Load and Response Calculation from Breaking Wave Impacts on Columns of Semisubmersible Platforms

Abstract

Marine structures are subjected to slamming loads during their operating life. Increasing concerns are raised regarding the calculations of extreme loading caused by breaking waves. Slamming loads are associated with high-velocity impacts, large water pressures and short durations. They are challenging to describe and to design against. Traditional methods describing the phenomenon used by regulatory agencies might give inaccurate results. Further, the access to relevant direct numerical calculation approach is rapidly developing.

This study summarizes the results from slamming impacts on different structures in order to assess the role of hydroelasticity using the coupling between a nonlinear FEM analysis and CFD calculations. The link between hydrodynamic flow and response of the structure is discussed, and comparison with rigid body pressure calculations are included. The effects of hydroelasticity, such as the reduction in pressure and deformation, are presented. The importance of hydroelasticity for impact of this magnitude is crucial and needs to be considered.

Using a FEM model with similar characteristics and structural layout as an actual column of mobile offshore unit, the analysis of the response of the platform's column subjected to an extreme slamming load is also carried out Its response and structural integrity are discussed, along with the uncertainties linked to the description of the breaking wave phenomenon. The structure displays deformations within acceptable range for an extreme loading and the operability and load bearing function of the structure is moreover not directly endangered.