Study On Fatigue Life Of Ancient Masonry Pagoda Under Train Vibration

The Beijing Liangxiang Pagoda,as a 7th key cultural relic protection unit in China,is adjacent to the Beijing-Guangzhou Line.The long-term vibration of the trains on the Beijing-Guangzhou Line will have a certain adverse impact on the pagoda.Based on the field vibration test,the dynamic characteristics of Liangxiang Pagoda are studied,the influence of train vibration on the pagoda is deeply analyzed,and the fatigue life of pagoda is estimated in this paper.The main contents are as follows:1.Using pulsation method,the field dynamic test of Liangxiang pagoda is carried out.The horizontal velocity at the first to fifth floors of the pagoda and the horizontal and vertical acceleration at the ground level of the pagoda are collected under the influence of the ground pulsation and the train,respectively.The self-power spectrum,cross-power spectrum and phase spectrum are calculated by self-programming using matlab,and the nature frequency,vibration mode and damping ratio are analyzed based on the random vibration theory and the half power band width method.The dynamic response of the pagoda under the influence of passenger train and freight train is analyzed from the maximum velocity and the maximum effective value of the velocity.2.The three-dimensional finite element numerical model of Liangxiang pagoda is established by ansys.After checking the model from the aspects of modal and dynamic response,on the one hand,the dynamic response of the pagoda under the impact of passenger train and freight train respectively is calculated.According to the existing specifications,the safety and integrity of the pagoda are evaluated.On the other hand,the stress of the pagoda under the impact of passenger train and freight train respectively is calculated,and the most dangerous position of the ancient tower is located at the wall opening of the inner corridor wall of first floor of the tower body,which also provides the basis for the calculation of the subsequent fatigue life.3.This paper introduces the basic concept of fatigue failure,S-N curve of the ancient masonry material and fatigue damage theory.Based on the S-N curve of ancient masonry material,stress of the most dangerous position of pagoda and fatigue damage theory.It is estimated that the fatigue life of the Liangxiang Pagoda under the impact of gravity and passenger train is 5.26xl07 times,and under the impact of gravity and freight train is 2.83×107 times.4.On the basis of theoretical calculation,fe-safe is used to analyze the overall distribution of fatigue life of ancient pagoda.