TRUE ICE FORCE BY DECONVOLUTION

摘要

Moving ice exerts high static and dynamic loads against fixed offshore structures. To justify design criteria ice force in-field measurements are needed. However it is not possible to measure ice forces directly. With slender structures the dynamic response interferes in the measurement signal. The effects of dynamic response of the structure can be removed by deconvolutlon. This paper presents methods how to use transfer functions and deconvolution for analyzing ice force measurement signals from steel lighthouses at the Gulf of Bothnia. Transfer functions were measured by exciting lighthouses with a 1.0 MN negative step loading function. Poor coherence disabled the direct utilization of measured transfer functions. Noisefree analytical transfer functions are calculated by using finite element methods and modal decomposition. Theoretical transfer functions were calibrated by comparing to measurement data. Implementing calibrated transfer functions into digital signal analyzer and actual ice force measurement data processing is still going on.