A study on the effectiveness of floor isolation considering seismic diversity

Abstract

In nuclear power plants, seismic reinforcement has been done after the Fukushima accident. For dynamic equipment, such as pump and valve, it is difficult to increase the seismic capacity, so the reduction of seismic force is important issue. Since installation of seismic isolation system to entire building is not rational for existing structures, seismic isolation floor would be a one of promising strategy. In this study, the effect of introducing seismic isolation floor is investigated both deterministically and probabilistically. Then the effect of reducing the seismic risk of the parallel system with diversity is also examined. In the deterministic analysis, the response acceleration cannot be reduced unless the eigen period of equipment is longer than 0.8[s], however the displacement is increased in the longer period range, that is the risk of damage due to the displacement increases. According to the probability evaluation, we found that the seismic risk was reduced even at about 0.4[s], and the risk of damage due to displacement is in the acceptable range even at a longer period. With the system with seismic diversity, the damage risk can be reduced by both acceleration and displacement by adding seismic diversity.