In this paper a simplified numerical procedure is developed which takes into account some of the significant factors affecting the behaviour of soil structure systems. One of these factors is the nonlinear behaviour of the subgrade material. To achieve this aim the following steps are followed: The foundation plates are represented by an equivalent framework model. A mathematical expression of the subgrade soil is developed to suit the solution technique. The stiffness matrix of a plane grillage element resting on soil, with linearly variable subgrade modulus along the beam length, is deduced. An incremental iterative procedure is used to handle the problems under consideration in this work. Within each increment an iteration process is used to reach an equilibrium state, compatible with the stress-strain or load-deflection relation of the physical nonlinear subgrade material. Also, within each iteration, any tensile stresses between the plate and supporting media are eliminated and the solution is modified to no-tension condition.

In order to study the effect of nonlinear behaviour of the subgrade four problems are considered as examples of applying the proposed approach. Cases of eccentrically loaded isolated footings, and an interior panel of raft foundation, with different rigidities, are solved using both linear analysis and the present nonlinear method. The analysis results are presented and compared.

purchase the full-text of this paper (price £20)

go to the previous paper
go to the next paper
return to the table of contents
return to the book description
purchase this book (price £78 +P&P)