Study On Earthquake Damage Mechanism Of Damaged Masonry Pagoda

There are a large number of existing ancient masonry pagodas in China,which have been damaged by natural environment and human beings for a long time,resulting in structural damage.The earthquake has a very serious threat to the permanent preservation of the existing ancient masonry,even caused some collapse and disappear.In the basic works of protecting to ancient masonry pagodas structure,evaluating its seismic capacity plays an important roll.The earthquake damage mechanism of ancient masonry pagodas with initial damage which is an important basis for determining the seismic performance evaluation index.This paper taken the damaged ancient masonry pagodas as the object,according the mechanical property test and insitu dynamic test results of the ancient pagodas substructure to analyze its seismic damage problem,then determined the damage parameters of the ancient pagodas,combined with the ABAQUS,the numerical model is established,then using this model to analyze dynamic characteristics and seismic damage analysis of the ancient pagodas structure,as the result we can research the basic laws of the structural seismic response and seismic damage evolution.The main research contents and conclusions are as follows:(1)Research on the damage mechanical properties of ancient masonry pagodas substructureReferring to the prototype structure of the ancient pagodas,the substructure model is designed and manufactured.Meanwhile the masonry mortar,masonry test block and substructure compression performance test are carried out.This paper analyzed the compression bearing capacity of the substructure,then determined the basic mechanical properties and damage parameter indexes of the ancient pagodas.As the result,obtained the characteristic parameters about the the compression damage of the ancient pagodas structure.(2)The identification for the ancient pagodas structure about its dynamic characteristics and initial damageBased on the in-situ pulsation test of Bayun pagodas in Zhouzhi County,Shaanxi Province.The dynamic parameters such as frequency,vibration mode and damping ratio of Bayun pagodas are obtained.Meanwhile recognized and analyzed the pagodas structure’s initial damage,and using the ABAQUS established the numerical calculation model,after the calculation and analysis,the vibration characteristics is obtained.By compared the model’s results with the test,the numerical model’s rationality can be verified.(3)Analysis of earthquake damage mechanism about the ancient masonry pagodasAccording to the plastic damage parameters of the ancient pagodas,implanted the initial damage of structure into the calculation model of the B ayun pagodas.At the meanwhile,inputing multiple seismic waves.By analyzing the structure’s seismic response,damage mode and mechanism,the failure mode of the B ayun pagodas under the earthquake action can be predicted.The results show that under the small earthquake action,the damage value and area both are relatively small,that means the struture is relatively safe.Under the moderate earthquake action,compression damage only occurred in the first floor of Bayun pagodas,not in others,but there is obvious tensile damage near the holes and eaves of each floor,and the main damage location is on the first floor.Under the large earthquake action,compression damage mainly occurred in the first and second floor,and the first floor structure is the most serious and widely distributed in the tensile damage.(4)Evaluation and analysis of seismic capacity of ancient masonry pagodas based on damage indexAccording to the seismic response analysis result of the plastic damage model of Bayun pagodas,taken the inter story displacement angle,shear stress and main tensile stress as the evaluation indexes,based on the evaluation criteria of the seismic capacity of the ancient pagodas,and combined with the seismic damage analysis results of Bayun pagodas,the seismic performance of Bayun pagodas under the earthquake action is evaluated.The results show that the Bayun pagodas structure is relatively safe under the action of small earthquakes.while under the action of medium and large earthquakes,there will be obvious damage,even when under the action of large earthquakes,there will be the threat of disintegration and collapse.