Critical configurations of systems subjected to wide-band input

It is well known that the response of harmonically loaded structures can be sensitive to small variations in the structure's parameters. For instance, if a change in a parameter causes a natural frequency to become tuned to the input frequency, the response will exhibit a resonance peak. This paper explores the possibility of sensitive response patterns when the input is wide-band. It was found that large increases or reductions in the mean-square response can occur when two or more natural frequencies are closely spaced. Closed form expressions are derived to characterize these response fluctuations. The results show that sensitive response patterns are associated with significant correlation between model responses, as well as veerings and crossings of natural frequencies.