Damage quantification based on drift ratios and axial capacity degradation for RC columns under low-velocity impact loads

Damage determination and quantification are critical issues in conducting damage assessment and performance-based design for RC columns under low-velocity impact loads. An impediment in these issues lies in defining reasonable damage criteria. To this end, a framework inspired by existing experimental results is proposed to quantify the damage of RC columns. The core concept of this framework is to establish the relationship between the engineering demand parameter (i.e., drift ratio) and the damage index based on residual axial capacity and to convert the damage index threshold to the drift ratio threshold using a reliability-based method. According to the proposed framework, damage criteria are developed for RC columns in two typical impact scenarios, including the mid-span and near-base impacts. During this process, linear relationships between the maximum drift and the residual one at the impact location are developed by statistically analyzing the existing experimental data (a total of 212 test samples). Based on experimentally validated numerical models, empirical formulas for estimating the residual axial capacity of RC columns are established. The maximum drift, the residual drift, and the axial capacity degradation are interrelated in the proposed damage criteria, overcoming the limitation that the current deformation-based damage criteria used for low-velocity impact loads lack physical significance.