Pathology, appraisal, repair and management of old prestressed concrete beam and slab bridges

The beam and slab bridges named in France VIPP are viaducts with multiple single spans made of prestressed concrete beams that are precast on site and post-tensioned, and then assembled transversely by prestress. A great number of those bridges were built in France at the beginning of the development of the prestressing technique. Some of them present strong losses of prestress related to the corrosion or the rupture of tendons. After a presentation of the pathology and its various causes, the paper presents the difficulties of the appraisal and the methodology that has been developed to assess their residual load-carrying capacity. The appraisal method is based on several levels of investigations and re-calculations. Then the paper addresses the problem encountered with the management of such structures by emphasising the interest of the risk analysis for helping owners to optimise the management of such bridges, with respect to safety. Finally, different solutions of repair that have been used with success to maintain or to strengthen the capacity of these structures are reviewed.