フェイルセーフ構造の耐震性に及ぼす地震動位相特性の影響

概要

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It is known that fail-safe structures which have redundant subsystems can exhibit stable seismic resistance against earthquakes with unknown predominant periods. In this paper, effects of phase characteristics of ground motions on the seismic resistance of the fail-safe structures are investigated using numerically simulated ground motions with various phase characteristics. The phase characteristics are represented by maximum instantaneous energy input and change of predominant period in time domain. It is observed that the fail-safe structure has less seismic resistance than single structures when the predominant period changes from a shorter period to a longer period in time domain and the maximum instantaneous energy input is large. In the worst case when an accelerograms has shorter period components in the first half and longer period components in the latter half, seismic resistance of the fail-safe structure is about 0.7 times those of single structures. A method of estimating such effects of phase characteristics is proposed on the bases of energy input time history, which gives a fairly good prediction to precise responses obtained from dynamic analysis. Effects of phase characteristics of real ground motions are also investigated using recorded accelerograms of the 1995 Hyogoken-nanbu earthquake, however, no clear effects on the seismic resistance of the fail-safe structures are observed.
1999-08-30