Developing a Finite Element Computer Code for the Analysis of Rectangular Raft Foundations for a New Two Parameter Subgrade Model

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Addis Ababa University


In order to design safe and economical foundation structure, it has to be analyzed appropriately. An analysis method is said to be appropriate if the real behavior of the materials is implemented in the computational model. In order to implement the real behavior of the materials, advanced material models have to be applied. Formulating a computational model that uses advanced material models accurately is difficult. However, it is possible to formulate computational models that implement the advanced material models approximately. This is possible by using sophisticated 3D numerical methods. Nevertheless, running sophisticated 3D numerical models in routine personnel computers need significant time. Therefore, alternative computational models that are simplified and yet effective have to be formulated or selected. There are practical cases in which soil behavior is characterized by elastic material models. In addition to this, there are poor practices of including a soil effect on a foundation structure. This study is intended to develop a linear 3D equivalent finite element model for a plate on an elastic foundation based on the current findings of subgrade models. This model is formulated such that design oriented results can be obtained easily by running the program on routine personal computers. The developed finite element model is formulated based on a Kerr-equivalent subgrade model and Mindlin’s theory for plates of intermediate thickness. In order to run the developed program on common personal computers easily, computer implementation techniques of finite element formulation are applied. All the operations of the developed program are coded by using the programming language of MATLAB. The results of the developed finite element model are compared with the results of PLAXIS 3D FOUNDATION. As per the observation of the comparison results, an attempt has been made to adjust the subgrade model. PLAXIS 3D FOUNDATION has been used for this purpose. The final comparison after the application of adjustment factors shows that the solution of the developed finite element model is fairly in good agreement with the solutions of full-fledged finite element software such as PLAXIS 3D FOUNDATION. The developed elastic finite element computer program is used for the analysis of rectangular raft foundations.



Parameter Subgrade Model, Raft Foundations, Finite Element, Analysis