'X' bars on site. Incase of doubt concerning the elongation capacity ofbars, approximately half the UK manufacturersprovide reinforcement suppliers with appropriate testinformation. It should therefore be relatively easyfor the contractor to confirm suitability with hisreinforcement supplier.

Bars that are currently produced in the UK using ahot forming process may be assumed to beappropriate for use with the '10%' limits. All20 mm diameter bars produced by majormanufacturers in the UK currently are hot formed,as are, often, 1 6 mm bars.

27

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Composite Connections

STEP 1A REINFORCEMENT YIELDING (continued)

Cl)Cl)

a)

___________ StrainTotal elongation at Minimum elongation

maximum force at fracture(� 5% for BBOOB to ( according to

DD ENV 10080) BS 4449)

Figure 4.5 Elongation limits for reinforcement

Table 4. 1 Minimum area of reinforcement - 'compact' and 'plastic' connections

Type Steel Rebar

ElongationLimit

Beam Depth (mm)

203 254 305 356 406 457 533 610

Compact 5275 5% 500 500 500 500 500 600 750 1150

10% 500 500 500 500 500 550 650 800

5355 5% 500 500 500 500 500 600 750 1150

10% 500 500 500 500 500 550 650 800

Plastic 52755%:'H

500 500 500 650 1100 1450 1800 3000

10% 560 500 500 500 500 600 750 1150

5T355 5% 500 500 600 1400 2100 3100 - -

10% 500 500 500 500 650 900 2000 2850

Note: A dash (-) in the table indicates that excessive reinforcement is required, options are nottherefore practical

28

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STEP 1A REINFORCEMENT YIELDING (continued)

Maximum area of reinforcement where:

Beam-to-Column Connections

The reinforcement area must also be limited to amaximum value in order to:

S prevent local concrete crushing failure underunbalanced loading

. keep the compression zone in the lower half ofthe steel beam.

The reasons for these limits are discussed below.

To consider potential concrete crushing failure, atruss model has been developed to represent howdouble sided composite connections behave whenthe applied moments on either side are unequal8.Figure 4.6 illustrates the components in the truss,showing that the connection resistance relies on theability of the concrete to bear against the column onthe low moment side. The net force in thereinforcement is therefore limited by the strengthand area of concrete in bearing. An enhancementfactor may be applied to the concrete strengthbecause of its confinement23.

111111 1

N

-it111111

Effective truss members formed by::11= longitudinal reinforcement= transverse reinforcement

— concrete

Figure 4.6 Truss model for connectionbehaviour under unbalanced moment

According to the truss model, the area oflongitudinal reinforcement must not exceed:

A � 0.6 bc O' (1.2)!L fy

bc width of column

d5 = depth of slab above decking

Ccu cube strength of concrete

f = yield strength of the rebar

Ii 5 a function of the difference in applied moments,and beam depths, either side of the node:

12=1_Mt0 'r1 (1.3)Mhigh hr2

M,0 = the smaller applied moment (may betaken as the smaller connectionmoment capacity when 'plastic'connections are used)

Mhigh = the larger applied moment (may betaken as the larger connection momentcapacity when 'plastic' connectionsare used)

hri = reinforcement lever arm on the highmoment side

hr2 = reinforcement lever arm on the lowmoment side

In general, unbalanced moments will not beexcessive in braced frames, so maximumreinforcement area limitations should not berestrictive. In a symmetric situation p is zero,meaning that there is no upper limit onreinforcement area implied by this model.

Transverse reinforcement acts as a tension memberin the truss model (see Figure 4.6). The area oftransverse reinforcement must satisfy the followinglimit:

where:

Fleft /

I 11

_____________Fright /2

Effective width of slab(see Section 5 fordefinition)

Fright /2Fleft /

Fright > F left

0.35 LALAT �I e-1-— - 0.3eL

(1.4)

29

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Composite Connections

STEP 1A REINFORCEMENT YIELDING (continued)

where:

eL 2.Ob (this is the outer limit of thelongitudinal reinforcement from thecolumn centre line)

eT z 3.Ob

eL and eT are identified in Figure 5.1.

It is assumed that the longitudinal and transversereinforcing bars have the same nominal yieldstrength. When 'plastic' connections are used, thetransverse reinforcement area will only beapproximately one tenth of the longitudinalreinforcement area, and BS 81 10(11) minimumpercentage limits may govern the area of transversereinforcement.

In theory, the length of transverse reinforcementmust be limited so that, whilst sufficient anchorageis provided for the bars to act in the truss, they donot affect the behaviour of the 'transverse beamconnections'. In practice, this should not be critical.Detailing rules are given in Section 5.

To ensure adequate strain in the reinforcement,compression must be restricted to the lower half ofthe steel beam (i.e. the plastic neutral axis must notbe higher than the mid-depth of the web).

Another possible reason for limiting thereinforcement area is to avoid the need for columncompression stiffeners. For information, Table 4.2indicates maximum values of reinforcement areathat can be used, in combination with differentnumbers of tension bolts, before columncompression stiffeners become necessary. Valuesare given for column sizes generally used in building,considering both S275 and 5355 steel. The limitsare based on the application of design Step 2A.This table may be used to assess the relativeeconomics of different options, remembering thatcolumn stiffening is expensive.

30

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Beam-to-Column Connections

Table 4.2 (a) Maximum areas of reinforcement that can be adopted withoutcolumn compression stiffening, S275 columns

Columnserial size

Allowable area of reinforcement (mm2)

1 row M20 2 rows M20 1 row M24-

2 rows M24

356x368x202 2160 1851 1936 1413

356x368x177 1664 1356 1440 918

356x368x153 1271 963 1048 525

356x368x129 906 598 683 160

305x305x198 2783 2474 2559 2036

305x305x158 1897 1589 1673 1150

305x305x137 1477 1169 1253 730

305x305x118 1105 797 881 358

305x305x97 788 479 564 41

254x254x167 2659 2351 2436 1913

254x254x132 1783 1475 1559 1036

254x254x107 1223 915 1000 477

254x254x89 797 488 573 50

254x254x73 520 212 297 0

203x203x86 1125 817 902 379

203x203x71 694 386 470 0

203x203x60 530 221 306 0

203x203x52 347 39 123 0

203x203x46 240 0 16 0

Note: 4x1 6 mm bars = 804 mm26x16 mm bars = 1210 mm28x16 mm bars = 1610 mm210x16 mm bars = 2010 mm2

4x20 mm bars = 1 260 mm26x20 mm bars = 1890 mm28x02 mm bars = 2510 mm210x20 mm bars = 3140 mm2

Values are based on Vm 1 .05 and sk 460 N/mm2

31

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Composite Connections

Table 4.2 (b) Maximum areas of reinforcement that can be adopted withoutcolumn compression stiffening, S355 columns

Columnserial size

Allowable area of reinforcement (mm2)—____________

I row M20 2 rows M20 I row M24 2 rows M24

356x368x202 2926 2618 2703 2180

356x368x177 2287 1979 2063 1541

356x368x153 1780 1472 1557 1034

356x368x129 1324 1016 1100 578

305x305x198 3730 3422 3506 2983

305x305x158 2586 2278 2363 1840

305x305x137 2045 1737 1822 1299

305x305x118 1564 1255 1340 817

305x305x97 1153 845 929 406

254x254x167 3570 3262 3346 2824

254x254x132 2440 2132 2216 1694

254x254x107 1717 1408 1493 970

254x254x89 1180 872 956 434

254x254x73 —810 502 587 64

203x203x86 1591 1283 1367 845

203x203x71 1045 737 822 299

203x203x60 822 514 598 75

203x203x52 584 276 361 0

203x203x46 447 139 224 0

Note: 4x16 mm bars = 804 mm26x16 mm bars = 1210 mm28x16 mm bars = 1610 mm210x16 mm bars = 2010 mm2

4x20 mm bars = 1260 mm26x20 mm bars = 1890 mm28x02 mm bars = 2510 mm210x20 mm bars = 3140 mm2

Values are based on Ym 1 .05 and sk 460 N/mm2

32

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Beam-to-Column Connections

STEP 1 B END PLATE OR COLUMN FLANGE BENDING AND/OR BOLTYIELDING

This check is carried out separately for the columnflange and the end plate.

The potential resistance in tension of the columnflange or end plate, r ' is taken as the minimumvalue obtained from the three Equations (1.5), (1.6)and (L7), below.

when mode 1 governs, connection behaviour isalways ductile,

. when mode 2 governs, connection ductilityshould be demonstrated by testing,

. when mode 3 governs, connection behaviour isalways non-ductile. where:

r potential resistance of the bolt row, or boltgroup

(1.5) p, = enhanced bolt tension capacity where pryingis taken into account (see Table 4.3)

Pt, = total tension capacity for all the bolts in thegroup

M = plastic moment capacity of the equivalentT-stub representing the column flange orend plate

= LeffXt2XPy (1.8)4

Leff effective length of yield line in equivalentT-stub (see Tables 4.4, 4.5 and 4.6).

t = column flange or end plate thickness

py = design strength of column/end plate

m = distance from bolt centre to 20% distanceinto column root or end plate weld (seeFigure 4.8)

n = effective edge distance (see Figure 4.8)

Mode 3 Bolt failure

Lo't (1.7)

Note that:.

-* Pt'

N

P = ____

Mode I Complete flange or end plate yielding

Prying force, Q

Pr/2 + Q

Pr/2 + QPrying force, Q

Mode 2 Bolt failure with flange/end plate yielding

(1.6)

Prying force, Q

Pt'

Pt'

Prying force, Q

r 2M+n(P')m + n

Pr

33

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Composite Connections

STEP 1 B (continued)

Table 4.3 Tensile capacity of a single 8.8 bolt

Bolt Size BS 5950:Part 1 : P

Enhanced value:

P'

M20M24M30

(450 N/mm2)

llOkN159kN252kN

(560 N/mm2)

137kN198kN314kN

Notes

1 450 N/mm2 is the tension strength of boltaccording to BS 59590: Part 1

2 560 N/mm2 is the enhanced tension strengththat may be used when prying action isconsidered explicitly (see Reference 4)

• :

Backing Plates

For small section columns with thin flanges, loosebacking plates can increase the resistance of thecolumn flange by preventing a Mode 1 bendingfailure of the flange. Design rules for backing platesare given in Step 6B.

Stiffeners

For end plate or column flange bending, bolt groupsmust be considered separately between stiffeners orthe beam flange, as shown in Figure 4.7. The yieldpattern of any bolt row below a stiffener (or flange)

thethe

cannot combine with any row(s) above

stiffener/flange on the side wherestiffener/flange is.

Figure 4.7 Influence of stiffeners

34

Column fIcombinati

-ngens

-}-} Ji

, End platecombinations

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Table 4.4 1eff for equivalent T-stubs for bolt row acting alone

Beam-to-Column Connections

Pair of bolts separated by a web in a column flange or end plate

__

. Table 4.5 shows which of the above expressions have to be considered.

. Table 4.6 shows which parts of the above expressions have to be combined when bolt rows act asa group.

. Dimensions m, e, e are shown in Figure 4.8.

. The value of a is determined from the chart in Figure 4.9.

. Leff 5 the length of the equivalent T-stub, not the length of the pattern shown.

35

Pattern (i)Circular yielding

Leff 2Em

Pattern (ii)Side yielding

Leff 4 m +1.25e

Pattern (iii)Side yieldingnear beamflange or astiffener

Leff _ am1

Pattern (iv)Side yieldingbetween two

stiff eners

Leff am1 +a'm1 - (4m1 +

1.25e)(a is calculated

using m2a' is calculated

using m2L)

ext Pattern (v)Corner yielding

Leff 2m +O.625e +

Notes:

Pattern (vi)Corner yieldingnear a stiffener

Leff am1 -(2m1 +

O.625e) + e

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Composite Connections

Table 4.5 1eff to be considered for a bolt row acting alone (expressions to be used fromTable 4.4)

Bolt row notinfluenced by a

stiffener or a freeend

Use: Mm {ii,i}

Bolt row next to astiffener

Use: Min{Max{ii,iii},l}

Bolt. row below thebeam flange

If g > O.7Bb or Tb< O.8tUse:

I I(÷..1 .1II tJ

otherwiseUse:

Min{Max{ii,iii}, l}(this is an interim

rule)

Bolt row betweenfree end and

stiffeners

Use:

Min{Max{v,vi},Max{ii,iii},I}

Bolt row betweenstiffeners

Use: Min{Max{iv, iii(m2), iii(m2L), ii},l}(m2 and m2 are as

Bolt row next to afree end

Use: Mm {v, ii, I)

Notes:. Effective length expressions are given in Table 4.4.. Any other bolts, above or below are ignored when considering a single bolt row.. The expressions signified by the pattern numbers determine the effective length to be used. They

take account of any benefit due to the proximity of a stiffener or adverse effect due to a free end.. Min{Max{ii,iii},l} means: firstly determine a maximum from patterns (ii) and (iii), then take the

minimum of this result and pattern (il), e.g. if patterns (il), (ii) and (iii) gave lengths of 300 mm,200 rhm, 100 mm respectively, then the result would be 200 mm.

36

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Beam-to-Column Connections

37

Top or bottomrow of a group

next to astiffener

Use:Iii (... iñl p

Max—,i iii——12 2)j 2

Top or bottomrow of a groupnext to a free

edgeUse:I iii pMIne,—÷—2J 2

Table 4.6 Leff to be considered for bolt rows acting in combination (expressions to be usedfrom Table 4.4)

Top or bottomrow of a group

i Ialonga clear

P1

-;-p

-.4-i

-$-I

Intermediaterowofagroup

Use:p

—--

-'-Bolt row of agroup below

the beam flangeIf g > O.7Bb or

Tb < O.8tUse:

MaxLL,l+22 2J 2otherwise

Use:

MaxT,(iii_!!.)l+2.2)j 2 sIp

Typical Examples

Group of three rows in a clear length Group of three rows in a flush end plateLeff pattern (ii) + 2p where Tb < O.8t

:. Leff fo group = 4 m + 1 .25e + 2p Leff Max of: i!+!L÷2 or22 22? ..Leff for group = Max of: 4m + 1 .25e + 2p

or O.5am1 + 2m + 0.625 + 2p

Notes:. Effective length expressions for individual rows are given in Table 4.4.. The total effective length of the equivalent T-stub for a group of bolts is the sum of the

effective lengths for each row, as given above.

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Composite Connections

CONNECTION GEOMETRY

HF.

.

: ..LL_r

T' . ,. U , . .. .

.' : •::'': .' :: : :— Row

— Row3

m =2 2

e =P g22For the column flange:

m = ---O.8r (1.11)22e 22The effective edge distance, dimension in' used inthe Mode 2 formula, is taken as:

for an end plate, the minimum of

S 'e' for the column flange

. 'e' for the end plate

. 1 .25 m for the end plate

for a column flange, the minimum of:

S 'e' for the column flange(1.9) . 'e' for the end plate

. 1 .25 m for the column flange.

