THE STRUCTURAL RESPONSE TO WAVE SPECTRUM AND FATIGUE STRENGTH Of HIGH SPEED ALUMINUM TRIMARAN

The use of aluminum alloy for ship structures has weight efficiency and good corrosion resistance. Nevertheless, the heat affected zone (HAZ) of aluminum alloy will reduced the material strength noticeably, the fracture toughness and fatigue life of aluminum alloy are much lower than steel. This paper investigated the structural response of a 1,700 tons aluminum alloy trimaran in ocean waves. For the spectral response analysis, we considered that the frequency of waves ranges from 0.2 rad/s to 1.80 rad/s, in increments with 0.1 rad/s; and the wave heading angle ranges from 0 degree to 360 degree, in increments with 15 degrees. In this study, the structural response will be analyzed by finite element method. The wave response sensitive zones of ship structures are examined. The wave loads on the trimaran were analyzed by the BV hydrodynamic code – HydroStar. Combining the calculated stress response amplitude operators (RAO) and spectral fatigue analysis (SFA) with the JONSWAP wave spectrum for North Atlantic Ocean and ABS wave scatter diagram, the statistic response of structural components were calculated for the fatigue assessment. In the service life of ship different variation of loads (e.g., variation of full load and light ship and dynamic pressures of wave loads) were considered.