Simulation of reinforcing bar buckling in circular reinforced concrete columns

The buckling of longitudinal reinforcing bars is a significant damage stage for reinforced concrete (RC) structures subjected to seismic loads. This study is concerned with understanding the critical parameters that control the buckling response of reinforcing bars in typical circular RC columns subjected to lateral loads. A series of nonlinear finite element (FE) simulations of laterally loaded RC columns are first carried out to simulate reinforcing bar buckling behavior Next, to achieve computational efficiency and enable a large range of simulations for a parametric study, a simplified "beam-on-springs" model is developed, wherein the longitudinal reinforcing bar in a column is isolated and simulated as a flexural member The restraining mechanism provided by transverse reinforcement is represented by springs at the location of each transverse bar The simplified model is validated through comparison of average stress-strain curves with simulations obtained from high-fidelity FE analyses. It is shown that stress-strain response is primarily a function of the ratio of the buckling length to the diameter of the longitudinal bar Findings from this work provide insight into key factors that influence bar buckling in circular RC columns and provide guidelines for constitutive modeling of the compression behavior of reinforcing bars.