Time-frequency analysis of wind effects on structures

As many physical processes of interest to Civil Engineers manifest nonlinear and nonstationary features, their complete characterization may not be accomplished via Fourier transforms, necessitating a new analysis framework in the time-frequency domain. This paper overviews recent developments in wavelet-based analysis of a number of physical processes of relevance to the Civil Engineering community. It is shown that the dual nature of wavelet transforms, being a simultaneous transform in time and frequency, permits adaptation of a number of traditional system identification and analysis schemes. For example, the extension of wavelet transforms to the estimation of time-varying energy density permits the tracking of evolutionary characteristics in the signal using instantaneous wavelet spectra and the development of measures like wavelet-based coherence to capture intermittent correlated structures in signals. Similarly, system identification methodologies originally referenced in either the time or frequency domain can be extended into the realm of wavelets. Though the application of wavelet transforms in Civil Engineering is in its infancy, as the examples in this study demonstrate, its future shows great promise as a tool to redefine the probabilistic and statistical analysis of wind effects.