Stresses, deformations and damages of various joints in precast concrete segmental box girder bridges subjected to direct shear loading

Precast segmental concrete bridges involve multiple concrete segments joined together by posttensioning, and have the advantages of rapid construction, low-cost, and excellent quality control. Joints that represent locations of discontinuity are prominent factors affecting overall structural behavior of segmental bridges. In this study, a comprehensive analysis is performed for thirteen tested specimens with different joint types, subjected to direct shear loading, to assess the shear behavior of joints in precast box girder segmental bridges. The analysis focused on understanding the role of prestressing force, concrete compressive strength, presence of epoxy, and number of shear keys on: the stress and strain level in reinforcing bars, prestressing strands, displacements, type, time and mechanisms of sequential cracking and of damage level in the joints. The results showed that increasing of the confining pressure to 4.5 MPa and/or number of shear keys from 6 to 10, can highly improve both of the elastic stiffness and the plastic ductility of the segmental bridges, and changes the brittle behavior of the epoxied joints to a gradual strength degradation mode; the relative displacement of the dry joints is double of that in their identical epoxied joint; and the strains in the top layer reinforcement of the top slabs for keyed joints are ten times higher than that in the flat joint specimens.