Basics of Structural Reliability

This chapter discusses structural reliability methods for the design of marine structures with emphasis on their practical application—for example, in ship structures. Focus is given to basic concepts, methodologies, and applications. Examples are given to demonstrate the application of the methodology. This chapter discusses simple analytical equations that are based on lognormal assumptions. The papers on numerical approaches are also mentioned briefly. This chapter explains the following subjects in detail: reliability of marine structures, reliability-based design and code calibration, fatigue reliability, probability, and risk-based inspection planning, etc. In general, a marine structural analysis deals with the load effects and the structural strength. Uncertainty analysis is the key in any reliability evaluation, such as reliability-based design and requalification for marine structures, which is explained in this chapter. Certain concepts are introduced in this chapter for the reliability evaluation at a component level, which means that the concern is on the failure probability of problems modeled by a single limit-state function. The system reliability analysis section deals with the formulation and evaluation of failure probability in problems where more than one limit-state function must be considered (i.e., system reliability analysis). Reliability methodology can be used as a tool to reassess structural integrity. Target probabilities are chosen to minimize total expected costs over the service life of the structure. A cost–benefit analysis approach may be used effectively to define target probability for design in which failures result in only economic losses and consequences.