Effect of bi-directional ground motions on the seismic pounding of adjacent NPP structures

This study aims to investigate the structural pounding of two adjacent RCB and AB under bi-directional ground motions. Furthermore, this study also investigates the influence of strong bi-directional ground motions on the seismic response interaction of adjacent RCB and AB. Finite element models (FEM) for both RCB and AB are constructed in SAP2000 using multi-layer shell model (MLSM) with a design level separation (i.e., seismic gap). Two sets of ground motions are utilized to perform time history analyses of the combined RCB and AB, in which each set of motions comprising 10 bi-directional design-based earthquakes (DBEs), and 10 strong bi-directional ground motions ever recorded respectively. Seismic displacement is monitored at the two most susceptible locations of AB and RCB. The observation shows that RCB is prone to experience damage due to seismic impact of adjacent AB under very strong bi-directional ground motions. Additionally, it is noticed that the probability of the occurrence of seismic pounding between adjacent RCB and AB increases significantly when the PGA of strong bi-directional motion is higher than 1.5g. These results emphasize that the current design separation of 5.08 cm gap between adjacent RCB and AB may not be sufficient to prevent seismic impact during strong earthquakes.