Extension of seismic fragility evaluation program for reinforced concrete structures based on nonlinear solid model. Application to nuclear reactor building

The conventional model used in seismic fragility evaluation of nuclear buildings is so-called stick model which was constituted of beam elements and concentrated mass. Finite element models, especially three-dimensional solid models considering material nonlinearity, not only can simulate damage more closely, but also extend the applicability to complex shaped structures and external actions other than earthquake. However, this approach is not realized for fragility evaluation yet because of the excessive computational load and lack of support environment for pre/post processing of multi-case analyses and fragility derivation. Then, in the previous report, the authors have developed the prototype for the automation platform of fragility evaluation which is combined with the FEM program available in a parallel computer. In the present report, the trial calculation for more realistic building-ground coupled system was conducted after the expansion of operating environment from a PC cluster to the supercomputer in CRIEPI and the development of a rebar arrangement tool for reinforced concrete structures with complicated shapes. As for the model of 270,000 nodes, the time required from the beginning of 48 analysis cases considering uncertainty to the display of the resulting fragility curves was 10 days with the PC cluster and 1 day with the supercomputer. Comparing with the result based on a stick model, the input acceleration for the damage probability to rise became large in the solid model. Although the material model used here is still necessary to be verified, it implies the possibility to rationalize the fragility. (author)