Table of Contents

Cover

Series

Title

FOREWORD

PREFACE

LIST OF SYMBOLS AND ABBREVIATIONS

Chapter 1: INTRODUCTION

1.1 GENERAL
1.2 DEFINITIONS
1.3 MATERIAL CHOICE
1.4 FABRICATION AND ERECTION
1.5 COSTS
1.6 DESIGN APPROACHES
1.7 DESIGN TOOLS
1.8 WORKED EXAMPLES

Chapter 2: STRUCTURAL ANALYSIS AND DESIGN

2.1 INTRODUCTION
2.2 JOINT MODELLING
2.3 JOINT IDEALISATION
2.4 JOINT CLASSIFICATION
2.5 DUCTILITY CLASSES

Chapter 3: CONNECTIONS WITH MECHANICAL FASTENERS

3.1 MECHANICAL FASTENERS
3.2 CATEGORIES OF CONNECTIONS
3.3 POSITIONING OF BOLT HOLES
3.4 DESIGN OF THE BASIC COMPONENTS
3.5 DESIGN OF CONNECTIONS

Chapter 4: WELDED CONNECTIONS

4.1 TYPE OF WELDS
4.2 CONSTRUCTIVE CONSTRAINTS
4.3 DESIGN OF WELDS
4.4 DISTRIBUTION OF FORCES IN A WELDED JOINT

Chapter 5: SIMPLE JOINTS

5.1 INTRODUCTION
5.2 STEEL JOINTS
5.3 COMPOSITE JOINTS
5.4 COLUMN BASES

Chapter 6: MOMENT RESISTANT JOINTS

6.1 INTRODUCTION
6.2 COMPONENT CHARACTERISATION
6.3 ASSEMBLY FOR RESISTANCE
6.4 ASSEMBLY FOR ROTATIONAL STIFFNESS
6.5 ASSEMBLY FOR DUCTILITY
6.6 APPLICATION TO STEEL BEAM-TO-COLUMN JOINT CONFIGURATIONS
6.7 APPLICATION TO STEEL COLUMN SPLICES
6.8 APPLICATION TO COLUMN BASES
6.9 APPLICATION TO COMPOSITE JOINTS

Chapter 7: LATTICE GIRDER JOINTS

7.1 GENERAL
7.2 SCOPE AND FIELD OF APPLICATION
7.3 DESIGN MODELS

Chapter 8: JOINTS UNDER VARIOUS LOADING SITUATIONS

8.1 INTRODUCTION
8.2 COMPOSITE JOINTS UNDER SAGGING MOMENT
8.3 JOINTS IN FIRE
8.4 JOINTS UNDER CYCLIC LOADING
8.5 JOINTS UNDER EXCEPTIONAL EVENTS

Chapter 9: DESIGN STRATEGIES

9.1 DESIGN OPPORTUNITIES FOR OPTIMISATION OF JOINTS AND FRAMES
9.2 APPLICATION PROCEDURES

BIBLIOGRAPHIC REFERENCES

Annex A: Practical values for required rotation capacity

Annex B: Values for lateral torsional buckling strength of a fin plate

End User License Agreement

List of Tables

Chapter 1: INTRODUCTION

Table 1.1 – Types of hollow section joints in lattice structures
Table 1.2 – List of components covered by Eurocode 3 Part 1-8
Table 1.3 – List of components covered by Eurocode 4 Part 1-1

Chapter 2: STRUCTURAL ANALYSIS AND DESIGN

Table 2.1 – Four main approaches for frame analysis
Table 2.2 – Selection between elastic and plastic (elasto-plastic) analysis and design process
Table 2.3 – Types of joint modelling
Table 2.4 – Joint modelling and frame analysis
Table 2.5 – Simplified modelling for joints according to EC3
Table 2.6 – Approximate values for the transformation parameter β
Table 2.7 – Stiffness modification factor
Table 2.8 – Joint classification boundaries

