Dynamic analysis of the Xiaoyan Pagoda in China: Mechanisms for resisting rare earthquakes

The Xiaoyan Pagoda in Xi'an stands as a UNESCO World Cultural Heritage site, having endured severe damage from numerous powerful earthquakes without collapsing. To comprehensively understand its behavior during earthquakes, a Block Discrete Element (3DEC) analysis method was employed. The numerical model underwent scrutiny aligned with in-situ dynamic test results. The dynamic response of the pagoda was calculated separately while subjected to the influence of three seismic waves under two conditions: rigid foundation and considering soil-structure interaction (SSI), and the damage process was analyzed. The calculation results reveal that under conditions of a rigid foundation, the ancient pagoda experiences displacement increases suddenly of each floor and eventual collapse when subjected to an intensity of 8-degree (PGA=0.40 g) earthquake. However, when accounting for the constructive characteristics of the foundation soil and considering soil boundary effects, the pagoda of dynamic characteristics differ, resulting in a seismic response lower than that of the rigid foundation scenario. During a rare earthquake of intensity of 9-degree (PGA=0.62 g), observed block detachment occurs at the top floor and the pagoda eaves of the middle floor, aligning with historical patterns of damage seen in the Xiaoyan Pagoda. These research outcomes offer valuable insights, serving as a reference for enhancing the seismic resilience of the Xiaoyan Pagoda structure and predicting its earthquake collapse risks.