模擬地震動波形のフーリエ位相特性に関する基礎的研究

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It is important to clarify the relation between Fourier (amplitude, phase) spectra and the corresponding time function, in order to generate simulated earthquake ground motion based on those spectra expressed in frequency domain. In this paper, the meaning of the Fourier phase of a corresponding time function is investigated based on an analytical expression in time domain of a band-pass filter with linear phase. The analytical expression f_e(t). showed as eq. (8), is a closed form time function with 5 parameters A,t_<gr>, ω_0,ω_c, φ_0. Because the meanings of the parameters are respectively clear, the expression is useful to comprehensive understanding of a role of Fourier phase in the corresponding time function. Especially effect of φ_0 on the maximum, minimum, and their occurrence time of f_e(t) is investigated. η_<e,max>(φ_0), η_<e,min>(φ_0), τ<max>(φ_0), τ<min>(φ_0), respectively, normalized maximum, minimum, and their occurrence time of f_e(t), are plotted versus'φ_0 in Figs.6〜9. Figs.10〜17 are results in cases of 1st and 2nd time differentials of f_e(t). From these figures, the following remarks can be made, that maximum, minimum, and their occurrence time of f_e(t) are deterministically prescribed, and that maximum, minimum of f_e(t) change sinusoidally on φ_0 and their occurrence time does linearly. The same remarks can be made on the time differentials. These mean that φ_0 is a significant parameter in simulating a time function based on Fourier spectra. f_e(t) described by eq. (8) can be approximate causal function. So it is possible to generate a simulated earthquake ground motion wave f(t) by superposing f_e(t). A method of generating f(t) by probablistic superposition of band-pass filters with linear phase, is presented. The sample functions of f(t) generated by the method are showed.
社団法人日本建築学会の論文
1987-05-30

著者

木村正彦
小山工業高等専門学校

模擬地震動波形のフーリエ位相特性に関する基礎的研究

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