—i

11i2- ____p2_3 b

<Column side Beam side

Figure 4.8 Connection geometry

For the end plate:

Section A-A

(1.10)

where:

g = horizontal distance between boltcentrelines (gauge)

b = end plate width

(1. 12) B = column flange width

tb beam web thickness

tc = column web thickness

sww = leg length of fillet weld to beam web

Swf leg length of fillet weld to beam flange.

Note: Dimensions m, n and e, though usedwithout subscripts, commonly differbetween column and beam sides.

38

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Beam-to-Column Connections

a CHART

27t 5.5 4.756 5 4.5

0.4 0.5 0.6 0.7 0.8 0.9>1

,% 1

-4-

--4.-.

4:1

Minimum value ofa= 4.45

( 4.5

- ii 5.5

Note: Mathematical expressions for a are given in Reference 4

Figure 4.9 Values of a for bolt rows adjacent to a stiffener or beam flange

39

1.4

4.45

21

1.3

1.2

1.1

1.0

0.9

0.8

0.7

0.6

0.5

0.4

0.3

0.2

0.1

0

\ \\\\

0 0.1 0.2 0.3

m2

if)1Ili =m+e

m2'2 m1 e

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Composite Connections

STEP 1C WEB TENSION IN BEAM OR COLUMN

Note: Web tension failure is non-ductile andtherefore must not be allowed to govern themoment capacity of a 'plastic' connection.

General

This check is carried out separately for both thebeam web and the column web. The potentialresistance in tension of a web, for a row or agroup of bolts, is taken as:

Pt = Lxtxp (1.13)

where:

Stiffeners

Web tension will not govern for any row orgroup of bolts where stiffeners are presentwithin the tensile length, L.

L = effective length of web assuming amaximum spread at 600 from the bolts tothe centre of the web (Figure 4.10)

thickness of the web

design strength of the steel in the columnor beam

tw

pv

L

Note: Only two examples of web tension checks are illustrated.of rows must be considered.

Figure 4. 1 0 Typical web tension checks

Each row and combination

40

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Beam-to-Column Connections

STEP 1 D MODIFICATION OF BOLT ROW RESISTANCES

The method given in Steps 1 A, 1 B and 1 C fordetermining potential resistances in the tensionzone is based on a plastic distribution ofreinforcement and bolt forces. This distribution isonly appropriate when sufficient deformation cantake place to plastify the end plate or columnflange adjacent to the bolts, and yield thereinforcement.

To ensure sufficient end plate/column flangedeformation at working values of rotation, a boltrow must be at least 200 mm above the plasticneutral axis (top of compression zone). The limitof 200 mm is derived from test results. Becausethe position of the plastic neutral axis is calculatedlater, in Step 2B, iteration may be required toestablish appropriate bolt row resistances. Theworked example (Appendix A) demonstrates howthe procedure operates in practice.

For bolt rows that are less than 200 mm abovethe neutral axis (but still in tension), a triangularlimit must be imposed to establish the resistance.For example, the resistance of a row 1 50 mmfrom the neutral axis would only be three quartersof the full potential resistance (see Figure 4. 1 1).

The detailing requirements given in Section 5 mustalso be respected to validate the use of the fullbolt row resistance. Readers familiar withReference 4 may be interested to note thatsatisfying these detailing requirements makes anexplicit check of Step 1 C in that publicationunnecessary.

If.

:2:oo-;nII

.

Neutral2

Dislocation representsslip at steel/concreteinterface

Strain requiredto produce fullbolt force

—-- 15Omm

Figure 4. 1 1 Triangular limit to bolt forces

41

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Composite Connections

STEP 1 WORKSHEET: TENSION ZONE

PotentialResistance

From Step 1A

42

RowStep

Column

I B Flange

Side

Step I C Web

Beam Side

Step 1 B Step 1 C Web

Bending Tension Plate Bending Tension

Reinforcement

Step 1DModify bolt

forces

reinfI Ii I

Row 1least of6 gives

boxes 2 to

I 141 I 151 I 161 'cr1 1 171

Row 2 a/one

I 1101 I liii least of boxes:

rows (1 +2) combined: 8 to 1 1 andrr rrii hAl I IiiI i i I I iLLJ 1 6 to 20 gives

I 1181 I li1 I 1201 Pr21 1211

row 3 a/one

I 1241 I 251

cornbinedrows (2+ 3)

1T"1I p28,

rri29iL___J__J

I 1321 I 1331least of boxes

. combined rows (1 + 2 + 3):22 to 25 and

i"Tiboxes 6 & 20:

1T1L___J..__J

° to 33 and

38 to 42 gives

I 1401 I 141 I I 1421 '°r3I43l

See the worked example using the worksheet in Appendix A

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Note

Column Web Crushing (Bearing)

= (b1 + n2) x t x p

where:

b1 = stiff bearing length based on a 45°dispersion through the end plate from theedge of the welds

n2 length obtained by a 1 :2.5 dispersionthrough the column flange and root radius

tc = column web thicknessPVC = design strength of the columntp = end plate thicknessT = column flange thicknessr = column root radius

Column Web Buckling

The area of web providing resistance to bucklingis calculated assuming a web length as shown inFigure 4.13 (BS 5950: Part 1: Cl 4.5.2.1).

where:

Note: b1, n1, n2 must be reduced if:

the end plate projection is insufficient forfull dispersal

. the column projection is insufficient for fulldispersal

Beam-to-Column Connections

STEP 2A COMPRESSION CHECK - COLUMNRESISTANCE OF THE COLUMN WEB IN THE COMPRESSION ZONE

The resistance in compression of the column webmay be governed by bearing or buckling. Checksfor both cases are given below.

For the resistance of stiffened columns, referenceshould be made to Step 6A.

Column web crushing (bearing) and buckling areboth non-ductile failure mechanisms, which cannottherefore be allowed to govern the momentcapacity of a 'plastic' connection.

The area of web providing resistance to crushingis calculated assuming a force dispersion length asshown in Figure 4.12 (BS 5950: Part 1: Cl 4.5.3).

(b

Figure 4.13

(b1+

Length for web buckling

.i P

Tb

Figure 4. 1 2 Force dispersioncrushing

PC = (b1 + n1) x t x p (1. 15)

b1 = stiff bearing length as abovenl = length obtained by a 45° dispersion

through half the depth of the column,which is equal to the column depth (Do)

tc = column web thicknessPC = compressive strength of the column web

from BS 5950: Part 1 Table 27(c) withA = 2.5d/t

for web d depth of web between fillets

The above expression assumes that the column(1. 14) flanges are laterally restrained relative to one

another (BS 5950: Part 1 Clause 4.5.2.1 .). If thisis not the case, reference should be made toBS 5950: Part 1 Clause 4.5.1.5 and 4.5.2.1.

43

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Composite Connections

STEP 2B COMPRESSION CHECK - BEAMRESISTANCE OF THE BEAM FLANGE AND WEB IN THE COMPRESSION ZONE

Beam Flange Crushing (Bearing)

Pyb = design strength of the beamk Bb>

Tb the beam flange thickness

8b the beam flange breadth (with dueconsideration of any notching)

Figure 4.14 Compression in beam flangeonly

The centre of compression is taken as the mid-depth of the beam compression flange, as shownin Figure 4. 1 4. This accords with the behaviour ofconnections under test24.

Allowing the flange-only compression stress toexceed the yield stress by 40% is justified by twolocalised effects; strain-hardening and dispersioninto the web at the root of the section. Typically(for UB sections) each of these effects willaccount for around 20% 'overstress', so that aneffective 1 4Pyb can be taken when the flange areais assumed to act alon&4. This value should onlybe used when flanges are either Class 1 (plastic)or 2 (compact).

When the compression capacity of the flangealone is exceeded, as it often will be due to thepresence of significant reinforcement, a L shapedcompression zone should be considered, extendingsome distance up the web (see Figure 4.1 5).

Note that:

. The stress in this section must be limited to1 .2p. since the contribution of the web is nowbeing taken into account explicitly. Flangesshould be either Class 1 (plastic) or 2(compact).

. The centre of compression is redefined as thecentroid of the section, and the leverarms tothe bolts and reinforcement are reducedaccordingly.

J\ bk Bb

Figure 4. 1 5 Compression in beam flangeand portion of web

. An iterative calculation process will becomenecessary if the height of the neutral axis issuch that bolt resistances need modifying(Step 1 D). The worked example(Appendix A) demonstrates how theprocedure operates in practice.

Because compression in the beam extends into theweb, and a limiting stress of 1 .2p assumesplastification to take place, the web should beClass 1 (plastic) or 2 (compact). Becauseconnection detailing rules limit the depth ofcompression to the lower half of the beam, allpractical rolled sections effectively satisfy thisrestriction. If fabricated sections with a Class 3(semi-compact) web are used, they may be treatedas Class 2 by ignoring part of the web. Theeffective section should be defined by consideringa depth of web equal to 1 9te adjacent to both thecompression flange and the neutral axis (where tis the web thickness and e =

As a first check, the potential resistance of theflange in compression is taken as:

PC = 1.4XpybXTbXBb (1.16)

where:PC-)

44

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The resistance of an unstiffened column web panelin shear is:

Pv = O.6xpxtxDwhere

PVC = design strength of the column

tc = column web thicknessD = column section depth

The resultant panel shear from connections to bothcolumn flanges must be taken into account

For a two-sided connection with balanced(1. 1 7) moments, the shear is zero, but in the case of a

connection with unbalanced moments the shear isthe difference between the two opposing forces.

The resistance of stiffened columns can bedetermined by reference to Step 6D.

Beam-to-Column Connections

STEP 3 DESIGN FOR COLUMN PANEL SHEARRESISTANCE OF THE COLUMN WEB PANEL IN SHEAR

when checking the web, as shown in Figure 4.16.

F =C2-C1

Figure 4. 1 6 Web panel subject to shear force

45

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Composite Connections

STEP 4 CALCULATION OF MOMENT CAPACITY

Force Distribution

The reinforcement and bolt row resistancescalculated in Step 1 can only be fully realised ifsufficient compression zone resistance is available(Step 2). They are therefore 'potential' resistances,and must be reduced if necessary to ensureequilibrium. Figure 4.1 7 shows the transition frompotential resistances (P) into actual forces (F).

To maintain equilibrium, the sum of the tensileforces must satisfy the following equation:

einf + N =

where N is the axial load in the beam(positive for compression)

and F is the smallest of the following:

einf Pj + N (1. 19)

or ,° (column web crushing (bearing)). Notethat this is an unacceptable failuremechanism for a 'plastic' connection, andmust not govern moment capacity in suchcases.

or P (column web buckling). Note that this isan unacceptable failure mechanism for a'plastic' connection, and must not governmoment capacity in such cases.

If the first of these conditions limits the actualtensile forces it means that the full 'potential'resistances can be mobilised. If one of the latterthree conditions governs, it means that the full'potential' resistances cannot be achieved becauseof compression limitations.

If there is an excess potential resistance in thereinforcement or bolts in tension, then the forcesshould be reduced. Reduction should start withthe bottom row of bolts and work up progressivelyuntil equilibrium is achieved between the tensionand compression forces.

For the reinforcement: Frejflf � reinf

For each bolt row: Frj� ri

where:

reinf = potential resistance of reinforcement

ri = potential resistance of bolt row i

Freinf = final force in reinforcement

Fri = final force in bolt row i

Column web panel shear requirements must alsobe satisfied (see Step 3).

(1.18)

or '° (beam crushing (bearing))

F reinf. . •tireinf. .

Fri h1Fr2 *

h2Fr3

h3

F — — -

46

Figure 4. 1 7 Translation of potential resistances into allowable forces

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Beam-to-Column Connections

STEP 4 CALCULATION OF MOMENT CAPACITY (Continued)

Moment Capacity'

Assuming that there is no significant axial load inthe beam, the basic moment capacity of theconnection is given by:

M = 'einf X hrejflf + (Fri X h1) (1.20)

where:hreinf = distance from the centre of

compression to the reinforcementh = distance from the centre of

compression to bolt row I.

Moment Capacity Modified by Axial Load

The presence of significant axial load must beallowed for when checking equilibrium betweenthe tension and compression forces(Equation 1 . 1 8). For simplicity in the connectiondesign, it is assumed that the axial force acts atthe centre of compression in the beam. However,this shift in the line of action of the force, from the(composite) beam neutral axis, means that thecoincident moment that is considered to be appliedto the connection should be reduced. The totalapplied moment (M) is therefore considered ascomprising a reduced moment (Mm) plus aneccentric axial force (N x hN).

The presence of axial load is therefore allowed forconservatively in the moment capacity calculationprocedure by considering the axial load in thecheck on compression capacity (Equation 1 .18),and increasing the connection moment capacity tocompensate for this conservatism:

N

(1.21)

where:

M = basic connection moment capacity

N = axial force

hN distance of axial force from centre ofcompression

47

)Mm

Mjm= M,+(NxhN)

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Composite Connections

STEP 5 DESIGN FOR VERTICAL SHEAR FORCES

Comprehensive capacity checks for steel end plateconnections subjected to vertical shear are givenin Joints in simple construction, Volume 1(1).

However, for full depth fully welded end platesmany of these checks can be safely omitted. Thevertical shear capacity is calculated using areduced value for bolt rows which are in thetension zone, plus the full shear strength for boltrows which are ignored when calculating momentcapacity. The slab and reinforcement are assumedto make no contribution to the shear capacity.

Major axis connectionsIt is required that:

V � (n x + (n x P) (1.22)

where:

V = design shear forcen = number of shear bolts

— number of tension bolts

= shear capacity of a single bolt in shearonly, which is the least of:

pA for bolt shear, or

d t Pb for bolt bearing on the end plate,or

d T Pb for bolt bearing on the columnflange

Pts = shear capacity of a single bolt in thetension zone, which is the least of:

Pb minimum value of bearing strength foreither the bolt, Pbb' or the connectedparts, Pbs (BS 5950: Part 1 : Tables 32 &33)

Bolt sizeBolts in shear

only kN

Bolts in shear& tension

kN

M20 91.9 36.8

M24 132 53

M30 210 84.2

Capacities are based on the tensile area of thebolt. See Table 4. 8 for bearing capacities.

0.4 pA for bolt shear, or

d t pPb for bolt bearing on the end plate,or

d Tp for bolt bearing on the columnflange

PS = shear strength of the bolt (BS 5950:Part 1 Table 32)

A = shear area of the bolt (the threaded areais recommended)

= tolumn flange thickness

= end plate thickness

Minor axis connectionsThe following rules only apply to double sidedminor axis composite connections. If required,information concerning single sided minor axisconnections may be found in Reference 3. Checks(i) to (iv) must all be satisfied.

