Shear Behavior of Dry Joints with Castellated Keys in Precast Concrete Segmental Bridges

Precast concrete segmental bridges with dry joints have the advantages of rapid construction speed and low cost. The shear strength and shear behavior of dry joints with castellated keys in precast concrete segmental bridges are still debatable. In this paper, full-scale dry joints with castellated keys were tested under different confining stress levels. The main parameters for tests were the number of keys, the confining stress, the depth in key geometry, and the distance between two keys. For comparison purposes, flat joints, monolithic joints, and joints with steel fibers were also tested. The shear behavior, shear capacity, and crack pattern of the joints were investigated as well. Two crack modes for the single-keyed joints are explicitly proposed. The phenomenon of sequential failure of multikeyed dry joints from the inferior key to the superior one was observed in the tests and verified by finite-element simulation. The experimental results obtained in these tests were compared with the design provisions. A shear failure mechanism of sequential failure for multikeyed dry joints is presented to explain the differences between the test results and the formula used. Based on the new explanation and test results, a reduced coefficient of 0.7 is recommended for the shear strength of three-keyed dry joints. Pending more test data, this conclusion could be extended to the shear strength of multikeyed dry joints to improve the formula.