Chapter 3: CONNECTIONS WITH MECHANICAL FASTENERS

Table 3.1 – Bolts classes and nominal values of yield strength f_yb and ultimate tensile strength f_ub.
Table 3.2 – Bolt areas in accordance with EN ISO 898 (CEN, 2013)
Table 3.3 – Minimum and maximum spacing, end and edge distances
Table 3.4 – Design shear resistances F_v,Rd in kN (for γ_M2 = 1.25)
Table 3.5 – Design tension resistances F_t,Rd in kN (for γ_M2 = 1.25)
Table 3.6 – Nominal values of F_p,C in kN
Table 3.7 – Friction surface classes and slip factors
Table 3.8 – Additional rotation for the combined method
Table 3.9 – Values for t_b,resin and β
Table 3.10 – Design formulae for pin connections
Table 3.11 – Minimum plate thickness
Table 3.12 – Reduction factors β₂ and β₃

Chapter 4: WELDED CONNECTIONS

Table 4.1 – Conditions for welding cold-formed zones and adjacent material
Table 4.2 – Correlation factor β_w for fillet wed design
Table 4.3 – Values of β_w and f_w,u,end for steels according to EN 10025 and minimum “full strength” required weld thickness in case of double fillet end welds (plate thickness smaller than 40 mm; γ_M0 = 1.0 and γ_M2 = 1.25)

Chapter 5: SIMPLE JOINTS

Table 5.1 – Minimum required “full strength” weld thickness a in case of double fillet welds. Plate thickness smaller than 40 mm; γ _M0 = 1.0 and γ _M2 = 1.25

Chapter 6: MOMENT RESISTANT JOINTS

Table 6.1 – Reduction factor ω for interaction with shear
Table 6.2 – Effective lengths for an unstiffened column flange in a bolted connection
Table 6.3 – Effective lengths for a stiffened column flange in a bolted connection
Table 6.4 – Effective lengths for an end-plate
Table 6.5 – Overview of components covered by EN 1993-1-8 and list of active components for different joints
Table 6.6 – Values of the ψ coefficient
Table 6.7 – Good guess of the initial stiffness for typical beam-to-column joint configurations
Table 6.8 – Stiffness coefficients

Chapter 9: DESIGN STRATEGIES

Table 9.1 – Parties and their roles in the design/fabrication process of a steel structure
Table 9.2 – Variations in joint detailing and relative savings in fabrication costs
Table 9.3 – Boundaries for variance between actual and approximate initial stiffnesses
Table 9.4 – Boundaries for actual initial stiffness (given fixity factors)
Table 9.5 – Strength recommendations for joints during preliminary design

List of Illustrations

Chapter 1: INTRODUCTION

Figure 1.1 – Classification of joints according to stiffness
Figure 1.2 – Modelling of joints (case of elastic global analysis)
Figure 1.3 – Elastic distribution of bending moments in a simple portal frame
Figure 1.4 – M − ϕ characteristics for member cross section and joint
Figure 1.5 – Ductility or rotation capacity in joints
Figure 1.6 – Schematic of the proportion of effort for global analysis and for ULS checks
Figure 1.7 – Different types of joints in a building frame
Figure 1.8 – Joints and connections
Figure 1.9 – Sources of joint deformability
Figure 1.10 – Loading of the web panel and the connections
Figure 1.11: Deformability of a minor axis joint
Figure 1.12 – Loading of a double-sided minor axis joint
Figure 1.13 – Example of a 3-D joint
Figure 1.14 – Deformation of a beam splice
Figure 1.15 – Deformation of a column splice
Figure 1.16 – Deformation of a beam-to-beam joint
Figure 1.17 – The two connections in a column base
Figure 1.18 – Particular response of a composite joint configuration
Figure 1.19 – Definition of design resistance, gap and overlap of a K joint
Figure 1.20 – Lamellar tearing
Figure 1.21 – Examples of steel beam-to-column joints, beam-to-beam joints and beam splices joints covered by Eurocode 3 Part 1-8
Figure 1.22 – Examples of composite joints covered by Eurocode 4 Part 1-1
Figure 1.23 – Design sheets (CRIF et al)

Chapter 2: STRUCTURAL ANALYSIS AND DESIGN

Figure 2.1 – Various ways for the global analysis and design process
Figure 2.2 – Flexural characteristic of the rotational spring
Figure 2.3 – Definition of the transformation parameter β
Figure 2.4 – Forces applied at the periphery of a web panel
Figure 2.5 – Definition of the level arm z
Figure 2.6 – Shear force in a column web panel
Figure 2.7 – Extreme cases for β values
Figure 2.8 – Definition of the transformation parameter β
Figure 2.9 – Bi-linearisation of moment-rotation curves
Figure 2.10 – Linear representation of a M − ϕ curve
Figure 2.11 – Rigid-plastic representation of a M – ϕ curve
Figure 2.12 – Non-linear representations of a M – ϕ curve
Figure 2.13 – Stiffness classification boundaries
Figure 2.14 – Strength classification boundaries
Figure 2.15 – Shape of joint M – ϕ characteristics
Figure 2.16 – Plastic rotation capacity

