Damage evaluation of experimental reinforced concrete cantilever columns under bidimensional loading using D_iem

Material-based damage indices (DIs) provide more accurate damage assessment for reinforced concrete (RC) columns under multi-directional seismic loading compared to response-based DIs. D_iem, a multi-level material-based DI for RC columns, has been proposed. However, further validation is required to enhance its reliability and applicability. This study evaluates the damage of nine bidirectional hysteretic experimental RC columns using D_iem. Hysteretic simulations and damage evaluations are performed using the D_iem analysis program. A comparison is made between the corresponding drift ratio to varies damage grades and the corresponding DIs to the same damage grades. The study also compares failure drifts obtained through the traditional 80% residual strength criterion to those based on D_iem. Results show that D_iem exhibit strong consistency with observed damage patterns of the experimental columns. Specifically, D_iem exhibits a coefficient of variation approximately nine times lower than that of drift ratios, suggesting a stronger correlation with actual damage states. Furthermore, the analysis reveals that orthogonal loading effects in bidirectionally loaded columns influence the hysteretic shear-drift response, potentially reducing the accuracy of failure drifts determined by the traditional criterion. In contrast, the D_iem-based failure drift criterion, independent of hysteretic curve characteristics, provides a more reliable damage assessment for columns under complex loading conditions.