Numerical investigation of rigidity and flexibility parameters effect on superstructure foundation behavior using three-dimensional finite element method

Abstract

A comprehensive three-dimensional finite element of the superstructure foundation model includes the effect of lots of important parameters on the structure performance. Among these parameters, rigidity and flexibility of raft foundations and soil interactions become an important aspect of design due to their efficient, practical and economic performance compared to the isolated foundation for buildings and heavy projects. In this study, the elastoplastic constitutive model based on the three-dimensional finite element (FE) method is employed to investigate rigidity and flexibility parameters' effect on superstructure foundation behavior. The model is developed and calibrated using SAFE 12 and ABAQUS programs by comparing two case studies. Utilizing the Winkler approach, flexible soil foundations are designed. In addition, technics like turning the raft into a boxed-raft or piled raft are evaluated to improve the performance of the raft from a rigidity and flexibility point of view. Then, the effects of various factors and conditions which affect design such as geometry, modulus of subgrade reaction, stiffness of the foundation, the effect of soil and thickness of foundation, piled raft foundations (PRF) and boxed raft foundations are studied. The results demonstrate that the superstructure components such as shear walls and basement walls can significantly affect the deflection, shear stress, and bending moment of the raft and its structural design subsequently. Also, shear walls, as structural parts which transmit an important part of vertical and lateral loads to the foundation, can play an important role in the rigidity of the raft. It is concluded that using PRF instead of the simple raft, results in a much rigid foundation with more bearing capacity and less differential deflection. The results of this study have the potential to be utilized in the design of advanced superstructure, in which rigidity and flexibility act as the basic elements.