Spectral proper transformation of wind pressure fluctuations: application to a square cylinder and a bridge deck

The results of spectral proper transformation (SPT) analyses applied to the pressure fluctuations on a square cylinder and on a bridge box deck are presented in this paper. The main objective of the paper is that of comparing the results obtained using SPT with those obtained through a covariance proper transformation (CPT) analysis, to understand whether additional information is provided by SPT with respect to CPT. The meaning of the frequency dependency of the spectral eigenvalues and eigenvectors is also investigated. It is observed that a correspondence between SPT and CPT modes can be found in some cases, if the phase shift between the components of the SPT complex modes is properly accounted for. It is also found that the frequency variation of the SPT eigenvalues is related to the characteristic frequencies of the different physical phenomena causing the pressure fluctuations.