Change detection in vibration structures subject to transient natural excitations

An appropriate signal processing technique for analysing both the transient natural excitations and the vibration structures response, capable of identifying the time variations in the amplitude and in the frequency content of these structures, is presented. This technique makes use of an impulse invariant transformation for obtaining an equivalent model of the vibration structure, represented by a parallel form realization of second order subsystems, corresponding to different modes of vibration having as input a stationary independent and identically distributed sequence. The method was applied for detection of changes in dynamic characteristics of a vibrating structure: a multi story concrete building subject to an earthquake ground motion. Some of these results are presented.