Shaking Table Test On The Seismic Behavior Of Composite Isolation Technology For Rural Masonry Buildings

Rural buildings of cold areas with high seismic intensity are facing two major natural disasters, which are earthquake and frozen soil. Economic factor is the major obstacle to the application of existing earthquake relief measures like constructional columns and the circle beams,moreover,it is neither feasible nor effective to only improve seismic resistance.Based on the rural buildings of cold areas with high seismic intensity,a new composite seismic isolation system is presented.But our team hasn't researched on the overall seismic performance of masonry buildings founded on composite seismic- isolated structure.In order to carry out the shake table test, according to 1/4 scale, four two-story masonry models are designed which have two rooms on each floor.The four masonry models are as follows: Ordinary structure model,composite seismic- isolated structure model,sliding and damping structure model,and sand cushion seismic- isolated structure model.The main processes of the analysis are presented as follows:(1) The purpose of the shake table test, model designing, the identification of similar relations, observing project, loading control and the selection of earthquake waves are described in detail by collecting and analyzing massive domestic and foreign literature on the isolation and vibration reduction technology of rural buildings.(2) The shake table test scheme is designed. The construction of the four models,hoisting and the installation of instrument are completed.Ordinary structure model and composite seismic- isolated structure model are chosen in the shake table test, moreover, the test phenomenon is described in detail.(3) In order to verify the differences of ordinary structure model and composite seismic- isolated structure model as well as the validation of theoretical analysis and to study the damping effects, the test phenomenon,dynamic characteristics,acceleration and displacement response of the two models are analyzed and compared.Through the test phenomenon and data analysis, the following conclusions are obtained:(1) It was found that the isolation rate of the composite isolation structure was basically between 12% and 48%, which showed that the composite isolation structure had better isolation effect.(2) The ordinary structure model was damaged when the input peak acceleration got to 0.44 g, while the top floor of the composite seismic- isolated structure began to crack when the input peak acceleration got to 1.02 g, which proved that the building with composite seismic- isolated structure could withstand a 8.5 degree seldom-occurred earthquake.(3) The acceleration magnification factor of the roof of composite seismic- isolated structure model decreased when the peak acceleration increased, and the model remained intact, which showed that sand cushion and sliding layer could dissipate earthquake energy. Meanwhile, the acceleration response and acceleration magnification factor was smaller than that of the ordinary structure model.The main innovations of this paper are as follows:(1) In this experimental shake table study,solid model of composite isolation system, which combines sand cushion and sliding layer, is adopted. In the past studies, the destruction of masonry and the reduction of seismic response couldn't be observed because they only used concrete block instead of masonry building.(2) A new sliding material consisting of steel balls and modified mortar(Talcum powder mixed with 5% of M2.5 mortar) is adopted.(3) Combine the study of seismic isolation and of resistance to frost heaving in a creative way. The research results can be used to solve two large hazards of Xinjiang rural buildings,earthquake and frost heaving of foundation.