Evaluate The Seismic Performance Of The Structure Of The Xiaoyan Pagoda By Using IDA

Ancient pagoda as a historical and religious building,with great human art appreciation value and high scientific value,is a valuable historical and cultural heritage of all mankind.However,at present,China's existing ancient pagoda,mostly experienced natural disasters and man-made damages,there are material strength reduction and structural damage and other issues.As a typical representation of our ancient pagoda,the structure of Xi'an Xiaoyan pagoda has also experienced the impact of war and earthquake,anti-seismic reliability is reduced,anti-seismic performance evaluation is necessary immediately.In this article,the incremental dynamics analysis(IDA)is used to analyze the seismic performance of the Xiaoyan pagoda structure,and the corresponding anti-seismic performance evaluation is carried out.The main research work is as follows:(1)According to the historical literature and the archives of the Xiaoyan pagoda,the geometric characteristics,existed damage,material composition and main characteristics of the Xiaoyan pagoda structure were determined by field investigation and measurement.The main dynamic characteristics of the Xiaoyan pagoda structure were mastered.The results show that the situation of whole structure of the Xiaoyan pagoda is well basically,but the crack of main body structure is a little more,the weathering is much serious,some loess is exposed,masonry is defective.In addition,according to the actual measurement,the mortar strength of the pagoda is about 0.4MPa,the masonry compressive strength is about 0.7MPa,the basic period is about 0.74 s,the damping ratio is about 0.902,indicating that the strength of the pagoda structural material is low,anti-seismic performance evaluation is necessary.(2)According to the measured data,the compressive strength of the ancient glutinous rice mortar was tested,and the result is that the compressive strength was close to the measured value.At the same time,the ancient brick and the ancient glutinous rice mortar were selected as the substrate to make 6 ancient masonry specimens to simulate axial compression and shear test,and testing the corresponding compression,shear performance.Based on the analysis of the test results and the constitutive characteristics of the existing uniaxial compression masonry materials,the suitable constitutive relation of the anti-seismic performance analysis in the masonry structure is established,which can be used to analyze the anti-seismic performance of the Xiaoyan pagoda.(3)The low-cycle repeated quasi-static tests of three 400 mm,370mm and 490 mm thickness masonry wall specimens were carried out to study the relationship between the failure form and the displacement angle of the Xiaoyan pagoda structure.Combing anti-seismic performance assessment,the limit state performance of the Xiaoyan pagoda is divided into five levels,including basic intact,minor damage,moderate damage,serious damage and collapse,and refer to the relevant literature,the definition of Interlayer displacement angle limits interval in each state is determined which provides a basis for evaluating the anti-seismic performance of Xiaoyan pagoda.(4)Based on the field investigation and test results,the finite element analysis model of the Xiaoyan pagoda structure was established,and 10 seismic waves were selected to do the IDA analysis of Xiaoyan pagoda respectively,and obtaining the corresponding curve cluster.By the statistical analysis,the IDA curve is got in the probability statistic sense and the interlayer displacement angles are 1/2845,1/1381,1/944,1/422 and 1/178,corresponding to the five performance points on the mean quantile curve.In addition,the article also studied the seismic response of Xiaoyan pagoda structure under different vibration strength and the floor displacement and interlayer displacement angle of each layer under different performance state.The results show that the weak layer of Xiaoyan pagoda is the 10 th floor,the change of stiffness is existed in 10-13 floor which is easy to damage;most of the floor are damaged under the 8-degree earthquake,the upper part of the floor is collapsed,the earthquake protection is necessary urgently.