COUPLING JOINTS OF PRESTRESSING TENDONS IN CONTINUOUS POST-TENSIONED CONCRETE BRIDGES.

Large cracks and ruptured tendons encountered in the coupling joint vicinity of post-tensioned, continuous concrete bridge structures in the Federal Republic of Germany have, in recent years, led to an intensified bridge inspection program and extensive investigations. The results of the inspection program and the investigations into the probable causes for the encountered cracks are summarized and discussed in this paper to provide a basic understanding of the complex behavior of these coupling joints. Low fatigue stress limits for tendon coupler assemblies and stress crack corrosion are shown to be the main reasons why cracks in the coupling joint vicinity are so detrimental to the structural integrity. To avoid these cracks in the seemingly insensitive vicinity of the point of inflection for sustained loads, special design considerations have to be made in determining possible moment variations at that point.