CFRP confinement in retrofitted RC columns via CSB technique under reversed lateral cyclic loading

Abstract

This paper reports the results on an experimental investigation on the efficiency of confinement with carbon fiber reinforced polymer (CFRP) in retrofitting square reinforced concrete (RC) columns. The study was designed to evaluate the effect of the recently developed corner strip-batten (CSB) method on the seismic behavior of RC columns. In the CSB method, FRP battens are bonded, similar to flat coupons, at the sides of the section while each adheres on the CFRP corner strips at the two ends. For the purposes of this study, five large-scale RC columns were subjected to constant axial and cyclic lateral loads. The main parameter examined was the method employed for confining the columns. The RC columns were investigated in terms of their failure mode, hysteretic and envelope curve, enhanced lateral strength and ductility, equivalent damping ratio, stiffness degradation, and energy dissipation. The results indicated that RC columns retrofitted with CFRP composites exhibited a ductile behavior under cyclic lateral loading. Furthermore, seismic loading tests revealed that the transverse FRP sheets applied through recently developed CSB technique at the potential plastic hinge areas led to considerable enhancements in lateral strength, energy dissipation, and ductility. This is evidenced by enhancements of 51.6%, 30.3%, 27.2% and 24.6%, respectively, in the ductility, equivalent viscous damping ratio, energy dissipation, and lateral strength of columns retrofitted via the CSB technique, relative to the control column.