Experimental study and numerical analysis of a novel concrete slab-steel truss composite joint for large-span railway cable-stayed bridges

This paper proposes a novel composite joint for concrete slab–steel truss composite beams tailored for large-span railway cable-stayed bridges. The joint consists of a concrete upper chord, an inverted “Π”-shaped steel chord, a gusset plate, diagonal and vertical steel web members, and a stay cable, with studs and T-type Perfobond Leiste (PBL) shear connectors employed to ensure composite effects of concrete and steel. An experimental and numerical investigation was conducted to elucidate the complex force transmission mechanism and stress distribution characteristics of this joint. A six-directional planar loading test was performed on a 1:3 scaled specimen, capturing load-displacement responses, deflection profiles of the upper chord, steel–concrete interface slips, and strain distributions. A finite element model (FEM) was subsequently developed and validated against the experimental results, enabling further analysis of ultimate capacity, failure mechanisms, design optimization, and other design loading conditions. The results demonstrate that: (i) the joint exhibits robust load-transfer and load-bearing capacities under multi-directional loading, with yield and ultimate capacities reaching 3.81 and 4.72 times the design load, respectively, and the steel–concrete composite chord attaining a maximum load capacity of 4927.4 kN; (ii) the steel–concrete interface shows excellent performance, with a maximum slip of only 0.12 mm (below the safe limit of 0.2 mm) even under three times the design load; and (iii) the curved segment of the gusset plate at the diagonal web is identified as the most critical zone prone to stress concentration and should be reinforced for design optimization. Collectively, these findings confirm that the proposed composite joint is structurally reliable and suitable for application in prefabricated cable-stayed bridge structures of large-span railway bridges.