Seismic Retrofit of Diagonal Tension Members in Steel Deck-Truss Bridges Using CFRP Sheets

Abstract

This study entailed axial cyclic loading tests conducted on full-scale diagonal tension members of steel deck-truss bridges to evaluate the effects of seismic retrofitting methods using carbon fiber–reinforced polymer (CFRP) sheets. The loading tests were performed on CFRP-retrofitted specimens with varying anchoring lengths of the CFRP sheets. The results indicated that the proposed retrofitting methods, which employed the intermediate-modulus CFRP type (390–450 GPa) and polyurea putty (a ductile adhesive), delayed the plastic buckling of the flanges and substantially increased the load-carrying capacities, stiffnesses, and ductility capacities of the retrofitted diagonal tension members. Additionally, the polyurea putty effectively suppressed the peeling failure of the CFRP sheets. It maintained the cross-sectional integrity between the steel members and CFRP sheets even after the plastic buckling of the flanges and rupture failure of the CFRP sheets. Further, finite-element analyses accurately reproduced the loading test results by considering the nonlinear bond-slip performance of polyurea putty, anisotropic characteristics of the CFRP sheets, and cyclic plasticity properties of steel.