In previous post we have discussed many aspects of raft foundation including different parameters used in mat foundation design. We have already discussed about modulus of subgrade reaction, assumptions and considerations to analyze mat as rigid or flexible foundation, loads that should account in mat foundation design, thickness rigidity relationship of mat, and thickness deflection relationship of mat. In this post we will learn about analysis model that are used in computer software SAFE. We will discuss the foundation idealization in two posts as part-1 and part-2. Please stay tuned with this blog.
In this model finite elements are formed from object based model. Rectangular finite element mesh is developed depending on maximum allowable element size.
Computer oriented method for structural analysis is used to solve plates(raft) supported on elastic foundation. These rectangular finite elements are interconnected to adjacent one only at corners (nodes) and a isolated spring that resembles to soil are used in modeling.
Raft foundation is analyzed in SAFE based on classical theory for thick plates supported on the winkler foundations. The isolated spring assumed in modeling soil is called winkler foundation. This theory takes in to account the deformation due to transverse shear of the plate. This model is shown in the figure below.