(i) For column web shear:

V1 + V2 � 2P (1.23)

V1 = shear applied from beam 1

['V

nPss

c*M*Figure 4. 1 8 Tension and shear bolts

Table 4.7 Shear capacities of single 8.8 bolts

Ttp

48

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Beam-to-Column Connections

STEP 5 DESIGN FOR VERTICAL SHEAR FORCES (continued)

A =p =

ns2

e � 5d

d = bolt diameter

tc = column web thickness

Avnet A — nt)Dhtc/2

Dh hole diameter

Us = ultimate tensile strength of column

(ii) For bolt shear:

V1 � X PA) + x O.4pA)

and

V2 � (n2 x PA) + x O.4pA)

(1.25) t1 = end plate thickness on side 1

tp2 = end plate thickness on side 2

web Pb the minimum of Pbb (bolt) or Pbs (plate)

(iv) For web bearing:

(1.26) V1/(n1 + n) + V2/(n2 + n) � dtp

where:

(1.27) Pb is the minimum of Pbb (bolt) or Pbs (web)

n tensiobolts

n2 shearbolts {

v21 V1

Column web

V + V2 V + V22 2

Figure 4. 1 9 Shear in minor axis beam-to-column connection (slab notshown for clarity)

49

where:V2 = shear applied from beam 2

Pv = local shear capacity of column web= smaller of O.6p,A and O5UsAvnet

[P + + n2 - 2)p/2 + e1t (1.24)

bolt pitch

number of shear bolts on side 2

PS = strength of the bolt in single shear

nsl = number of shear bolts on side 1 (seeFigure 4.19)

(iii) For end plate bearing:

V1 � 's1 p1Pb (1.28)

and

V2 � (n2 + dtp2pb (1.29)

where:

(1.30)

Critical sections

1. n tension) bolts

'-'n51 shear

; - J bolts;.tc

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Composite Connections

STEP 5 DESIGN FOR VERTICAL SHEAR FORCES (continued)

Table 4.8 Capacities for ordinary bolts to BS 3692 and BS 41 90*

Capacities in kN for bolts in 2 mm clearance holes � 24 mm diameter3 mm clearance holes > 24 mm diameter

Values given in the table are applicable to both old and new standards.

50

8.8 bolts passing through design grade S275 material

Bearing capacity at 460 N/mm2 for e � 2d

Bolt.

size

Tensilestressarea

Tensile capacity

BS5950: EnhancedPart 1 at value at

450 560N/mm2 N/mm2

Shear capacityat 375 N/mm2threads in the

shear plane

5

46.

55.

Thickness in mm of plate passed through

mm2 kN kN Single Double

M20 245 110 137 91.9 184

M24 353 159 198 132 265

Bolt

size

Tensilestressarea

8.8 bolts passing through design grade S355 material—capacity

Enhancedvalueat

560N/mm2

Tensile

BS5950:Part 1 at

450N/mm2

kN

Shear capacityat 375 N/mm2threads in the

shear plane

mm2

Bearing capacity at 550 N/mm2 for e � 2d

kN Single Double

.!2. 245 110 137 91.9 184

M24 353 159 198 132 265

Thickness in mm of plate passed through

* Although still commonly used, these standards have been replaced by:Bolts : BS EN 24014 and 24016Nuts : BS EN 24032, 24033 and 24034Screws : BSEN24017and24018

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Beam-to-Column Connections

STEP 6A DESIGN OF COLUMN COMPRESSION STIFFENERS

The resistance in the compression zone, of acolumn web reinforced with full depth stiffeners asshown in Figure 4.23 is the lower value fromEquations 1 .31 and 1 .32 below. This must equalor exceed the compressive force, F derived inStep 4.

In addition, a further check must be made toensure that the stiffeners alone can carry, inbearing, 80% of the applied force. SeeEquation 1 .33. This is usually the formula whichgoverns.

These rules are taken fromBS 5950: Part I : 1 990, and are likely to beamended in subsequent editions of the BritishStandard. Appropriate modifications should bemade to these procedures as necessary.

Effective Outstand of Compression Stiffeners

The outstand of 5275 compression stiffeners bsgshould not exceed 1 9t (see Figure 4.20)

where:

bsg stiffener outstand (see Figure 4.20)ts = thickness of stiffener

When the outstand is between 1 3t and 1 9t,design should be on the basis of a core sectionof 13t. (Refer to BS 5950: Part 1 whenstiffeners are designed in other grades of steel.)

Stiffener/Column Web Crushing and Buckling

(BS 5950: Part 1 Clauses4.5.5.)

4.5.4.1, 4.5.4.2 and

Stiffeners are usually designed in S275 steel. It isrecommended that they be at least as thick as thebeam flange, and specified in thicknesses of 1 5,20 or 25 mm only.

Note that the presence of stiffeners may interferewith erection of orthogonal beams, whose endplates may themselves increase the bucklingstrength of the column web.

Section A - A

Figure 4.20 Stiffener bearing and buckling

and:

'cbearing= (1.33)

0.8

where:

A = allowable area of column web forbuckling (see Section A-A in

Figure 4.20), � 40 t x t

Asg gross area of stiffeners

= 2 x bsg X t (bsg � 1 3t) (1.34)

= net area of stiffeners in contact with20t column flange

= 2 x x t (1.35)

PC = compressive strength of stiffeners fromBS 5950: Part 1 Table 27(c) withA = 0.7LIr*

PC buckling = (A + Asg) X p (1.31)

PC crushing = EAsn X p,] + [(b1 + n2) x tc Xpy1

(1.32)

bsg

ts-

V

><tc

= 2Otc

C

51

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Composite Connections

L = length of stiffener = D - 2T

= radius of gyration of effectivearea (as shown in Section A-A,Figure 4.20)

= lesser of the design strength ofstiffener or column

= design strength of stiffener= effective bearing length along

web (see Step 2A)

Note *: The effective buckling length of thestiffener given here assumes that ti,e columnflanges are laterally restrained relative to oneanother. For other cases refer to BS 5950: Part 1Clause 4. 5. 1.5.

Weld Design

The welds connecting compression stiffeners tothe column web and flanges will generally be filletwelds and should be designed to BS 5950: Part 1Clauses 4.5.9 and 4.5.1 1 as follows:

Welds to Flanges

When, as is normally the case, the stiffener isfabricated to achieve a bearing fit to the inside ofthe column flange, the weld to the flange needonly be nominal, say a 6 mm fillet weld. In othercases, the welds should be designed as fullstrength.

52

Welds to Web

For double sided connections, the web welds mustbe designed to carry the larger of the beam flangeforces, assuming that the forces act in oppositedirections.

STEP 6A DESIGN OF COLUMN COMPRESSION STIFFENERS(continued)

r

py

pys(b1 + n2)

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Beam-to-Column Connections

STEP 6B DESIGN USING COLUMN FLANGE BACKING PLATES

Mode 1 Complete Flange Yielding

= 4MP+2MbP

Mode 3 Bolt failure

tbp thickness of the backing plate

py = design strength of the backing plate

other variables are defined in Step 1 B.

The width of the backing plate, bbp should not be(1.36) less than the distance from the edge of the flange

to the toe of the root radius, and it should fitsnugly against the root radius.

The length of the backing plate should not be lessthan the length of effective T-stub for the boltgroup (Leff) and be sufficient so that the plateextends not less than 2d beyond the bolts at itsextremities (d is the bolt diameter).

This type of strengthening is only useful forsmaller section columns were flanges areparticularly thin. The plates are generally suppliedloose or tack-welded in place and their effect is to

(1.37) prevent or increase the resistance to a Mode 1bending failure. Neither Mode 2 nor Mode 3 isaffected.

P =

where:

MbpLeff X tbp X

4

(1.38)

(1.39)

53

The potential resistance in tension of a columnflange strengthened by backing plates is taken asthe minimum value obtained from Equations 1 .36,1.37 and 1.38.

m

Qr /2 + Q

r /2 + QQ

Mode 2 Bolt failure with flange yielding

P = 2M+n(')m+n

Figure 4.21 Column flange backing plates

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Composite Connections

STEP 6C DESIGN OF TENSION STIFFENERS

General

Tension stiffeners, as shown in Figure 4.22, aregenerally used to supplement the tension capacityof the column web and/or the capacity of thecolumn flange in bending. Although it isrecommended that the stiffeners be full depth,design rules for partial depth stiffeners may befound in Reference 4.

From a practical point of view, the presence ofcolumn web stiffeners may interfere with theerection of orthogonal beams.

Stiffener Net Area

The net area of the stiffeners, must satisfy therequirements of Equations 1 .40 and 1 .41 for webtension and flange bending respectively.

Web Tension

The stiffener, in combination with the columnweb, is designed to carry the tensile load from thebolts immediately above and below it.

Basic requirement:

(F. +F.'' ri rJJ(t) (1.40)py

where:

= net area of both stiffeners

= 2(b xt)= net width of stiffener

ts = thickness of stiffener

Fri tension from bolt row above the stiffener

Fri tension from bolt row below thestiffener

pv = the design strength of stiffener orcolumn web (the lesser of the two)

limited by the presence of adjacent bolts(see Figure 4.23)

tc = web thickness

The gross width of stiffener, bsg should generallybe proportioned so that the stiffener extends atleast 75% across the available flange width, (B -t)I2

Figure 4.22 Tension stiffeners

4— Row i

Stiffener

;,— Row

/ 1.73 6O0

1.73 [>6OO

Rowi

Stiffener

Row

. Maximum amountof web available

—to adjacent row

Figure 4.23 Effective web lengths

Flange Bending

The force carried by the stiffeners is assumed tobe inversely proportional to their distance from thebolts.

fly

ts---

Cornersnipe

ii TIIbsg

fly

LrLf

� p/2't'

1-

—-

L = available length of web assuming amaximum spread of load at 600 from thebolts - the spread may be

54

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Beam-to-Column Connections

STEP 6C DESIGN OF TENSION STIFFENERS (continued)

Basic requirement:

c; ÷ 1 (1.41)L (m1 + m2L) (in1 + m2u)j

where:

= net area of both stiffeners

= 2 (b x t) (1.42)

py = the design strength of stiffener orcolumn (the lesser of the two).

m1 m2L m2u Fri and Frj are defined in Figure 4.24

Row i, Tension = F ki'm2 _l,k_t

m2 —k-Row j, Tension = F ki'

- m1 (=m)

Figure 4.24 Geometry for force distributionto stiffeners

Weld Design

Full strength welds should be provided to theflanges and web.

55

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Composite Connections

STEP 6D DESIGN OF SUPPLEMENTARY WEB PLATES

General Column Web Tension

A supplementary web plate (SWP) may be For the purpose of the column web tensionprovided to increase the capacity of the column calculation (Step 1 C), the effective web thickness,web. Its effect (according to EC3) is to: teff, should be taken as:

. Increase web tension resistance by: For an SWP on one side only, teff 1 .5t50% with a plate on one side, or100% with plates on both sides For SWPs on both sides, teff 2t

. Increase web crushing resistance by: t is the column web thickness.50% with a plate on one side, or1 00% with plates on both sides

Column Web Crushing and Buckling. Increase web panel shear resistance by:

about 75% (see expression for P ). For the purpose of column web crushing andV buckling calculations (Step 2A), the effective web

Note that in the case of panel shear, plates on thickness, teff, should be taken as:

both sides provide no additional increase over aplate on one side. For an SWP on one side only, teff 1 .5t

The supplementary web plate must satisfy the For SWPs on both sides, teff 2tfollowing criteria: •

tc 15 the column web thickness.

. Thickness, t not less than the column webthickness.

Column Panel Shear

S The same material strength as the column. The resistance, of a column web panel with anSWP on one side, is given by:

. Welds all round should be, as a minimum, filletwelds of leg length equal to the plate thickness. p = 0.6 < < A (1.45)However, if the supplementary web plate isbeing used to increase web tension resistance, where:the vertical weld on the side where theincreased capacity is required should be a 'fill ,, design strength of the columnin' weld (see Figure 4.25). Plug welds arerequired if b exceeds 37t (for 5275 steel) or A = shear area of the column web and SWP33t (S355). combined

= tx(D+b). Breadth, b that satisfies:

b � d - 2t (1.43) There is no further increase in the shear area if an(b = d for a "fill in" weld) SWP is added on the other side of the web.

. Length,L�g+D+D/2+D+e (1.44)

where:g = horizontal spacing of bolts (gauge)

Db depth of beamD = . depth of columnDr depth to reinforcemente = projection of end plate beyond beam

(25 mm for standard details)

56

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Beam-to-Column Connections

STEP 6D DESIGN OF SUPPLEMENTARY WEB PLATES (continued)

Plug welds dia � tspaced � 37twhenb> 37t3for grade S275

Continuous fillet weld.Leg length equal toplate thickness

57

'Fill in' butt weld wherEincreased web tensionresistance is needed

Figure 4.25 Dimensions and welds

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Composite Connections

STEP 7 DESIGN OF WELDS

Tension Flange Welds

The welds between the tension flange and the endplate may be full strength, or should be designedto carry a force which is the lesser of:

(a) The tension capacity of the flange,= BxTxp (1.46)

(b) The total tension force in the top two boltrows (see Figure 4.26)= + (1.47)

II II

Figure 4.26 Forces in welds

A full strength weld to the tension flange can beachieved by:

. a pair of symmetrically disposed fillet welds,with the sum of the throat thicknesses equal tothe flange thickness, or

. a pair of symmetrically disposed partialpenetration butt welds with superimposedfillets, or

. a full penetration butt weld.

If designing a partial penetration butt weld withsuperimposed fillet, as shown in Figure 4.27, notethat:

. The weld throat required should be calculatedbased on the strengths given in BS 5950: Part 1Table 36, (i.e. 215 N/mm2 for S275 and255 N/mm2 for S355).

The shear and tension stresses on thefusion lines should not exceed O.7p and1 .Op respectively. (See BS 5950: Part 1clause 6.6.5.5).

The depth of preparation should be 3 mmdeeper than the required penetration.

The angle between the fusion faces for aiv, preparation should be normally not lessthan 45°.

The minimum penetration of 2/t specifiedin BS 5950: Part 1 clause 6.6.6.2 does notapply to the detail shown in Figure 4.27.

For most small and medium sized beams, thetension flange welds will be symmetrical, fullstrength fillet welds. Once the leg length of therequired fillet weld exceeds 1 2 mm, then a fullstrength detail with partial penetration butt weldsand superimposed fillets may be a moreeconomical solution.

The transition between the tension flange weldand the web weld should take place where theroot of the section meets the web.

Although the approach given above may appearconservative, at ultimate limit state there can be atendency for the end plate to span verticallybetween the beam flanges. As a consequence,more load is attracted to the tension flange thansimply that due to the adjacent bolts. For thisreason, care should be taken not to undersize theweld to the tension flange. A simple and safesolution is to provide full strength welds.

