Thick Raft Foundation Of Nonlinear Interaction Between Numerical Analysis And Topology Optimization

Superstructure, raft and soil is an integrated structural system. When the interaction model is established, two nonlinear problems must be considered. One is material nonlinearity of soil that can be solved by selecting suitable constructive relationship of soil; another is status nonlinearity caused by sliding and separating between raft and soil. In this paper, a three-dimensional finite element model of interaction among superstructure raft and soil is established by using Drucker-Prager elastoplastic property of soil and simulating the status nonlinearity of soil-foundation interface, non-linear numerical analysis is performed based on the medium-thickness plate theory. The irregular boundary is simulated as eight nodes isoparametric element, Mindlin model for moderate thickness in which transverse shear is considered is used in order to improve the accuracy of calculation. The Superstructure is worked out using substructure can be used for calculating reduced superstructure stiffness matrix and reduced load vector. The computation results show that the subgrade reaction and foundation settlement are coincident with testing value.The complexity of superstructure lead to complicated stress distribution of raft. Using variable density method, a topology optimal model is derived based on finite element analysis considering interaction between raft and soil. And the sequential linear programming is chosen to solve the optimal problem. Furthermore, a topology optimal solving model based on Genetic Algorithms is established. Compared with routine method, the way presented by this paper is more accurate and the results show the macroscopic distribution of stress of raft more clearly.