Analysis and Design of Steel

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1 Analysis and Design of Steel and Composite Structures Qing Quan Liang CRC Press Taylor & Francis Croup Boca Raton London New York CRC Press is an imprint of the Taylor & Francis Croup, an informa business

2 Preface Acknowledgements xvn xix 1 Introduction Steel and composite structures Limit state design philosophy Basic concepts and design criteria Strength limit state Stability limit state Serviceability limit state Structural design process Material properties Structural steel Profiled steel Reinforcing steel Concrete Short-term properties Time-dependent properties 11 References 12 2 Design actions Introduction Permanent actions Imposed actions Wind actions Determination of wind actions Regional wind speeds Site exposure multipliers Terrain/height multiplier (MZ CJ Shielding multiplier (MJ Topographic multiplier (MJ Aerodynamic shape factor Calculation of aerodynamic shape factor Internal pressure coefficient 23 vii

3 viii External pressure coefficient Area reduction factor Combination factor Local pressure factor Permeable cladding reduction factor Frictional drag coefficient Dynamic response factor General Along-wind response Crosswind response Combination of long-wind and crosswind response Combinations of actions Combinations of actions for strength limit state Combinations of actions for stability limit state Combinations of actions for serviceability limit state 29 References 35 3 Local buckling of thin steel plates Introduction Steel plates under uniform edge compression Elastic local buckling Simply supported steel plates Steel plates free at one unloaded edge Post-local buckling Design of slender sections accounting for local buckling Steel plates under in-plane bending Elastic local buckling Ultimate strength Design of beam sections accounting for local buckling Steel plates in shear Elastic local buckling Ultimate strength Steel plates in bending and shear Elastic local buckling Ultimate strength Steel plates in bearing Elastic local buckling Ultimate strength Steel plates in concrete-filled steel tubular columns Elastic local buckling Post-local buckling Double skin composite panels Local buckling of plates under biaxial compression Post-local buckling of plates under biaxial compression 67

4 ix Local buckling of plates under biaxial compression and shear Post-local buckling of plates under biaxial compression and shear 70 References 70 4 Steel members under bending Introduction Behaviour of steel members under bending Properties ofthin-walled sections Centroids Second moment of area Torsional and warping constants Elastic section modulus Section moment capacity Member moment capacity Restraints Members with full lateral restraint Members without full lateral restraint Open sections with equal flanges I-sections with unequal flanges Design requirements for members under bending Shear capacity of webs Yield capacity ofwebs in shear Shear buckling capacity of webs Webs in combined shear and bending Transverse web stiffeners Longitudinal web stiffeners Bearing capacity ofwebs Yield capacity of webs in bearing Bearing buckling capacity of webs Webs in combined bearing and bending Load-bearing stiffeners Design for serviceability 107 References Steel members under axial load and bending Introduction Members under axial compression Behaviour of members in axial compression Section capacity in axial compression Elastic buckling of compression members Member capacity in axial compression Laced and battened compression members 119

5 x 5.3 Members in axial tension Behaviour of members in axial tension Capacity of members in axial tension Members under axial load and uniaxial bending Behaviour of members under combined actions Section moment capacity reduced by axial force In-plane member capacity Out-of-plane member capacity Design of portal frame rafters and columns Rafters Portal frame columns Members under axial load and biaxial bending Section capacity under biaxial bending Member capacity under biaxial bending 141 References Steel connections Introduction Types of connections Minimum design actions Bolted connections Types of bolts Bolts in shear Bolts in tension Bolts in combined shear and tension Ply in bearing Design of bolt groups Bolt groups under in-plane loading Bolt groups under out-of-plane loading Welded connections Types of welds Butt welds Fillet welds Weld groups Weld group under in-plane actions Weld group under out-of-plane 6.6 Bolted moment end plate connections 167 actions Design actions Design actions for the design of bolts, end plates and stiffeners Design actions for the design of flange and web welds Design of bolts Design of end plate Design of beam-to-end-plate welds 171

6 xi Design of column stiffeners Tension stiffeners Compression stiffeners Shear stiffeners Stiffened columns in tension flange region Stiffened columns in compression flange region Geometric requirements Pinned column base plate connections Connections under compression and shear Concrete bearing strength Base plates due to axial compression in columns Column to base plate welds Transfer ofshear force Anchor bolts in shear Connections under tension and shear Base plates due to axial tension in columns Column to base plate welds Anchor bolts under axial tension Anchor bolts under tension and shear 187 References Plastic analysis of steel beams and frames Introduction Simple plastic theory Plastic hinge Full plastic moment Effect of axial force Effect of shear force Plastic analysis of steel beams Plastic collapse mechanisms Work equation Plastic analysis using the mechanism method Plastic analysis of steel frames Fundamental theorems Method of combined mechanism Plastic design to AS Limitations on plastic design Section capacity under axial load and bending Slenderness limits 214 References Composite slabs Introduction Components of composite slabs Behaviour ofcomposite slabs 219

