Computation of wave fields and soil structure interaction

The basic message of the lecture is that the determination of the temporal and spatial variation of the free-field motions is the most important part of any soil-structure interaction analysis. Any interaction motions may be considered as small aberrations superimposed on the free-field motions. The current definition of the soil-structure interaction problem implies that superposition must be used, directly or indirectly, in any rational method of analysis of this problem. This implies that the use of nonlinear procedures in any part of a soil-structure interaction analysis must be questioned. Currently the most important part of the soil-structure interaction analysis, the free-field problem, cannot be solved by nonlinear methods. Hence, it does not seem reasonable to spend a large effort on trying to obtain nonlinear solutions for the interaction part of the problem. Even if such solutions are obtained they cannot legally be superimposed on the free-field motions to obtain the total motions of the structure. This of course does not preclude the possibility that such an illegal procedure may lead to solutions which are close enough for engineering purposes. However, further research is required to make a decision on this issue