Fragility Analysis of Overturning Resistance of Hybrid Base-Isolated Structures in Diesel Engine Buildings of Nuclear Power Plants

This paper validates the effectiveness of the modeling approach based on the finite element analysis of shaking table tests, establishing finite element models for both a base-isolated structure and a hybrid base-isolated structure designed to address overturning issues in the diesel engine building of a nuclear power plant. By using the Incremental Dynamic Analysis (IDA) method, a fragility analysis of the overturning resistance was conducted for both isolation systems. This study demonstrates that the hybrid base isolation scheme, which incorporates additional dampers, effectively enhances the structure’s overturning resistance and reduces the probability of failure. When evaluating the seismic fragility of the structure by using the TP value, which is related to the tensile stress of the isolation bearings, as a damage index, the results are more conservative compared with those obtained by using shear strain (γ). This highlights the importance of improving the tensile capacity of the isolation bearings in structural design. Furthermore, fragility assessment using γ as a damage index can provide design references for the collision limit of the isolation moat in the base-isolated structure of the diesel engine building in nuclear power plants.