RESPONSE OF AN SDOF SYSTEM TO PERIODIC EXTERNAL AND PARAMETRIC EXCITATIONS WITH RANDOM-PHASE MODULATIONS

A single-degree-of-freedom system is considered, which is excited simu ltaneously by external and parametric time-variant loadings. Both thes e dynamic loads are assumed to be periodic in time with some random di sorder, or phase modulations. Response analysis is made for this syste m by using stochastic averaging with subsequent application of the met hod of moments to the resulting set of the shortened Ito SDEs. The res ults of steady state mean square response analysis are presented in te rms of the corresponding amplification factor, illustrating its depend ence on excitation/system bandwidth ratios and detuning between expect ed excitation frequencies and the system's natural frequency. (C) 1996 Academic Press Limited