Les cables porteurs du pont d' Aquitaine, mis en service en 1967, sont constitues de torons de type cables clos, dont les fils elementaires ne sont pas galvanises. La protection contre les infiltrations est assuree par un revetement en produit bitumineux. Malgre sa renovation en 1985, cette protection s' est averee insuffisante. En 1998, une auscultation specifique a montre que la corrosion des fils atteignait un stade critique. La demarche adoptee pour apprecier l' aptitude au service de l' ouvrage et surveiller l' evolution de la corrosion des cables porteurs est presentee. La methode utilisee pour determiner la resistance residuelle du cable et evaluer sa tension maximale en service est decrite. Les principes d' une approche probabiliste sont developpes. L' analyse des risques est detaillee, puis la metrologie mise en place pour mettre l' ouvrage sous " haute surveillance ". Enfin, les resultats de cette surveillance sont presentes et analyses. L' apparition de pathologies aussi graves sur un ouvrage relativement recent est une incitation a ameliorer encore la durabilite des ouvrages et a developper les technologies d' entretien preventif. (A). (Titre en anglais : Close monitoring and service capacity evalutaion of the Aquitaine suspension bridge). CLOSE MONITORING AND SERVICE CAPACITY EVALUATION OF THE AQUITAINE SUSPENSION BRIDGE. The suspension cables on the Aquitaine Bridge, in service since 1967, are composed of locking cable-type strands, with non-galvanized elementary wires. Protection against infiltration has been offered by means of a bituminous-component lining. Despite a renovation project completed in 1985, this protection has proven inadequate. In 1998, a special examination revealed that wire corrosion had reached a critical stage. The approach adopted for assessing service capacity of the structure and for monitoring the evolution of bearing cable corrosion will be presented herein. The method employed to determine the cable's residual strength and evaluate its maximum tension during service will also be described and the principles behind a probabilistic strategy laid out in detail. The discussion will include a risk analysis and the metrology introduced to place the structure under "close surveillance". Lastly, results from this monitoring effort will be provided and analyzed. The appearance of pathologies this serious on a relatively recent structure serves as an incentive to further improve structural durability and develop preventive maintenance technologies.
Abstract