Numerical modeling of a Trimaran vessel to analyze the fatigue of its transverse deck

The trimaran is a multi-hull float consisting of a long, slender main body with two smaller side hulls, and a transverse deck connects the side hulls to the main hull. Trimaran vessels have been studied by designers due to their unique configuration, low resistance at high speeds, transverse stability and good navigation. Also, due to the possibility of special location of the equipment due to the existence of a wide transverse deck and as a result of high transport capacity, the owners of the marine industry have paid special attention to it and extensive research has been done on it. Most of these studies focus on the hydrodynamic parameters of this vessel and there are very few comprehensive and reliable studies on the subject of structural fatigue strength. The phenomenon of fatigue in the transverse deck of the Trimaran float is very important due to the special structure and consequently the intensity of the stresses, and therefore the evaluation of fatigue strength in the preliminary design stage of the float is quite critical. In this paper, a Trimaran vessel is designed according to the operational needs of the Navy and is modeled in Mastro software. Using the software wave module, hydrodynamic analysis was performed at different floating speeds and different angles of the wave on the float and the pressure distribution on the hull was obtained. In the next step, this pressure distribution is applied to the floating body in Mastro finite element software and fatigue analysis is analyzed on the transverse deck using the limit analysis module. The results showed that the amount of fatigue damage at the junction of the front of the transverse deck to the main body at zero speed and chest and oblique waves of the chest has the highest amount compared to other points, which decreases with increasing speed. It was also found that the side waves have the least amount of fatigue damage compared to other angles of the wave collision.