SEISMIC ANALYSIS OF BASE-ISOLATED NUCLEAR POWR PLANT CONSIDERING SOIL-STRUCTURE INTERACTION

摘要

This paper proposes an efficient method to obtain the non-linear seismic response of a base isolated nuclear power plant(NPP) considering the soil-structure interaction(SSI). Hybrid methods combining frequency and time domain techniques are often considered as useful tools to solve SSI systems with structural non-linear behavior. However, most former hybrid methods need the iterative techniques to match SSI systems at time domain and frequency domain. A slightly new methodology, direct-hybrid-frequency-time-domain method, is proposed to get more realistic dynamic response at nonlinear SSI problem. The proposed method is rigorous technical background without iteration scheme for convergence of restoring force. Under the assumption structural non-linear behavior is only occurred at the base bearings of base isolated NPP, this method is applied to solve the non-linear seismic response of the base isolated NPP structure with the next three main steps. First step is the calculation and extraction of transfer functions which are the frequency-dependent displacements on attached nodes for a whole SSI system corresponding to the unit motion. Second step includes the separating super-structure system from SSI system and computing the real time force of the interface nodes defined at contact surface between super-structure basemat and soil region. Non-linear equation of motion using well-known conventional time domain analysis technique is applied as a final step. To show the validation of the proposed methodology, the dynamic analyses for a typical NPP isolated by the lead-rubber bearing is executed. The calculated responses are demonstrated by way of comparison with the results obtained by the proposed methodology on the linear and non-linear states.