RELIABILITY OF SECONDARY SYSTEMS WITH UNCERTAIN TUNING.

First-order reliability methods are used to investigate the failure probability of secondary oscillators attached to primary structures. The properties of the two subsystems, including their natural frequencies and damping ratios, are uncertain and are modeled as random variables. The system is subjected to stochastic input at the base of the primary structure. The uncertainty in the properties is found to have significant contribution to the failure probability, even when the input is a wide-band process. The primary contributor is the uncertainty in the natural frequencies whose effect is most prominent when the mean frequencies of the subsystems are closely spaced. The contribution from the uncertainty in damping ratios is found to be less significant.