EvaDéOS

The purpose of this industrial research project is to propose a global methodology for following the status of reinforced concrete structures, which includes the following phases: condition assessment, diagnosis and prognosis of degradations, and decision-making. The linking between the phases, which is also an objective of the project, is expected to be achieved by bringing together the partners specializing in each phase and harmonizing their actions with respect to the goals and needs of the owners/managers. The approach as a whole, comprising evaluation, prediction, and optimization of inspection and maintenance strategy, is based upon probabilistic methods associated with Non Destructive Testing. The partnership gathers together most of those having an interest in the follow-up process, from the owners/managers or their representatives to the specialists of NDT and experts in decision-making. The target structures comprise road bridges (although the methodology can be extended to other types of transport), electricity supply infrastructures and residential buildings. In order to set reasonable bounds on the project, only the corrosion of reinforcement will be considered, which remains a major concern for the deterioration of reinforced concrete structures. Unlike other projects that have focused on this degradation, EvaDéOS is turned towards a preventive approach, intervening when the degradation is not yet revealed but the necessary conditions are present for its more or less short-term onset. This preventive approach is an original asset of the project. Assessing the condition of structures where damage is not yet visible implies using and possibly improving NDT methods. An attractive challenge for strengthening their potential is to prove the value of their contribution in the framework of the project, where the probabilistic prediction approach requires the spatial and time variability of numerous data to be provided. The selection and development, if appropriate, of degradation models suited to a probabilistic context is another main objective of the project. Firstly, attention will be paid to models predicting the ingress of aggressive agents leading to the depassivation of reinforcement and thus to the initiation of corrosion. Secondly, models predicting the propagation of corrosion and the expansion of corrosion products will be considered. Sophisticated models, based upon the Finite Element Method, but also simpler end-user models employed in daily engineering practice will be under consideration and their combined use will also be looked into. The aim is that the outputs of the predicting models will be incorporated into degradation indices, previously defined with respect to the needs and practices of owners/managers, and thereafter utilized in the decision-making process. A methodology will be proposed on the basis of decision criteria chosen upstream by the owners/managers, so as to optimize the dates of inspection and maintenance operations, taking into consideration the probabilistic prevision of degradations, the costs involved and the updating of the observation data.