Dynamic Soil-Structure-Interaction. An implicit transmitting Boundary for Direct Time Integration

Ph.D. project by Lindita Kellezi.
For a complete analysis of the full dynamic soil-structure-interaction problem, a very important aspect is modelling the dynamic response of the unbounded region of soil beyond the vicinity of the generalized structure. A lot of work has been done in this area in the framework of the Substructure or Direct methods for steady state or transient analysis. In this project we focus our attention on the Direct Method which avoids calculation of convolution integrals in a transient analysis. The central problem is design of a nonreflecting, transmitting TB, or absorbing boundary applicable for finite element calculations which can properly simulate readiation condition at the edges of the mesh.
Our total physical system, soil and structure, is considered separated into near and far fields. This is an imaginary separation where the attention is focused more in the analysis of the near field where the structure is placed or the interesting observed area is situated. The total computational system contains only the near field which in the area of contact with the far field, is closed from a surface or zone where transmitting boundaries are implemented. These boundaries which are capable of absorbing the energy distinated to be radiated in the far field, can be interpreted as the constitutive equations for the interaction forces between near and far fields. To simulate the infinite medium realistically in numerical solution of these problems we need to describe these forces correctly.