Comparative Three-Dimensional Finite Element Analysis of Piled Raft Foundations

Document Type : Research Note

Authors

1 Civil Engineering,University of Tehran,Tehran,Iran

2 Department of Civil Engineering, Islamic Azad University, Ahvaz branch, Ahvaz, Iran

Abstract

3-dimensional finite element method as a general method to solve complex problems is one of the most powerful numerical methods which can be used for piled raft foundation analysis. These models can consider the complex interaction between soil and structure. Among available 3D FEM  software for modelling pield raft foundations, in this paper MIDAS GTS is used due to its various element type and modeling abilities. In this article, different pile modeling techniques in MIDAS GTS software (like pile modeling by solid elements, modeling by beam elements connected to soil elements and modeling by EPM  ) are compared with a real pile loading test data. Results showed that all three methods have excellent compatibility with the results of loading test in the linear area of the load-settlement curve, and SEM  and EPM kept their conformity further in the non-linear area as well. One of the most critical problems in 3D FEM modeling process of piled raft foundations with SEM was an increase in the number of elements when the number of piles increases and that leads to model's slowness and convergence problem. Piles modeling by EPM needs much lower elements; using this method, skin friction resistance, tip resistance and displacement between pile and soil can be easily calibrated with a pile loading test data which facilitates piled raft analysis with a large number of piles. After comparing different pile modeling techniques through MIDAS GTS software, the ability of the software for modeling piled raft foundations had been verified; Results show acceptable agreement between software output and monitored values and also outputs from other methods and software.

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