Small-capacity Shaking Table Test On The Influence Of Seismic Damage On The Dynamic Behavior Of Masonry Pagoda

As the important cultural relics of historical architecture, masonry pagodas have a long history in China. Due to their large self-weight, low material strength, complex structure, and the external damaged situation such as wind, rain, war and so on, these pagodas have been damaged seriously, and their structural performance has been reduced, especially those pagodas which were suffered from the earthquake. Thus, it is very important for finding out the structural dynamic characteristics of these pagodas under seismic damage to put forward measures about how to increase their seismic performance and how to protect these pagodas from the seismic damage in the future. In this paper, it was that the dynamic response, failure characteristic, damage distribution and damage evolution of the pagodas under seismic damage studied by electromagnetic shaking table test. It is very helpful and meaningful to protect the cultural relics such as masonry pagodas from seismic damage on both theoretical and practical aspect.(1)A test model was conducted by comparing with similar pagodas. Characteristics of the structure, common failure forms and damage characteristics were summarized. As LongHu pagoda being structure prototype, according to the structural characteristics of pagodas, the geometrical dimension, the material characteristic, the structural characteristics and the power of the test bench, the model used to test is developed. On the basis of choosing the appropriate geometrical dimension, the similarity ratio of geometric size, weight and prototype structure of the model was analyzed. The similarity relationship between the strength of the material and the modulus of elasticity of the material was further calculated and the similarity of the parameters was determined on the basis of similarity criterion. The technology of model production was researched to ensure the model of the technical instructions.(2)The small scale models of small wave shaking table test of seismic record method was studied, so the three test models were carried out on the shaking table. It was chosen the Wenchuan seismic wave in 2008 which was recorded in shifang, Sichuan as the experimental site seismic wave. According to similarity relationship, the initial seismic wave data was filtered, modified, compressed and other procession to obtain the experimental seismic wave. The processed seismic wave was input into shaking table, and through multiple iterations nonlinear correction, vibration table drive signal was used to ensure the output signal of the shaking table with spectral characteristics of seismic waves. Shaking table test load program was developed, and shaking test was performed on the test model, and the experimental data and the model dynamic reaction procession ware recorded in the shaking table test.(3)The data of shaking table text of three models was analyzed, and that index changes of dynamic response before and after the seismic damage of model structure were studied in order to receive the impact of seismic damage on dynamic characteristics of the model structure. According to the response data of shaking table text of model structure, using special software for processing data, we can extract the natural frequency, damping ratio, response of peak acceleration and the amplification coefficient of acceleration, peak velocity, response of peak displacement, and the interlayer displacement angle etc under different loading conditions and compare with the recorded videos of dynamic response of the model structure, so as to analyze the influence of the damage to the natural vibration period, damping ratio, the characteristics of acceleration response spectrum, acceleration and peak displacement of model structure.Finite element software of ABAQUS of model structure is run by nonlinear time history analysis, the numerical results were compared with experimental data to further validate injury on the dynamic characteristics of the model. The structure of the damping ratio increases; injury severity tower between the structural layer significantly enlarged displacement; accumulation of structural damage, and continue to reduce the stiffness of the structure; the weak parts of the tower will be the first to enter the partial collapse of the state, when the top of the tower and the moment the main structural separation, the main structural rigidity might suddenly enlarged, structural response is also rapid amplification, in particular earthquake, the tower structure have the possibility of further collapse.Due to the limits of the model structure, it was impossible to accurately simulate the comprehensive seismic damage of pagodas. Therefore, it just provided a reference for studying earthquake damage dynamic property of pagodas, so it needs a further study.