Duration effect of spectrally matched ground motion records on collapse resistance capacity evaluation of RC frame structures

Summary As one of the most important characteristics of strong ground motion, duration is intuitively expected to influence the seismic responses of structures. Up to now, the prescriptive provisions on ground motion duration are not clear in current seismic design codes around the world. For collapse resistance capacity evaluation of the structures under severe earthquake, it is more urgent to investigate the influence of ground motion duration and appropriate consideration for evaluation. Because the factors to be considered in the modeling and dynamic analysis are not very comprehensive, previous studies on the effect of ground motion duration on structural response have not got a consistent conclusion. In this study, a spectral matching approach is used to decouple the influence of the frequency content of ground motion on structural seismic response. And the effect of the infill wall, the strength and stiffness degradation of the structural components, and the axial‐shear‐flexure interaction are also considered. First, the 60 ground motion records with different duration and peak ground acceleration were selected from PEER strong ground motion database and matched spectrally. Then, the three‐dimensional numerical model for an infilled RC frame structure was built via OpenSees, and the incremental dynamic analysis was carried out under the matched ground motion records. The geometric mean incremental dynamic analysis curves of the structure for 30 long‐duration ground motion records and 30 short‐duration ground motion records were obtained. And the correlation between maximum residual roof displacement and maximum residual inter‐story drift ratio with the significant duration was further investigated. Finally, the correlation between collapse resistance capacity in terms of the spectral acceleration at the fundamental period of the structure Sa(T1) and significant duration of all ground motion records was discussed, and collapse probability under different Sa(T1) were obtained. The analytical results show that with the same intensity measure, ground motion records with longer duration may induce larger inter‐story drift ratio, larger residual displacement, and higher collapse probability for the structure. It is also shown that the collapse resistance capacity of the structure tends to decrease with the increase of the significant duration of ground motion.