The design earthquake is usually specified as a single event in most of modern seismic codes. However, one earthquake is often followed by a series of aftershocks called seismic sequence. Such cases are quite common, especially in near-fault regions, which could cause additional accumulated damage to structures. In this paper, a new methodology for evaluating the effect of near-fault seismic sequences on the accumulated damage of reinforced concrete (RC) frame structure is proposed, in which different initial damage levels (i.e., postmainshock global damage index) of structure after the mainshock are considered. Meanwhile, a quantitative description of the damage demands and the relative intensity index between mainshock and aftershock are provided. For this purpose, the nonlinear dynamic response of an eight-story RC frame structure subjected to single earthquake and seismic sequence is compared in terms of structural performance indices (collapse capacity, story damage demands, postmainshock damage level and normalized hysteretic energy) and relative intensity index. The results indicated that seismic sequences lead to reduced collapse capacity of postmainshock-damaged structures. Moreover, the near-fault pulse-like aftershock records would induce larger structural story damage demands than ordinary (i.e., non-pulse-like) aftershock records. Furthermore, the relative intensity index proposed in this paper has significant effects on the structural story damage demands, incremental dynamic analysis curves of aftershock and normalized hysteretic energy.
Seismic sequence Near-fault ground motion Story damage demand Damage index Relative intensity index Reinforced concrete frame structure
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The authors gratefully appreciate the supports by National Science & Technology Pillar Program during the Twelfth Five-year Plan Period of China under Grant No. 2014BAL05B03 and the National Natural Science Foundation of China under Grant No. 51378092 and 51578113.
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