Force transfer performance of chambers in steel-concrete joint section of railway composite beam cable-stayed bridge

To investigate the force transfer mechanism and mechanical properties of these joint sections, a single-cell chamber of a joint section from a railway composite cable-stayed bridge was selected as the research object. By eliminating the front bearing plate and embedded steel beam section from the preliminary design of the actual bridge, a theoretical formula for shear transfer length was derived. Based on this theoretical formula, a single-cell test model with a scale ratio of 1∶2.5 was designed and constructed. The stress distribution, load-bearing capacity, and force transfer characteristics of the joint section under axial compression conditions were analyzed. A finite element model was established to investigate the force transfer mechanism, load-bearing performance, and accuracy of the shear transfer length formula under varying parameters. Results indicate that two equal shear transfer lengths exist within the joint section, determined solely by the axial compression stiffness of steel and concrete, along with the stiffness of the continuous spring layer at the interface. The model's load-bearing capacity reaches six times the equivalent bearing capacity. The measured surface stress distribution and axial force transfer ratio exhibit rapid changes at both ends while stabilizing in the middle. Shear connectors at both ends demonstrate high utilization rates, with measured shear transfer length values deviating no more than 5% from theoretical values. According to the influence analysis of force transfer mechanism parameters, the variation patterns of force transfer ratios and relative slip under different parameters align with experimental measurements, with the force transfer mechanism remaining fundamentally consistent. The finite element values for shear transfer length exhibit less than 20% deviation from theoretical values. Changes in bearing plate thickness and joint section length have no effect on shear transfer length. The factors influencing shear transfer length are chamber width, chamber height, perforated steel plate thickness, and others, ranking from greatest to least in impact. The difference in connection group utilization rate across varying joint section lengths can reach 15%. The utilization rate influence ranking of relative slip and connection group is as follows: joint section length, chamber width, chamber height, and others. In design, the joint section length should be appropriately selected. Additionally, the density of shear connectors at both ends can be increased while the number in the middle can be reduced to enhance utilization rate.