Abstract:Considering the stiffened plate as a composite system of grillage beams and slab,the superstructure as an equivalent rigidity plate,a semi-analytical and semi-numerical method,which makes use of compatible analysis of force and displacement among beams and slabs and columns and ground,is developed to analyze interaction between stiffened raft foundation and subsoil considering the rigidity of superstructure. The method has good preciseness and less unknown variables and it is convenient to be used in practice. Numerical examples and practical engineering case both show that superstructure rigidity has an important influence on deformation and interal force of stiffened raft foundation;and practical engineering proves that the presented method has good preciseness and practicality. Especially,it is convenient to calculate the coefficient of subsoil settlement with the data of geotechnical engineering investigation.