SEISMIC PERFORMANCE OF RC FRAMES RETROFITTED BY FRP AT JOINTS USING A FLANGE-BONDED SCHEME

Abstract– A new, FRP flange-bonded scheme, with practical application to 3D RC frames and with the aim of relocating plastic hinges away from the joints is presented and its performance is compared with that of the web-bonded scheme. For this purpose, nonlinear pushover analyses of detailed Finite Element (FE) models of retrofitted joints of a benchmark RC frame are carried out. The optimal thicknesses of the Fibre Reinforced Polymer (FRP) sheets for relocating the plastic hinges are first determined. The moment-rotation curves of the joints are then utilised to create a representing model for the RC frame. Further, nonlinear pushover analyses are carried out on the retrofitted and the original frame to evaluate their capacity curves and seismic performance parameters such as ductility, behaviour factor and performance points in relation to a specified demand earthquake. The results are then compared with those of the same frame when retrofitted with the web-bonded scheme as well as with steel bracing. Results point to the marked superiority of the flange-bonded scheme compared to the web-bonded scheme in different aspects including, capacity, ductility and the performance level and cost. The performance of the FRP flange-bonded scheme also compares well with that of the steel bracing method. Keywords–