Metallic Structures. Zhao. Xiao-Ling. FRP-Strengthened (CJ*; CRC Press. Taylor & Francis Croup. Taylor & Francis Croup, an informa business

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1 FRP-Strengthened Metallic Structures Xiao-Ling Zhao (CJ*; CRC Press Taylor & Francis Croup Boca Raton London New York CRC Press is an imprint of the Taylor & Francis Croup, an informa business

2 Contents Preface Acknowledgm ents Notation Author xm XV xvn XXV 1 Introduction Applications of FRP in strengthening metallic structures Improved performance due to FRP strengthening Current knowledge on FRP strengthening of metallic structures Layout of the book 11 References 11 2 FRP composites and metals General Fibre-reinforced polymer Carbon fibre-reinforced polymers Glass fibre-reinforced polymers Adhesives Cast/wrought iron, steel, and aluminium Cast/wrought iron Steel Aluminium Future work 24 References 25 3 Behaviour of the bond between FRP and metal General 29 v

3 vi Contents 3.2 Testing methods Methods of bond test Methods of strain measurement Failure modes Typical failure modes Key parameters affecting failure modes Bond-slip model Strain distribution Bond-slip curves Bond-slip model Estimation of bond strength and effective bond length Hart-Smith (1973) model and Xia and Teng (2005) model for bond between CFRP plate and steel Modified Hart-Smith model (Fawzia et al. 2006) for bond between CFRP sheets and steel Effect of temperature on bond strength Influence of subzero temperature on bond strength Influence of elevated temperature on bond strength Theoretical analysis of effect of elevated temperature on bond Effect of cyclic loading on bond strength Effect of impact loading on bond strength Effect of impact loading on material properties Effect of impact loading on bond strength Durability of bond between FRP and metal Future work 61 References 62 4 Flexural strengthening of steel and steel-concrete composite beams with FRP laminates 67 J. G. TENG AND D. FERNANDO 4.1 General Failure modes General In-plane bending failure Lateral buckling 72

4 Contents vii End debonding Intermediate debonding Local buckling of plate elements Flexural capacity of FRP-plated steel/composite General FRP-plated steel sections FRP-plated steel-concrete composite sections 76 sections Neutral axis in the concrete slab Neutral axis in the steel beam Effects of preloading Moment-curvature responses Lateral buckling Debonding failures General Interfacial stresses in elastic FRP-plated beams Cohesive zone modelling of debonding failure End debonding General FE modelling Analytical modelling Suppression through detailing Intermediate debonding Local buckling Design against flange and web buckling Additional strengthening 4.6 Other issues 101 against local buckling Strengthening of beams without access to the tension flange surface Rapid strengthening methods Fatigue strengthening Design recommendation General Critical sections and end anchorage Strength of the maximum moment section Moment capacity at in-plane failure Moment capacity at lateral buckling failure Design against local buckling Design example 106

5 viii Contents Geometric and material properties of the beam ln-plane moment capacity of plated section Suppression of end debonding Design against local buckling Conclusions and future research needs 113 References Strengthening of compression members General Methods of strengthening Structural behaviour Failure modes Load versus displacement curves Capacity offrp-strengthened steel sections C R?-strengthened CHS sections Modified AS 4100 model Modified EC3 model Design curves GFRF'-strengthened CHS sections CFR?-strengthened SHS sections Bambach et al. stub column model Shaat and Fam stub column model CFR?-strengthened lipped channel sections Modified EC3 stub column model Modified AISI-DSM stub column model CFRP-strengthened T-sections Capacity of CFRP-strengthened steel members CFRP-strengthened SHS columns Fibre model and FE analysis Shaat and Fam column model CFRP-strengthened lipped channel columns Modified EC3 column model Modified AISI-DSM column model Plastic mechanism analysis of CFRP-strengthened SHS under large axial deformation Equivalent yield stress due to CFRP strengthening Plastic mechanism analysis 155

6 Contents ix 5.7 Design examples Example 1: CFRF'-strengthened CHS stub column Solution using the modified AS 4100 model given in Section Solution using the modified EC3 model given in Section Example 2: CFRF'-strengthened SHS stub column with local buckling Example 3: CFRF-strengthened SHS stub column without local buckling Example 4: CFRP-strengthened SHS slender column Future work 168 References Strengthening of web crippling of beams subject to end bearing forces General Cold-formed steel rectangular hollow sections Types of strengthening Failure modes Behaviour Increased capacity Design formulae Design formulae for unstrengthened RHS Design formulae for CFRPstrengthened RHS (if web buckling governs for unstrengthened RHS) Design formulae for CFRPstrengthened RHS (if web yielding governs for unstrengthened RHS) Aluminium rectangular hollow sections Types of strengthening Failure modes Behaviour Increased capacity Design formulae 189

7 x Contents Modified AS 4100 formulae for unstrengthened aluminium RHS Modified AS 4100 formulae for CFRP-strengthened aluminium RHS AS/NZS formula for web bearing capacity of aluminium RHS Modified AS/NZS formula for web bearing capacity of CFRPstrengthened aluminium RHS LiteSteel beams Types of strengthening Failure modes and behaviour Increased capacity Design formulae Modified AS 4100 formulae for unstrengthened LiteSteel beams Modified AS 4100 formulae for CFR?-strengthened LiteSteel beams Open sections Types of strengthening Failure modes and increased capacity Design formulae Modified Young and Hancock (2001) formulae for CFRPstrengthened channel section Modified AS 4100 formulae for CFRP-strengthened I-section Design examples Example 1 (cold-formed RHS) Solution according to AS 4100 given in Section for unstrengthened RHS Solution according to modified AS 4100 given in Section for CFRP-strengthened RHS Example 2 (aluminium RHS) Solution according to modified AS 4100 given in Section Solution according to modified AS given in Section Example 3 (LiteSteel beams) 207

8 Contents xi 6.7 Future work 208 References Solution according to modified AS 4100 given in Section for unstrengtbened LSB Solution according to modified AS 4100 given in Section for CFRP-strengthened LSB Enhancement of fatigue performance General Methods of strengthening Improvement in fatigue performance Fatigue crack propagation Prediction of fatigue life for CCT (centrecracked tensile) steel plates strengthened by multiple layers of CFRP sheet Boundary element method approach Boundary element method BEM model of CCT steel plates strengthened by multiple layers of CFRP sheet BEM simulation results Fracture mechanics approach Fracture mechanics formulae for CCT steel plates Average stress in steel plate with CFRP sheet Effective stress intensity factor in steel plate with CFRP sheet Fatigue life of CCT steel plates strengthened by multiple layers of CFRP sheet Stress intensity factor for CCT steel plates strengthened by CFRP Existing approaches Stress intensity factor for CCT steel plates without CFRP Influence on stresses in steel plate due to CFRP 236

9 xii Contents Influence of crack length and CFRP bond width on SIF SIF for CCT steel plates strengthened by CFRP Influence of key parameters on SIF reduction due to CFRP strengthening Future work 248 References 248 Index 253