Response sensitivity of structural systems subjected to fully non-stationary random processes

A method for the evaluation of the statistics of response sensitivity of both classically and non-classically damped discrete linear structural systems under fully non-stationary stochastic seismic processes is presented. To do this the evolutionary frequency response function, also referred in literature as the time-frequency varying response function, plays a central role in the evaluation of the spectral characteristics of non-stationary response. The proposed approach requires the following items: a) to write governing motion equations in state-variables, which are very suitable to evaluate the statistics of the response of both classically and non-classically damped discrete linear structural systems by an unified approach; b) to evaluate in explicit closed form solutions the derivatives of time-frequency response vector functions with respect to the parameters that define the modified structural model; c) to obtain the sensitivity of the structural response statistics by frequency domain integrals. A numerical application shows that the proposed approach is suitable to cope with practical problems of engineering interest.