A study on the connection effects of subsurface slabs to exterior walls in the KNGR seismic analysis

The soil-structure interaction (SSI) analyses are being performed for the Korean next generation reactor (KNGR) design, because the KNGR is developed as a standard nuclear power plant concept enveloping various soil conditions. The SASSI program, which adopts the flexible volume method is used for the SSI analyses. Since the impedances are computed based on the assumption of a rigid foundation in the KNGR design, the impedances are computed at a single point around the center of the basemat. The base model used in the SSI analyses assumed that the subsurface slabs are free and not connected to the exterior walls. This results in a more flexible structure than reality. This study is performed to address the concern of the potential dynamic effect of this modeling assumption on the overall structural response. The super-structure model is modified with the subsurface portions of the sticks being laterally rigid, so that the entire subsurface cavity together with the super-structure model acts laterally rigid. For the comparison, the in-structure response spectra using the rigid subsurface model arc compared with the original spectra without considering the connection effects.