Evaluating existing post-tensioned concrete bridges equipped with prestressing steel susceptible to stress corrosion cracking

Due to extending lifetime of infrastructure in general and post-tensioned concrete bridges in particular the importance of durability aspects increases. Therefore investigations of existing structures and numerical calculations are necessary to recognize and prevent the possible failure of the structures in time and to minimize risk for the owner during remaining lifetime.

Especially older prestressed bridges built in the 1960s and 1970s in Germany are subject of these investigations. Some of these post-tensioned concrete bridges used tension wires with high susceptibility to stress corrosion cracking as we know nowadays. Due to this high corrosion susceptibility these structures are characterized by a fracture behavior determined by sudden collapse instead of a favoured preannouncement of failure. To use these bridges in the future with minimized risk of a sudden collapse special evaluation is necessary.

This paper deals with recalculation and evaluating methods for post-tensioned concrete bridges including reliability analysis for endangered bridges. The currently recommended approach for assessment and evaluation of these specially endangered bridges in Germany is illustrated and the essential parameters are presented. The procedure is shown exemplarily at an existing multi girder bridge. To compare the results of the assessment with the recommended approach and to show the influence of the basic variables e. g. material properties, cross section of the tendons, additionally reliability analysis has been carried out. Finally the results are presented and the contribution closes with a conclusion including recommendations concerning the future handling of post-tensioned concrete bridges with prestressing steel endangered to stress corrosion cracking.