Compression Flange WeldsIn cases where the compression flange has aproperly sawn end, a bearing fit can be assumedbetween the flange and end plate and nominal8 mm fillet welds will suffice. For some of thelighter beams (with flange thicknesses of 1 2 mmor less) 6 mm fillet welds may be appropriate.This 'bearing' assumption will be the usual casefor most plain beams. Guidance on the necessarytolerances for a bearing fit can be found in theNSSS9.

Fri— Fr2*— Fr3*

F —

—(F, + Fr2)assumed

— Web- welds

— Tension flangeweld

ield design force

M)

N

58

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STEP 7 DESIGN OF WELDS (continued)

Beam-to-Column Connections

If a bearing fit cannot be assumed, the weld mustbe designed to carry the full compressive force, F.

Web Welds

It is recommended that web welds in the tensionzone should be full strength.

For beam webs up to 1 1 .3 mm thick, full strengthcan be achieved by 8 mm fillet welds. It istherefore sensible to consider using full strengthwelds over the full web depth, in which case nocalculations are needed for either tension or shear.

For thicker webs, the welds may be treated in twodistinct parts; a Tension Zone around the boltswhich have been dedicated to take tension, andthe rest of the web acting as a Shear Zone.

1 . Tension Zone:Full strength welds should be used. These will begenerally fillet welds with the sum of the throatthicknesses not less than the web thickness, tb.

The welds should extend below the bottom boltrow resisting tension by a distance of 1 .73g/2(see Figure 4.28). Dimension g is the gauge of thebolts.

2 . Shear Zone:The capacity of the beam web welds for verticalshear should be taken as:

(1.48)

where:a = fillet weld throat thickness (O.7s)

pw = design strength of fillet weld (BS 5950:Part 1 Table 36)

= length of shear zone welds= Db 2 (Tb + 'b) - (1.49)

Note: The tension zone welds are assumed tostart at the bottom of the root radius.

Figure 4.28 Force distribution in welds

59

fillet

Figure 4.27 A partial penetration butt weldwith superimposed fillets

Jm 2

Db

F

Fr2

— Row 1

— Row 2

— Row 3

V

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Composite Connections

4.3 BEAM-TO-BEAM CONNECTIONS

Beam-to-beam connections are usually detailed suchthat notching of the supported beams allows theirtop flanges to be made level with that of the support(see Figure 4.29). The supported beams must thenadopt a partial depth end plate. The tension boltforces that can be generated with such a detail arelow, and, for simplicity, can be ignored whencalculating the composite connection momentcapacity without excessive simplicity. Theconnections should be treated as pinned at theconstruction stage. A range of connections of thistype has been tested in order to validate the designprocedures presented in this publication. Alternativedetailing should be considered if there is a need togenerate significant tension forces in the steelwork.

60

As in connections to column webs, it is importantthat there is a direct load path to transfercompressive forces between the bottom flanges ofopposing beams. It is therefore recommended thatthe two supported beams should be of the sameserial size. Because the torsional stiffness of thesupporting beam is relatively low compared with theflexural stiffness of the supported beams, the latterare effectively treated as a semi-continuous beam ona knife edge support.

The following design steps, derived from those givenin Section 4.2 and maintaining the same numberingsystem, should be used to calculate the momentcapacity of a beam-to-beam connection.

Figure 4.29 A typical beam-to-beam connection

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STEP 1A REINFORCEMENT YIELDING

Beam-to-Beam Connections

Potential resistance

The potential resistance of the reinforcement intension is given by:

— fyAreinf (2.1)

f = design yield strength of reinforcement

Areinf = area of reinforcement within theallowable width of slab (seeFigure 5.2).

Ym = partial safety factor for reinforcement(taken as 1 .05)

Detailing rules for the reinforcement are given inSection 5.

Minimum area of reinforcement

In general, the rotation capacity of a connectionincreases as the area of reinforcement increases. Aminimum area is therefore needed to ensure that'compact' connections can undergo sufficientrotation to strain the reinforcement to yield (as isassumed in the moment capacity model). Minimumareas of reinforcement are given in Table 4.1 as afunction of:

beam size

• beam steel grade

• reinforcement properties

• connection type - 'compact' or 'plastic'.

The minimum reinforcement limits in Table 4.1 aremore onerous for 'plastic' connections, because inaddition to the need for yielding of thereinforcement, the connection must have sufficientrotation capacity to behave as a plastic hinge.

For a given beam size and steel grade, the minimumvalues in Table 4.1, marked '5%', should generallybe used. These values are appropriate for high yieldbars complying with current British StandardBS 4449 grade 460B20.

This grade of reinforcement has a mandatoryrequirement of 1 4% minimum elongation at fracture,and a non-mandatory requirement of 5% minimumelongation at maximum force. Grade B500B barscomplying with BS EN 10080(21) are required tohave similar properties; they must be able to achieve5% total elongation at maximum force. Elongationat fracture and total elongation at maximum forceare defined in Figure 4.5.

Minimum reinforcement limits are also given inTable 4.1 for connections that use reinforcement

. which is capable of achieving 10% minimumelongation at maximum force. The increasedreinforcement ductility offers considerableadvantages in some cases, because it permits theuse of less reinforcement.

It is essential that when a design is based on theuse of 1 0% elongation bars this is made clear in theproject specification. This can be done by giving thebars an 'X' designation, rather than the 'T' generallyused for high tensile bar&22. The 'X' informs thecontractor that the bars need specific, non-standardproperties. It is recommended that, if possible, thereinforcement supplier uses coloured labels toclearly distinguish the high elongation 'X' bars onsite. In case of doubt concerning the elongationcapacity of bars, approximately half the UKmanufacturers provide reinforcement suppliers withappropriate test information. It should therefore berelatively easy for the contractor to confirmsuitability with his reinforcement supplier.

Bars that are currently produced in the UK using ahot forming process may be assumed to beappropriate for use with the '10%' limits. All20 mm diameter bars produced by majormanufacturers in the UK currently are hot formed,as are, often, 1 6 mm bars.

Maximum area of reinforcement

The reinforcement area in a beam-to-beamconnection must be limited to a maximum valuein order to keep the compression zone in thelower half of the steel beam. This restrictionensures that the reinforcement strains sufficientlyto produce yielding.

einfYm

61

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Composite Connections

STEP 2B COMPRESSION CHECK - SUPPORTED BEAMRESISTANCE OF THE BEAM FLANGE AND WEB IN THE COMPRESSION FLANGE

Beam Flange Crushing (Bearing)

Pyb = design strength of the beamTb = the beam flange thicknessBb = the beam flange breadth

The centre of compression is taken as the mid-depthof the beam compression flange, as shown inFigure 4.30. This accords with the behaviour ofconnections under test24.

Allowing the flange-only compression stress toexceed the yield stress by 40% is justified by twolocalised effects; strain-hardening and dispersioninto the web at the root of the section. Typically(for UB sections) each of these effects will accountfor around 20% 'overstress', so that an effective1 4Pyb can be taken when the flange area isassumed to act alone4. This value should only beused when flanges are either Class 1 (plastic) or 2(compact).

When the compression capacity of the flange a/oneis exceeded, as it often will be due to the presenceof significant reinforcement, a I shapedcompression zone should be considered, extendingsome distance up the web (see Figure 4.31).

Note that:

. The stress in this section must be limited to1 .2p. since the contribution of the web is nowbeing taken into account explicitly. Flangesshould be either Class 1 (plastic) or 2 (compact).

. The centre of compression is redefined as thecentroid of the .J section, and the lever arms tothe bolts and reinforcement are reducedaccordingly.

flkTbkXXX\} 'x1

k Bb

_JjjJbk Bb

Figure 4.31 Compression in beam flange andportion of web

Because compression in the beam extends into theweb, and a limiting stress of 1 .2p,, assumesplastification to take place, the web should be Class1 (plastic) or 2 (compact). Because connectiondetailing rules limit the depth of compression to thelower half of the beam, all practical rolled sectionseffectively satisfy this restriction. If fabricatedsections with a Class 3 (semi-compact) web areused, they may be treated as Class 2 by ignoringpart of the web. The effective section should bedefined by considering a depth of web equal to1 9te adjacent to both the compression flange andthe neutral axis (where t is the web thickness andC = /(p/275)).

As a first check, the potential resistance of theflange in compression is taken as:

PC= l.4XpybXTbXBb (2.2)

where:

PC-

Figure 4.30 Compression in beam flange only

62

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STEP 4 CALCULATION OF MOMENT CAPACITY

Beam-to-Beam Connections

Force Distribution

The reinforcement resistance calculated in Step 1can only be fully realised if sufficient compressionzone resistance is available (Step 2). It is thereforea 'potential' resistance, and must be reduced ifnecessary to ensure equilibrium. Figure 4.32 showsthe potential resistances (P) translated into actualforces (F).

Equilibrium is satisfied by:

Freinf + N = F

where N is the axial load in the beam(positive for compression)

and F is the smaller of the following:"reinf N

or P (beam crushing)

For the reinforcement: 1enf Ijfwhere:Freinf _ final force in reinforcement

(2.3)

If there is an excess potential resistance in thereinforcement then the forces should be reduceduntil equilibrium is achieved between the tensionand compression forces.

Moment Capacity

Assuming that there is no significant axial load inthe beam, the basic moment capacity of theconnection is given by:

M1 = Freint X hreinf (2.4)

Moment Capacity Modified by Axial Load

The presence of significant axial load must beallowed for when checking equilibrium between thetension and compression forces (Equation 2.3). Forsimplicity in the connection design, it is assumedthat the axial force acts at the centre ofcompression in the beam. However, this shift in theline of action of the force, from the (composite)beam neutral axis, means that the coincidentmoment that is considered to be applied to theconnection should be reduced. The total appliedmoment (M) is therefore considered as comprising areduced moment (Mm) plus an eccentric axial force(N x hN).

The presence of axial load is therefore allowed forconservatively in the moment capacity calculationprocedure by considering the axial load in the checkon compression capacity (Equation 2.3), andincreasing the connection moment capacity tocompensate for this conservatism:

where:M = basic connection moment capacity

(2.5)

where:N = axial force

hreinf = distance from the centre ofcompression to the reinforcement

hN distance of axial force from centre ofcompression

63

)Mm

Mjm MJ+(NxhN)

Figure 4.32 Translation of potential resistances into allowable forces

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64

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5 CONNECTION DETAILING

5.1 BEAM-TO-COLUMN CONNECTIONS

Appropriate connection detailing for 'compact'connections is necessary in order to:

. prevent premature failure of the tension bolts orreinforcement

. ensure sufficient deformation takes place togenerate the tension bolt and reinforcementforces assumed in the design

. prevent concrete crushing against the columnunder unbalanced loading.

In addition, for 'plastic' connections, more onerousdetailing rules are necessary in order to:

S ensure that the connections have sufficientrotation capacity to form a plastic hinge.

The detailing rules that follow apply to both'compact' and 'plastic' connections. They shouldbe used in conjunction with minimum reinforcementarea requirements given in Table 4.1, which dohowever differ for the two types of connection.

Reinforcement and shear connection

Conventional reinforcement detailing according toBS 8110(11) should be adopted. Bar diametershould not be less than 1 6 mm, since smallerdiameter bars are generally less ductile. Effectiveanchorage of the reinforcement is achieved bycurtailing the bars in the compression zone of theslab. This zone normally starts at about 0.2 timesthe beam span on either side of the support, andsufficient anchorage length should be providedbeyond this point, as in conventional reinforcedconcrete practic&1 1) (for example 40 times the bardiameter for a 'Type 2 deformed' bar in concretewith a cube strength of 30 N/mm2). Althoughreinforcing mesh may also be present in the slab tocontrol cracking, its contribution to momentcapacity should be ignored.

The following detailing rules are shownschematically in Figure 5.1 . Limitations on thepositions of reinforcing bars ensure that they canwork effectively as components in a truss to resistunbalanced loads (see Section 4.2 Step 1A).

1. Longitudinal reinforcing bars should beuniformly spaced either side of the column(see Figure 5.1), with the nearest bars

approximately 20 mm from the column edge,to achieve adequate cover. The furthest barsto be included in the effective area should notbe more than approximately 2b from thecolumn centreline (dimension eL).NOTE: eL s a function of the column width,rather than the beam span.

2. Transverse reinforcing bars (which arenecessary to resist forces in the concrete'behind' the column when unbalanced loadingis applied) should not extend more than therequired anchorage length1 1) beyond points2b either side of the column centre line. Thisshould ensure that the orthogonal connectionbehaviour is not significantly influenced bythese bars.

3. Transverse reinforcing bars should beuniformly spaced either side of the column(see Figure 5.1), with the nearest barsapproximately 20 mm from the column edge.The furthest bars included in the effective areashould not be more than approximately 3bfrom the column face (dimension eT).

4. Longitudinal reinforcing bars should be placedapproximately 20 mm above the top of thedecking, to ensure adequate concrete cover.Whether the transverse bars are placed aboveor below the longitudinal bars will depend onthe orientation of the decking and the depth ofslab above the decking; all the bars must bepositioned so that they have adequate cover tothe decking and the top of slab11.Keeping the longitudinal bars close to the topof the decking minimises the strain they mustundergo to achieve a given rotation.

5. The first shear connector should be at least1 00 mm from the face of the column.This limitation ensures that reinforcing bars arestrained over a substantial length, so thatsufficient rotation can take place.

Steelwork6. The end plate thickness should be not more

than 60% of the bolt diameter; 1 2 mm forM20 bolts and 1 5 mm for M24 bolts. Endplates should be made from 5275 steel.

7. Horizontal spacing of the bolts (gauge) shouldbe not less than 90 mm.

65

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-De%J

-a0Ca)0-C0)Ca)

Figure 5.1 Geometrical detailing rules - beam-to-column connections

These steelwork restrictions ensure that, as theconnection rotates, end plate deformation is the'weak link'. Steelwork details complying with theserules have been shown in tests to possess sufficientrotation capacity to satisfy both 'compact' and'plastic' connection requirement&4. Alternatively,steelwork details which fail in Mode 1 may be used(see Section 4.2 Step 1 B).

5.2 BEAM-TO-BEAM CONNECTIONS

For beam-to-beam details, the following detailingrules should be respected for both 'compact' and'plastic' connections. These are required for thesame reasons as specified in Section 5. 1 , exceptthat concrete crushing against the column is clearlynot relevant.

Reinforcement and shear connectionConventional reinforcement detailing according toBS 81 1 0(1 1 ) should be adopted. Bar diametershould not be less than 1 6 mm, since smallerdiameter bars are generally less ductile. Effectiveanchorage of the reinforcement is achieved bycurtailing the bars in thecompression zone of theslab. This zone normally starts at about 0.2 times

66

the beam span on either side of the support, andsufficient anchorage length should be providedbeyond this point, as in conventional reinforcedconcrete practic&1 1) Although reinforcing meshmay also be present in the slab to control cracking,its contribution to moment capacity should beignored.