7 xii 8.4 Shear connection ofcomposite slabs Basic concepts Strength ofshear connection Degree of shear connection Moment capacity based on Eurocode Complete shear connection with neutral axis above sheeting Complete shear connection with neutral axis within sheeting Partial shear connection Moment capacity based on Australian practice Positive moment capacity with complete shear connection Positive moment capacity with partial shear connection Minimum bending strength Design for negative moments Vertical shear capacity of composite slabs Positive vertical shear capacity Negative vertical shear capacity Vertical shear capacity based on Eurocode Longitudinal shear Punching shear Design considerations Effective span Potentially critical cross sections Effects ofpropping Design for serviceability Crack control ofcomposite slabs Short-term deflections ofcomposite slabs Long-term deflections ofcomposite slabs Span-to-depth ratio for composite slabs 242 References Composite beams Introduction Components ofcomposite beams Behaviour of composite beams Effective sections Effective width of concrete flange Effective portion of steel beam section Shear connection of composite beams Basic concepts Load-slip behaviour of shear connectors Strength of shear connectors Degree of shear connection Detailing of shear connectors Vertical shear capacity of composite beams Vertical shear capacity ignoring concrete contribution Vertical shear capacity considering concrete contribution 263

8 xiii 9.7 Design moment capacity for positive bending Assumptions Cross sections with y < 0.5 and complete Nominal moment capacity Mhc Plastic neutral axis depth 268 shear connection Cross sections with y < 0.5 and partial shear connection Nominal moment capacity Mh Depth of the first plastic neutral axis Depth of the second plastic neutral axis Cross sections with y = 1.0 and complete shear connection Nominal moment capacity Mbfc Plastic neutral axis depth Cross sections with y = 1.0 and partial shear connection Nominal moment capacity Mhf Depth ofthe first plastic neutral axis Depth of the second plastic neutral axis Cross sections with 0.5 < < y Minimum degree of shear connection Design moment capacity for negative bending Design concepts Key levels of longitudinal reinforcement Maximum area ofreinforcement PNA located at the junction of the top flange and web PNA located in the web PNA located at the junction of the web and bottom flange PNA located at the junction of the bottom flange and plate Plastic neutral axis depth Design negative moment capacity Transfer of longitudinal shear in concrete slabs Longitudinal shear surfaces Design longitudinal shear force Longitudinal shear capacity Longitudinal shear reinforcement Composite beams with precast hollow core slabs Design for serviceability Elastic section properties Deflection components of composite beams Deflections due to creep and shrinkage Maximum stress in steel beam 309 References Composite columns Introduction Behaviour and design of short composite columns Behaviour of short composite columns 318

9 xiv Short composite columns under axial compression Short composite columns under axial load and uniaxial bending General Axial load-moment interaction diagram Non-linear analysis ofshort composite columns General Fibre element method Fibre strain calculations Material constitutive models for structural steels Material models for concrete in rectangular CFST columns Material models for concrete in circular CFST columns Modelling of local and post-local buckling Stress resultants Computational algorithms based on the secant method Axial load-strain analysis Moment-curvature analysis Axial load-moment interaction diagrams Behaviour and design of slender composite columns Behaviour of slender composite columns Relative slenderness and effective flexural stiffness Concentrically loaded slender composite columns Uniaxially loaded slender composite columns Second-order effects Design moment capacity Biaxially loaded slender composite beam-columns Non-linear analysis of slender composite columns General Modelling ofload-deflection behaviour Modelling ofaxial load-moment interaction diagrams Numerical solution scheme based on Mutter's method Composite columns with preload effects General Non-linear analysis of CFST columns with preload effects Axially loaded CFST columns Behaviour of CFST beam-columns with preload effects Composite columns under cyclic loading General Cyclic material models for concrete Cyclic material models for structural steels Modelling of cyclic load-deflection responses 369 References Composite connections Introduction Single-plate shear connections 377

10 xv Behaviour of single-plate connections Design requirements Design of bolts Design of single plate Design of welds Tee shear connections Behaviour of tee shear connections Design of bolts Design oftee stems Design of tee flanges Design of welds Detailing requirements Beam-to-CEC column moment connections Behaviour of composite moment connections Design actions Effective width of connection Vertical bearing capacity Horizontal shear capacity Detailing requirements Horizontal column ties Vertical column ties Face-bearing plates Steel beam flanges Extended face-bearing plates and steel column Beam-to-CFST column moment connections Resultant forces in connection elements Neutral axis depth Shear capacity of steel beam web Shear capacity of concrete Semi-rigid connections Behaviour of semi-rigid connections Design moments at supports Design of seat angle Design ofslab reinforcement Design moment capacities of connection Compatibility conditions Design of web angles Deflections of composite beams Design procedure 409 References 409 Notations Index