A type of side structure named Y-shape is introduced in this paper and is applied on a 300,000DWT FPSO to prevent oil leakage in case of collision accident. Its crashworthiness is analyzed with the nonlinear numerical simulation. The calculated results are obtained, including the structural damages, the curves of collision force against penetration, the curves of energy absorption against penetration and the curves of energy absorption proportions of the different structural components. They are compared with those of the general side structure under the same collision scenarios, to evaluate the advantage of crashworthiness of the Y-shape side structure.
The general design for the side structure of FPSO adopts the design for VLCC, which applying the horizontal flat girders between the double hulls. Because the FPSO works at the oil field through all of its service life and the crude oil is transported by the shuttle tanker, there is some possibility that the shuttle tanker strike the FPSO during the offloading operation, which will cause severe structural damage, oil leakage, loss of possessions and lives, and the environmental pollution. Therefore, the side structure of FPSO is required to have a nice crashworthiness to keep the FPSO in safe condition.
It is recognized that the side structure of FPSO must meet the mandatory requirement for VLCC, which requires that the side structure be able to bear the head-on collision by the ship with 5000DWT in 2m/s velocity. Furthermore, Chinese oil production branch made a stricter rule which requires that there be no oil leakage in case of the shuttle tanker with 50,000~60,000DWT in 1m/s velocity striking the side structure of the FPSO in a head-on direction. On purpose of improving the crashworthiness of the FPSO and the shuttle tanker, many new types of side structure designs have been invented.