The following detailingschematically in Figure 5.2.

rules are shown

1 . Longitudinal reinforcing bars must be locatedwithin the effective width of the concrete slabfor the beam in hogging, as defined inBS 5950: Part 3: Section 3.1 Clause 4.6.Note: Effective width is not the same as forbeam-to-column connections.

2. Reinforcing bars should be placedapproximately 20 mm above the top of thedecking, to maintain adequate cover to thedecking and the top of slab11.

3. The first shear connectors on the supportedbeams should be at least 200 mm from thecentre line of the support.

Composite Connections

-a"4

-Ja)

Transversereinforcement

Longitudinalreinforcement

a) Plan (decking and mesh omitted for clarity)

Approx.60 mm

b) Elevation

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Figure 5.2 Geometrical detailing rules -

beam-to-beam connections

Steelwork detailing4. The end plate thickness should be not more

than 60% of the bolt diameter; 12 mm forM20 bolts and 15 mm for M24 bolts. Endplates should be made from S275 steel.

5. Horizontal spacing of the bolts (gauge) shouldbe not less than 90 mm.

Connection Detailing

67

Plan (decking and mesh omitted for clarity)

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68

Page 75: Joints in Steel Construction Composite Connections · specified in either BS 4449 or BS EN 10080. Detailing rules are therefore given for two cases; bars that just meet the code requirements

References

REFERENCES

1 THE STEEL CONSTRUCTION INSTITUTE and THE BRITISH CONSTRUCTIONAL STEELWORKASSOCIATION LTDJoints in simple construction - Volume 1 : design methodsSCI, BCSA, 1993

2 THE STEEL CONSTRUCTION INSTITUTE and THE BRITISH CONSTRUCTIONAL STEELWORKASSOCIATION LTDJoints in simple construction - Volume 2: practical applicationsSCI, BCSA, 1992

3 THE STEEL CONSTRUCTION INSTITUTE and THE BRITISH CONSTRUCTIONAL STEELWORK ASSOCIATION LTDJoints in steel construction: simple connectionsSCI, BCSA, 1998

4 THE STEEL CONSTRUCTION INSTITUTE and THE BRITISH CONSTRUCTIONAL STEELWORK ASSOCIATION LTDJoints in steel construction: moment connectionsSCl, BCSA, 1995

5 BRITISH STANDARDS INSTITUTIONBS 5950: Structural use of steelwork in buildingPart 3: Design in composite constructionSection 3.1 : 1 990: Code of practice for design of simple and continuous composite beamsBSI, 1990

6 BRITISH STANDARDS INSTITUTIONBS 5950: Structural use of steelwork in buildingPart 1 : 1 990: Code of practice for design in simple and continuous construction: hot rolled sectionsBSI, 1990

7 BRITISH STANDARDS INSTITUTIONDD-ENV 1 993-1 -1 : 1 992 Eurocode 3: Design of steel structuresPart 1 .1 General rules and rules for buildingsBSl, 1993

8 EUROPEAN COMMISSIONCOST Cl Semi-rigid behaviour of civil engineering structural connectionsComposite steel-concrete joints in braced frames for buildingsEC, 1996

9 THE BRITISH CONSTRUCTIONAL STEELWORK ASSOCIATION LTD and THE STEEL CONSTRUCTION INSTITUTENational structural steelwork specification for building construction (3rd edition)BCSA, 1994

10 BRITISH STANDARDS INSTITUTIONDD-ENV 1 994-1 -1 : 1 994 Eurocode 4: Design of composite steel and concrete structuresPart 1 .1 General rules and rules for buildingsBSI, 1994

1 1 BRITISH STANDARDS INSTITUTIONBS 81 10: The structural use of concretePart 1 : 1 997: Code of practice for design and constructionBSI, 1997

12 AHMED, B., and NETHERCOT, D. A.Effect of high shear on the moment capacity of composite cruciform end plate connectionsJournal of C,onstructional Steel Research, Vol. 40, No. 2, November 1996

13 Building Regulations 1991 (1994 edition)The Stationery Office

69

Page 76: Joints in Steel Construction Composite Connections · specified in either BS 4449 or BS EN 10080. Detailing rules are therefore given for two cases; bars that just meet the code requirements

Composite Connections

14 NEAL, B. G.The plastic methods of structural analysisScience Paperbacks and Chapman & Hall, 1965

15 COUCHMAN,G.H., and WAY, A.Ductility requirements for composite connections(To be published)

16 WYATT, TA.Design guide on the vibration of floorsThe Steel Construction Institute and CIRIA, 1989

17 JOHNSON, R.P., and ANDERSON, D.Designers' handbook to Eurocode 4 Part 1 . 1 : Design of composite steel and concrete structuresThomas Telford, 1993

18 THE INSTITUTION OF STRUCTURAL ENGINEERSManual for the design of steelwork building structuresIstructE, 1989

19 COUCHMAN, G.H.Design of semi-continuous braced framesThe Steel Construction Institute, 1997

20 BRITISH STANDARDS INSTITUTIONBS 4449: 1 988: Specification for carbon steel bars for the reinforcement of concreteBSI, 1988

21 BRITISH STANDARDS INSTITUTIONBS EN 1 0080: 1 996: Steel for the reinforcement of concrete.Weldable ribbed reinforcing steel B500.Technical delivery conditions for bars, coils and welded fabricBSI, 1996

22 BRITISH STANDARDS INSTITUTIONBS 4466: 1 989: Specification for scheduling, dimensioning, bending and cutting of reinforcement for concreteBSI, 1989

23 LI, T.Q., NETHERCOT, D.A., and CHOO, B. S.Behaviour of flush end plate composite connections with unbalanced moment and variable shear/moment ratios - II. Prediction of

moment capacityJournal of Constructional Steel Research, Vol. 38, No. 2, 1996

24 BAILEY, J.R.Strength and rigidity of bolted beam-to-column connectionsProceedings, Conference on structuresUniversity of Sheffield, 1970

70

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Appendix A

APPENDIX A Worked Example

The following calculation demonstrates the procedure used to calculate the moment capacity of an internal beamto column flange composite connection.

The procedure to allow for interaction between several rows of tension bolts does not differ from that given inReference 4, and is therefore not included in the worked example. More details may be found in Reference 4.

Contents:

1. Connection details

2. Tension zone

3. Compression zone

4. Column panel shear zone

5. Calculation of moment capacity

6. Calculation of vertical shear capacity

71

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72

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K7The SteelConstructionInstitute

Job 'SheetComposite Moment Connections

Ii oI 9

Title

Silwood Park, Ascot, Berks SL5 7QNTelephone: (01 344) 623345

Worked example for a bolted end plate

ClientFax: (01344) 622944

CALCULATION SHEET

SC//BCSA Connections Group

Calcs by I Checked by ' DateGHC AW May 1998

1. CONNECTION DETAILS

. 6 No. 16 mm diameterrebars

. 1 ro w M20 8. 8 tension12O bolts

0 200 x 12 S275 endplate

. 4O6x178x54UB

. 2O3x2O3x52UC

The beam and column areboth S275. The rebar isgrade 460B to BS 4449.

2. TENSION ZONE

2. 1 Rebar Step 1A

Potential resistance

For 6 No 1 6 mm bars, Arejflf 12 1 0 mm2 I 530 I 1

(seef x Areinf 460 x 12 10 x iO-3 worksheet,

reinf =Ym

=1.05

530. 1 kN page 77)

Check minimum area of reinforcement

Beam is grade 5275

From Table 4. 1, minimum allowable area of rebar for a 'plastic' connection toan 5275, 406 deep beam = 1 150 mm2 < 12 10 mm2 OK

Check maximum area of reinforcement

To prevent concrete crushing:

0.6 x b x d 0.6 x 204.3 x (120 - 50) 30A x x—=L ,j f p 460

73

Steelwork details are as shown on page 87.

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Title SheetWorked example for a bolted end plate 2 019

For this example, it is assumed that a connection of equal strength will be

adopted on the opposing column flange, .: p = zero, so AL �So Areinf 12 10 mm2 is OK.

In addition, in a 'balanced'situation, only nominal transverse reinforcement willbe required.

2.2 Bolt Row 1 (only row in tension)

Column side geometry (with reference to Figure 4. 7): Step lB

m =-_EO.8xr=-4-O.8XlO.2=32.9mrn

B-g 204.3-90e =

2=

2 =57.2mm

n = minimum of e, 1. 25m or e (beam side, see belo w)

= 57.2 or 1.25 x 32.9 or 55 = 41. 1 mm

Column flange bending

From Table 4. 5, Leff 5 given by Mm (ii,i)

From Table 4.4, Pattern (i):

2rrrn = 2tr x 32.9 = 206.7mm

Table 4. 4, Pattern (ii):

4m + l.25e = 4 x 32.9 + 1.25 x 57.2

Hence Leff = 203. 1 mm

M for the column flange:

M — Leff X T2 x p _ 203. 1 x 12. 2 x 2 75 X 1 0p —

4= 2181.7kNm

Critical failure mode is minimum of:

4M 4 x 2181.7Mode 1. P, = = = 265 kNm 32.9

. 2M +n x 2 x 2181.7 +41.1 x 2 x 137Mode2. P, = ' =

m +n 32.9 +41.1= 211.lkN

74

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K7The SteelConstructionInstitute

Job I SheetComposite Moment Connections I of 9

Title

Sitwood Park, Ascot, Berks SL5 7QNTelephone: (01 344) 623345

Worked example for a bolted end plate

ClientFax: (01344) 622944

CALCULATION SHEET

SCI/BCSA Connections Group

Calcs by I Checked by I DateGHC AW May 1998

Mode3. P, =1P'= 2x 137 = 274kN 1211121

HencePr _ 211.lkN

Column web tension Step 1 C

L =45x1.73x2 =155.7mm

Pt = L x t x p = 1 55. 7 x 7. 9 x 2 75 x iO- = 338 kN I 338 I 3 1

Beam side geometry: Step lB

m =---O.8xs, =

= 34.8 mm(assume 8FW)

b-g 20090e =

2 = —:--- - -i = 55 mm

n = minimum of e, l.25m or e (column side, see above)= 57.2 or 1.25 x 34.8 or 55 = 43.5 mm

End plate bending

From tables, Leff 1f5 given by:

Mm (Max (ii, iii), i) since g 0. 7 Bb and Tb 0. 8 t,,

From Table 4.4 Pattern (ii):

4m + 1. 25e = 4 x 34. 8 + 1. 25 x 55 = 208. 0 mm

Table 4. 4 Pattern (ill):

Le = i, where a is obtained from Figure 4.9.

Using:

1=

, m = 34. 8 mm

m2 =Pl-T-O.8xswf=60-10.9-(0.8x10) =41.1mm

75

Page 82: Joints in Steel Construction Composite Connections · specified in either BS 4449 or BS EN 10080. Detailing rules are therefore given for two cases; bars that just meet the code requirements

TitleWorked example for a bofted end plate

Sheet4 of 9

m1 34.8A1 =

m1 ÷ e=

34.8 + 55= 0.39

m2 41.1A2 =

m1 + e=

34.8 + 55= 0.46

So from Figure 4. 9 a = 2 r

ctm1 = 218.7 mm

.: Max (ii, iii) = 2 1 8. 7 mm

Pattern (i):

2im = 218.7mm

Hence Leff = 2 18. 7 mm

So M —L8ff X t, X p _ 218.7 x 122 x 275 x i03'p 4

—4

= 2165.1 kNm

Critical failure mode is minimum of:

4M 4 x 2165.1Mode 1. P1 = = 249 kN

m 34.8

2M +n x IF" 2 x 21651 +435 x 2 x 137Mode2 P — t— ________________

. r— m+n 34.8+43.5208 kN

Mode 3. IPt' 2 X 1 37 2 74 kN F208 I 4 I

Beam web tension Step 1 C

The underside of the beam flange is only 49. 1 mm above bolt row 1. The I N/A I 5 1flange is therefore within the web tensile length, so beam web tension can bediscounted.

76

Page 83: Joints in Steel Construction Composite Connections · specified in either BS 4449 or BS EN 10080. Detailing rules are therefore given for two cases; bars that just meet the code requirements

K7The SteelConstructionInstitute

Job I Sheet

Composite Moment Connections I of 9

Title

Silwood Park, Ascot, Berks SL5 7QNTelephone: (01 344) 623345Fax: (01 344) 622944

CALCULATIONSHEET

Worked example for a bolted end plate

Client

SCI/BCSA Connections Group

Calcsby ICheckedbv 'Date

GHC AW May 1998

Step 1D

ModifyBolt

Forces

From Step 1A

Dreinf

153011 I

least of boxes2 to 6 gives

Pr1 =

12081 7

least of boxes:

8 to 1 1 and16 to 20 gives

STEP 1 WORKSHEET: TENSION ZONE

Row

Beam Side

Step lB Step 1CPlate Web

I Bending Tension

PotentialResistance

Reinforcement

IN'41 6- INALIr:;w 2 alone

1101 I ill

rows(1 + 2) combined:

I I I I Iil4i I il5i

Pr2=I 12111181 I kiow 3 alone

1241 I 1251

med rows(2 +3):

28 : 1291_____L__J LJJ

1321 I 1331

medws(1 +2+3):

361 1 37_____&___j

xes 6 & 20:

1401 I 1411

least of boxes

22 to 25 and

30 to 33 and

38 to 42 gives

I 1421 p,3=1 1431

77

Page 84: Joints in Steel Construction Composite Connections · specified in either BS 4449 or BS EN 10080. Detailing rules are therefore given for two cases; bars that just meet the code requirements

Title SheetWorked example for a bolted end plate 6 of 9

3. COMPRESSION ZONE

3. 1 Column Web Crushing Step 2A

b1 = Tb + 2SWf + 2t,,, = 10.9 + 2 x 10 + 2 x 12 = 54.9 mm

n2 =2.5[T,+r]x2=(2.5x112.5+1O.2DX2 =113.5mm

.:P = (b1 + n) x t x p = (54.9 + 113.5) x 7.9 x 275 x icr3= 365.8kN

3.2 Column Web Buckling Step 2A

n1 = 206.2 mm

PC iS obtained from Table 27(c) of BS 5950 Part 1 using:

2.5d 2.5 x 160.8A =

tc=

7.9= 50.9

For p, = 2 75 N/mm, p, = 2 19 N/mm2

.: C 451.7kN

Therefore, column compression resistance = 366 kN

3.3 Beam Flange Crushing Step 2B

The potential resistance of the flange alone is:

C 14Pyb X Tb X Bb 1.4 x 275 x i0- x 10.9 x 177.7 = 745.7kN

4. COLUMN PANEL SHEAR ZONE Step 3

For this balanced situation, column panel shear is zero.

