強震観測・常時微動計測に基づく中低層建物の入力損失効果に関する研究

概要

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This paper discusses input loss effect of 9 low and medium-rise buildings systematically using large amount of small to medium level seismic records and microtremor records. The following results are obtained. (1) Predominant frequency of input earthquake motion can be estimated by equivalent predominant frequency expressed as PGA/PGV/2π or PGV/PGD/2π. PGA, PGV and PGD mean peak ground acceleration, velocity and displacement respectively. (2) Input loss effect can be evaluated in the unified form for acceleration and velocity using nondimensional frequency calculated from equivalent predominant frequency of input earthquake motion, foundation width and average shear-wave velocity of ground. As nondimensional frequency become high, input loss effect become larger. Embedded buildings have lager input loss effect than other buildings. (3) Using Fourier spectrum ratio of foundation and ground, input loss effect of seismic and microtremor records show same characteristic depending on frequency for large scale and embedded buildings, however, they are much different for other buildings. This is caused by the difference of input mechanism of earthquake motion and microtremor, because spatial vibration of earthquake is coherent and that of microtremor is incoherent.
2005-01-30