Seismic optimization design for uniform damage of reinforced concrete moment-resisting frames using consecutive modal pushover analysis

In this study, a practical optimization procedure is developed for uniform damage design of reinforced concrete moment-resisting frames using consecutive modal pushover analysis based on the framework of performance-based earthquake engineering. Consecutive modal pushover, which can capture the higher-mode effect well, is employed to derive the inelastic seismic demands of structures subjected to considered seismic hazards. Furthermore, the optimization problems are formulated using the profile of inter-story drift ratios and component hinge rotations to redistribute the steel reinforcements from components with low damage to ones that experience high damage under the constant-cost constraint, until a state of uniform damage distribution prevails. By applying the proposed design procedure to two prototype frames with five and eight stories designed using the Chinese Seismic Design Code (GB 50011-2010), the efficiency of the method as well as the variation of steel reinforcements is demonstrated. The seismic performances of final solutions and prototype frames are compared through nonlinear dynamic analysis for scenarios of 22 ground motions matching well with the code-compliant spectrum. The results show that the proposed method allows for a significant reduction of maximum story drifts combined with more evenly distributed story drifts and component hinge rotations, indicating better seismic performance for the optimized structures.