Shear strength of joints in precast concrete segmental bridges

Post-tensioned girder bridges composed with precast concrete segmental boxes have become quite popular in the last a few decades. Performance of these girder bridges depends greatly upon the joints. Those joints between segments in such a bridge represent locations of discontinuity through which compression and shear force are transmitted, though they are always unreinforced, and prone to damage during construction. However, there is a lack of experimental data to estimate the shear strength of these joints. In this study, serials of joints with the geometry close to an actual one, flat or keyed, dry or epoxied, single-keyed or multiple-keyed, have been tested using a direct shear experimental set-up. Shear behavior and strength of the joints are investigated. Parameters affecting behavior of the joints, including prestressing level, epoxy thickness and shape of keys, have been analyzed. It was found that strength of epoxied joints is consistently higher than that of dry ones. A special failure mode, so called 'shear-off' failure, of keyed joints, always controls the ultimate shear capacity of the joints. Empirical formulas are proposed to assess the shear strength of different kinds of joints, which are also compared with the widely used AASHTO provisions