The Performance of a Recently Developed Two-Parameter Foundation Model for the Analysis of Raft Foundation
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Date
2025-06
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Addis Ababa University
Abstract
Different viewpoints on modeling the Soil-Structure interaction (SSI) in mat foundation design exist in engineering practice. Some believe that modeling the SSI using a few mechanical elements during design is sufficient, while others contend that modeling the soil as a continuum model is necessary to produce an adequate analysis.
Commonly, the analysis and design of mat foundations is done by performing static analysis of a plate resting on vertically uncoupled Winkler springs. Despite being a somewhat simplified idealization of reality and the emergence of more accurate techniques, the Winkler spring methodology continues to be the state-of-the-practice because it is simple to implement in most commercial structural analysis computer programs.
This and related shortcomings have meanwhile been addressed by a number of improved models including Worku's two-parameter subgrade model (2014). Worku’s model is a mechanical equivalent of an originally elastic continuum idealization of the soil under the foundation, whereby all components of the continuum deformation and the stress and strain tensors are retained. This is unlike a number of previous similar attempts by other authors, who proposed simplified versions of such a continuum representation. The implementation of this analytically rigorous model into applications such as beams and plates on elastic foundations and laterally loaded plates has been under investigation showing promising results.
This thesis deals with a comparative study of the performance of the model to rectangular raft foundations against existing methods of analysis. To this effect, a recently adjusted version of the model under an on-going PhD research is employed.
A finite element algorithm developed under this project and written in MATLAB to solve the resulting partial differential equation of the plate along with a calibration chart for different loading conditions was used and compared with a rigorous continuum based finite element model of the plate-soil system (cFEM). The findings show that the model adequately represents the behavior of rectangular plates on elastic foundations showing remarkable agreement with the cFEM outputs.
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Keywords
soil-structure interaction, Raft foundation, Two-parameter model, Winkler’s spring model, continuum finite element analysis (cFEM).