Jincheng Cao

Precast segmental ultra‐high‐performance concrete bridge presents broad application prospects. UHPC keyed joints play significant roles in the structural performance of such bridges, which require systematic investigation to comprehend their shear behavior and mechanism thoroughly. This study aimed to explore the shear mechanism of UHPC epoxied‐keyed joints. Experimental and numerical investigations were conducted to investigate the influence of key size, key number, key angle, and reinforcement form on the shear performance. The test results showed that the failure mode was primarily affected by the key number and reinforcement form, which can be divided into three categories: direct shear, segmental shear, and stepwise shear failure. The large‐keyed joints exhibited superior shear performance compared to the three‐keyed joints. The initial shear stiffness, ultimate bearing capacity, and normalized shear stress were 15%, 5.3%, and 5.6% higher, respectively. Furthermore, the mechanism of the two reinforcement forms was clarified. The key rebars mainly improve the ductility of the specimens, while the dowel action of the embedded rebars can enhance the shear efficiency and synergistic force ability of the joints. The numerical simulation results indicated that 2.7% was the best ratio of key rebar, and embedded rebars with larger diameters can strengthen the shear capacity and post‐peak performance of the joints.

The difference between the shear performances of Perfobond Leiste (PBL) shear connectors embedded in steel fiber-reinforced cementitious composite (SFRCC) structure and normal strength concrete (NC) structure was investigated by push-out tests and finite element (FE) simulations. Push-out tests were carried out on nine steel-SFRCC specimens and nine steel-NC specimens. The mechanical behavior of the PBL shear connector was examined according to the failure modes, load-slip curves, and strain distribution laws of the push-out specimens. Experimental results revealed that the extension of cracks in SFRCC was hindered by steel fibers, and the number and width of cracks in SFRCC were smaller than those in NC. The failure mode of the steel-SFRCC specimens and the single-hole steel-NC specimens was the shear failure of the penetrating reinforcement, whereas that of the multi-hole NC specimens was concrete slab cracking. The ultimate shear bearing capacity of PBL shear connectors in the steel-SFRCC specimens was 47.8% greater than that in the steel-NC specimens. Furthermore, an FE model verified by the test results was established to conduct parametric analyses. It was found that the hole diameter and thickness of the steel plate and the yield strength of the penetrating rebar greatly affected the shear bearing capacity of PBL shear connectors. Finally, based on the experimental and FE simulation results, an expression for calculating the ultimate shear bearing capacity of PBL shear connectors in the steel-SFRCC composite structure was developed by considering the bearing effects of concrete dowels, penetrating rebars, and end parts.