Parametric study of wave impact pressure impulse and characteristic pressure on a square column with overhanging deck

Semi-submersible platforms may suffer safety accidents due to severe wave impacts on the decks and columns in extreme ocean environment. The pressure impulse considering the cumulative effect of time is significant for the dynamic response analysis of offshore and coastal structures, and has attracted attentions in recent years. In this study, wave impact tests on a square column with overhanging deck were carried out under a series of fifth-order Stokes waves with large steepness to investigate the influence parameters on the impact pressure impulse. A novel definition of characteristic pressure is proposed from the perspective of pressure impulse, meanwhile, its dimensionless relation with the peak impact pressure is presented. The spatial distributions of the pressure impulse and characteristic pressure on the square column with overhanging deck, as well as the influences of several environmental and model parameters are discussed in detail. The results show that the spatial distributions and vertical variations of wave pressure impulse are affected significantly by the wave parameters, initial air gap, column incline angle and wave incidence angle. In general, the wave impact on the overhanging deck and the upper part of column is severer, and the inclination of column can reduce the pressure impulse to some extent. The research findings may provide references for further research and the predesign of the column–deck structure of semi-submersibles.