Investigation and analysis of response behavior for a Tension Leg Platform under impulse and limit Loads (To investigate the phenomenon of tendon disconnection)

Given the increasing development of exploitation of deepwater oil and gas resources, access to realistic solutions for analyzing and designing offshore platforms is a significant factor in facilitating the exploitation of oil and gas resources in these areas. There are many oil reservoirs in deep water beds, and a Tension leg platform (TLP), as a compliant structure, is suitable for oil extraction in deep water. The advantage of using these platforms is their low amplitude rotational DOFs. Surge motion The TLP is a 120-second long period; In high-amplitude and low period waves, the platform faces a tendon rupture due to high waves forces and bad weather conditions. These conditions are heavier and more prevalent in the harsh seas, such as the Gulf of Mexico and the North Sea. In principle, the momentary instability of the structure and the sudden moments caused during the tendon rupture are essential for analysis because the lack of examination of these cases due to the long duration of the wave power leads to unsustainability and inefficiency of the platform in inappropriate marine conditions. This thesis first explores the irregular waves of the sea and provides a suitable method for modelling the artificial time history of the sea elevations. Then, the formulation for modelling this random process is driven; moreover, a scientific and computational procedure for modelling the equivalent impact load to floater has been examined. In the end, the behaviour of a seastar TLP platform under these impact loads and the probability of tandem failure resulting from the sudden surges or pitch movements caused by these shock loads is studied. The entire process is developed coherently. Finally, these equivalent impulses have been compared numerically, and the most suitable impulse for use in this method is specified