Chapter 3: CONNECTIONS WITH MECHANICAL FASTENERS

Figure 3.1 – Bolt assemblies
Figure 3.2 – Bolted connection
Figure 3.3 – Symbols for end and edge distances and spacing of fasteners
Figure 3.4 – Shear-tension interaction of bolts
Figure 3.5 – Load transfer in a non-preloaded and a preloaded connection in a shear connection
Figure 3.6 – Load-deformation diagram of a shear connection
Figure 3.7 – Force triangle in a tension connection
Figure 3.8 – HRC systems: Principle of tightening
Figure 3.9 – Direct tension indicator
Figure 3.10 – Principle of tightening with a direct tension indicator
Figure 3.11 – Failure modes for a plate in bearing
Figure 3.12 – Block tearing failure
Figure 3.13 – Injection bolts in a double lap joint
Figure 3.14 – Geometrical requirements for pin ended members
Figure 3.15 – Design bending moment M_Ed in a pin
Figure 3.16 – Flow drill connection for joining end plates to RHS
Figure 3.17 – Flow drill process
Figure 3.18 – Lindapter “HolloFast”
Figure 3.19 – Nailed connection
Figure 3.20 – Local eccentricities in a bolted angle
Figure 3.21 – Angle connected by one leg (one bolt line)
Figure 3.22 – Single and double overlap joints (lap joints)
Figure 3.23 – Bolted and welded lap joints
Figure 3.24 – Single and double bolted overlap joints
Figure 3.25 – Different stages of bolt force distribution in shear bolted connections
Figure 3.26 – T-stub geometry
Figure 3.27 – Visualisation of equivalent T-stubs in bolted connections
Figure 3.28 – Failure modes in the actual component and in the equivalent T-stubs
Figure 3.29 – Failure modes of an equivalent T-stub
Figure 3.30 – Definition of _{e_min (for example in a beam-to-column joint)}
Figure 3.31 – Possible yield line mechanisms
Figure 3.32 – Type of failure according to the geometry of the T-stub
Figure 3.33 – Influence of the bolt geometry on the yield lines
Figure 3.34 – RHS flange-plate connection in tension (plate bolted on two sides)
Figure 3.35 – SHS flange-plate connection in tension (plate bolted on four sides)
Figure 3.36 – Bolted CHS flange-plate connection
Figure 3.37 – Examples of gusset plate connections using welds and bolts
Figure 3.38 – Failure modes in a gusset plate
Figure 3.39 – Block tearing failure
Figure 3.40 – Buckling lengths
Figure 3.41 – Gusset plate yielding
Figure 3.42 – Example of verification for the global failure mode
Figure 3.43 – Lap joint length

Chapter 4: WELDED CONNECTIONS

Figure 4.1 – Butt welds with full penetration
Figure 4.2 – Examples of types of bevelled edges
Figure 4.3 – Butt welds with partial penetration
Figure 4.4 – Schematic representation of various fillet weld joint configurations
Figure 4.5 – Improved corner joint
Figure 4.6 – Continuous and intermittent fillet welds
Figure 4.7 – Fillet welds all round
Figure 4.8 – Plug welds
Figure 4.9 – Weld positions
Figure 4.10 – Welds with successive runs
Figure 4.11 – Effects of the gap on weld penetration
Figure 4.12 – Examples of weld defects
Figure 4.13 – Geometry of intermittent fillet welds
Figure 4.14 – Throat thickness of a fillet weld
Figure 4.15 – Throat thickness of a deep penetration fillet weld
Figure 4.16 – Stresses on the throat section of a fillet weld (unit length)
Figure 4.17 – Butt weld with full penetration
Figure 4.18 – Butt weld with partial penetration
Figure 4.19 – Tee-butt joint with superimposed fillet welds
Figure 4.20 – End fillet and side fillet welds
Figure 4.21 – Elastic and plastic distributions of forces
Figure 4.22 – Example of elastic and plastic distributions
Figure 4.23 – Elastic distribution of shear stresses along the welds
Figure 4.24 – Effective width for unstiffened tee-joints
Figure 4.25 – Geometry of intermittent welds
Figure 4.26 – Single fillet or single-sided partial penetration butt welds

