Abstract
Many works have been carried out in order to examine the phase characteristics of earthquake ground motions for the improvement of earthquake resistant design of building structures. Especially the phase difference distribution has lately attracted considerable attentions as it approximately determines the envelope of time history. This paper examines phase characteristics of recorded motions and their effects on the response spectra by use of the phase difference concept, and discusses the role of phase characteristics which should be considered in simulating motions. The standard deviation of phase differences, σ_<ΔΦ>, for components in a narrow frequency band was found to be considerably less than that for all components. It was also revealed that only the representation of σ_<ΔΦ> is not sufficient to express the phase characteristics of motions in terms of the peak acceleration, Amax, the envelope shape and response characteristics. Then, the narrow band phase difference tendency is cons- idered to be applied in simulating motions. A method of generating artificial ground motions with consideration for phase characteristics in narrow frequency ranges is proposed in this paper. Fourier phases are derived from phase differences generated with consideration for phase characteristics in narrow frequency ranges. The standard deviation of phase differences in a narrow frequency band is set to be about 0.75 times of that for all components which is supposed to be equal to σ_<ΔΦ> of recorded motions. Simulated motions according to the proposed method were confirmed to posess Amax, σ_<ΔΦ> and response spectra satisfactorily close to those of recorded motions.