5. CALCULA TION OF MOMENT CAPACITY Step 4

A t this stage, potential reinforcement and bolt forces may need to be modifiedto satisfy certain criteria and maintain equilibrium.

5. 1 Equilibrium

Totalpotential tensile force (from reinforcement + bolts) is taken from Step 1Worksheet Boxes 1 and 7 respectively:

= einf P,1 = 530 + 208 * = 738 kN

(* this value may need to be modified when Step 1D is applied)

The potential compression resistance of the beam flange alone

78

Page 85: Joints in Steel Construction Composite Connections · specified in either BS 4449 or BS EN 10080. Detailing rules are therefore given for two cases; bars that just meet the code requirements

K7The SteelConstructionInstitute

Job I SheetComposite Moment Connections I

' of 9Title

Sliwood Park, Ascot, Berks SL5 7QNTelephone: (01344) 623345

Worked example for a bolted end plate

ClientFax: (01344) 622944

CALCULATION SHEET

SCI/BCSA Connections Group

Calcs by I Checked by I DateGHC AW May 1998

PC = 746kN

.: None of the beam web will be subject to compression.

Other compressive capacities (calculated above) are:

Column web crushing, 366 kN*

Column web bucking, 452 kN*

* Neither of these column capacities can be allowed to govern thebehaviour of a 'plastic' connection.

As column web crushing is critical, the column requires compressionstiffening, as detailed below. Alternatively, a more economic solutionmight be to use a heavier column section which does not needstiffening.

5.2 Column Compression Stiffeners Step 6A

Beam flange thickness Tb = 10.9 mm

therefore, try 15 mm thick stiffeners

Let width of each stiffener, bsg _ 95 mm ( = 6. 3t)

with a corner snipe of 12 mm

Buckling resistance of stiffener + column

PC buckling = (A + x p

where A = 40 t, x t = (40 x 7. 9) x 7. 9 = 2496 mm2

Asg 2 bsg X t = 2 x 95 X 1 5 2850 mm2

Derivation of p

r['s/w+Asg)] [(

15

)/(79x 316 + 15 x 2 x 95)]

. = 42.6 mm

L = D-2T = 206.2-2x12.5 = 181.2mm

79

Page 86: Joints in Steel Construction Composite Connections · specified in either BS 4449 or BS EN 10080. Detailing rules are therefore given for two cases; bars that just meet the code requirements

0.7 x L.A = ry

So from BS 5950 Part 1 Table 27(c), for p, = 275 N/mm2:

PC = 275 N/mm2

.: 'CbuCkIing = (A + A) x PC (2496 + 2850) x 275 x iG

= 147OkN

resistance of stiffener + column

= (ASflxp)+[(bl+n2)xtCxpJ

= 2b x t = 2 x (95- 12) x 1 5 —

b1 = (calculatedabove) =

n2 = (calculated above)

.: '°C Crushing = ((2490 x 2 75) + [(54. 9 + 1 13.5)

Bearing resistance of stiffener alone

P —x _ 2490 x 275 x iO-3

Cbearing 0.8 0.8

= 856kN

Compression resistance of stiffened column is the minimum of 1470 kN,1051 kN, and 856 kN

856 kN > 738 kN , so the stiffened column is adequate in compression, OK

5.3 Moment Capacity

il4 = (Creint X hreinf) + (Fri X hri)= [530 x (402. 6 + 80 - 1 0. 9/2) + 208 x (402. 6 - 60-10.9/2)]

x i0-

Title SheetWorked example for a bolted end plate 8 of 9

07 x 181242.6 2.98

Crushing

P C Crushing

where; 2490 mm2

54.9 mm

= 113.5 mm

x 7.9 x 275]) x i0

= lO5lkN

Step 4

= 252.9 + 70.1 = 323 kNm

80

Page 87: Joints in Steel Construction Composite Connections · specified in either BS 4449 or BS EN 10080. Detailing rules are therefore given for two cases; bars that just meet the code requirements

The SteelConstructionInstitute

Job 'SheetComposite Moment Connections I of 9

Title

Silwood Park, Ascot, Berks SL5 7QNTelephone: (01344) 623345

Worked example for a bolted end plate

ClientFax: (01344) 622944

CALCULATION SHEET

SCI/BCSA Connections Group

Calcs by Checked by I DateGHC AW May 1998

53OkN< 1T_________________

80

__ 601208 kN <

'402.6

738kN >loj

Note: The capacity table on page 86 gives a moment capacity of3 1 7 kNm. The difference from the value calculated above isbecause the tabulated value is based on a conservative estimationof the rebar height. The capacity table also states that rebarmust be able to achieve not less than 10% elongation atmaximum force for a 'plastic' connection with a 406 mm deepgrade S355 beam, and may need this level of ductility with anS275 beam. However, Table 4. 1 shows that '10% ' rebar is notrequired in this case.

6. CALCULA TION OF VERTICAL SHEAR CAPACITY Step 5

Shear capacity — n x + n x

where n, = 2

Pss = 91. 9 kN from tab/es for an M20 bolt

n = 2

Pts is the lesser of:

36. 8 kN for bolt shear (from tables)

1 10 kN for end plate bearing

1 15 kN for column flange bearing

. = 36.8kN

.: Shear capacity 258 kN (as given in the capacity table on page 86)

81

Page 88: Joints in Steel Construction Composite Connections · specified in either BS 4449 or BS EN 10080. Detailing rules are therefore given for two cases; bars that just meet the code requirements

82

Page 89: Joints in Steel Construction Composite Connections · specified in either BS 4449 or BS EN 10080. Detailing rules are therefore given for two cases; bars that just meet the code requirements

Appendix B

APPENDIX B Design Tables for Standard Composite 'Plastic'

B.1 INTRODUCTION

Connections

Tables are presented for composite beam-to-column'plastic' connections, suitable for use in framesdesigned using the procedures outlined in Section 3.Connections using M20 8.8 bolts, with flush endplate details, are followed by similar details with M248.8 bolts. For each steel detail, a range of eightreinforcement options is given. A reinforcementstrength of 460 N/mm2 is assumed.

Tabulated moment capacities are given for beams indesign grade 5275 or 5355, although somerestrictions apply (see tables). All end plates aregrade 5275. Column side capacities for grades 5275and 5355 must be checked as described below.

For a connection to work in the intended manner, itis important that the reinforcement details, plate sizeand steel grade, bolt sizes, weld sizes and dimensionsare rigidly adhered to. Deviating from them mayeither reduce the resistance of the connection,compromise its ductility or invalidate the columncheck. A table of dimensions for detailing to suitindividual beams is provided in Appendix B.

The standard connection capacities are based on theassumption that there is no axial force in the beam.

B.1.1 Beam side

Moment capacityThe moment capacities given for the beam side of theconnections were calculated using the procedurespecified in Section 4.2. Reinforcement and bolt rowforces are included in the tables.

For some details (highlighted with an asterisk *) a'plastic' connection can only be achieved whenreinforcement can attain 10% strain at peak load. Insome cases this restriction only applies to 5355beams; reference should be made to Figure 4.7 tocheck requirements for 5275 beams.

Values given in bold indicate that the detail may onlybe used with 5355 beams. This restriction may benecessary either:

. to maintain the neutral axis in the lower half ofthe steel beam

• to ensure that the connection capacity is lessthan that of the adjacent beam, thereby ensuring

that any plastic hinges will form in theconnections rather than at the beam ends.

Dimension ADimension 'A' is the lever arm from the centre ofcompression to the lowest row of tension bolts. Itcan be used to calculate a reduced moment capacitywhen tension forces are limited by the column flangestrength (see tables).

Weld sizesAll flange welds must be full strength, with aminimum visible fillet of 10 mm. All web weldsshould be continuous 8 mm fillets. For furtherinformation on details of the welds see Section 4.2,Step 7.

B. 1.2 Column side

Tension zoneA tick I in the table indicates that the column flangeand web in tension have a greater capacity than thebeam forces indicated in the beam side table. Wherethe column has a smaller capacity in flange bending,reduced bolt row forces are shown. A reducedmoment capacity may be determined from theselower forces, or the column flange may be stiffenedin the tension zone (Section 4.2, Step 6C). If thecolumn capacity is governed by web tension, an S inthe table indicates that tension stiffeners (or similarstrengthening) are needed to avoid potential non-ductile failure.

The capacities have been calculated assuming thatthe column top is at least 1 00 mm above the beamflange or top row of bolts.

Compression zoneA tick I in the table indicates that the column webhas a greater compression capacity than the sum ofthe reinforcement and bolt forces. The check wasmade assuming a stiff bearing length from the beamside of the connection of 50 mm.

An S in the table shows that the column webcompression capacity is lower than the sum of thereinforcement and bolt forces. The web must be

83

Page 90: Joints in Steel Construction Composite Connections · specified in either BS 4449 or BS EN 10080. Detailing rules are therefore given for two cases; bars that just meet the code requirements

Composite Connections

B. I .3 Worked example using thecapacity tables

An example is given below to illustrate the use of thecapacity tables. The starting point is some waydown the design flow chart given in Figure 3.2.

Worked example using the capacity tables

Choose a composite connection to suit the following member sizes and applied forces:

Column (internal):Beams:

254x254x167 UC, grade S355406x1 78x67 UB, grade S355

Try a connection adopting one row of M20 bolts, with ten 1 6 mm reinforcing bars (page 86).

Beam Side Column Side

Moment capacity 486kNm (page 86) > 435kNm OK Tension zone: / OK

. High elongation reinforcement is not needed[there is no in the tab/el

Beam is suitable in S355 only [capacity isgiven in bo/d type]

Compression zone: / OK(no stiffening required - there isno S in the tab/e)

Vertical shear 258kN (page 87) < 400kN Unsatisfactorywithout optional shear row

442kN (page 87) > 400kNOK with optional shear row

Column web panelshear

Opposing beams give zero shearacross the column web. OK

84

stiffened to resist these forces (see Section 4.2,Step 6A).

Panel shear zoneThe panel shear capacity is that of the column web.The applied web panel shear must take account ofbeams connecting • onto both flanges (seeSection 4.2, Step 3).

Applied moment:Applied shear:

435 kNm400 kN

Page 91: Joints in Steel Construction Composite Connections · specified in either BS 4449 or BS EN 10080. Detailing rules are therefore given for two cases; bars that just meet the code requirements

Appendix B

B.2 CAPACITY TABLES

Contents

M20 bolted connections

End plate Tension bolt rows Page

200x12 1 86

200x12 2 88

250x12 2 90

M24 bolted connections

End plate Tension bolt rows Page

200x15 1 92

200x15 2 94

250x15 2 96

Dimensions for detailing are shown on page 98.

85

Page 92: Joints in Steel Construction Composite Connections · specified in either BS 4449 or BS EN 10080. Detailing rules are therefore given for two cases; bars that just meet the code requirements

Composite Connections

I ROW M20 8.8 BOLTS200 x 12 5275 END PLATE

EAM SIDEB

BEAMSerialSize

Effective reinforcement (option, number and size of bars, Areiflf, Freinf)

ANo. 16

804 mm2351 kN

B6 No. 4161210 mm2

529 kN

C8 No. 4161610 mm2704 kN

D10 No. 4162010 mm2

878 kN

E4 No. 4201260 mm2

551 kN

F6 No. 4201890 mm2826 kN

G8 No. 4202510 mm21097 kN

H10 No. 4203140 mm21372 kN

'A'mm

MckNm

'A'mm

MckNm

'A'mm

MckNm

'A'mm

MckNm

'A'mm

MckNm

'A'mm

MckNm

'A'mm

MckNm

'A'mm

MckNm

457x191x98

89

82

74

67

398

395

392Q :398

395

392

390

z

362*

359*

358*

356*

398

395

392

390

454*

451*

449*

447*

398

395

392

384

546*

543*

540*

531*

398

395

392

390

373*

371*

369*

367*

398

395

392

39Q3

518*

515*

513*

510*

508*

398

395

392

390

661*

648*

654*

651*-

398

395

-

807

802

457x152x82

74

67

60

52

396

aa:

.9J.388j

2jZ.

2..:

2.:.:

396

394

391

388

!!i

361*

359*

356*

355*

396

394

385

388—

453*

450*

443*

445*—

396382

391

545*

529*

538*

396

394

391

388

!±_

372*

370*

368*

366*

!:

396

386

391

517*

506*

511*

396

387

—=—

660*

648*

——.

406x178x74

67

60

54

345

342

340

337

239*

237*

236*

234*

345

342

340

337

323*

321*

319*

317*

345

342

340

337

406*

4Q3*

401*

399*

345

336

489

486345

342

340

333

333*

331*

33Q*

324*

345

342

340

464*

461*

459*

345 593—

406x140x46

39

338

334

235*

232*

338 317*— — — —

338—

328*— — — — — — —

356x171x67

57

5 1

45

296

292

289

287

211*

209*

207 *

206*

296

292

289

287

286*

284*

282*

280*

296

292

289

361

357

355

289——

428——

296

292

289

287

296*

293*

29 1

289*

296292—

413

409—

296——

528——

356x127x3933

281280

203*202* — — — — — — — — — — — —

305x165x54

46

40

244

241

238

182

180

179

244

241

238

248

246

244

244——

313——

244

238

238

256

254

252

244——

359——

305x127x48

42

37

244

241

232

182

181

171

237

224

231

239

221

233

239——

308——

235

222

229

244

225

238

305x102x33

28

25

230

211—

163

143—

254x146x43

37

31

193

191

177

151

149

128

188

175—

195

176

187

172

199

179

254x102x2825

172—

121—

398 Beam may be either grade S275 or grade S355369 Beam must be grade S355 to satisfy neutral axis position requirements2.4 Beam must be grade S275 to satisfy minimum reinforcement requirements (see Table 4.1)* Reinforcement requires a guaranteed strain at maximum load of at least 1 0% for S355 beams, and possibly for S275

beams (check using Table 4.1)256 Connection capacity exceeds 0.8 N1 of composite beam in hogging (see Section 3.2.1 for significance of this)The value of Fri is based on the assumption that the NA is at least 200 mm below the bolt row. It should be reduced inaccordance with Section 4.2 Step 1 D when necessary.

86

Page 93: Joints in Steel Construction Composite Connections · specified in either BS 4449 or BS EN 10080. Detailing rules are therefore given for two cases; bars that just meet the code requirements

Appendix B

1 ROW M20 8.8 BOLTS200 x 12 5275 END PLATE COLUMN SIDE

S275

ColumnSerialSize

S355

Compression ZoneTension

ZoneWeb

Compn.Cap.

PanelShearCap.

PanelShearCap.

WebCompn.

Cap.

