Research On Damping Properties And Seismic Response Of Soil-Structure-Dynamic-Interaction (SSDI) System

With the rapid development of economic construction in china, many public infrastructures, industrial and civil buildings are constructed. Therefore, works to develop and improve the existing theory for earthquake resistance of engineering structures and guide seismic engineering practice is particularly important.Soil-Structure-Dynamic-Interaction (SSDI) has been one of the most important issues of earthquake engineering in the world for near forty years. Since it is a crossing subject revolving many science areas, there are many problems difficult to study. The seismic design method of buildings is based on the rigid ground hypothesis in current code, although this hypothesis is relatively simple, with the accumulation of earthquake damage data and the study of soil-structure-dynamic-interaction problems in theory and experiment, people discover that the rigid ground hypothesis does not conform to the actual condition in some cases, sometimes is unsafe for the seismic design of buildings.By integrating with the Natural Science Foundation of China“Study on the damping and seismic response spectrum for concrete filled double-skin steel tubes frame structure- foundation interaction system”(NO.50778070), Doctoral Fund of Ministry of Education of China“Study on the energy dissipation and damping model in nonlinear dynamic analysis”(NO.20020532002) and Key Project of Chinese Ministry of Education“The research and application of damping model for structure and material in strong earthquake”(NO.200001127), the damping properties, dynamic characteristics, response spectrum and seismic response of soil-structure-dynamic-interaction system is studied by the paper. The main research and investigation are done as follows:In order to make up for deficiencies of traditional simplified calculation method with no quality foundation, an improved calculation model with quality foundation is put forward that fully considering the dynamic interaction between foundation and structure, foundation and subgrade soil. Based on the simplified calculation model, the paper deduces the nonlinear coupling damping ratio formula, through choosing various non-linear parameters, taking into account the nonlinear damping of superstructure, the damping of pile-soil interaction system, the material damping and radiation damping of soil with different nature, as well as the foundation type and depth of foundation. At the same time, the article also examined the affection law of the size of nonlinear coupling damping ratio in soil-structure-dynamic- interaction system, by considering the seismic input, the nature of the subgrade soil, the foundation conditions and characteristics of superstructure factors and so on, all of the above provide a theoretical basis for engineering practice and seismic design.Based on Duhami integral calculation for the forced vibration of SDOF system under seismic action, the paper gains the seismic response spectrum of soil-structure interaction system under the condition of different seismic wave with different frequencies and different soil types. In line with the research of existing seismic design response spectrum, the article suggests the damping reduction factors Ba based on different soil condition and different natural vibration period, and comes to a fitted formula for the damping reduction factors. At the same time, through modifying acceleration response spectrum based on the damping characteristics of long-period SSDI system, it obtains the nonlinear acceleration response spectrum of SSDI system. Furthermore, the paper detailed study the seismic design response spectrum long-period SSDI system with different damping ratio.In the paper, modifying factors?for seismic influence coefficient i?s defined just integrating with the study of earthquake resistant design code, and it puts forward a modify seismic influence coefficient formula of soil-structure-interaction system, accordingly gets the seismic action calculation formula. At the same time, the article raised the seismic reduction factor formula for the SSDI system.The paper adopts finite element method based on the ANSYS procedure, and realizes the simulation of soil constitutional relationship through choosing Davidenkov soil model with proper parameters and using restartup method in ANSYS. Then, the procedure makes the soil nonlinearity simulation come true by using parameter design language of APDL. Element Combin14 is be used to simulate viscoelastic boundary and radiation damping effect. At the same time, it presents integrated damping matrix for considering the coupling of different damping of soil and structure. Finally, an example of soil-structure interaction calculated by ANSYS, then the dynamic reaction for the superstructure with rigid foundation compared with that with nonlinear soil foundation, and the variation of the structural dynamic reaction at different heights is studied. At the same time, the dynamic properties of the soil-structure-dynamic-interaction (SSDI) system about the displacement, velocity and acceleration response of different soil basements are studied.It drawn a conclusion that the finite element method is very practicable based on comparison with the existing test results, and the results agree with the actual working mechanism of SSDI system.Finally, an engineering case calculated in the paper. In succession, the dynamic properties and Seismic response effects of soil-structure-dynamic-interaction (SSDI) system is studied, by considering different soil property, different structural types, seismic excitations, foundation types, foundation depth of embedment, and so on. All of the conclusion for the calculation of the soil-structure-dynamic-interaction system will provide theoretical basis for the engineering practice.