Estimation of modal correlation coefficients in wind buffeting spectral analysis

The dynamic response of large and slightly damped civil engineering structures subjected to buffeting winds is usually studied in the modal basis and in the frequency domain. These choices respectively reduce the analysis to a few modes instead of many degrees-of-freedom and provide a simple estimation of the statistics of the modal responses as a sum of background and resonant components, avoiding generation of long time series. In many cases, the proper combination of modal responses, which is necessary to estimate design quantities, requires taking account of the correlation between the modal responses. This paper provides a review of available techniques to estimate the covariances of modal responses with the same objectives of rapidity and accuracy as the background-resonant decomposition, developed by Davenport for the computation of variances.