| The rigid ground assumption has been used for earthquake response analysis in the seismic design in which superstructure is considered only in the calculation model. A vast amount of theoretical and test researches demonstrate that dynamic interaction has a great influence on the dynamic characteristics of superstructures, and the seismic response of interaction system may greatly change when the site is soft. The interactive design of foundation and superstructure parts as a whole is necessarily and primly emphasized by majority researchers and engineers in practice.As a part of the projects financed by nature science national fund, analysis of soil-foundation-structure dynamic interaction (NO.50278033), analysis of isolation of structures based on soil-structure interaction (NO.50578062), series tests of soil-structure dynamic system had been done. On that basis seismic performance of the soil-structure interaction system is studied by changing the nature of the soil surrounding the foundation.The article is divided into five chapters, as follows:(1) With the review of the development history, various analysis methods, and some major problems of dynamic soil-structure interaction research.The applications of the research results of the field in domestic and foreign seismic design codes and the MSC.MARC—an advanced nonlinear finite element program, are introduced in this chapter.(2) The tests of a 1/4 scale steel frame model are introduced in this chapter. All of the tests were carried out on rigid groundsill and soil-trough respectively in door. Dynamic properties—fundamental frequencies, damping ratio, vibration shapes of the model—were obtained respectively by the tests. The discount of fundamental frequency of the system is increased with the relative stiffness ratio between the superstructure and the groundsill, and the relationship between them was obtained by data fitting.(3) Researches of the influence of the content of geotextiles and confining pressure on the soil dynamic parameters (such as dynamic shear modulus, dynamic damping ratio, and so on) were done by the dynamic triaxial test indoor of reinforced dry sand. The relationship between Modulus ratio and dynamic strain was obtained by data fitting. (4) In this chapter, a 1/4 scale steel frame finite element is established by using MSC.MARC progame. Some rules of soil-structure interaction are obtained from earthquake response of different frequency spectrum features ground motions.At the same time, the influence of different soil dynamic characteristics is studied too by changing the nature of soil surrounding the foundation. It is found that sand cushion or reinforced sand cushion is filled around the foundation, shear force reduced significantly.(5) Practical calculation method of soil-structure interaction problems is introduced in this chapter. The soil-structure interaction system is equivalent to a base fixed single degree of freedom system by two steps. The response spectrum for seismic design of rigid foundation systems can be used conveniently by revising the structures's dynamic parameters to consider the dynamic interaction effects, from the example and the test results,it is very good.
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