Time-dependent nonlinear fatigue analyses of the TLP in the Arabian sea environment

Abstract The tension leg platform (TLP) is a new concept in the design of platforms. It combines the facilities of both floating, drilling, and production platforms. The deck is secured by vertical tension legs attached to pile foundation templates on the sea bed. An attempt has been made in this paper to calculate the short and long term statistics of the stress response to the natural short and long crested sea and the resulting fatigue damage for certain critical members of a proposed TLP. A probabilistic approach is adopted utilising a spectral method for calculating the number of wave induced cycles at different stress levels. The nonlinear finite square stress element method is used to determine root mean square deflections and root mean fracture in randomly excited TLPs. Program RANDOM is developed to solve various theoretical equations and to evaluate the fatigue life. The basic input to the program consists of material properties, SN—curve and environmental data.