Structural behaviour of a lightweight craft

The main purpose of this paper is to present both the global and local structural response of a fast craft, when subjected to the effect of slamming and flooding of watertight adjacent compartments. The studies were accomplished using the Finite Element Method (FEM) applied to the vessel model, giving special attention to the bow and stern of the craft when submitted to slamming effects and jet thrust loads, respectively. The modes and frequencies of vibration were determined to check for structural resonance problems due to slamming induced loads, considering the sea conditions where the craft operates. The forced frequency response of a specific region on the bow was also determined when subjected to slamming loads applied in a frequency range from 25 to 80 Hz. The results revealed that the maximum stress induced in the structure was lower than the yield strength of the materials used in the production of the craft, the aluminium alloys 5083-H111 e 6082- T6. Hypothetical flooding of watertight compartments was also simulated in the ship’s section comprehended between bulkheads no. 17 and 20 and in the engine and waterjet’s compartments, separately.