A New Method for Predicting Site-Specific Wave-Induced Hull Girder Loads Acting on Ship-Shaped Offshore Installations in Benign Conditions

Abstract

The aim of this study is to establish an innovative method for predicting wave-induced hull girder loads acting on ship-shaped offshore installations. Unlike in trading ships, the determination of hull girder loads of ship-shaped offshore installations must consider site-specific environmental conditions. However, the accurate determination of wave-induced loads is not straightforward owing to uncertainties in the ocean environmental conditions and location-dependent complexities, among other factors. This study proposes a probabilistic approach to determine the site-specific design values of wave-induced loads acting on ship-shaped offshore installations that also accounts for the effects of mooring system type. Six target regions – the North Sea, Gulf of Mexico, western coast of Africa, the eastern coast of South America, southeastern coast of Asia and northwestern coast of Australia – were studied to compare the results corresponding to various sea states. A set of wave scenarios representing all possible wave events for each target region were selected using the Latin hypercube sampling technique. To demonstrate this method, the design values of the wave-induced vertical bending moments were determined for a very large crude oil carrier (VLCC)-class structure with a hypothetical floating, production, storage and offloading (FPSO) unit. The effects of the mooring system type (e.g., single-point mooring versus spread mooring) on the wave-induced hull girder loads of the ship-shaped offshore installations were also evaluated. The validation of the developed method was made by comparison with existing results in the literature, its novelty is associated with a new methodology that can accurately determine wave-induced hull girder loads of ship-shaped offshore installations taking into account the effects of site-specific ocean environmental conditions and mooring system type, and its main contribution to the industry is to provide core technology for the safe and economical design of ship-shaped offshore hull structures.