Among the compliant platforms, Tension Leg Platform (TLP) is a vertically moored structure with excess buoyancy. TLP is designed to behave in the same way as any other moored structure in horizontal plane, at the same time inheriting the stiffness of fixed platform in the vertical plane. Dynamic response analysis of TLP to deterministic first order wave forces and low frequency wind forces is presented, considering coupling between the degrees-of-freedom surge, sway, heave, roll, pitch and yaw. The analysis considers nonlinearities produced due to changes in cable tension, nonlinear hydrodynamic drag forces and variable submergence. The sea state is characterised by Pierson-Moskowitz spectrum. The wave forces on the elements of the pontoon structure are calculated using Airy's wave theory modified by Chakrabarti (1971) and Morison's equation ignoring diffraction effects. The nonlinear equation of motion is solved in the time domain by Newmark's beta integration scheme. The influence of different parameters on the response of TLP is investigated. High frequency effects such as springing and ringing have not been considered. The fluctuating wind has been estimated using Emil Simiu's wind velocity spectrum for offshore structures.
Tension Leg Platform (TLP) is a kind of compliant type offshore platform which is generally used for deep water oil exploration. As reflected by its name, it is a buoyant structure anchored by pretensioned cables to the sea bed. They are designed to be more responsive to external loading then the fixed type offshore platforms. The cabling system of the platform may be vertical or splayed which restrains vertical movements, but permits some horizontal displacement. The terminal of such a platform remains virtually horizontal (Fig. 1). The tension cabling system consists of four or more tension legs, each leg being comprised of multiple parallel tension members terminated at the base of the structure.
