Developing a Finite Element Computer Code for the Analysis of Rectangular Raft Foundations for a New Two Parameter Subgrade Model
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Date
2019-07
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Addis Ababa University
Abstract
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.
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Keywords
Parameter Subgrade Model, Raft Foundations, Finite Element, Analysis