Modeling of Reinforcement Buckling in RC Columns Confined with FRP

A model of the buckling behavior of the longitudinal reinforcement in RC columns confined with fiber reinforced polymers (FRP) is proposed. The model includes three significant aspects: (i) the model takes into account the flexural stiffness of cracked cover concrete jacketed with FRP to estimate the buckling length and critical stress; (ii) the asymptotic compressive stress of the buckled longitudinal bars under a cyclic load is modified considering the restraining effect of the FRP; and (iii) it is assumed that at least one of the lateral reinforcing bars (made of mild steel) yield to allow the concerned longitudinal bars to buckle. The model was implemented in the form of a two-dimensional finite element algorithm to compute the hysteric response of the RC columns. The finite element analysis conducted herein considers spalling of the cover concrete due to the buckling along the longitudinal reinforcement. The analysis compared well overall with the test results of four RC columns.