Chapter 5: SIMPLE JOINTS

Figure 5.1 – Beam-to-column joint configurations
Figure 5.2 – Beam-to-beam joint configurations
Figure 5.3 – Beam splices and possible locations of simple beam splice joints
Figure 5.4 – Bracing configuration
Figure 5.5 – Column base joint configuration
Figure 5.6 – Header plate connection
Figure 5.7 –Fin plate connection
Figure 5.8 – Web cleat connection
Figure 5.9 – Other simple connections
Figure 5.10 – Contact and evolution of the bending moment
Figure 5.11 – Geometrical characteristics of the joint and illustration of contact between the beam and the supporting element
Figure 5.12 – Contact and evolution of the bending moment
Figure 5.13 – Geometrical characteristics of the joint and illustration of the contact between the beam and the supporting element
Figure 5.14 – Forces at supporting member side
Figure 5.15 – Compression zone
Figure 5.16 – Forces on the supporting element side
Figure 5.17 – Forces on the supporting element side for cleats with long legs
Figure 5.18 – Header plate notations
Figure 5.19 – Fin plate notations
Figure 5.20 – Various composite joints
Figure 5.21 – Classical column base detailing, configured with two and four anchor bolts
Figure 5.22 – Various types of anchoring systems
Figure 5.23 – Components in a simple column base
Figure 5.24 – Flexible base plate modelled as a rigid plate of equivalent area
Figure 5.25 – Concrete block geometrical dimensions
Figure 5.26 – T-stub under compression
Figure 5.27 – Stress distribution in the grout
Figure 5.28 – T-stub idealisation (case with prying effects)
Figure 5.29 – Effective length of an embedded anchor bolt
Figure 5.30 – Column bases in shear
Figure 5.31 – Column base loaded by shear and tension force

