| The Boundary Element Method (BEM) is applied in the study of three dimensional dynamic soil-structure interaction phenomena. Surface rigid foundations subjected to externally applied harmonic or transient forces are considered. The soil medium is an idealized linear viscoelastic, isotropic, homogeneous or layered half-space. The problem is formulated and solved in the frequency domain. Transient results are obtained via Fast Fourier Transform.; Initially, a formulation for the rigid surface foundation problem is established and some related computational and modelling aspects are considered, such as the use of "relaxed" versus "non-relaxed" boundary conditions and the type of elements used in conjunction with the BEM discretization of the boundary of the domain of interest. The above formulation is used, with minor adjustments, for problems of multiple foundations as well. Thus, the interaction of a number of railway ties resting on an isotropic, homogeneous, and linear viscoelastic half-space and connected by an overlaying flexible rail system is studied. It is determined that the presence of the superstructure and material damping significantly affect the response of the foundations to externally applied loads.; A BEM representation of a 3-D layered half-space in the frequency domain is also formulated and combined with the above proposed methodology for the study of the interaction of single and multiple foundations with the underlying soil medium. Each layer in this formulation is assumed to consist of an isotropic, homogeneous, and linear viscoelastic material. A number of parametric studies regarding the effects of material damping, foundation mass, and the distance between adjacent foundations are presented.; The computer codes generated for this work were run on an IBM model 3090 supercomputer which provides efficient scientific subroutines and vector facilities that help reduce the computational time considerably. A parametric study regarding the use of the vector facility is also presented. |
