The proposal entails the utilisation of a replaceable steel-hybrid composite beam, accompanied by an adhesive joint bridge panel and a removable high-strength bolt-shear bond. In order to analyze the influence mechanism of different joint forms on the mechanical properties of the fully assembled composite beam in the positive moment zone, four composite beams with different bridge panel joint forms were designed and prepared, and a static loading test was completed. The mechanical characteristics of each specimen, including failure mode, bearing capacity, ductility, flexural stiffness and interface slip, were analyzed. The findings indicate that, in comparison to cast-in-place beams, which demonstrate failure in bending, fully assembled composite beams manifest bending-shear failure, with the main crack occurring near the adhesive joint, indicating concrete cohesion failure. Linear, stepped and dovetail joint beams showed a reduction in flexural capacity of 4.78%, 2.07% and 2.04% respectively compared to cast-in-place beams. The bridge deck dominated by compression has a relatively minor impact on the bearing capacity of the jointed beam. The presence or absence of joints exerts a significant influence on the overall ductility of the composite beam. The ductility coefficient of the cast-in-place beam is 14.39%, 34.87% and 7.75% higher than that of the straight joint, stepped joint and tongue-and-groove joint, respectively. The overall elastic stiffness of composite beams is not significantly affected. The elastic stiffness of the lap joint beams are reduced by 0.55%, 5.43% and 2.06% respectively. The slip at the end of the cast-in-place beams is the largest, while the maximum slip of fully assembled composite beams occurs near the joints. Among different joint forms, the tongue and groove joint exhibits the best performance in terms of strength and stiffness. Finally, based on plastic theory, the calculation formula for the flexural capacity of fully assembled composite beams considering the influence of high-strength bolted joints and adhesive joint bridge panels is proposed.