Chapter 6: MOMENT RESISTANT JOINTS

Figure 6.1 – “Column sway” buckling mode of an unstiffened web
Figure 6.2 – Spread of compression stresses to the column web
Figure 6.3 – Reduction factor k_wc
Figure 6.4 – Equivalent T-stub flange representing a column flange in bending
Figure 6.5 – Modelling a stiffened column flange as separate T-stubs
Figure 6.6 – Values for α for effective length of bolt-rows adjacent to a stiffener
Figure 6.7 – Modelling an extended end-plate as separate T-stub
Figure 6.8 – Influence of the gap between the beam and the column
Figure 6.9 – Concentrated force F_c and compression force F
Figure 6.10 – Strut-tie model [Fig 8.2 from EC4]
Figure 6.11 – Example of joint with contact plates in compression
Figure 6.12 – Joint with one bolt-row in tension
Figure 6.13 – Joint with more than one bolt-row in tension
Figure 6.14 – Joint with a thick end-plate
Figure 6.15 – Joint with a thin end-plate
Figure 6.16 – Plastic distribution of forces
Figure 6.17 – Elasto-plastic distribution of internal forces
Figure 6.18 – Plastic mechanisms
Figure 6.19 – Flow-chart for the assembly procedure
Figure 6.20 – Joint with a symmetrical geometry
Figure 6.21 – M-N resistant curve for a joint proposed in EN 1993-1-8
Figure 6.22 – Example of row numbering with an extended end-plate connection
Figure 6.23 – Possible group effects between three bolt rows
Figure 6.24 – Example of a M-N resistance interaction curve obtained for a four bolt row joint
Figure 6.25 – Successive steps for the evaluation of (black and white dots respectively)
Figure 6.26 – Definition of the weld section
Figure 6.27 – Possible stress distributions in the weld section and position of neutral axis
Figure 6.28 – Spring model for an unstiffened welded joint
Figure 6.29 – Spring model for a beam-to-column end-plated joint with more than one bolt-row in tension
Figure 6.30 – Non-linear response of a joint
Figure 6.31 – Plane deformation of the joint section
Figure 6.32 – Classification criteria for the rotational ductility of bolted joints
Figure 6.33 – Classification criteria for the rotational ductility of welded joints
Figure 6.34 – Bolted endplate joints with various reinforcing stiffeners
Figure 6.35 – Weak axis beam-to-column joints with H or I members
Figure 6.36 – Beam splice with endplate connection exhibiting four bolts per row
Figure 6.37 – Beam-to-column joints with RHS members
Figure 6.38 – Bolted flange plate connection in a beam-to-column joint with an RHS column
Figure 6.39 – Beam-to-column connections with a continuous RHS beam
Figure 6.40 – Simplified design model for bending resistance
Figure 6.41 – Lever arm for simplified method
Figure 6.42 – Joint in a steel building frame and joint detailing
Figure 6.43 – Bolt rows and groups of bolt rows
Figure 6.44 – Bolt rows and groups of bolt rows
Figure 6.45 – Loads which can be supported individually by the rows
Figure 6.46 – Maximum loads which can be supported by the rows, taking into account of the group effects
Figure 6.47 – Final loads which can be supported by the rows
Figure 6.48 – Common splice configurations (Moreno et al, 2011)
Figure 6.49 – Bearing type splices (Moreno et al, 2011)
Figure 6.50 – Non-bearing type splices (Moreno et al, 2011)
Figure 6.51 – Typical column bases (Moreno et al, 2011)
Figure 6.52 – Stiffened column base
Figure 6.53 – Embedded column joint configuration
Figure 6.54 – Classical pinned and moment resisting joint configurations
Figure 6.55 – Equivalent rigid plate under axial compression force
Figure 6.56 – Force equilibrium under axial force
Figure 6.57 – Force equilibrium under axial force and bending moment
Figure 6.58 – Equilibrium of forces on the base plate (with the effective area under the flanges only)
Figure 6.59 – Mechanical stiffness model for a column base plate joint
Figure 6.60 – Types of joints- H- shaped column (Anderson et al, 1999)
Figure 6.61 – Choice of joint configurations
Figure 6.62 – Sheet and slab dimensions
Figure 6.63 – Studied double-sided composite joint configuration (dimension in [mm])
Figure 6.64 – Row numbering
Figure 6.65 – Considered reference point to compute the applied bending moment at the joint
Figure 6.66 – Definition of z⁺ and z−
Figure 6.67 – Computation of (dashed arrow) for the bolt rows
Figure 6.68 – Resistance interaction curves predicted through the proposed procedure (Demonceau, 2008)

Chapter 7: LATTICE GIRDER JOINTS

Figure 7.1 – Ring model for chord plastification under axial brace loading (Togo, 1967)
Figure 7.2 – Yield line model for T, Y and X joints
Figure 7.3 – Analytical model for chord shear failure
Figure 7.4 – Effective width for punching shear failure
Figure 7.5 – Effective width for brace failure

Chapter 8: JOINTS UNDER VARIOUS LOADING SITUATIONS

Figure 8.1 – Composite joint subjected to sagging moment
Figure 8.2 – Full strength optimised beam-to-column joint solution

Chapter 9: DESIGN STRATEGIES

Figure 9.1 – Two solutions: different economy
Figure 9.2 – Traditional design approach (simple/continuous joints)
Figure 9.3 – Modelling of pinned and rigid joints (elastic global analysis)
Figure 9.4 – Consistent design approach
Figure 9.5 – Optimization of rigid joints
Figure 9.6 – Example for the optimization of rigid joints
Figure 9.7 – Optimisation with semi-rigid joints
Figure 9.8 – Costs of steel structures depending on the relative joint stiffness
Figure 9.9 – Design strategy when semi-continuous joints (elastic global analysis)
Figure 9.10 – Check of the stiffness requirement for a rigid joint
Figure 9.11 – Check of stiffness requirement of a semi-rigid joint
Figure 9.12 – Beam end rotation
Figure 9.13 – Design strategy for partial-strength joints in non-sway frames

ECCS EUROCODE DESIGN MANUALS

ECCS EDITORIAL BOARD

Luís Simões da Silva (ECCS)

António Lamas (Portugal)

Jean-Pierre Jaspart (Belgium)

Reidar Bjorhovde (USA)

Ulrike Kuhlmann (Germany)

