Experimental and Numerical Analysis of Seismic Response Characteristics in Nuclear Safety–Level Digital Control Equipment

This study investigates the seismic response characteristics of nuclear safety–level digital control system (SDCS) equipment through combined experimental testing and numerical simulation. Seismic qualification tests comprising five operating basis earthquake events and one safe shutdown earthquake event are conducted on a prototype SDCS cabinet. A refined finite element model is established, validated against experimental results, and subsequently employed for transient dynamic analysis to capture time-dependent structural behavior. Results reveal distinct anisotropic dynamic characteristics, with first-order natural frequencies of 11.5 Hz (left–right direction) and 32 Hz (front–back direction). The cabinet successfully meets all seismic qualification requirements, with response spectrum analysis showing a maximum von Mises stress of 212 MPa at the front column base, below the Q235B yield strength (235 MPa). Transient analysis demonstrates significant time-varying stress characteristics, with peak stresses ranging from 19 MPa to 220 MPa at different excitation moments. A pronounced height-dependent acceleration amplification is observed in the left–right direction, with top acceleration reaching 10 g, a fivefold increase relative to base excitation. A case-specific cubic polynomial relationship (R2 = 0.9996) is established to describe the height-dependent acceleration distribution for the cabinet considered in this study. Based on these findings, design recommendations are proposed, including reinforcement of the front column–base connection and optimal orientation of vibration-sensitive components. This integrated methodology provides both a reference for seismic performance verification and a theoretical basis for the seismic design of SDCS equipment structures.