Residual Capacity of Axially Loaded Circular RC Columns after Lateral Low-Velocity Impact

RC bridge columns that are at risk for collision loading must be designed for lateral impact load. Because bridge columns must also support axial loads, evaluating the residual axial capacity and collapse risk of impact-damaged columns is important. This study examined axial performance characteristics of RC columns using compression after impact (CAI) testing of twelve circular columns. As residual deformations caused by lateral impact loading increased, residual axial strengths were found to decrease. Additionally, damage modes induced by impact loading were found to have an obvious influence on residual axial capacity. Shear-dominated impact damage was observed to result in greater reduction of axial capacity than did flexure-dominated damage. Because the maximum load imposed during a collision is usually unknown, an assessment method based on the postimpact state (deformation and damage mode) is proposed and was demonstrated to be capable of predicting postimpact residual axial capacity. The effects of reinforcement ratio and axial load ratio on postimpact capacity were parametrically investigated, and an empirical formula derived from the results was developed for estimating residual strengths.