DOE-ANOVA for Identifying the Effect of Extreme Sea-States over the Structural Dynamic Parameters of a Floating Structure

Abstract

Sea extreme events affect the integrity and operation of the offshore structures, then, it is important to analyze wind-waves-currents loads over the structural dynamics. Traditional offshore designing identifies structural parameters with certain limitations: physical modeling involves using shaking tables in dry conditions; numerical simulations have not sufficiently considered the effects of combined extreme waves-wind-current loads over the structure and the significance of the near and far hydrodynamic field over the structure. The non-linear interactions in the near hydrodynamic field generate viscous damping that modifies the dynamic structural parameters of the offshore structures. The traditional determination of structural parameters considers the hydrodynamic forces computed from wave records, omitting fluid-structure interactions that could generate unexpected damped periods and amplification peaks. This study applied physical modeling to determine floating structural parameters, considering combined loads and the effect of far and near hydrodynamic field in the fluid-structure interaction. The calculated transfer functions in the near hydrodynamic field revealed the highest amplification of the structural accelerations, and the transfer functions in the far field did not evidence structural resonance. Finally, this study recommends measuring the near hydrodynamic field and applying DOE-ANOVA for offshore designing to assess the viscous damping that may provoke dangerous structural amplifications.