AN IMPROVED METHOD OF THE CALCULATION OF EQUIVALENT NODAL FORCES IN VISCOUS-ELASTIC ARTIFICIAL BOUNDARY

The viscous-elastic artificial boundary is widely used in the analysis of site seismic response and dynamic structure-soil system interaction problems. Seismic input is usually taken as equivalent nodal forces incorporating in the viscous-elastic artificial boundary, and stress in the control area of any artificial boundary node in the conventional method is considered as uniform distribution. However, its distribution is actually uneven. An improved method is proposed for the seismic input of wave propagation scattering problem in infinite domain. In the proposed method, an viscous-elastic artificial boundary is first introduced; seismic input is considered as the equivalent node forces to be incorporated directly in these local boundaries, and the node force obtained using the mesh refinement process combining stress integration of adjacent node regions is changed along the artificial boundary nodes, and its computation error is effectively reduced; the two-dimensional wave propagation problem in time-domain is then solved using the explicit finite element method. The numerical simulation of two-dimensional finite element site models of wave propagation problem with various mesh sizes and incidence angles are presented to demonstrate the performance of the improved method in this paper. The simulating nephogram of wave propagation and values of response displacement show that the calculating precision of the improved method is closely related to the mesh size and wave incidence angle, and increases with decrease of the mesh size and incidence angle. The simulation result also shows that the calculating precision of the improved method is significantly higher than that of the conventional method in the case of the same mesh size and incidence angle.