Ultra-high performance concrete beam-to-beam connections in continuous bridges: Experimental full-scale tests, FE analyses and design

This paper investigates the mechanical performance of ultra-high-performance concrete (UHPC) beam-to-beam joints in steel–concrete composite bridges, proposing an alternative to conventional reinforced concrete (RC) joints in continuous beams. The authors employed UHPC with steel end-plates and studs to connect the UHPC crossbeam with the steel beams and RC slab. These connections provides advantages like eliminating the need for on-site welding, simplifying construction, and handling potential tolerance issues. The research includes full-scale experimental tests, a benchmark test on an RC joint, validation of finite element models, parametric analyses, and the development of analytical models to predict the joint's moment–rotation curve, initial stiffness, and ultimate bending capacity. Full-scale experiments revealed that the maximum longitudinal concrete stress in UHPC continuity joints occurs at the interface between the composite steel–concrete beam and the UHPC cross-beams, resulting in crack widths substantially below code limits. The parametric analyses identified critical factors affecting UHPC joint performance, such as concrete strength, steel yield strength, and horizontal stud dimensions. Additionally, the study validated existing formulations for predicting the capacity and stiffness of the joints against the results from the finite element (FE) parametric analyses.