Thesis
Analysis of geothermal pile foundations under combined axial and moment loading
Washington State University
Master of Science (MS), Washington State University
2013
Handle:
https://hdl.handle.net/2376/102016
Abstract
Geothermal pile foundations provide numerous advantages over conventional piles in terms of sustainability. Geothermal piles are similar to conventional reinforced concrete piles but with additional polyethylene tubing secured to the inside of the reinforcing cage. The additional tubing circulates a liquid which, when used with a heat pump system, can be used to heat and cool the structure the piles support. The heat transfer characteristics between geothermal piles and the surrounding soil have been investigated extensively, but very little research has been done examining the structural integrity or performance of the piles. The structural performance of geothermal reinforced concrete piles was compared to conventional reinforced concrete piles using a cross sectional analysis program, Xtract, and the finite element program, Abaqus. Xtract was used to quantify and compare the differences in moment-curvature diagrams between cross sections with and without the tubing and Abaqus was used to develop a three dimensional model with similar cross sections to compare with Xtract. Xtract results showed no differences between the various cross sections for curvature values up to 0.02 1/m. Curvature values in excess of 0.1 1/m showed marginal differences for the estimated moment, except for the case of completely unconfined concrete. Curvature results from Abaqus results were within 30 to 40 percent of those predicted by Xtract for the finest mesh. Limitations due to convergence issues from the tensile behavior of the concrete prevented larger moments to be reached. The moment and curvature values of the model were only able to reach between 20 and 60 percent of the maximum moment predicted by Xtract. The results from both Xtract and Abaqus showed that the structural performance of the pile is highly dependent upon the longitudinal reinforcement of the pile, rather than the confined concrete within the transverse reinforcement. Therefore, conventional and geothermal reinforced concrete piles perform similarly under static, axial, and moment loading conditions
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Details
- Title
- Analysis of geothermal pile foundations under combined axial and moment loading
- Creators
- Michael Gray
- Contributors
- Balasingam Muhunthan (Degree Supervisor)
- Awarding Institution
- Washington State University
- Academic Unit
- Civil and Environmental Engineering, Department of
- Theses and Dissertations
- Master of Science (MS), Washington State University
- Publisher
- Washington State University; [Pullman, Washington] :
- Identifiers
- 99900525401701842
- Language
- English
- Resource Type
- Thesis