As the offshore wind industry matures and projects begin to expand to deeper water regions, various floating systems are being considered to support wind turbines. This paper explores the feasibility of a Tension Leg Platform (TLP) support system anchored with synthetic rope tendons attached to a gravity base template to provide a platform for a wide range of water depths with acceptable operating nacelle accelerations. In this paper, the NREL 5MW wind turbine is selected in order to provide a comparison to previous studies of steel tendon TLPs. A fully-coupled numerical modeling tool is used to assess the effects of extreme irregular sea loads on the TLP. A series of numerical simulations are carried out to compare the response of a Single Column (SC) TLP for three different water depths and three different environments. The responses are compared with the steel tendon model. The use of synthetic rope tendons potentially offers more efficient installation options and enlarges the range of acceptable water depths. The use of a gravity base/suction pile foundation may improve the installation cost and schedule. The fully coupled nonlinear, time domain analysis tool used provides a unique look into the fully operating wind turbine under stable motion characteristics of the TLP.

Offshore platforms, fixed or floaters, are a well-established design concept for oil explorations. It is fundamental to design these structures such that they can resist moderate to severe earthquakes without causing any severe damage to the occupants and to maintain the integrity of the structure. Hence, it is important to examine the behavior of these offshore structures for all kinds of earthquake scenarios to determine the risk levels that may occur in the structure. This paper intents to compare the seismic responses for a fixed offshore structure by employing ground motion records generated using three different methods. The design spectrum determines the seismic hazard of a region. Therefore, it is necessary to use acceleration records compatible with the design spectrum in seismic analyses. In this paper, Scaling, Spectral matching and Stochastic methods were used for comparison. Peerscaled tool was used for scaling in the time domain. RspMatch was used for the Spectral Matching. New acceleration records were generated by QuakeSim. A series of non-linear time histories using acceleration records of scaled ground motions were carried out to compare the damage levels and responses of a fixed offshore structure. Spectral matching method was observed to cause higher displacements than scaling method. The occurrence of inelastic events, such as buckling was observed to be high when the acceleration records considered the near-fault effect. And, permanent deformation was observed when acceleration records considered the fling effect. Ground motion records generated by different methods if adopted while performing seismic assessments of offshore structures will reduce the risk level for the structure.