A basic understanding of the hydrodynamic response behavior of the two-body system isimportant for a wide variety of offshore operations. This is a complex problem andmodel tests can provide data that in turn can be used to retrieve key informationconcerning the response characteristics of such systems. The current study demonstratesthat the analysis of these data using a combination of statistical tools and systemidentification techniques can efficiently recover the main hydrodynamic parametersuseful in design.The computation of the statistical parameters, spectral densities and coherence functionsprovides an overview of the general response behavior of the system. The statisticalanalysis also guides the selection of the nonlinear terms that will be used in the reversemulti-input / single-output (R-MI/SO) system identification method in this study. Withappropriate linear and nonlinear terms included in the equation of motion, the R-MISOtechnique is able to estimate the main hydrodynamic parameters that characterize theoffshore system. In the past, the R-MISO method was primarily applied to single bodysystems, while in the current study a ship moored to a fixed barge was investigated. The formulation included frequency-dependant hydrodynamic parameters which wereevaluated from the experimental measurements. Several issues specific to this extensionwere addressed including the computation load, the interpretation of the results and thevalidation of the model. Only the most important cross-coupling terms were chosen tobe kept based on the estimation of their energy. It is shown that both the heading and theloading condition can influence system motion behavior and that the impact of the wavein the gap between the two vessels is important. The coherence was computed to verifygoodness-of-fit of the model, the results were overall satisfying.
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