LAUSR

This paper presents the use of infinite element boundary conditions for physical and engineering problems in a three-dimensional unbounded domain, subjected to seismic loading, with a view to compare results with the traditional viscous boundary. Boundary conditions are discussed in general with an emphasis on understanding the pros and cons of each method used. Also, a comparison is drawn between the different types of boundary conditions used for the optimal solution of physical problems especially the models under seismic loading. Infinite elements can be implemented easily with lesser computational time. It provides “quite” boundaries to the models and can be used effectively for the accurate numerical solutions of physical issues. This paper presents the complete details of node setting and numerical computation for the infinite element boundaries and compares results of a three-dimensional free field soil model and a soil–tunnel model under seismic loading using infinite boundary, and a similar model using a spring/dashpot system. The results verified the use infinite element boundary to evaluate the seismic behaviour of the model and suggest that in the time domain, this method can be combined easily with the finite element and other methods such as boundary element method directly.