Direct Shear Strength of UHPC Large-Keyed Epoxy Joint: Theoretical Model and Experimental Verification

Abstract

With the development trend of accelerated bridge construction, the precast ultra-high-performance concrete (UHPC) segmental bridge might be increasingly used due to the advantages of lightweight superstructure and advanced structural performance. However, there is still lack of study on the UHPC keyed epoxy joint, especially in terms of theoretical aspects. In this study, a theoretical model was developed to predict the shear capacity of UHPC large-keyed epoxy joints. In the proposed model, the shear capacity of joint was determined as the superposition of the shear contributions of the flat part and the keyed part. For the flat part, the shear strength mainly depends on the bond shear performance at the joint interface, which could be determined though test results of flat epoxy joints. To obtain the shear strength of the keyed part, the failure envelopes for UHPC were determined based on Mohr–Coulomb shear failure criterion, and the theory of Mohr’s circle was adopted. Then, the direct shear test was performed on 15 UHPC large-keyed epoxy joint specimens and four flat epoxy joint specimens to obtain their failure modes and shear resistance for verification. In addition to the test data in this study, test results of related existing studies were also utilized to validate the proposed theoretical model. Furthermore, the AASHTO equation and the existing formulas for epoxy joint were also used for comparison. Results indicated that the proposed model performed well in both the accuracy and the variation degree.