A SIMPLIFIED FINITE ELEMENT FORMULATION OF SHALLOW FOUNDA-TIONS FOR CIVIL ENGINEERING STRUCTURES SEATED ON SOFT CLAY SOIL

The estimation of the structural response of civil engineering structures as they are subjected to different combination of loadings is currently done by the use of numerical models, and its effectiveness depends on how boundary conditions are included into the mod- el. In the case of constructions seated on clay soils, a numerical difficulty resides in how to model the soil-foundation interaction as well as the non linear material behavior of soil. In this work a practical engineering solution is presented in which a set of some simplified foun- dation elements is integrated into the conventional analysis of a building. A simplified numer- ical strategy of four steps is proposed in order to include the soil-foundation interaction into the calculations of a global structure. Regarding to the soil-foundation interaction, two super- elements called "Isolated Foundation Element (IFE)" and "Continuous Foundation Element (CFE)" are numerically formulated, being able to take into account the non linear material behavior of a stratified soil -in particular, long term deformability -, the influence of the soil region in the vicinity of the embedded foundation and their effects in the whole structural sys- tem. Both formulations include different criteria for evaluating soil stress distribution (Bous- sinesq, Westergard, Fhrohlich) as well as the evaluation of the volumetric deformation for a stratified soil (Zeevaert semi-empirical criteria). In order to evaluate the robustness of the proposed strategy, some foundation cases are analyzed in the finite element codes ANSYS and GeoStudio, as well as using the IFE/CFE elements: the comparison of the numerical results shows a good performance of the proposal, with a reduced number of calculations and less complexity.