Wavelet transforms and ice actions on structures

A wavelet cross-correlation analysis was applied to ice loads and corresponding acceleration signals measured at the Norströmsgrund lighthouse in the Gulf of Bothnia, Sweden. It was shown that the excitations of the lighthouse by actions from ice floes are influenced by structural responses with dominant excitation frequencies in the same range as the frequencies of the responses. The lengths of intervals with synchronized excitations and responses are predicted to be from 1.9 to 8.6 s. Local ice loads were found to be synchronized in the same intervals and for the same frequencies, but for a slightly shorter time. This synchronization causes simultaneous ice actions which can trigger higher global ice loads on the structure than has been obtained during brittle non-simultaneous crushing.