DESIGN OF STEEL STRUCTURES – 2^ND EDITION
Luís Simões da Silva, Rui Simões and Helena Gervásio
FIRE DESIGN OF STEEL STRUCTURES – 2^ND EDITION
Jean-Marc Franssen and Paulo Vila Real
DESIGN OF PLATED STRUCTURES
Darko Beg, Ulrike Kuhlmann, Laurence Davaine and Benjamin Braun
FATIGUE DESIGN OF STEEL AND COMPOSITE STRUCTURES
Alain Nussbaumer, Luís Borges and Laurence Davaine
DESIGN OF COLD-FORMED STEEL STRUCTURES
Dan Dubina, Viorel Ungureanu and Rafaelle Landolfo
DESIGN OF JOINTS IN STEEL AND COMPOSITE STRUCTURES
Jean-Pierre Jaspart and Klaus Weynand
DESIGN OF STEEL STRUCTURES FOR BUILDINGS IN SEISMIC AREAS
Raffaele Landolfo, Federico Mazzolani, Dan Dubina, Luís Simões da Silva and Mario d’Aniello

AVAILABLE SOON

DESIGN OF COMPOSITE STRUCTURES
Markus Feldman and Benno Hoffmeister

ECCS – SCI EUROCODE DESIGN MANUALS

DESIGN OF STEEL STRUCTURES, U. K. EDITION
Luís Simões da Silva, Rui Simões, Helena Gervásio and Graham Couchman

INFORMATION AND ORDERING DETAILS

Design of Joints in Steel and Composite Structures

2016

Published by:

ECCS – European Convention for Constructional Steelwork

publications@steelconstruct.com

www.steelconstruct.com

Sales:

Wilhelm Ernst & Sohn Verlag für Architektur und technische Wissenschaften

GmbH & Co. KG, Berlin

All rights reserved. No parts of this publication may be reproduced, stored in a retrieval system, or transmitted in any form or by any means, electronic, mechanical, photocopying, recording or otherwise, without the prior permission of the copyright owner.

ECCS assumes no liability with respect to the use for any application of the material and information contained in this publication.

ISBN (ECCS): 978-92-9147-132-4

ISBN (Ernst & Sohn): 978-3-433-02985-5

Photo cover credits: Klaus Weynand

FOREWORD

With this ECCS book “Joints in Steel and Composite Structures” the authors succeeded in placing the joints on the rightful place they deserve in the structural behaviour of steel and composite steel-concrete structures. The many times used word “details” for the joints in structures by far underestimates the importance of joints in the structural behaviour of buildings and civil engineering structures. In their chapter “Aim of the book” the authors clearly explain how the design and safety verification of structures runs in an integral manner where all structural components, including the joints, play balanced roles leading to economic structures.

This book can be seen as a background document for Eurocode 3 “Design of Steel Structures” and for Eurocode 4 “Design of Composite Steel and Concrete Structures” as far as it concerns structural joints. The central theme in describing the behaviour of joints is using the component method and this is leading all over in this book. The book contain many aspects such as design, fabrication, erection and costs.

In this book attention is paid on joint modelling and idealisation, joint classification for strength and stiffness and deformation capacity. This all for connections with mechanical fasteners and for welded connections, for simple joints and moment resistant joints. Also lattice girder joints are described.

The book provides the designer with design strategies to arrive at economic structures.

The authors based themselves on many bibliographic references covering a time span of about 65 years. Many of these references present research of the authors themselves and of the other members of the ECCS-Technical Committee TC10 “Structural Connections”.

It was really a privilege to have been the chairperson of this committee from 1998 till the end of 2012 and I thank the authors Prof. Dr. Ir. Jean-Pierre Jaspart and Dr.-Ing. Klaus Weynand for their large effort in writing this book.

Prof. ir. Frans Bijlaard

PREFACE

Steel constructions and composite steel-concrete constructions are generally erected on site by the assembly of prefabricated structural parts prepared at workshop. These parts may themselves be the result of an assembly of individual elements. An example is the assembly by bolting on site of built-up sections welded in the workshop.

In these construction types, joints and connections play a key role and recommendations and guidelines are required for engineers and constructors faced to the conception and design, the fabrication and the erection of such structures. In the Structural Eurocodes, all these aspects are mainly covered in the execution standard EN 1090-2 and in the design standards EN 1993-1-8 (Eurocode 3 for steel structures) and EN 1994-1-1 (Eurocode 4 for composite structures).

