Prediction of Fatigue Life on Double Hull Oil Tanker with Single and Double Longitudinal Bulkheads

A tanker is a specific ship where the payload could be oil, chemical, gas, and other cargo that can cause fire and explosion. These payloads are very dangerous not only for the ship but also the environmental condition. Besides, the external and internal loads act randomly and cyclic to hull's ship during the voyage and influence the ship's structural behavior. Also, during the operation period, it is essential to analyze the fatigue life due to the internal and external loads acting on the ship's hull. To resist the internal and external loads, the hull construction must be durable. One of the essential construction elements which support the longitudinal strength of the ship is a longitudinal bulkhead, particularly for a double hull tanker. Also, the longitudinal bulkhead in the cargo tank contributes to the fatigue life of the ship. Therefore, the present study focuses on the influence of the longitudinal bulkhead to fatigue life on a double hull tanker. For the analysis method, the spectral fatigue analysis and JONSWAP wave spectral are used. The result calculation of JONSWAP spectral, then continue for Response Amplitude Operator (RAO) and spectral response stress calculations to obtain the zero and second moment by using Simpson's rule. From this, the stress cycles can be obtained. The Palmgren-Miner method is adopted to determine the failure cycle based on the S-N curve. On the S-N curve, a the-X parameter is used as the main parameter. It is obtained that the fatigue life for single bulkhead is 24 years, and for double bulkhead is 29 years.