SOME OBSERVATIONS ON TIME DOMAIN AND FREQUENCY-DOMAIN BOUNDARY ELEMENTS

The numerical solution of problems in elastodynamics involving infinite media calls for the use of discrete techniques such as the boundary element method and the finite element method. These techniques can, in turn, be formulated in the time or frequency domains, and have each relative merits and drawbacks. This paper presents a comparative study of the accuracy and limitations of three different implementations of these methods. The problem studied is that of transient loads on the surface of homogeneous elastic halfspaces, and of finite depth strata. In each case, the response is computed first for an uninterrupted (continuous) medium, and then for a medium that includes a trench (or cavity). Three independent computer programs were used that incorporated the following methods: (i) frequency domain boundary element method (FD‐BEM), using a discrete fundamental solution; (ii) time domain boundary element method (TD‐BEM) using an analytical fundamental solution; and (iii) a coupled time domain boundary element‐finite element model (BEM/FEM). It is found that for convex domains (halfspace or stratum without a trench) the three independent implementations are in excellent agreement, while for non‐convex domains (trench in the path of the waves), numerical errors associated with non‐causal behaviour become evident in some cases. Copyright © 1990 John Wiley & Sons, Ltd