The Dynamic Response Analysis Of Xi’an City Wall Structure Under Traffic Random Loads

With the rapid development of our country’s economy, some phenomenon such asincreasing speed accelerate, vehicles, vehicle load are performed very well in the aspectof road traffic. Vehicle vibration load is a random load, then the ground vibration also israndom. The phenomenons such as dynamic responses, structure cracks in body of wall,loose, subsidence of the foundation, reduce of the strength of its neighbor buildings willbe produced because of the ground vibration caused by vehicle load effect for a longtime. The wall of Xi’an is the largest and most complete ancient wall at present in ourcountry. It is not only a sign of xi ’an, but also one of the most representative ancientbuilding style in China. Although which through vicissitudes of life, due to the dynamicfatigue and foundation subsidence and so on will lead to the destruction of the ancientcity walls, or shorten the life, and its safety is a serious threat under the action ofvibration in the growing traffic of ground for a long time.In this paper, the ancient citywall of south gate in xi ’an is researched, the dynamic response and its influence on thewall due to the transportation vibration on the ground are analysised and discussed onthe basis of the monitoring of the vibration response in the ground traffic of the southgate of xi ’an city wall. At the same time, the three-dimensional finite element modelabout the city walls-the foundation soil is established for simulation, analysis andcontrast, which provides the theoretical foundation for the ancient city wallprotection.Main research contents are as follows:(1) The process of vibration signal: Xi ’an city wall is tested and monitored forcontinuous24hours for the first time, the vibration response (acceleration anddisplacement) in the ground traffic in this test. Based on the pretreatment to themonitoring vibration signals, such as removing dc, smoothing and eliminating thetendency item, that eliminated the noise and interference of the outside world, make the data more realistic, which lays the foundation for the analysis to the vibration responseon the ground transportation.(2) The analysis of vibration response: Select the typical period of time,determine the amplitude of acceleration and displacement as a evaluation of vibrationquantity, and make the time domain and frequency domain analysis of vibrationresponse. In terms of parameter identification, using the measured data of the vibrationresponse in the ground traffic directly, and getting the free decay response by means ofrandom decrement method, then making it as input, preparing the correspondingMATLAB calculation program, making modal parameter identification on south gatestructure of the wall take advantage of ITD method.(3) Numerical simulation and data analysis: The ancient city wall and randomload are refered to, then the three-dimensional finite element model about the city walls-the foundation soil is established using ANSYS. Through the analysis for the modal,the natural frequencies and natural vibration period of ancient city wall are obtained;The classic model of the vehicle is choosed, which was simulated by applying Randomload on the vehicle, dynamic response on the wall caused by the traffic vibration atground when the vehicle at different speed, single and double line was got. Through theanalysis for the simulated response, vibration effect law and attenuation regularity onthe wall caused by the traffic vibration at ground were reached, and compared withexperimental data and analysis, that the wall structure model and vehicle model isreasonable were proved.