Fatigue Performance of an Innovative Steel–Concrete Joint in Long-Span Railway Hybrid Box Girder Cable-Stayed Bridges

Abstract

An innovative steel–concrete joint (SCJ) was applied to long-span railway hybrid box girder cable-stayed bridges to achieve favorable force transfer and deformation performance with a running train. The fatigue performance of each component was investigated by performing a full-scale 3 million cycle fatigue test. All components remained intact over the first 2 million cycles, indicating sufficient fatigue resistance over the designed service life. Turning points appeared in the curve for the shear stud on the first layer of the bottom plate and top plate after loaded 2.2 and 2.4 million loading cycles, respectively, resulting from the separation between the steel and concrete near end bearing plate, indicating that this area was the least favorable aspect of this innovative SCJ. Cracks then developed at the weld joint between the top plate and the end bearing plate after 2.4 million loading cycles, indicating that the fatigue life of the weakest weld joint exceeded 167.5 years. Numerical analysis with a nonlinear finite-element model was developed to further investigate the fatigue performance of the SCJ. The results indicated that the thickness of the end bearing plate and diameter of the shear studs significantly influenced the fatigue performance, and a 44–70-mm-thick end bearing plate and no less than 19-mm shear stud diameter is accordingly recommended. The outcomes of this study provide a reference for the further application of SCJ technology to long-span railway hybrid girder cable-stayed bridges.