Mechanical behavior of an innovative steel–concrete joint for long-span railway hybrid box girder cable-stayed bridges

Abstract This research proposes an innovative steel–concrete joint, which utilizes front and rear bearing plates and concrete filled steel cells, for long-span railway hybrid box girder cable-stayed bridges. This study investigates the mechanical behavior of the steel–concrete joint through a model test and finite element analysis, aiming to understand the stress distributions, shear lag effects, deformations, and force transfer pathway of the joint under axial and shear loads. A large-scale model (scale: 1/5) was designed following the similarity theory. The model was fabricated and tested under representative load cases. Based on the model test, a three-dimensional finite element model was established and validated using the model test results. Then, the finite element model was utilized to perform a parametric study on the effects of the length of the joint, the thickness of the bearing plates, the height of steel cells, and the stiffness of shear connectors. The results show that the proposed steel–concrete joint provides desired stress distribution and force transfer behavior, in terms of the force transfer rate and uniformity. In the composite section of the joint, the rear bearing plate transfers 57% the total axial force. This study is expected to promote the design and applications of hybrid girders.