Utility and Information Analysis for Optimum Inspection of Fatigue-Sensitive Structures

Abstract

Fatigue cracking is considered the most prevalent damage for welded steel structures like bridges and ships. Inspections are normally planned in the service life to assess fatigue damages in order to ensure structural safety and serviceability. Whether or not cracks are found, the inspection results provide value for fatigue damage assessment and risk mitigation. This paper aims to emphasize the value of inspection based on the information gained for fatigue crack prognosis. The probabilistic inspection results are used to update the prior distribution to a posterior distribution of fatigue damage. The change from prior to posterior distribution is quantified as the information gained from inspection. The time-variant inspection information metrics are further analyzed with utility theory to consider the attitude and preference of the decision maker toward the inspection outcome at a certain point in time. This paper presents an integrated decision-making framework for inspection planning, addressing the information perspective of inspection choice and schedule. The recommended optimum inspection plan is expected to provide the highest utility to the decision maker in the life-cycle management of aging structures. The proposed framework is applied to a fatigue-critical detail of a ship structure.