Abstract: Accurate and reliable seismic input is a prerequisite for seismic response analysis of engineering structures. Based on the artificial boundary substructure method, the frequency-wavenumber domain (FK) semi-analytical method was integrated into the open-source finite element platform OpenSees. Combined with message passing interface (MPI) parallel computing technology, this integration enables equivalent input of P-waves, SV-waves, and SH-waves at arbitrary angles. After verifying the correctness of the developed seismic wave input methodology, a nuclear island structure located in a non-bedrock site was selected to analyze the effects of soil nonlinearity and geotechnical medium properties on its seismic response under oblique SV-wave incidence, considering soil-structure interaction (SSI). The research findings indicate: (1) Soil nonlinearity reduces the peak ground acceleration of the containment structure and significantly alters the internal force responses at the top and bottom of the pile foundation; (2) Variations in the dynamic properties of geotechnical media lead to changes in the stiffness of the soil-pile-nuclear island system, profoundly impacting the structural dynamic response. Specifically, sandy or silty soil layers with dynamic characteristics exhibit strong filtering effects on high-frequency seismic components, amplifying the bending moments in pile foundations adjacent to such layers. This study provides an effective tool for addressing external seismic input problems using the OpenSees platform.

Key words: seismic wave input, OpenSees, artificial boundary substructure method, soil-structure interaction, second development