Simulation Analysis using 3-D Nonlinear FEM model for Onagawa Unit 2 Control Building at the time of the 2011 off the Pacific coast of Tohoku Earthquake

摘要

This report provides the results of the simulation analysis for Unit 2 Control Building of Onagawa Nuclear Power Station, Tohoku Electric Power Co., Inc., performed to verify integrity of the building structure using the lumped mass model and the 3-D nonlinear FEM model based on the observed records of the off the Pacific coast of Tohoku Earthquake (March 11 earthquake) and off-Miyagi Prefecture Earthquake (April 7 earthquake) occurred in 2011. This building had been subjected to several large earthquakes, and the predominant frequency of the structure gradually decreased from the values at the time of construction according to analysis of the observed records. Based on this fact, the 3-D nonlinear FEM model assumes stiffness of the building that corresponds to the predominant frequency observed in the earthquake on March 9, 2011, immediately before March 11 earthquake. The analysis results of the 3-D nonlinear FEM model using the observation records of March 11 and April 7 earthquakes represented the observation records and state of cracking of walls. It was also confirmed by the analysis that reinforcement bar remained within the elastic region during both earthquakes. Based on the above, it was confirmed that the building was subjected to significant seismic load during 2011 off the Pacific coast of Tohoku Earthquake in 2011 but its structural integrity is maintained.