強震記録に基づく進化戦略手法による建物の振動特性評価

概要

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Understanding of dynamic characteristics of building structures is a key issue in the seismic design technology. From this point of view, Building Research Institute (BRI) is operating the strong motion network for buildings since 1957. The BRI annex building is a one of the stations of the BRI strong motion network and densely instrumented with 22 accelerometers. In this paper, variation of dynamic characteristics of the annex building is discussed using strong motion records. Decreasing of fundamental natural frequencies of the annex building with the passage of time is recognized from the optimizing analysis of 158 strong motion records using a single-degree-of-freedom system. 16 records with relatively big displacements are selected in order to examine such phenomena in detail. The Evolution Strategy (ES) is applied to the optimizing analysis using a multi-storey sway-rocking model. ES is a powerful problem-solving tool based on natural evolution. Building stiffness, rocking stiffness, swaying stiffness and building modal damping ratio are targets of the optimization. The rocking stiffness, the swaying stiffness and the modal damping ratio of the building show stable behavior with the passage of time. Consequently, it is confirmed that the decreasing of the natural frequencies is caused by the softening of the building stiffness.
社団法人日本建築学会の論文
2006-04-30