Damage-based seismic performance design of reinforced concrete bridges using capacity-based inelastic displacement dual spectra

A damage-based seismic performance design method using capacity-based inelastic displacement dual spectra was proposed for reinforced concrete (RC) bridges, where the Park and Ang's damage index was introduced as the performance objective. The proposed method was composed of the recommended force-based seismic design method (Phase I) and the imperative pushover-based seismic evaluation procedure (Phase II), with a main focus on the damage evaluation of each bridge column given that the damage index can be well correlated to the strength deterioration state and visual damage condition of the bridge columns. It was verified against the nonlinear time-history analysis of various irregular bridges that the average result of the seismic evaluation utilizing the uniform and modal pushover analyses can provide reliable and acceptable evaluation results in terms of the maximum displacement and damage index profiles of the bridges when subjected to transverse seismic excursions. In addition, design illustration of the proposed design method was conducted using two long-period ($T_n\ge$ 0.7 s) and another two short-period ($T_n<$ 0.7 s) hypothetical bridges with regular and irregular configurations and compared to the design results per current Taiwan code, Caltrans SDC, and AASHTO's Guide Specification. It was found that the designed long-period irregular bridges and the short-period regular and irregular bridges could suffer severe damage when subjected to a maximum credible earthquake with the near-fault effect. The damage severity of a bridge will be determined by the interactively combined effects of ground motion characteristics, relative structural strength, structural period, bridge regularity, and damage potential.