A finite difference/finite element approach to dynamic soil-structure interaction modelling

Abstract

In the recent past, much effort has been devoted to developing techniques for analysis and design of buried structures that are subjected to stress transients generated by earthquakes or by surface disturbances such as conventional or nuclear explosions. The analysis technique that is proposed here is based on a combined Finite Difference/Finite Element (FD/FE) approach. The Finite Difference technique is well suited for analyzing wave propagation in continuous media with nonlinear constitutive properties and large strain deformations; the Finite Element method is an obvious choice for analyzing the structure. In this approach, two existing computer programs were modified and merged to create the FD/FE program; using central differences in the time domain, the Finite Difference code calculates, in each cycle, the soil stresses and velocities, as well as the displacements of the soil grid points that are on the soil-structure boundary. The displacements of the current time step are passed to the Finite Element code for calculation of the soil-structure nodal forces corresponding to the deformed structures' stress state. The nodal forces are passed back to the Finite Difference code for calculations in the next time step. This approach combines the best features of the Finite Difference and Finite Element techniques to provide the analyst with the capability to model the complete effects of soil-structure interaction, including material and geometric nonlinearities. The method and its computer implementation are briefly described and the results of two example analyses are presented.