Tubular joints reliability and fracture analyses for development of underwater inspection of offshore steel structures

Tubular joints of offshore structure are subject to cyclic loading of wave during the service life of the platform. This normally lead to fatigue failure, crack growth and fracture of the joints. All these failures will lead to reduction of platform reliability for safe operations. Operating oil company spent millions of dollar to carry out underwater inspection of tubular joints of offshore structures. Inspections are normally carried out in a fixed interval time period (i.e. 4, 5 years and etc.) determined by either company standard practice or international codes. The interval period may be increased or reduced if proper analyses of the joints reliability can be systematically established. This paper outlines the analytical basis and the calculation method used in the derivation of reliability indices, fracture assessment and the development of an outline inspection schedule for critical joints of offshore platform.