TensionZone Compression Zone

Fri Reinforcement option

A B C D E F G HReinforcement option

A B C D E F G HFri

(kN) (kN) (kN)(kN) (kN) (kN)

1000849725605

1141

935766605

////

1//1

1/1S

1/SS

1SSS

1/IS

1SSS

SSSS

SSSS

356x368x202x177x 153x129

II1I

II/I

IIIS

IISS

IIII

IISS

ISSS

SSSS

IIII

14861217974788

13021105944787

1037816703595503

14321051858692553

111//

/11/S

I11SS

I/SSS

ISSSS

IIISS

IISSS

ISSSS

SSSSS

305x305

x198x158x137x118x97

IIII/

II/IS

IIISS

IIISS

II,(

IS

IIISS

IISSS

ISSSS

IIIII

186513681116909713

13501062915774649

882685551

434360

1384992744557436

/////

/11S5

/11SS

/1SSS

/5SSS

I1SSS

I5SSS

ISSSS

SSSSS

254x254

x167x132x107x89x73

III//

IIISS

IIISS

IISSS

IIISS

/ISSS

ISSSS

ISSSS

IIIII

18021292969725563

1149892717566465

459353322272245

701512440360313

v'///198

,'SSSS

SSSSS

SSSSS

SSSSS

SSSSS

SSSSS

SSSSS

SSSSS

203x203

x86x71x60x52x46

I//SS

ISSSS

ISSSS

SSSSS

ISSSS

SSSSS

SSSSS

SSSSS

IIIII

913666568464404

598460415351

316Tension Zone:/ Column satisfactory for bolt row tension values shown for the beam side.1 95 Recalculate moment capacity based on reduced bolt row force (1 95 kN) using dimension 'A' to derive appropriate lever

arm - or provide tension stiffener at the appropriate bolt row level.Compression Zone:/ Column capacity exceeds ZF = Frejflf + FS Provide compression stiffener.

87

Page 94: Joints in Steel Construction Composite Connections · specified in either BS 4449 or BS EN 10080. Detailing rules are therefore given for two cases; bars that just meet the code requirements

Composite Connections

2 ROWS M20 8.8 BOLTS200 x 12 5275 END PLATE

E SB AM IDE

BEAMSerialSize

Effective reinforcement (option, number and size of bars, Areinf, Freint)

A4No.416804 mm2351 kN

B6No.161210 mm2

529 kN

C8No.161610 mm2704 kN

D1ONo.162010 mm2

878 kN

E

4No.4201260 mm2

551 kN

F6No.4201890 mm2

826 kN

G8No.4202510 mm2

1097 kN

H

1ONo.2O3140 mm21372 kN

'A'mm

MckNm

'A'mm

MckNm

'A'mm

MckNm

'A'mm

MckNm

'A'mm

MckNm

'A'mm

MckNm

'A'mm

MckNm

'A'mm

MckNm

533x210x122

109

101

92

82

.4Q378

354*

1Q

aziQ.

384

380

378

375

575*

571*

569*

566*

384

380

378

375

372

681*

676*

674*

670*

995*

a?.Q

iZ

j iz.:472*

384

380

378

375

.L623*

649*

645*

642*

639*

384

380

378

375

813*

807*

791*

800*-

377

380

378

-

967*

973*

969*

-

457x191x98

89

82

74

67

.QQ

ai_Q..

1Q.4..

302*

308

305

302

300

97

403*

401*

398*

396*

39L

308

305

302

3Q1J

495*

492*

490*

487*

44

308

305

302

300-

588*

584*

572*

579*

-

308

305

302

300

97

415*

412*

410*

408*4

308

305

302

3002

560*

556*

553*

551*

54

301

305

302

-

693*

699*

695*

-

308

—-

848

—-

457x152x82

74

67

60

52

1Q

Qj.Q.QL

306

304

301

288

402*

400*

397*

386*

:!z.:

306

295

285

292—

494*

482*

472*

479*

294

304

293

571*

583*

570*

306

304

296

286

!Z

414*

411*

404*

395*

!2?2

297

285

295

548*

531*

546*

301

——

693*

——

406x178x74

67

60

54

255

252

250

247

273

271*

270*

268*

255

252

250

233

357*

355*

353*

331*

255

244

250

440*

425*

435*

243

252

502

520

255

252

245

247

368*

365*

357*

361*

247

252

485*

495*

250

——

618

——

406x140x4639

237235

255*255* — — — — — — — — — — — —

398 Beam may be either grade S275 or grade S355369 Beam must be grade S355 to satisfy neutral axis position requirements2.: Beam must be grade S275 to satisfy minimum reinforcement requirements (see Table 4.1)* Reinforcement requires a guaranteed strain at maximum load of at least 1 0% for S355 beams, and possibly for S275

beams (check using Table 4.1)256 Connection capacity exceeds O.8Mp of composite beam in hogging (see Section 3.2.1 for significance of this)The value of Fri 15 based on the assumption that the NA is at least 200mm below the bolt row. It should be reduced in

accordance with Section 4.2 Step 1 D when necessary.

88

Page 95: Joints in Steel Construction Composite Connections · specified in either BS 4449 or BS EN 10080. Detailing rules are therefore given for two cases; bars that just meet the code requirements

Appendix B

2 ROWS M20 8.8 BOLTS200 x 1 2 5275 END PLATE N SIDECOLUM

S275

ColumnSerialSize

S355

PanelShearCap.

WebCompn.

Cap.

TensionZone Compression Zone Compression Zone

TensionZone

WebCompn.

Cap.

PanelShearCap.Reinforcement option

A B C D E F G HFri 'r2Fri Fr2 Reinforcement option

A B C D E F G H (kN) (kN) (kN)(kN) (kN) (kN)

1000849725605

1141935766605

1 11 1/ // /

11/S

11SS

1SSS

SSSS

I SI SS SS S

SSSS

SSSS

356x368x202x177x153x129

III/

II/S

IISS

ISSS

IIIS

IISS

ISSS

SSSS

I II II /I I

14861217974788

13021105944787

1037816703595503

14321051858692553

/ 1/ 11 11 1/ /

111SS

11SSS

11SSS

1SSS55

1 1S

S S55

S

SSSSS

SSSSS

305x305

x198x158x137x118x97

II/I/

II/IS

IIISS

IISSS

IIIIS

IISSS

ISSSS

ISSSS

I II II fI I/ /

186513681116909713

13501062915774649

882685551

434360

1384992744557436

/ 11 1/ // /1 1

111SS

1/SSS

b'SSSS

I IS IS S55S S

ISSSS

SSSSS

SSSSS

254x254

x167x132x107x89x73

IIIIS

IIISS

IISSS

IISSS

IIISS

IISSS

ISSSS

ISSSS

I II II II II I

18021292969725563

1149892717566465

459353322272245

701512440360313

,' I/ // /1 1198 97

ISSSS

SSSSS

SSSSS

S S555555S S

SSSSS

SSSSS

SSSSS

203x203

x86x71

x60x52x46

ISSSS

ISSSS

SSSSS

SSSSS

ISSSS

SSSSS

SSSSS

SSSSS

I I/ // /I II ,'

913666568464404

598460415351316

Tension Zone:/ Column satisfactory for bolt row tension values shown for the beam side.1 95 Recalculate moment capacity based on reduced bolt row force (1 95 kN) using dimension 'A' to derive appropriate lever

arm - or provide tension stiffener at the appropriate bolt row level.Compression Zone:/ Column capacity exceeds F = Fejnf + FriS Provide compression stiffener.

9o-

Vertical Shear Capacityl515kN I

89

Page 96: Joints in Steel Construction Composite Connections · specified in either BS 4449 or BS EN 10080. Detailing rules are therefore given for two cases; bars that just meet the code requirements

Composite Connections

2 ROWS M20 8.8 BOLTS250 x 12 5275 END PLATE

BEAM SIDE

BEAMSerialSize

Effective reinforcement (option, number and size of bars, Areiflf, Freinf)

ANo. 416

804 mm2351 kN

B6 No. 4161 21 0 mm2

529kN

C8 No. 161 61 0 mm2

7O4kN

D10 No. 416201 0 mm2

878kN

E4 No. 4201 260 mm2

551 kN

F6 No. 4201 890 mm2

826kN

G8 No. 4202510 mm21O97kN

H10 No. 42031 40 mm2

1372kN

'A'mm

MckNm

'A'mm

MckNm

'A'mm

MckNm

'A'mm

MckNm

'A'mm

MckNm

'A'mm

MckNm

'A'mm

MckNm

'A'mm

MckNm

533x210x122

109

101

92

82

Qazi: 1Q

ll.

:aa.

4.Z.Z..

471*

384

380

378

375

366

588*

583*

581*

578*

384

380

378

375

372

693*

688*

686*

682*

Z!

Q

gg

384

380

378

375

359

662*

657*

654*

651*:

384

375

367

375

---

825*

811*

800*

812*

375

380

378

-

976*

985*

981*

-

457x191x98

89

82

74

67

.QQ

308

305

302

300

413*

410*

408*

406*

308

305

302

294a

505*

502*

499*

491*

308

305

293

300

..=....

597*

594*

579*

588*-

308

305

302

300

2L

425*

422*

419*

417*

308

305

296

300

293

570*

566*

556*

560*

55

299

305

302

-

7Q1J*

708*

705*

-

308

—-

858

—-

457x152x82

74

67

60

52

.Qj

2...Q

j_

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306

304

296

285

.!?_

412*

409*

402*

393*

:!2±:

306

93283

504*

499*

475*

292

304

291——

578*

592*

577*——

306

304

294

298

a!!.

423*

421*

412*

416*

295

283294

555*

534*

553*

-_=-_.

300

——

701*

——

398 Beam may be either grade S275 or grade S355369 Beam must be grade S355 to satisfy neutral axis position requirements

2.Q.: Beam must be grade S275 to satisfy minimum reinforcement requirements (see Table 4.1)* Reinforcement requires a guaranteed strain at maximum load of at least 1 0% for S355 beams, and possibly for S275

beams (check using Table 4.1)256 Connection capacity exceeds O.8Mp of composite beam in hogging (see Section 3.2.1 for significance of this)The value of Fri IS based on the assumption that the NA is at least 200mm below the bolt row. It should be reduced inaccordance with Section 4.2 Step 1 0 when necessary.

90

Page 97: Joints in Steel Construction Composite Connections · specified in either BS 4449 or BS EN 10080. Detailing rules are therefore given for two cases; bars that just meet the code requirements

Appendix B

2 ROWS M20 8.8 BOLTS250 x 12 5275 END PLATE COLUMN SIDE

S275

ColumnSerialSize

S355

Compression ZoneTension

ZoneWeb

Compn.PanelShearCap.

PanelShearCap.

WebCompn.

Cap.

TensionZone Compression Zone

Fri Fr2 Reinforcement option

A B C D E F G HReinforcement option

A B C .D E F G HFri 12 Cap.

(kN) (kN) (kN)(kN) (kN) (kN)

1000849725605

1141

935766605

/ 1/ // 1/ /

1/1S

1/SS

1SSS

SSSS

I S/ SS SS S

SSSS

SSSS

356x368x202x177x153x129

III/

IIIS

IISS

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/IIS

IISS

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I II II II I

14861217974788

13021105944787

1037816703595503

14321051858692553

/ 11 1/ // 1/ 1

11/SS

1/SSS

1SSSS

1SSS55

1 1S

S SSS

SSSSS

SSSSS

305x305

x198x158x137x118x97

/IIIS

IIIIS

IIISS

IISSS

IIISS

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ISSSS

I II II II II I

186513681116909713

13501062915774649

882685551434360

1384992744557436

1 1/ 1f I1 1/ /

11ISS

11SSS

/SSSS

I IS IS S5555

ISSSS

SSSSS

SSSSS

254x254

x167x132x107x89x73

I/ISS

IIISS

/ISSS

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I'

SSSS

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I II II II II I

18021292969725563

1149892717566465

459353322272245

701

512440360313

1 '/ // 1/ 1198 97

SSSSS

SSSSS

SSSSS

S S555555S S

SSSSS

SSSSS

SSSSS

203x203

x86x71x60x52x46

/SSS.5

ISSSS

SSSSS

SSSSS

SSSSS

SSSSS

SSSSS

SSSSS

I II II II II I

913666568464404

598460415351316

Tension Zone:/ Column satisfactory for bolt row tension values shown for the beam side.1 95 Recalculate moment capacity based on reduced bolt row force (1 95 kN) using dimension 'A' to derive appropriate lever

arm - or provide tension stiffener at the appropriate bolt row level.Compression Zone:I Column capacity exceeds ZF = Frejflf+FrlS Provide compression stiffener.

91

Vertical Shear Capacity515 kN

Page 98: Joints in Steel Construction Composite Connections · specified in either BS 4449 or BS EN 10080. Detailing rules are therefore given for two cases; bars that just meet the code requirements

Composite Connections

1 ROW M24 8.8 BOLTS200 x 15 5275 END PLATE

BEAM SIDE

BEAMSerialSize

Effective reinforcement (option, number and size of bars, Areinf,_Freinf)

ANo. 416

804 mm2351 kN

B6 No. 4161 21 0 mm2

529kN

C8 No. 161 61 0 mm2

7O4kN

D10 No. 416201 0 mm2

878kN

E4 No. 2O1 260 mm2

551 kN

F6 No. 4201 890 mm2826kN

G8 No. 2O251 0 mm21O97kN

H10 No. 2O31 40 mm21372kN

'A'mm

MckNm

'A'mm

MckNm

'A'mm

MckNm

'A'mm

MckNm

'A'mm

MckNm

'A'mm

MckNm

'A'mm

MckNm

'A'mm

MckNm

457x191x98

89

82

74

67

395

392

.Q3p*

398

395

392

3903

401*

398*

396*

394*

2:

398

395

392

39Q

!L

493*

490*

487*

485*:

398

395

387

390-

585*

581*

572*

576*-

398

395

392

390L

412*

410*

407*

405*

398

395

392

390

2L

557*

554*

551*

549*

392

395

392

-

693*

696*

693*

-

398

—-

846

—-

457x152x82

74

67

60

52

aj.388

396

394

391

381

400*

397*

395*

386*

396

387

378

388—

492*

482*

473*

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386

394

385

572*

580*

570*

396

394

391

379

:!Z2

411*

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389

378391

548*

536*

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396

——

699*

——

406x178x74

67

60

54

345

342

340

337

272*

271*

269*

267*

345

342

340

337

357*

354*

353*

350*

345

336

340

440*

431*

435*

336

342

512

520

345

342

34Q

337

367*

365*

363*

360*

339

342

491*

495*

345

626

406x140x4639

331327

263*261* — — —

—— — — — — — — — —

356x171x67

57

51

45

296

292

289

282

240*

237 *

236*231*

296

292

289

315*

312 *

310*

296

292

390

386

296—

464—

296

292

289—

325*

32 1

319*—

296

442

— —

356x127x3933

273—

235*— — —

305x165x54

46

40

244

241

234

206

204

193

244

241—

272

270—

244——

337——

244

241—

280

278—

305x127x48

42

37

244

232

221

206

189

170

229

213—

242

216—

227

210—

246

219—

305x102x332825

215—

157—

254x146x43

37

31

193

183—

169

144—

180——

190

——

177——

193——

398 Beam may be either grade S275 or grade S355369 Beam must be grade S355 to satisfy neutral axis position requirements

2.Q.: Beam must be grade S275 to satisfy minimum reinforcement requirements isee Table 4. 1)* Reinforcement requires a guaranteed strain at maximum load of at least 1 0% for S355 beams, and possibly for S275

beams check using Table 4.1)256 Connection capacity exceeds O.8Mp of composite beam in hogging (see Section 3.2.1 for significance of this)The value of Fri 5 based on the assumption that the NA is at least 200mm below the bolt row. It should be reduced inaccordance with Section 4.2 Step 1 D when necessary. _______________________________________

92

Page 99: Joints in Steel Construction Composite Connections · specified in either BS 4449 or BS EN 10080. Detailing rules are therefore given for two cases; bars that just meet the code requirements

Appendix B

I ROW M24 8.8 BOLTS200 x 1 2 S275 END PLATE

c MN SIDEOLU

S275

ColumnSerialSize

S355

Compression ZoneTension

ZoneWeb

Compn.Cap.

