Shear Strength of Dry Joints in Precast UHPC Segmental Bridges: Experimental and Theoretical Research

摘要

Precast segmental bridges made of ultrahigh-performance concrete (UHPC) have gained wide research attention and application. The shear transfer of dry joints between UHPC segments is one of the major concerns due to the discontinuity and interruption of the reinforced bars. In this study, direct shear tests of UHPC joints were conducted. Parameters included confining stress, concrete type, joint type, joint shape and number of keys, and arrangement of steel reinforcement. Crack-formation sequences, cracking patterns, ultimate shear load, and vertical slippage were obtained, and typical normalized shear stress-relative displacement curves were calculated. The results show that a higher shear strength of UHPC joints can be achieved with higher confining stress, higher matrix tensile strength, and the addition of steel fibers. Concrete joints with fibers exhibited a limited area of concrete crushing compared with joints without fibers. Large-keyed joints showed a minor increase in shear capacity (9.7%) compared with three-keyed joints. A calculation method for the shear strength of concrete dry joints based on Mohr's circle was established, and a simplified formula for calculating the shear strength of UHPC dry joints with different compressive strengths was developed. The results of the proposed calculation method were found to agree well with the experimental values. The average ratio of the calculated results to the experimental results was found to be 1.01, with a standard deviation of 0.14. The simplified formula for UHPC joints was also found to have better agreement with the shear test results, with an average ratio of 0.96 and a standard deviation of 0.24, compared with 1.41 and 0.38, respectively, in the AASHTO provisions.