Effect on Risk Based Inspection of spatio-temporal dependence of ROC curves: Study of the corrosion of steel harbour structures
Owners of civil infrastructures base their maintenance decisions schemes mainly both on structural integrity assessment and consequence analysis. Some inputs come from information collected by non-destructive or destructive tools. Uncertainties and noise of measurements can lead to bad decisions but are rarely integrated into the process of decision. Nowadays, Risk Based Inspection (RBI) provides the basic concepts for optimizing the maintenance plans of existing structures while insuring a good safety and availability conditions during service life of structures. In this paper, concepts are applied on a steel sheet pile seawall submitted to uniform corrosion where spatio-temporal dependence of performance of ROC (Receiver Operating Characteristic) curves is studied. Résumé Les gestionnaires d’infrastructures de génie civil basent leurs schémas décisionnels de maintenance essentiellement à partir de l’évaluation de l’intégrité structurale des ouvrages et de l’analyse des conséquences en cas de défaillance. Certaines données d’entrée proviennent de contrôles destructifs ou non destructifs. Les incertitudes et le bruit sur les mesures peuvent conduire à de mauvaises décisions mais sont rarement pris en compte dans les processus de décision. Actuellement, les méthodes RBI (Risk Based Inspection) donnent les fondamentaux pour aboutir à des plans de maintenance optimisés tout en garantissant la sécurité et la disponibilité des ouvrages en service. Dans cet article, ces concepts sont appliqués à un quai constitué par un rideau de palplanches soumis à la corrosion uniforme et la dépendance spatio-temporelle de la performance des courbes ROC (Caractéristique Opérationnelle du Récepteur) est étudiée.
A unifying review of NDE models towards optimal decision support
Non-destructive evaluation (NDE) inspections are an integral part of asset integrity management. The relationship between the condition of interest and the quantity measured by NDE is described with probabilistic models such as PoD or ROC curves. These models are used to assess the quality of the information provided by NDE systems, which is affected by factors such as the experience of the inspector, environmental conditions, ease of access, and the precision of the measurement device. In this paper, we review existing probabilistic models of NDE and show how they are connected within a unifying framework. This framework provides insights into how these models should be learned, calibrated, and applied. We investigate and highlight how the choice of the model can affect the maintenance decisions taken on the basis of NDE results. In addition, we analyze the impact of experimental design on the performance of a given NDE system in a decision-making context.
AXIOMATISABILITY OF WEAKLY FLAT, FLAT, AND PROJECTIVE S-ACTS
ABSTRACT This paper gives necessary and sufficient conditions on a monoid S that the class of flat left S-acts be (first order) axiomatisable. It presents also a streamlined version of the result of Stepanova that the class of projective left S-acts is axiomatisable if and only if the strongly flat left S-acts are axiomatisable and S is left perfect.