In the present book which is part of the series of ECCS Eurocode Design Manuals, the main focus is given to design aspects, but references are also made to EN 1090-2 when necessary.

In comparison to some other fields, the design procedures for joints and connections have significantly evolved in the last decades as a result of the progressive awareness by practitioners of the significant contribution of joints and connections to the global cost of structures. Design for low fabrication and erection costs and high resistance is therefore the targeted objective of modern design codes, the achievement of which has justified the development of new calculation approaches presently integrated into the two afore-mentioned Eurocodes. This situation justifies the writing of the present manual with the main goal to demystify the design by explaining the new concepts to design the joints and to integrate their mechanical response into the structural frame analysis and design process, by providing “keys” for a proper application in practice and finally by providing well documented worked examples.

To refer to “modern” or “new” design approaches and philosophies does not mean that traditional ways are old-fashioned or no more valid. It should be understood that the design methods recommended in the Eurocodes are a collection of European practices including the results of intensive research efforts carried out in the last decades and so give many options and alternatives to the engineers to elaborate safe and economic solutions.

Chapter 1 introduces generalities about joint properties, aspects of materials, fabrication, erection and costs, design approach - and especially the so-called component method - and design tools available to practitioners for easier code application. The integration of the response of the joints into the structural analysis and design process is addressed in chapter 2. In chapter 3, the attention is paid to the design of common connections with mechanical fasteners. Preloaded bolts and non-preloaded bolts are mainly considered but the use of some less classical connectors is also briefly described. Welded connections are covered in chapter 5.

The three next chapters relate to three specific types of joints, respectively simple joints, moment resisting joints and lattice girder joints. For these ones, substantial novelties are brought in the Eurocodes in comparison to traditional national codes; and more especially for simple and moment resisting joints. A significant number of pages is therefore devoted to these topics in this manual.

The design of joints under static loading, as it is addressed in the seven first chapters, is essential in all cases but further checks or different conceptual design of the joints are often required in case of load reversal, fire, earthquake or even exceptional events like impact or explosion. Chapter 8 summarises present knowledge in this field.

Traditionally joints were designed as rigid or pinned, what enabled – and still enables – a sort of dichotomy between the design of the frame, on the one hand, and the design of the joints, on the other hand. The clear economical advantage associated in many situations to the use of semi-rigid and/or partial-strength joints leads however to “structure-joints” interactions that have to be mastered by the engineer so as to fully profit from the beneficial generated cost effects. The Eurocodes do not at all cover this aspect which is not falling within the normalisation domain but within the application by engineers and constructors in daily practice. From this point of view, chapter 9 may be considered as “a première” even if the content had already been somewhat described years ago in an ECSC publication.

Before letting the reader discover the contents of this book, we would like to express acknowledgment. We are very grateful to Prof. Frans Bijlaard for all the comments, suggestions and corrections he made through the review process of the present manual. Warm thanks are also addressed to José Fuchs and Sönke Müller who helped us in preparing the drawings. Last but not least we would like to thank our wives for their patience when we worked “on our project” during innumerable evenings and week-ends.

