The traditional linear elastic and Drucker–Prager (DP) models cannot truly reflect the strong nonlinear characteristics of the concrete and rock foundation of the dam under earthquake. Therefore, for comprehensive evaluation of the cumulative damage of the gravity dam structure caused by aftershock, the dynamic damage of the dam body concrete is analyzed by many scholars through the plastic damage mechanics method, but there is little research on rock material at the dam foundation with the method utilized; thus, the simulation of the whole dynamic damage evolution is worthy of investigation of the dam body and dam foundation. According to the randomness of ground motion, the transcendental probability (P) is introduced to express the statistical characteristics of aftershock intensity, and a new method for constructing main-aftershock sequences of ground motion is proposed in this paper. And then, the law of the damage evolution and energy characteristics of the concrete gravity dam under the combined action of the main shock and aftershock sequences is studied. The results are shown as follows: the smaller aftershocks do not cause further damage to the dam; as the aftershock intensity increases, the energy characteristics of the dam body and foundation have shown different changing rules; when the ratio of peak aftershock acceleration to peak main shock acceleration (∇PGA) approximately equals 0.68, the aftershock will cause larger secondary damage to the dam.

The seismic input of layered foundation is an essential part of seismic analysis of structurefoundation system. Most of the traditional seismic input methods only consider the first reflection process of seismic waves at the interface of different media, ignoring the subsequent reflection and refraction propagation process, which can not truly reflect the wave propagation process in the layered foundation. This paper proposes a new seismic input method for layered foundation, considering all reflected and refracted waves. Firstly, the viscous-spring artificial boundary model of the layered foundation is established, which can simulate the absorption of scattered waves and the elastic recovery capacity of semi-infinite foundation at the same time. Then, based on the wave mechanics theory, the equivalent nodal force calculation formula is derived to realize the vibration input of layered ground. Finally, the calculation results of the layered foundation and two-way surge tower engineering are verified. The results show that: compared to the traditional input method, the method proposed in this paper has a significant influence on the seismic response of layered foundation, and the method in this paper can better meet the accuracy requirements of engineering earthquake resistance, which provides an effective and practical calculation method for seismic analysis of layered foundation structure.

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