Force performance of steel-concrete sections in railway double-box hybrid girder cable-stayed bridge

To study the force performance and force transfer mechanism of railway double-box hybrid girder cable-stayed bridge and optimize its construction form and size, the front pressure plate, steel beam embedded section, and steel compartment in the preliminary design of the real bridge were canceled, and the density of the shear connector was minimized. A test model with a scale ratio of 1∶2.5 was then designed and constructed for the steel-concrete sections. The stress distribution, bearing performance, and shear transfer characteristics of the combined section were analyzed under calculation conditions of each real bridge design. The shell-solid finite element model was built to further analyze parameters including the effect of the combined section length, front pressure plate, and shear connector. Research results show that with the simplified structure, the scale model of the railway double-box hybrid girder cable-stayed bridge has seen a good linear correlation in the load-stress curve of all the measuring points under the influence of axial pressure and maximum positive/negative bending moment. The force of the steel-concrete joint section is still in the elastic stage. The load-slip relationship of the slip measuring point of the steel-concrete interface is approximately linear change, with a maximum slip value of 0.15 mm. The residual slip upon unloading can be ignored. There is also a cooperative force between the steel plate and concrete. Under the axial pressure condition, the shear force of the steel-concrete joint interface shows a horseshoe-shaped distribution featuring large ends and small middle. The larger the combined section length, the smaller the interface shear and relative slip. When the combined section length exceeds 2 times of the shear transfer length, the regional shear force and relative slip between the steel beam and the concrete beam are almost zero. The rear pressure plate, front pressure plate, and steel beam embedded section bear about 56.0%, 12.4%, and 11.0% axial force, respectively. The front pressure plate and steel beam do not change the positive stress change trend and axial force distribution characteristics of the steel structure and concrete in the steel-concrete section. No significant effect can be seen on the stress and force transfer of the steel-concrete section. The stress concentration at the rear pressure plate and the steel roof and bottom plate can be improved by the transverse partition plate.