研究発表

We compared the damage occurrence probabilities for two control designs, specifically, 1) minimizing the response to the design ground motions having a particular level of ground motion intensity (the conventional approach) and 2) minimizing the probability of damage occurrence (the proposed approach). The damage occurrence probability is calculated using a seismic hazard curve and a fragility curve. The fragility curves for the above two control designs were formulated based on the time-history response analysis using design ground motions with a wide range of ground motion intensities. As a result, while the former probability was 0.55% (the conventional approach), the latter probability was 0.44% (the proposed approach) thus clearly showing the improved performance. In addition, we confirmed that the proposed approach produces a smaller probability even when the structural parameters are changed from the initial design values.

In design of buildings, structural engineers take care of principal structural components. Through the experiences of earthquake disasters, the design techniques and regulations for these principal components have been improved to a certain level. On the other hand, non-structural components have not been considered well although the damage risk and threat to occupant’s life have been pointed out for long time. The seismic safety of ceilings, piping, and escalators are supposed to be secured by architects, equipment engineers, and mechanical engineers, respectively. Unfortunately, falling non-structural components caused a considerable number of casualties in the 2011 Tohoku earthquake. Consequently, regulations for ceilings of large-span buildings and escalators have been amended. However, there was no major revision in the fundamental regulation for non-structural components. This regulation sometimes fails to consider the resonance effect between a building and a non-structural component with similar natural periods. To achieve the comprehensive seismic safety of buildings, we have to discuss and address a problem of vertical division system in a building design.