Dynamic Response to Nonstationary Nonwhite Excitation

The root mean square responses of linear multidegrees-of-freedom system to nonstationary, nonwhite random excitation are computed analytically using the state space formulation. Each modal equation is augmented by a filter and the augmented system is driven by evolutionary white noise. Analytical expressions for the evolutionary covariance matrix of the augmented system are given. Modal RMS responses are then superposed to obtain the desired responses; all cross-correlation terms among modes are included. Nonstationary responses are computed for a four-degree-of-freedom system. The effects of nonstationary and nonwhiteness are quantified and examined. Responses are compared with those obtained by using an unfiltered formulation with different white noise intensities driving the modes.