Dynamic Characteristics And Seismic Response Analysis Of Xi’an Andingmen Gate Building

The building on the city gate has been existed since ancient times.The Xi’an Andingmen Tower is a national key cultural relic and a typical high stylobate ancient wooden structure.Its value is immeasurable.Its particular important to accurately evaluates the seismic performance of the tower and its structure under earthquake action.The high stylobate(city wall)is the base of the wooden structure of the tower.Its existence makes the overall height of the wooden structure of the tower increase,makes the material composition changes,and the overall structure becomes more complicated.In order to accurately evaluate the seismic performance of the tower,it is necessary to master the influence rule of existence of high stylobate on the dunamic characteristics and seismic response of wood structure.In view of this,this paper combines the in-situ dynamic characteristic test and the finite element numerical simulation method to study the dynamic characteristics and seismic response law of the tower when considering and not considering the high stylobate foundation.Furthermore,this paper analyzes the extended parameters of the whole structure.The main research work completed in this paper is as follows:(1)For the first time,the in-situ dynamic characteristics test under the environmental excitation was carried out on the Andingmen Gate Building in Xi’an,and the collected data was processed to obtain the dynamic characteristics(frequency,formation,etc.)of the wooden structure of the tower.(2)The finite element software ANSYS was used to establish the model of the wooden structure,high stylobate and overall structure(wood structure + high stylobate).In the modeling,different types of spring units are respectively used to simulate the special performance of the foundation,mortise-tenon joint and bucket.The solid model of the monolithic wall of the tower wall is established by Abaqus,to obtain the lateral stiffness is obtained to provide the same lateral stiffness resistance.The spring unit is equivalently replaced;the outer wall of the high stylobate and the semi-infinite body boundary are considered.(3)Modal analyses of the wooden structure,high stylobate and overall structure of the tower are conducted.The modal analyses results of wood structures are compared with the in-situ dynamic characteristics test results,so as to verify the accuracy of the model.The dynamic characteristics of the three models are compared and analyzed.The results show that the frequency of wood structures varies greatly and unstable.The frequency variation of the high stylobate is relatively small and stable.The first five-order frequency of the overall structure is close to the wood structure,and the sixth-order phase is relatively close to the high stylobate.The main vibration mode of the wood structure are two-stage translation and two-order subsequent torsion.Forever,the first-order and third-order modes of the high stylobate are translational,and the other modes are torsion.The vibration of the upper 5th mode of the whole structure is dominated by the vibration of the wood structure above,and the vibration mode of the 5th order is mainly the wood structure.The vibration of the vibration of the high stylobate co-vibrates;the contribution of the vibration mode of the wooden structure to the response is mainly concentrated in the first two steps,that is,the translation of the two directions.When considering the high stylobate,the contribution of the vibration mode of the overall structure to the response is mainly Focused on the first 8 steps,and the high stylobate mainly participates in vibration from the sixth stage.The existence of the high stylobate has changed the highorder dynamic characteristics of the 5th order of the wood structure of the tower.(4)The time-history response analysis of the wood structure and the whole structure under earthquake action show that under the same excitation,the displacement response of the wood structure increases gradually from the column foot to the roof.While the acceleration response decreases,and the dynamic coefficient is lower than 1.With the increase of excitation,the displacement response and acceleration response of wood structure increase correspondingly,while the dynamic coefficient decreases.The maximum interlayer displacement angle of wood structure is 1/64,which meets the specification limit(≤1/30).The displacement response,acceleration response and dynamic coefficient of the overall structure change similarly as the wood structure.But the overall dynamic coefficient is higher than 1,and the maximum interlayer displacement angle of the structure is 1/43,which also meets the specification limit.The existence of the high stylobate makes the input excitation of the wooden structure column foot of the tower increas,which can stimulate the energy dissipation capacity of the wood structure to a greater extent.But at the same time,the structural displacement response,acceleration response and floor shear force are greatly increased,and the relative growth rate of the column top displacement response is above 18.9%,and the absolute increase is above 25.1%.The absolute increase of the dynamic coefficient is above 63.1%,and the increase of floor shear force is above 19.9%.There are adverse effects for the seismic performance.(5)The extended parameter analysis of the whole structure shows that the increase in the elastic modulus of the high-base bauxite and the increase of the thickness of the outer wall tile reduce the seismic response of the whole structure,and the increase of the height of the foundation increases the seismic response of the overall structure.