Reliability-Based Methodology for Life Prediction of Ship Structures

Recent advances in structural analysis technology such as the finite element method, improvements in the ability to model realistic sea loads, development of fatigue and fracture mechanics methods, development of reliability analysis methods, and the rapid advancements in computing technology, make it possible to develop methods to evaluate the structural strength of a ship, considering the requirements of its mission. In assessing the life expectancy of a ship structure, one must consider the through life degradation of the structural system and its potential failure modes. This paper describes the fundaments of a reliability-based method for life expectancy analysis of ship structures, considering first-passage failure modes and fatigue failure mode, in an intact or degraded condition. As for fatigue analysis, a method based on probabilistic linear fracture mechanics and capable of modeling the effects of the weld induced residual stress is presented. The paper includes a detailed example of fatigue analysis of a typical ship structural joint using the probabilistic fracture mechanics method. The effect of the residual stresses and corrosion on the joint reliability is evaluated through a parametric study. 1 Professor and Director, Center for Technology and Systems Management, Department of Civil and Environmental Engineering, University of Maryland, College Park, Maryland. 2 Assistant Professor, Department of Mechatronics and Mechanical Systems, University of São Paulo, Brazil. Presently a visiting scholar in the Center for Technology and Systems Management, Department of Civil and Environmental Engineering, University of Maryland, College Park, Maryland.