Risk Analysis of Structures in Presence of Stochastic Fields of Deterioration: Flowchart for Coupling Inspection Results and Structural Reliability

F Schoefs

doi:10.1080/13287982.2009.11465011

Abstract

Inspection by non-destructive testing techniques of existing structures is not perfect and it has become a common practice to model their reliability in terms of receiver operating characteristic (ROC) curves. This paper suggests a method of building ROC curves in case of random fields of defects on a structure by using polynomial chaos decomposition. Knowledge of spatial distribution of defects allows a reliability analysis to be performed. When selecting stochastic finite element analysis to solve this problem, the format is the same as the one chosen for modelling inspections results. The paper shows how to link these quantities (ie. reliability and inspection results) in a risk analysis by using polynomial chaos decomposition as a common language.

Highlights

Reassessment of existing structures generates a need for up-dated materials properties
Non-destructive testing (NDT) tools are required for the inspection of coastal and marine structures where marine growth acts as a mask
Inspection of existing structures by a non-destructive testing (NDT) tool is not perfect and it has become a common practice to model its reliability in terms of probability of detection (PoD), probability of false alarms (PFA) and receiver operating characteristic (ROC) curves

Summary

INTRODUCTION

Reassessment of existing structures generates a need for up-dated materials properties. Inspection of existing structures by a NDT tool is not perfect and it has become a common practice to model its reliability in terms of probability of detection (PoD), probability of false alarms (PFA) and receiver operating characteristic (ROC) curves. These quantities are generally the main inputs needed by owners of structures in view to achieve Inspection, maintenance and repair plans (IMR) (Sheils et al, 2008). From the decision theory and a Bayesian description of inspection results, it is shown in section 4 how to introduce new events for risk-based inspection (RBI) Expressions of their likelihood as functions of PoD, PFA and γ, the probability of defect presence are presented. This section ends with a complete application of risk analysis of a corroded sheet-pile in steel

Hazards and uncertainties when assessing defect sizes on structures

Modelling capability of NDT tools in a probabilistic context

Definitions of PoD and PFA for stochastic deterioration model

MODELLING RANDOM FIELDS OF DEFECTS FROM NDT MEASUREMENTS

RISK-BASED DECISION AID-TOOLS BASED ON INSPECTION RESULTS

CONCLUSION