Probabilistic Combination of Forces in Tension Leg Platform Tethers

Abstract

Tension leg platforms (TLPs) are a class of compliant offshore structures that respond dynamically to ocean winds, waves, and currents. A TLP is tied to the ocean floor by tethers that, due to hull buoyancy, are in tension in the absence of environmental loads. Motions of a TLP lead to additional dynamic forces in the tethers. Also, depending on the deck height, there is a small likelihood of waves impacting the TLP deck. Wave impact induces tether forces that increase rapidly as a function of wave‐immersion distance into the deck. In this study, an extension of the point‐crossing method was used to predict the probability of waves impacting the deck of a TLP. This method was also used to predict the combination of dynamic forces (including wave‐impact loads) acting on a TLP tether. The results are used to calculate the reliability of a TLP tether under maximum tension loads.