Modal Identification And Dynamic Analysis Of Anyuan Gate Of Xi'an City Wall Under Environmental Excitation

Xi'an City Wall is the major historical and cultural sites protected at the national level.With the development of society,the influence of environment on ancient buildings is also increasing,and the health monitoring of ancient buildings under the influence of environmental vibration has become the focus of research.In order to better protect city wall and understand the impact of traffic vibration on ancient buildings,this paper,took the Weng city at the Anyuan gate of Xi'an city wall as research object to analyze its dynamic response under the influence of environmental vibration based on the on-site dynamic test,used various modal analytical methods to identify the modal parameters of wall's structure and studied the influences of different operating conditions on city wall.The main research contents and conclusions included:(1)Introduced the principle of modal parameter analysis in detail,deduced the modal parameter identification algorithms(including PP,ERA,SSI)and compared these algorithms'respective advantages and disadvantages to fi nd that PP has quick calculating speed and ERA and SSI have high precision.(2)By carrying out the on-the-spot environmental excitation test for Weng city wall and using time and frequency domain analysis,obtained the pattern of different areas' vibration response under the action of vehicles in peak and off-peak periods and evaluated the security of wall based on the maximum limit.The results show that the maximum vibration speed response of the city wall under the action of peak period is close to the standard limit value,so the monitoring and protection should be strengthened.(3)Used PP,ERA and SSI three methods to identify the modal parameters of various areas of city wall under different operating conditions and compared the modal parameters in peak and off-peak periods.Then according to the relationships between the modal parameters and physical parameters of wall's structure,found that the vibration of different vehicle flow has certain influence on the rigidity of wall.(4)Using ANSYS to build the three-dimensional finite element model of city wall,and verified the experimental results by finite modal analysis,which proved the feasibility of the existing modal parameter identification methods in the ancient city wall and based on the dynamic calculation results of the finite element method,the weak part of the city wall was determined.And concluded that vibration modes of different areas of wall was closely related to the change of stress by analyzing the stress spectrum curve of weak part.