Shear Strength of Dry Joints of Concrete Precast Segmental Bridges

The universally accepted theory to evaluate the shear strength of dry joints with shear keys considers that the shear stresses are transmitted across the joint through two qualitatively and quantitatively different mechanisms. The first mechanism represents the friction resistance that arises when two flat and compressed surfaces attempt to slide one against the other, the second mechanism considers the support effect of the castellated shear keys. Though the shear flow mechanisms across the dry joints are qualitatively well known, there is no consensus regarding its quantification. The application of the formulation proposed by the various authors leads to very different values of the ultimate shear capacity of the dry joints (with results that can vary 100%). This work presents a study of the behavior of segmental bridges, focusing on the response of dry castellated joints under shear, in service and ultimate limit states. Tests have been performed on panels with different levels of prestressing, evaluating the behavior of castellated dry joints under direct shear. The possible benefit of using steel fiber reinforced concrete (SFRC) is also evaluated, casting and testing reinforced and SFRC panels. The results obtained in these tests, as well as those found in the literature have been compared with several design formulae for assessing the load-carrying capacity of dry interlocked joints without epoxy, identifying the formulae that gives the best predictions.