Reliability Analysis of Double Pendulum ALP

An articulated tower is one of the compliant offshore structures connected to the sea-bed through a universal joint. This joint is subjected to reversal of shear stresses under random loading, which makes it vulnerable to fatigue damage. This paper describes a methodology for computation of reliability of universal joint of articulated offshore platform. The dynamic analysis of the tower has been carried out for eleven simulated sea state under wave alone and in combination with wind and wave. The response time histories so obtained are employed for reliability analysis of the joint. Fatigue criteria have been formulated using S-N curve and fracture mechanics approach. The crack in addition to the geometry, material, and loading of the joint are modeled as random variables to compute the reliability. The reliability analysis is carried out using Advanced First Order Reliability Method (FORM) and Monte Carlo Simulation technique. Important parametric studies have been carried out to obtain insight into the effect of important variables on the fatigue reliability. The effects of uncertainties in various random variables on articulated joint reliability are highlighted.