Structural Design of Helicopter Landing Platform on Offshore Ship

Abstract

There has been an increased of activities in exploration of oil and gas in offshore. Helicopters are used as a primary mean of personal transportation to offshore installations. Helicopter operations in offshore installations and vessels are risky and critical. Due to adverse weather conditions and space limitation, the design of the helicopter landing structures has to be considered carefully. A design using rule-based approach is presented in this thesis. It is to be installed on offshore construction and drilling vessel of LOA 115.4 metre. Based on mission objectives of the vessel, the design is developed from the initial phase. Analysis of various loads and load combinations is made according to DNV offshore standard, OS-E-401. Sikorsky S-92 is used as the largest helicopter to land on the structure. 16 different landing positions are considered. 30 load combinations for stowage condition due to ship motions are modelled to ensure the adequacy of strength. Aluminium alloy and high strength steel are used to save weight. Common structural arrangement and connections are applied and allowable stress level is checked according to Class requirements. The design is found to be less efficient compared to relevant designs from industry. The deficiency comes from the fact of using common structural arrangement as in steel constructions. Recommendations to improve the design features are presented finally.