Collapse load analysis for flexible footings by the boundary element method | |
| Author | Khadka, Muna |
| Call Number | AIT Thesis no.GE-03-07 |
| Subject(s) | Boundary element methods Equilibrium of flexible surfaces |
| Note | A thesis submitted in partial fulfillment of the requirement for the degree of Master of Engineering, School of Engineering and Technology |
| Publisher | Asian Institute of Technology |
| Series Statement | Thesis ; no. GE-03-07 |
| Abstract | Collapse analysis has always been an important aspect in the field of geotechnical engineering, especially in the design of foundations which requires a reasonable estimate of bearing capacity, that is, collapse load for a particular choice of foundation and soil system. In this research work, a numerical technique, called Boundary Element Method, has been used to predict the collapse loads for flexible shallow (surface) footings, viz., strip and square. A FORTRAN program BEMECH, developed for non-linear stress analysis of two- and three-dimensional solids has been used. Boundary element modeling meshes for the problems under study are prepared using Matlab program codes which can generate the geometrical and boundary condition input data compatible with the program BEMECH. The smooth flexible strip footing has been modeled as a two dimensional plane strain case whereas three dimensional modeling meshes have been prepared for the smooth flexible square footings. The footings are analyzed for two types of loading conditions, namely, undrained or short term and drained or long term loadings. While dealing with the problems, the soil has been treated as a non-linear elasto-plastic material. The undrained analysis has been carried out using the van-Mises model, while Mohr-Coulomb yield criterion has been used for the drained collapse analysis. The undrained results have been obtained in the form of central vertical load-displacement responses, whereas the drained analyses have been resulted into the friction angle versus collapse load responses. The undrained collapse analysis of strip footing has resulted the collapse load of 5.14 Cu, where Cu is the undrained cohesion. This is a theoretically exact solution from different techniques. Similarly, the undrained collapse load for the square footing has been computed to be 6.05 Cu, which is also very close to the available semi-analytical and numerical solutions. The drained collapse load for the strip footing with the friction angle of 20° has been obtained to be 11.5 c, where c is the cohesion intercept in c - ¢ soil. The f1iction angle versus collapse load plots obtained for both strip and square footings have shown that the collapse loads for smaller friction angles well agree with the analytical solutions, whereas they are found to be underestimated when the friction angles are higher. |
| Year | 2003 |
| Corresponding Series Added Entry | Asian Institute of Technology. Thesis ; no. GE-03-07 |
| Type | Thesis |
| School | School of Engineering and Technology (SET) |
| Department | Other Field of Studies (No Department) |
| Academic Program/FoS | Geotechnical Engineering (GE) |
| Chairperson(s) | Park, Kyung Ho |
| Examination Committee(s) | Noppadol Phien-wej Glawe, Ulrich |
| Scholarship Donor(s) | Government of Japan |
| Degree | Thesis (M.Eng.) - Asian Institute of Technology, 2004 |