Dynamic And Static Interaction Research Of Mega-Frame-Raft Foundation-Sand Gravel Soil Structure

Mega-frame structure is a new type of large-scale structure, and gradually begins to be widely used as the urbanization and economic development. For Mega-frame structure has the character of complex system, if it is built depended on the hypothesis of rigid foundation without regard to the interaction of superstructure and base, the result will be unreasonable and cause a big discrepancy between calculation and reality. Superstructure, base and foundation are an organic whole which connect and influence each other. And the interaction of Mega-frame structure becomes an unavoidable key scientific question in some important real projects. So, the paper's aim at only one kind of mega-frame structure and research on static and dynamic interaction carefully.Based on the developing trends of the interaction research,the paper used theoretical analysis, soil tests and numerical simulation to study the interaction of the mega frame structure - based raft - sand gravel foundation. The main works and conclusions in this paper are as follows:(1) Static and dynamic characteristics of sand gravel are analyzed and the numerical model of foundation is researched. Based on the results of consolidated and drained triaxial shear tests, the transmogrification of sand gravel is studied. Based on the dynamic triaxial tests, the rule about the dynamic characters of sandy gravel soil under different confining pressure, solidify ratio and vibration frequency are analyzed. Among these work, the conclusion that the strength and elastic modulus of sand gravel can use Duncan-Chang Model to calculate, but the transmutation and poisson ratio need crewel model to determine are innovative. The numerical equation about the maximum dynamic modulus and the maximum poisson ratio are also innovative. Finally, the soil medel of Wrinkler are improved and the numerical parameters are gained.(2) The calculated method about raft foundation on sand gravel is investigated. The equation of raft based on the theory about elastic thin plate and the finite element method of orthotropic plate for Wrinkler is analyzed. Base on the thin plate theory, the moderately-thick plate theory and the space elastic theory, three numerical models about raft are calculated. After the deformation and internal force of raft under different theory are compared and analyzed, the conditions for the application of theoretical calculations are innovative.(3) The nonlinear analysis about raft foundation and sand gravel interaction are researched. The elastic-plastic characteristic of sand gravel, reinforced concrete raft foundation and the contact nonlinear are analyzed. The nonlinear numerical calculation are performed, the nonlinear characteristic about three parts will change the result of calculation. So the analysis about raft foundation and sand gravel interaction would adopt nonlinear calculation, and the priority is given to the nonlinear characteristic of sand gravel in the simplify process.(4) The static interaction of Mega frame-raft foundation-sand gravel soil is analyzed by numerical calculation. After the numerical model about the mega-frame structure considering the vertical static load under interaction are calculated, the response about mega-frame under interaction are analyzed, and the characteristic of interaction are researched by soil foundation, thickness of raft, theoretical calculation about raft, hypo-frame and others. Among these work, the innovative conclusions in this paper are as follows: the hypo-frame at the bottom of mega-frame structure adjust the uneven settlement of foundation; the raft foundation has a best thickness to be felicitous; the stiffness soil will weaken interaction when the foundation increase its thickness; the whole deformation of foundation aroused the settlement of raft and the local deformation determined the stress distribution of raft.(5) The dynamic interaction of mega frame-raft foundation-sand gravel soil is analyzed by numerical calculation. The area and boundary truncation of foundation under earthquake waves are researched by the finite element method. The calculation model about the upper part of the mega-frame structure is researched, and the hypo-frame can change the dynamic response of mega-frame structure based on the numerical calculation of mega-frame structure under earthquake. Finally the dynamic interaction are analyzed by numerical calculation. Among these work, the innovative conclusions in this paper are as follows: the increasing stiffness by hypo-frame is quite to the reducing stiffness by interaction; the raft foundation which are thin will be disadvantage to the top parts of structures; the soil foundation and raft foundation has nonnegligible influences on the dynamic response about the bottom of structures.