Behavior of Precast Bridge Deck Joints with Small Bend Diameter U-Bars

The Interstate Highway System plays a vital role in our economic development by providing a continuous corridor for transporting goods and services. Currently, there is a need for repair and expansion of the existing highways, which include all bridges along its path. Because of the high demand for the highway system, repair and expansion must occur rapidly and efficiently. In recent years, precast bridge deck systems have become an efficient way to reduce construction time during repair.

This thesis presents the experimental research of the behavior of the U-Bar joint detail used in precast bridge deck systems. This detail consists of staggered reinforcement extending beyond the precast deck portion into the joint. Six specimens utilizing the U-Bar detail were constructed and tested. Three specimens were tested in flexure to simulate the forces applied in a longitudinal deck joint, while three specimens were tested in pure tension to simulate the forces experienced in a transverse deck joint located over an interior pier. A tight 180° bend at 3db was desired in order to minimize the thickness of the deck. To achieve this tight bend, deformed wire reinforcement was chosen for the U-Bar detail due to the favorable material properties of deformed wire reinforcement. The purpose of the testing was to determine if the joint details could generate a precast deck system that could emulate the monolithic cast-in-place deck systems already in use. For monolithic behavior in a precast deck system, the joints must be able transfer shear, tension and moments.

In this research, the joint overlap length was the most dominant variable, and should not be less than 152.4 mm (6”). The precast bridge deck joint should consist of high strength concrete with f’c of at least 68.9 MPa (10 ksi). The longitudinal reinforcement spacing should be no greater than 152.4 mm (6”).