Experimental Study and Finite Element Analysis on the Bearing Capacity of a Novel Light-Steel Truss with Cap-Shaped Chords

Aiming to address the shortcomings of traditional large-span light-steel trusses, such as low bearing capacity and inconvenient on-site assembly, this paper proposes a novel cap-shaped chord light-steel truss. It consists of top and bottom cap-shaped chords with uniformly pre-drilled pilot holes and longitudinal stiffeners on both webs, and square/rectangular tubular web members, all connected by self-tapping screws. The novelty lies in the proposed splice geometry, the pilot-hole arrangement for screw connections, and the full-scale 18 m validation. Full-scale bending tests and finite element analyses were conducted on two 18 m span cap-shaped chord light-steel truss specimens subjected to uniformly node-distributed loading. The bearing capacity, stiffness, and failure modes of two specimens were analyzed and compared. Testing results indicate that the usage of edge-curled chord members effectively enhances both the bearing capacity and stiffness of the truss. The main failure mode observed for both specimens was local buckling of the upper chord in the mid-span. No deformation or shear failure occurred for the self-tapping screws at the chord-splice joints, and none of the web members exhibited significant deformation either. This demonstrates that the load-bearing behavior of the truss specimens is primarily governed by the compressive bearing capacity of the upper chord and its splices. The proposed light-steel truss offers advantages including a high degree of standardization, improved load-bearing capacity, and convenient installation.