Parameter Identification in FEM of Mechanical Structure Within NPP Based on Seismic Response

Reliable finite element models (FEMs) are required in seismic qualification of mechanical structures within a nuclear power plant (NPP). The relative displacement response of such mechanical structures is difficult to measure, and it is costly to extract enough modes. Therefore, the modification of the initial FEM by the common FEM updating method could not always be carried out smoothly. In this paper, a vibration control equation error-based two-stage FEM updating method is proposed to identify uncertain parameters in the FEMs, which is capable of employing seismic response in the form of acceleration. Optimal values of updating parameters are searched by using the Marquardt method, which is effective in avoiding the ill-conditioned iterative equation. Numerical simulation is performed for the steam pipeline to validate the actual feasibility and robustness of the proposed method. The fact that the distribution of damping is independent of the identification of parameters related to the mass and stiffness matrices is also demonstrated. Finally, experimental validation of the method is carried out on a load-bearing pipeline. The damping coefficients of the pipeline are modified independently by back propagation neural network.