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A comparative numerical study between the adaptive finite-impulse-response and Fourier transform techniques to monitor structural integrity

It is often desirable to describe the rate and manner in which structures deteriorate when subjected to random excitation. Oftentimes, structural deterioration is reflected by variations in the system’s stiffness or equivalently, natural frequency. This paper compares the performance of two continuous structural integrity assessment techniques in monitoring variations in the natural frequency of single degree-of-freedom systems when subjected to random loads. The first technique makes use of the Fourier transform and the second is an adaptive finite-impulse-response technique developed by the authors. The effectiveness and limitations of the techniques are evaluated using numerically simulated single degree-of-freedom vibratory systems subjected to random base excitation. The influence of damping, noise, and damage progression type (sudden and gradual) is evaluated and the results compared. The results show that, despite a greater sensitivity to noise and damping ratio, the digital finite-impulse-response technique is able to more precisely determine the natural frequency of the system and the time at which any changes occurred for a range of damage scenarios and extraneous noise levels when compared to the more conventional Fourier-based analysis techniques. This is significant as it allows for the accurate measurement of stiffness for systems that undergo rapid structural deterioration under random loading.