W Amin

Wetdeck slamming loads on a developed catamaran hullform – experimental investigation

ABSTRACT Catamaran wetdeck slamming has been experimentally investigated using a servo hydraulic slam testing system. A series of controlled-speed water impacts was undertaken on a rigid catamaran bow section with two interchangeable centrebows. Entry into the body of water was at two fixed trim angles: 0° and 5°. The vertical velocity was varied from 3 to 5 m/s in 0.5 m/s increments. This study presents a new dataset of pressure distributions and slam forces on the arched wetdeck structure of catamaran vessels. The relationships between the peak force magnitudes, relative impact angle and vertical velocity are observed, with a small reduction in slam force for an amended centrebow. Limited pressure measurements along the archway were not found to be representative of wetdeck slamming loads.

Wave-in-deck forces on fixed horizontal decks of offshore platforms

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Experimental investigation of extreme wave impacts on a rigid TLP model in cyclonic conditions

This paper describes a series of model tests of a rigidly mounted tension leg platform (TLP) subjected to extreme wave events corresponding to long-crested irregular wave trains of a 10,000-year cyclonic sea state. The experimental setup was instrumented to simultaneously measure wave surface elevations in the vicinity of the model, global wave impact forces and local pressure distribution on the underside of the models topside deck. Model accelerations were also monitored for each wave impact event so that the inertial force due to structural dynamic response could be identified. The deck–column intersection areas were found to experience large wave-in-deck slamming pressures, in particular around the aft columns. A reduction of the deck clearance was found to increase the magnitude of the global horizontal forces; however, the global vertical forces and local wave-in-deck slamming pressures did not follow this trend.

Measurements of global and local effects of wave impact on a fixed platform deck

This article describes a series of model tests conducted to examine extreme wave events associated with tropical cyclonic conditions and their impacts on an offshore deck structure. Extreme waves of a representative cyclonic sea state were examined in a towing tank within long-crested irregular wave trains. Experimental results presented include global forces and localised slamming pressures acting on a rigidly mounted box-shaped deck, which represents a simplified topside structure of a tension leg platform. The effect of static set-down on the still-water air gap was investigated by applying an equivalent reduction for the deck clearance. It was found that a small reduction of 20 mm (2.5 m full scale) in the original deck clearance can lead to a doubling of the magnitude of the horizontal force and the vertical upward-directed force components, as well as significantly increased slamming pressures in many locations on the deck underside.