Abstract
Because the time history of the response spectrum compatible earthquake motion (RSCEM) is affected by the assigned Fourier phase spectrum we propose a method to extract the uncertainty of Fourier phase spectrum form an observed earthquake motion at the design site and to simulate many sample Fourier phase spectra that can be used as the uncertainty of Fourier phase supectrum at the design site. We also can see some minor effects of the initial Fourier amplitude spectrum on a simulated RSCEM and therefore discussed a method to minimize this effect. Based on these studies we investigate the effect of Fourier phase spectrum uncertainty on the nonlinear response of a structural system. The structure considered is a designed one using the yield seismic coefficient demand spectrum that the response ductility is kept constant. Our main concern is to evaluate the uncertainty of response ductility of the designed structure caused by the uncertainty of Fourier phase spectrum uncertainty.
