On the influence of far-field model reduction techniques using a coupled FEM-SBFEM approach in time domain

To analyse soil-structure-interaction problems, often unbounded domain has to be taken into account. Since the finite element method (FEM) does not provide open boundary itself the scaled boundary finite element method (SBFEM) which fulfils the radiation condition for wave propagation to infinity is used. The coupling of FEM and SBFEM in time domain is very time and memory consuming, due to the almost fully populated acceleration unit-impulse matrices and the convolution integral, which has to be solved at every time step. This paper studies ways to overcome this drawback and describes the influence of different model reduction techniques: like extrapolated acceleration unit-impulse response matrices, geometric far-field decoupling and sub-structured far-fields which can be applied to the far-field and also their combination. The different techniques for a FEM-SBFEM coupling in time domain are evaluated in terms of accuracy and computational effort.