Reliability based fatigue design of maintained welded joints in the side shell of tankers

The present work deals with the application of reliability based techniques to the design welded joints subjected to the process of crack growth and repair. A formulation is presented for the assessment of the fatigue damage and of the reliability of the side shell of a ship hull structure. The potential cracks are considered to occur in the side shell, in the connections between longitudinal stiffeners and transverse web frames. The model accounts for the crack growth process applying linear elastic fracture mechanics. The long-term stress range acting on the elements is defined as a function of the local transverse pressure of internal cargo and outside water, combined with the stresses resulting from the longitudinal bending of the hull namely the a combination of horizontal and vertical bending moments. The fatigue reliability is predicted by a time variant formulation and the effects of maintenance actions in the reliability assessment are shown.