Research On The Influence Of The Seismic Performance Of The Ancient City Wall In The Layered Site

In recent years,seismic observations and earthquake damage investigations and experience have shown that the ground motion and building damage caused by different layered sites under earthquakes of the same magnitude are different,and layered sites have strong layers.Rationality is an important part of site effect research.Taking the Dajingmen ancient city wall in Zhangjiakou as an example,the seismic performance of the ancient city wall under the layered foundation is studied,the ancient city wall model and the soil-ancient city wall interaction model are established respectively,and the influence of different layered sites on the seismic performance of the ancient city wall is analyzed.The main research content and conclusions of the thesis are as follows:(1)Perform modal analysis and dynamic time history analysis on the ancient city wall model and the soil-ancient city wall interaction model.The analysis shows that the natural frequency of the soil-ancient city wall interaction model increases more gently than the ancient city wall model.Under the action of the soil layer,the natural frequency of the city wall structure is reduced and the period is prolonged.There is no significant change in the seismic wave waveform transmitted from the free-site bedrock to the surface,indicating that the soil layer has a certain amplification effect on the seismic wave,the high frequency part is filtered,and the seismic wave input from the soil layer also has a certain frequency filtering effect,and the amplification factor will It varies with different soil layers and different seismic waves.(2)Under different seismic excitations,the top displacement and acceleration response of the soil-ancient city wall model are both larger than the displacement and acceleration response of the ancient city wall model.The displacement response increases by 20%,and the acceleration response increases by 32%.While analyzing the seismic performance of the ancient city wall,the interaction between the structure and the lower soil layer can be considered to make the structure safer during earthquakes.(3)The equivalent linear model is used to approximate the nonlinearity of the response soil through iteration.The analysis shows that the top displacement and acceleration time history of the model in the linear analysis of the soil layer are greater than the displacement and acceleration time history under the nonlinear analysis,and the linear analysis displacement is non-linear.The linear analysis displacement is 1.36 times and the acceleration is 1.71 times.In the seismic performance analysis of the ancient city wall,in order to facilitate the seismic analysis of the ancient city wall,it is necessary to consider the influence of the nonlinearity of the soil on the structure.