Influence Of Layered Site With A Soft Layer On Dynamic-Stiffness Coefficients Of Strip Foundations

The seismic response of the site is an important problem to be studied of soil dynamics, geotechnical engineering and seism engineering. Every earthquake had the obviously different effects on Nankai and Heping district in Tianjin. That is for there's the soft soil layer in the field in Nankai districts but not in Heping districts. The study of Soil-structure interaction has been applied in many fields such as large-scale dynamic machine base, nuclear reactor, deepwater flat roof, high building, bridge, dam and so on. Dynamic excitations arise from machine, earthquake, wind, wave and other impact. Soil-structure interaction is complex problem which concern dynamic property of soil, form of base, shape of upside structure and dynamic reactor etc. Considering soil-structure interaction accord with the properties of structure under dynamic loads and is important to recognize the inherent action of structure under dynamic loads and control or utilize the rule, thus the study of this term has deeply theoretical and engineering significance.The study about dynamic input of underside soil domain on upside structure is an important problem, so called base impedance problem. And the key problem to solve it is to simulate the soil domain precisely. The surface flexibleness Green function of free field is calculated by means of direct-stiffness method of structural analysis based on wave propagation and indirect boundary element method. Then the dynamic stiffness of surface strip foundation is calculated. By calculating some examples, the influence of layered site including soft soil layer on dynamic stiffness of surface strip foundation are analyzed. The results show that the place and properties of soft soil layer have an obviously effect on the dynamic stiffness.