Date of Graduation
1996
Document Type
Thesis
Abstract
Soil-structure-fluid systems like U-lock, pipelines, and storage tanks are widely used in engineering practice. Relatively very few works can be found in the literature for the analysis of a soil-structure-fluid system subjected to externally applied loads or seismic excitations. The main purpose of this study is to develop a numerical method for the analysis of a soil-structure-fluid system. In the formulation of the presented numerical method, the flexibility of the thin plate structure is treated with a finite element formulation, while the difficulty in modeling the infinite extent of the soil is overcome by a boundary element formulation. The contained fluid is also modeled by a boundary element formulation. The boundary element method (BEM) is coupled with the finite element method (FEM) by enforcing compatibility and equilibrium conditions at the soil-structure, structure-fluid, and soil layers interfaces. The accuracy of the method is verified through comparison with results published in the literature for rigid foundations. A series of convergency studies is conducted to obtain the optimum truncation distances and the size of the boundary elements that maintains a good balance between accuracy and efficiency. Recommendations and guidelines are provided to select the optimum truncation distances and size of boundary elements. The response of the soil-structure-fluid system subjected to both externally applied loads and harmonic excitations are determined. The effects of salient factors such as the foundation stiffness, foundation mass, the foundation embedment, and the frequency of the external loads and harmonic excitations are valuated through numerical examples. The study indicates that the effect of the foundation stiffness is significant and can dramatically affect the response of the system. Specifically, stronger soil-structure-fluid interaction is observed for larger foundation stiffness. Systems with a stiffer foundation, a wider area is disturbed when subjected to external loads, or the propagation pattern is more significantly modified when subjected to harmonic excitations. The foundation embedment also plays an important role in the response of the system. The numerical examples show that the deeper the foundation embedment, the stronger the soil-structure-fluid interaction. When a system subjected to an external load, the displacement is reduced by increasing foundation embedment, especially for the imaginary part of the displacement. In the case of harmonic excitations, larger modification is observed for foundations with deeper embedment. Another important factor that affects the response of the system is the frequency of the applying loads or harmonic excitations. As expected, frequencies close to the fundamental frequency of the system result in larger soil-structure-fluid interaction. The effect of the foundation mass is not so significant as the other factors.
Recommended Citation
Xu, Chaojin, "Soil-structure-fluid interaction by hybrid FEM-BEM." (1996). Graduate Theses, Dissertations, and Problem Reports. 10062.
https://researchrepository.wvu.edu/etd/10062