Structural reliability assessment of aging ships using the concept of level of confidence

Abstract

It has been recognized that simple estimation tools adequate for initial ship design may no longer be suitable for the assessment of remaining life. This is because uncertainties in structural capacity and demand change over time. Therefore, the concept of level of confidence is proposed to quantify these changes.The advantage of this concept is it requires no knowledge of the analytical equation of the probability density function of its input parameters. It is fast and simple to use, dispensing away with sophisticated and time-consuming numerical simulations.One important area of application of the proposed procedure is in assessing the reliability of old vessels by incorporating the concept into finite element analysis. This provides a confidence level for strength calculations at every vessel age, hence giving designers and owners a more qualitative indication of the reliability of ships near or even beyond their intended design life.