Jean-Pierre Jaspart
Klaus Weynand

LIST OF SYMBOLS AND ABBREVIATIONS

SYMBOLS

b_eff: effective width
d_n: nominal diameter of the bolt shank
e_o: magnitude of initial out-of-straightness
g: gap (in a lattice girder gap joint)
f_u: material ultimate tensile strength
f_y: material yield strength
h_b: depth of beam cross section
h_c: depth of column cross section
h_r: the distance from bolt-row r to the centre of compression
h_t: distance between the centroids of the beam flanges
k_eq: equivalent stiffness coefficient
k_i: stiffness coefficient of component i
l_eff: effective length (of a T stub flange)
m_pl,Rd: design plastic moment of a plate per unit length
r_c: fillet radius of the structural shape used as column
t_f,b: thickness of the beam flange
t_f,c: thickness of the column flange
t_p: thickness of the end-plate
t_w,c: thickness of the column web
t₀: thickness of the chord
t_i: thickness of the braces i = 1.2
z: lever arm of the resultant tensile and compressive forces in the connection
z_eq: equivalent lever arm
xx: longitudinal axis of a member
yy: major axis of a cross section
zz: minor axis of a cross section
A_o: original cross sectional area
A_s: shear area of the bolt shank
A_v,c: shear area of the column web
E: Young modulus for steel material
F_b: tensile and compressive forces in the connection, statically equivalent to the beam end moment
F_b,Ed: design bearing force (bolt hole)
F_c,Ed: design compressive force
F_c,fb,Rd: design compression resistance of a beam flange and the adjacent compression zone of the beam web
F_c,wc,Rd: design resistance of a column web subject to transverse compression
F_t,Rd: design tension resistance per bolt
F_t,r,Rd: design tension resistance per bolt r
F_T,Rd: design tension resistance of a T-stub flange
F_t,wc,Rd: design resistance of a column web subject to transverse tension
F_t,wb,Rd: design tension resistance of the beam web
F_t,Ed: design tensile force
F_v,Ed: design shear force (bolts)
F_v,Rd: the design shear resistance per bolt
F_wp,Rd: plastic shear resistance of a column web panel
H: horizontal load
I: second moment of area
I_b: second moment of area of the beam section (major axis bending)
I_c: second moment of area in the column section (major axis bending)
L: member length
L_b: beam span (system length)
L_c: column height (system length measured between two consecutive storeys)
M: bending moment
M_b: bending moment at the beam end (at the location of the joint)
M_c: bending moment in the column (at the location of the joint)
M_j,Rd: design moment resistance of a joint
M_j,Ed: design bending moment experienced by the joint
M_j,u: ultimate bending moment resistance of the joint
M_pl,Rd: design plastic moment resistant of a cross section
M_u: ultimate bending moment
M_Ed: design bending moment
N: axial force
N_b: axial force in the beam (at the location of the joint)
N_c: axial force in the column (at the location of the joint)
N_j,Rd: axial design resistance of the joint
Q: prying force
P: axial compressive load
R_k: characteristic value of resistance
S: rotational joint stiffness
S_j: nominal rotational joint stiffness
S_j,app: approximate rotational joint stiffness (estimate of the initial one)
S_j,ini: initial rotational joint stiffness
S_{j,post−limit}: post-limit rotational joint stiffness
V: shear force or gravity load
V_b: shear force at the beam end
V_c: shear force in the column
V_cr: critical value of the resultant gravity load
V_Ed: design shear force in the connection
V_n: shear force experienced by the column web panel
V_wp,Rd: design plastic shear resistance of a web panel
W: gravity load
β: transformation parameter
ε_y: material yield strain
ε_u: material ultimate strain
δ: magnitude of the member deflection or local second-order effect
ϕ: the rotation of a joint (relative rotation between the axis of the connected members or sum of the rotations at the beam ends)
ϕ_cd: design rotation capacity of a joint
ϕ_b: rotation of the beam end
ϕ_t: rotation of the (beam + joint) end
γ: shear deformation
γ_F: partial safety factor for the loads (actions)
γ_M: partial safety factor for the resistance (strength function)
η: stiffness reduction factor (S_j/S_j,ini)
λ: slenderness
λ_L: load parameter
λ_cr: elastic critical load parameter (gravity loads)
λ_p: plastic load parameter
: reduced slenderness
θ_b: absolute rotation of the beam end
θ_c: absolute rotation of the column axis
σ_u: average ultimate stress
σ_com,Ed: maximum longitudinal compressive stress in a column due to axial force and bending
ψ: load combination factor
γ_M0: partial safety factor for plastic resistance of members or sections
γ_M1: partial safety factor for resistance to instability
γ_M2: partial safety factor for resistance of cross sections in tension to fracture or bolts or welds
Δ: sway displacement or global second-order effect

ABBREVIATIONS

SLS: Service limit state(s)
ULS: Ultimate limit state(s)
RHS: rectangular hollow section
CHS: circular hollow section

ECCS – SCI EUROCODE DESIGN MANUALS

Eurocode 3: Design of steel structures Part 1-8 – Design of Joints Eurocode 4: Design of composite steel and concrete structures

SYMBOLS

ABBREVIATIONS

Eurocode 3: Design of steel structures
Part 1-8 – Design of Joints
Eurocode 4: Design of composite steel and concrete structures