Seismic Vibration Analysis of a Vertical Mechanical Structure Subjected to Horizontal and Vertical 2D Excitation : 2nd Report, Nonstationay Random Wave Response

Abstract

This paper clarifies vibration response characteristics of a vertical mechanical structure subjected to horizontal and vertical nonstationary random excitation. The structure is modeled as a cantilever beam with a lump mass at its free end ; taking into account the first vibration mode for numerical computation of vibration response, response multiplication factor maps with respect to dominant frequencies, w_H and w_v, of both horizontal and vertical extitations are obtained for the structure's damping, , magnitude and randomness of vertical excitation. A very high response appears at w_v=2 and w_H=1 and its magnitude varies with a slight change in the power spectral density contained in nonstationary vertical excitation waves at w_v=2. For w_H=1, the conditions of unstable parametric random vibration are obtained for structure damping and magnitude of vertical excitations.