Prediction of blast response of RC columns considering dynamic bond-slip between reinforcement and concrete

Abstract

The bond behaviour between reinforcement and concrete is one of the critical factors that govern the capacity of reinforced concrete (RC) structures as it ensures the composite action that makes the reinforcements and concrete respond together to resist external loads. The influences of bond behaviour between steel reinforcement and concrete on RC structures under static loading have been intensively investigated. The influences under dynamic loading conditions, especially high-rate impact and blast load, however, are not well studied yet. For accurate prediction of RC structure responses subjected to blast or impact load, the influences of dynamic bond-slip should be considered. In this study, the dynamic pullout tests between reinforcement and concrete up to strain rate of 100/s were carried out first to investigate the strain rate effect on bond-slip relation. The obtained strain-rate dependent dynamic bond-slip relation was incorporated into a numerical model developed in LS-DYNA to predict RC column responses subjected to blast loads. The model was validated by simulating field blast test on an RC column carried out by other researchers. Using the validated numerical model, case studies representing different blast loading conditions were conducted to investigate the influences of considering or not considering, i.e., perfect bond assumption, the bond-slip on predictions of RC column responses. It is found that the numerical model considering dynamic bond-slip is capable of improving the prediction accuracy of blast responses of RC columns. The assumption of perfect bond has a minor effect on the predicted maximum mid-height deflection of the column, but results in an underprediction of the residual deflection and an overestimation of residual strength. As a result, neglecting bond-slip between rebar and concrete results in overprediction of RC column residual loading capacity. The results indicate the necessity of considering dynamic bond-slip in numerical simulation of RC structure responses subjected to blast or impact loads.