Dynamic analysis of soil-structure interaction problems considering infinite boundaries

Abstract EN

One of the limitations of the usage of the finite element method in dynamic soilstructure interaction arises when it is used for the modelling of an infinite domain if nothing is done to prevent from artificial reflections at the mesh boundary; errors are introduced into the results.

To handle reflections, different artificial boundaries have been proposed.

The aim of such boundaries is to make them behave as nearly as possible as if the mesh extends to infinity.

In this paper they are known as transmitting, absorbing or silent boundaries.

A brief description to two different approaches of absorbing boundaries is made, first by using infinite elements and the second by using viscous boundaries method.

For this purpose the computer program named “MIXDYN” is modified in this study to “Mod MIXDYN” by adding mapped infinite element model to the finite elements models of the program to be used for dynamic analysis of soil-structure interaction problems.

A new derivation of the mapped functions is made in this study for the cases when the infinite direction is extended to the left horizontally (at negative ξ direction) and down vertically (at negative η direction).

Two verification problems are solved to compare the results of the modified program with the results of other software, namely ANSYS and Open Sees representing other types of elements (dashpot elements) modelling boundaries as viscous boundary.

It was found that the transmitting boundary absorbs most of the incident energy.

The distinct reflections observed in the "fixed boundaries" case disappear in the "transmitted boundaries" case.

This is true for both cases of using viscous boundaries or mapped infinite elements.

The viscous boundaries are more effective in absorbing the waves resulting from dynamic loads than mapped infinite elements.

This is clear when comparing the results of both types with those of transient infinite elements.