Structural integrity assessment of offshore tubular joints based on reliability analysis

The paper presents a reliability-based approach and the investigations conducted based on it to assess the structural integrity of offshore tubular joints. The reliability analysis is carried out using Monte Carlo simulation technique and first order reliability method (FORM). The crack in addition to the geometry, material, and loading of the tubular joint are modeled as random variables to compute the reliability of the joint. Linear elastic fracture mechanics principles are employed to evaluate the crack growth. Degradation in the reliability of the tubular member due to crack propagation is estimated. Structural integrity assessment is carried out for joints having two adjacent discrete cracks to study the influence of the relative sizes of cracks on the reliability of the member. The significance of randomness in the variables modeled and the sensitivity of the reliability index on those variables are studied using example problems. The application of the results of the present study to schedule inspections with optimal time interval is highlighted. Finally, a method based on Bayesian approach is applied to update the reliability of the member based on the outcome of in-service inspections. The paper contributes to the knowledge of the application of reliabilitybased techniques for integrity assessment of offshore tubular joints.