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Inspection and maintenance of concrete bridges is a major cost factor in transportation infrastructure IntroductionDeterioration processes can reduce the reliability and the safety of engineering structures. Knowledge of the actual condition of the structure is therefore essential in order to comply with element and system target reliabilities (see [1][2][3]). Inspections and structural health monitoring are effective means of acquiring information on the actual condition of an ageing structure and should be utilized to reduce the uncertainty in engineering models and, ultimately, to optimize the management of deteriorating structures. This task is ideally carried out through a Bayesian analysis approach [4][5][6][7][8].As most deterioration processes are spatially distributed in structures and the deterioration progress at different locations in a structure is correlated, such an analysis should be performed considering the structure as a whole (e.g. [9][10][11][12]). However, the integral assessment of spatially distributed deterioration is computationally demanding, and novel computational strategies are required for probabilistic assessment and Bayesian updating of spatial deterioration [13,14]. Ultimately, the modelling approach and the computational methods should lead to software that can be used by engineers who are not experts in reliability analyses. Only in this way can Bayesian methods enhance the integrity management of ageing structures in practice.This paper describes an approach in which the uncertain system deterioration state of an ageing concrete structure is described by a Dynamic Bayesian Network (DBN) model of the underlying stochastic deterioration processes. This approach was motivated by the work of Straub [15] and Qin and Faber [16]. DBN models provide a computational framework that enables the evaluation of the joint distribution function of the system deterioration state based on the prior stochastic model and, in particular, Bayesian updating of the joint distribution function of the system deterioration state with observations of the underlying deterioration process, i.e. inspection and monitoring results.To prove the concept, the approach is implemented in a software prototype employing a DBN model of chloride-induced reinforcement corrosion, which can approximate the spatial correlation of the corrosion process. The prototype is applied to assess and update the deterioration state and structural reliability of a single-cell prestressed concrete box girder. This construction type is typical of long, multi-span highway bridges in Germany. However, the general solution strategy applies to all common concrete bridge structures.Section 2 gives an overview of the underlying system model. The deterioration model and the structural capacity model are described in more detail in sections 3 and 4. The implementation of the prototype is briefly described in section 5. A case study applying the prototype is summarized in section 6. System modelTo model the deterioration state, the box girder i...
Predictive information and maintenance optimization for deteriorating structures is concerned with scheduling (a) the collection of information by inspection and monitoring and (b) maintenance actions such as repair, replacement, and retrofitting based on updated predictions of the future condition of the structural system. In this article, we consider the problem of jointly identifying—at the beginning of the service life—the optimal inspection time and repair strategy for a generic welded joint in a generic offshore wind turbine structure subject to fatigue. The optimization is performed based on different types of decision analyses including value of information analyses to quantify the expected service life cost encompassing inspection, repair, and fatigue damage for all relevant combinations of inspection time, repair method, and repair time. Based on the analysis of the expected service life cost, the optimal inspection time, repair method, and repair time are identified. Possible repair methods for a welded joint in an offshore environment include welding and grinding, for which detailed models are formulated and utilized to update the joint’s fatigue performance. The decision analyses reveal that an inspection should be scheduled approximately at mid-service life of the welded joint. A repair should be performed in the same year after an indication and measurement of a fatigue crack given an optimal inspection scheduling. This article concludes with a discussion on the results obtained from the decision and value of information analyses.
Prepared f o r submissi.on t o IAEA panel on Accuracy o f Nuclear Materials Accountancy and Tec'hni cal Effectiveness o f Safeguards a t. Vienna, Austria, August 28-Septrin~ber 1 , 1972.. .
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