PanelShearCap.

PanelShearCap.

WebCompn.

Cap.

TensionZone Compression Zone

Fri Reinforcement option

A B C D E F G HReinforcement option

A B C D E F G HFri

(kN) (kN) (kN)(kN) (kN) (kN)

1000849725605

1141935766605

11//

111S

11SS

1SSS

SSSS

IISS

ISSS

SSSS

SSSS

356x368x202x177x153x129

I/II

IIIS

IISS

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ISSS

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14861217974788

13021105944787

1037816703595503

14321051858692553

111//

111/S

1115S

11SSS

1SSSS

1/ISS

1SSSS

1SSSS

SSSSS

305x305

x198x158x137x118x97

II/I/

I//IS

/IISS

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IIIIS

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IIIII

186513681116909713

13501062915774649

882685551434360

1384992744557436

/11/

297

I11SS

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254x254

x167x132x107x89x73

//IIS

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IIIII

18021292969725563

1149892717566465

459353322272245

701512440360313

/1297265204

1SSSS

SSSSS

SSSSS

SSSSS

SSSSS

SSSSS

SSSSS

SSSSS

203x203

x86x71

x60x52x46

I/SSS

ISSSS

SSSSS

SSSSS

ISSSS

SSSSS

SSSSS

SSSSS

III296263

913666568464404

598460415351316

I,, Column satisfactory for bolt row tension values shown for the beam side.1 95 Recalculate moment capacity based on reduced bolt row force (1 95 kN) using dimension 'A' to derive appropriate lever

arm - or provide tension stiffener at the appropriate bolt row level.Compression Zone:/ Column capacity exceeds F = Frejflf FriS Provide compression stiffener.

I 60

Vertical Shear Capacity370 kN without shear row634 kN with shear row

Tension Zone:

I • .'. .. I..'..,>•._ £ • •' :.

Optional

9OV shear row

6490 55

93

Page 100: Joints in Steel Construction Composite Connections · specified in either BS 4449 or BS EN 10080. Detailing rules are therefore given for two cases; bars that just meet the code requirements

Composite Connections

2 ROWS M24 8.8 BOLTS200 x 15 5275 END PLATE

BEAM SIDE

BEAMSerialSize

Effective reinforcement (option, number and size of bars, Areinf, Freinf)A

4No.416804 mm2351 kN

B6No.4161210 mm2

529 kN

C8No.4161610 mm2

704 kN

DlONo.4162010 mm2

878 kN

E

4No.2O1260 mm2

551 kN

F

6No.4201890 mm2826 kN

G8No.4202510 mm21097 kN

H1ONo.2O3140 mm2

1372 kN

'A'mm

MckNm

'A'mm

MckNm

'A'mm

MckNm

'A'mm

MckNm

'A'mm

MckNm

'A'mm

MckNm

'A'mm

MckNm

'A'mm

MckNm

533x210x122

109

101

92

82

.1:

.Q

434*

.Q

L

384

380

378

375

372

658*

653*

651*

647*:

384

380

370

362

366

763*

758*

744*

732*

Z!

.Q.a:

384

380

373

365

372

732*

727*

716*

706*

715*

384

366

375

370

895*

867*

886*

873*

367

380

-

1029*

1054*

-

457x191x98

89

82

74

67

Q2QQ

ll.ll.a

368*

308

305

302

295

93

471*

468*

465*

458*

4W

308

305

294

300

291

563*

560*

547*

554*

54

302

291

282

293-

647*

631*

610*

635*-

308

305

302

294

282

483*

479*

477*

468*

45

308

294

286300-

628*

610*

594*

617*

-

289

305

-

734*

766*

-

299

——

-

900

——

-457x152x82

74

67

6052

1Q.:

QJ287

1Z4azi

az.:.

306

294

284

291

470*

456*

443*

454*

293

279

292

545*

516*

544*

279

292

600*

534*

——

306

292

282

290—

481*

466*

45Q*

464*—

283

267

585*

549*

292

——

745*

——

406x178x74

67

60

54

255

252

245

232

331*

328*

320*

296*

255

243

231

212

415*

394 *

369*322*

242

228

469*

44 1

228——

510——

255

24 1

228

209

425*

4QQ*

374*

323*

232

2445Q3*

533*—

406x140x46

39

213—

251*— — — — — — — — — — — — — — —

398 Beam may be either grade S275 or grade S355369 Beam must be grade S355 to satisfy neutral axis position requirements

2.Q.: Beam must be grade S275 to satisfy minimum reinforcement requirements (see Table 4. 1)* Reinforcement requires a guaranteed strain at maximum load of at least 1 0% for S355 beams, and possibly for S275

beams (check using Table 4.1)256 Connection capacity exceeds O.8Mp of composite beam in hogging (see Section 3.2.1 for significance of this)The value of Fri 5 based on the assumption that the NA is at least 200 mm below the bolt row. It should be reduced inaccordance with Section 4.2 Step 1 D when necessary.

94

Page 101: Joints in Steel Construction Composite Connections · specified in either BS 4449 or BS EN 10080. Detailing rules are therefore given for two cases; bars that just meet the code requirements

Appendix B

2 ROWS M24 8.8 BOLTS200 x 15 5275 END PLATE

COLUMN SIDE

S275

ColumnSerialSize

S355

PanelShearCap.

WebCompn.

Cap.

TensionZone Compression Zone Compression Zone

TensionZone

WebCompn.

Cap.

PanelShearCap.Reinforcement option

A B C D E F G HFri Fr2;1 '2 Reinforcement option

A B C D E F G H(kN) (kN) (kN) (kN) (kN) (kN)

1000849725605

1141935766605

/ 11 1/ // /

/1SS

ISSS

SSSS

SSSS

ISSS

SSSS

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356x368

x202x177x153x129

/IIS

,(

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13021105944787

1037816703595503

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1 1/ 1/ // // /

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305x305

x198x158x137x118x97

III/S

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SSSSS

I II II II II I

186513681116909713

13501062915774649

882685551434360

1384992744557436

/ 11 11 11 1297/

11S5S

1SSSS

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254x254

x167x132x107x89x73

IIISS

IISSS

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IISSS

ISSSS

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SSSSS

I II II II II I

18021292969725563

1149892717566465

459353322272245

701512440360313

/ // /

297 204265 118204 90

S5S55

S5SSS

S5SSS

SSSSS

SSSSS

SSSSS

SSSSS

SSSSS

203x203

x86x71x60x52x46

ISSSS

SSSSS

SSSSS

SSSSS

SSSSS

SSSSS

SSSSS

SSSSS

I II II I296 198263 116

913666568464404

598460415351316

Tension Zone:/ Column satisfactory for bolt row tension values shown for the beam side.1 95 Recalculate moment capacity based on reduced bolt row force ( 1 95 kN) using dimension 'A' to derive appropriate lever

arm - or provide tension stiffener at the appropriate bolt row level.Compression Zone:I Column capacity exceeds F = Feinf FriS Provide compression stiffener.

95

Vertical Shear Capacity739 kN

Page 102: Joints in Steel Construction Composite Connections · specified in either BS 4449 or BS EN 10080. Detailing rules are therefore given for two cases; bars that just meet the code requirements

Composite Connections

2 ROWS M24 8.8 BOLTS250 x 15 5275 END PLATE

BEAM SIDE

BEAMSerialSize

Effective reinforcement (option, number and size of bars, Areinft Freinf)

A4No.16804 mm2351 kN

B6No.161210 mm2

529kN

C8No.4161610 mm2

7O4kN

D1ONo.162010 mm2

878kN

E4No.4201260 mm2

551 kN

F6No.42.O1890 mm2

826kN

G8No.4202510 mm21O97kN

HlONo.4203140 mm21372kN

'A'mm

MckNm

'A'mm

MckNm

'A'mm

MckNm

'A'mm

MckNm

'A'mm

MckNm

'A'mm

MckNm

'A'mm

MckNm

'A'mm

MckNm

533x210x122

109

101

92

82

.Q7.Q

gg

.Q

g:

384

380

378

370

353

671*

666*

664*

653*

632*

384

380

368

359L

777*

771*

754*

741*

ll.i

1Z

2:

384

380

371

363

745*

740*

727*

716*

Z!

384

364

378

369-

9Q9*

876*

899*

884*

-

365

374

-

1038*

1055*

-

457x191x98

89

82

74

67

QQ

--_j_379*

308

305

302

293

482*

478*

476*

466*:

308

299

292

280

289

574*

563*

554*

529*

551*

300

288

279

292

655*

633*

610*

643*

308

305

302

292

278

493*

490*

487*

476*

451*

308

292

283

294

639*

617*

596*

620*

287

299

-

736*

766*

--

298

——

-

908

——

-457x152x82

74

67

60

52

22g1

301

291

281

289—

475*

464*

445*

462*—

290

276

290

550*

516*

552*

276

290

——

599*

641*

——

300

289

279

288—

485*

473*

451*

472*—

280

263

585*

546*

398 Beam may be either grade S275 or grade S355369 Beam must be grade S355 to satisfy neutral axis position requirements2.: Beam must be grade S275 to satisfy minimum reinforcement requirements (see Table 4. 1)* Reinforcement requires a guaranteed strain at maximum load of at least 1 0% for S355 beams, and possibly for S275

beams (check using Table 4.1)256 Connection capacity exceeds 0.8 Mp of composite beam in hogging (see Section 3.2.1 for significance of this)The value of Fri 5 based on the assumption that the NA is at least 200 mm below the bolt row. It should be reduced in

accordance with Section 4.2 Step 1 D when necessary. ___________________________________________________

96

Page 103: Joints in Steel Construction Composite Connections · specified in either BS 4449 or BS EN 10080. Detailing rules are therefore given for two cases; bars that just meet the code requirements

Appendix B

2 ROWS M24 8.8 BOLTS250 x 15 5275 END PLATE

COLUMN SIDE

S275

ColumnSerialSize

S355

PanelShearCap.

WebCompn.

Cap.

TensionZone Compression Zone Compression Zone

TensionZone

WebCompn.

Cap.

PanelShearCap.Reinforcement option

A B C D E F G HFri Fr2Fri Fr2 Reinforcement option

A B C D E F G H(kN) (kN) (kN) (kN) (kN) (kN)

1000 1141 / / / 1 S S I S S S356x368

x202 / I I I I I S S I I 1486 1302849 935 1 1 1 S S S S S S S x177 / I S S I S S S I I 1217 1105725 766 / / S S S S S S S S x153 / S S S S S S S / I 974 944605 605 / / 5 5 S S S S S S x129

305x305

S S S S S S S S I I 788 787

1037 1432 1 1 1 1 1 5 / ( S S x198 I I I I I I I S I I 1865 1350816 1051 / / 1 5 5 5 5 S S S x158 I I I S I S S S I I 1368 1062703 858 / / S S S S S S S S x137 / I S S S S S S I I 1116 915595 692 / / S S S S S S S S x118 S S S S S S S S I I 909 774503 553 / / S S S S S S S S x97

254x254

S S S S S S S S I I 713 649

882 1384 / / / / / 5 1 S S S x167 I I I I I I I S I I 1802 1149685 992 1 1 1 5 5 5 5 5 5 S x132 I I I S I S S S I I 1292 892551 744 / / S S S S S S S S x107 / S S S S S S S / I 969 717434 557 / / 5 S S S S S S S x89 S S S S S S S S I I 725 566360 436 297/ S S S S S S S S x73

203x203

S S S S S S S S I I 563 465

459 701 / / S S S S S S S S x86 S S S S S S S S / I 913 598353 512 / / S S S S S S S S x71 S S S S S S S S / I 666 460322 440 297 204 S S S S S S S S x60 S S S S S S S S / I 568 415272 360 265 118 S S S S S S S S x52 S S S S S S S S 296 198 464 351

245 313 204 90 5 S S S S S S S x46 S S S S S S S S 263 116 404 316Tension Zone:I Column satisfactory for bolt row tension values shown for the beam side.1 95 Recalculate moment capacity based on reduced bolt row force (1 95 kN) using dimension 'A' to derive appropriate lever

arm - or provide tension stiffener at the appropriate bolt row level.Compression Zone:I Column capacity exceeds ZF = Freflf+F1

I S Provide compression stiffener. I

97

Vertical Shear Capacity739 kN

Page 104: Joints in Steel Construction Composite Connections · specified in either BS 4449 or BS EN 10080. Detailing rules are therefore given for two cases; bars that just meet the code requirements

Composite Connections

B.3 DETAILING TABLES

DIMENSIONS FOR DETAILING

Beamserial size

Dimension

a1mm

Dimensiona2

mm

End plateoverall depth

mm

533x210x1221091019282

425420415415410

245240235235230

600

457x191x9889827467

350345340340335

170165160160155

520

457x152x8274676052

345340340335330

165160160155150

520

406x178x74676054

295290285285

115110105105

470

406x140x4639

280275

10095 450

356x171x67575145

245240235230

————

420

356x127x3933

235230

—— 410

305x165x544640

190185185

———

360

305x127x484237

190185185

———

360

305x102x332825

195190185

———

370

254x146x433731

140135135

———

310

25 /t1!97t/

6QFa D

1 F

:44k20° or 250,,,

(see appropriate capacity table)

V25 _______60 '

- -±4--9o_ 4-

a2jL DF9-r.+L

or 250,4,(see appropriate capacity table)

254x1 02x282522

140135135

310

See capacity table diagram for plate thickness and other dimensions appropriate to the moment capacities.All plates to be S275.

98