Numerical Investigation of Different Superstructure Loading Type Effects in Mat Foundations

Abstract

With the ongoing developments in numerical analysis methods, it is possible to model the soil-foundation-structure interaction and nonlinear load-deformation behavior of soils in three-dimensional calculations. In light of these developments, the calculations of mat foundations can be made more realistically and economically by using advanced softwares, which take into account the interactions of these three components than the conventional methods. The aim of this paper is to present the effect of superstructure loading types on the analysis of mat foundations by using three-dimensional finite element analysis results. Thirty-six different models have been established to examine these effects on the internal forces and settlement behavior. The data of a three-storey existing building has been used and superstructure loads have been modeled in different ways such as uniformly distributed loads, column loads and by modeling all buildings. The building has been modeled with a mat foundation having a thickness of 50, 75 and 100 in separate models. The mat and superstructure elements have been modeled either with 2D plate elements or 3D volume elements in different models. The "Mohr-Coulomb'' material model has been used and soil properties have been represented as "normally loaded'' and "overconsolidated''. Results for total and differential settlements and internal forces have been presented in figures and graphs. An important finding is the place where the maximum displacement occurs. It is very different when the load is transmitted by modeling the whole structure and it causes to have different internal forces and different placement of reinforcement. Another finding is that the biggest decreases in differential settlements are seen in column and building loading when the soil properties improved, while this effect remains very small in distributed loading. For bending moments, the biggest difference in comparison to the loading types is that the maximum moments are calculated in different places independent of the location of shear walls, when the load is simulated as a uniformly distributed load. It has been found that the superstructure loading type affects the settlement pattern and internal forces, so this effect must be taken into account.