ZHAGN Y Q, PANG Y S, JIANG L X. Seismic fragility analysis of reinforced concrete frame structures subjected to sequence-type ground motions [J]. Journal of Henan Polytechnic University( Natural Science)， doi: 10.16186/j.cnki.1673-9787.2025020019.

doi: 10.16186/j.cnki.1673-9787.2025020019

Received： 2025-02-20

Revised： 2025-05-07

Online：2026-07-20

Seismic fragility analysis of reinforced concrete frame structures subjected to sequence-type ground motions (Online)

Zhang Yongqun1, Pang Yunsheng2, Jiang Lixue1

1. Shanghai Key Laboratory of Engineering Structure Safety, Shanghai Research Institute of Building Sciences Co., Ltd., Shanghai 200032, China;2. College of Civil Engineering, Tongji University, Shanghai 200092, China

Abstract: Objectives A strong earthquake is often followed by multiple aftershocks. Sequence-type ground motions can generate cumulative damage effects, leading to more severe structural damage in building structures that have already been subjected to mainshocks. However, current design codes only consider single seismic events when determining seismic design parameters. Therefore, quantitative analysis of the seismic fragility of reinforced concrete (RC) frame structures under sequence-type ground motions holds significant importance. Methods A finite element model was developed for a 5-story existing RC frame structure and validated using shaking table test data. Twenty-five real sequence-type ground motion records from actual stations were selected as input excitations for structural response analysis. The nonlinear response of RC frame structures is investigated based on the Incremental Dynamic Analysis (IDA) method. Fragility curves for RC frame structures under sequence-type ground motions are established, and the influence of aftershock intensity is analyzed. Results The predicted peak displacement response of the finite element model under seismic excitation aligned well with the shaking table test results, meeting engineering accuracy requirements. When the relative intensity coefficient of aftershocks did not exceed 0.4, the difference in seismic fragility of structures between sequence-type ground motions and the mainshock was negligible, indicating minimal aftershock impact. However, when the relative intensity coefficient exceeded 0.6, the difference in seismic fragility of structures exceeded 10%, demonstrating significant aftershock effects that warrant consideration. Additionally, aftershocks caused minor incremental structural damage when post-mainshock damage was limited, but the incremental damage increased substantially when the post-mainshock damage was severe. Conclusions When the relative intensity coefficient of aftershocks is high, or when structural damage after the mainshock is severe, the influence of aftershocks becomes significant. In such cases, the impact of sequence-type ground motions on the seismic performance of building structures must be considered in design and analysis.

Key words: sequence-type ground motions; reinforced concrete frame structure; FEM analysis; limit state; fragility analysis