Experimental and numerical research on out-of-plane flexural property of plates reinforced SHS X-joints

• A total of 13 specimens SHS X-joints under out-of-plane bending.
• Thickness of plates had an obvious effect on ultimate capacity of SHS X-joints.
• An extensive parametric study on the behavior of plates reinforced SHS X-joints.
• Design equations of ultimate capacity of the plates reinforced SHS X-joints.

The static tests of 13 SHS X-joints with different brace to chord side length ratios and different types of plates reinforcement under out-of-plane bending in brace were carried out. Experimental test schemes, failure modes of specimens, moment–vertical displacement curves, moment–deformation of the chord, and strain strength distribution curves were presented. The effects of brace to chord side length ratios and plates reinforcement types on out-of-plane flexural property of SHS X-joints were studied. Results show that punching shear of chord face disappeared, concave and convex deformation of chord decreased when either collar plates or doubler plates were welded on chord face. Moment–vertical displacement curves of all specimens have obvious elastic, elastic–plastic and plastic stages. As brace to chord side length ratio increased, the out-of-plane flexural ultimate capacity and initial stiffness of joints with the same plates reinforcement type increased, but ductility of joints decreased. With the same brace to chord side length ratio, the out-of-plane flexural initial stiffness and ultimate capacity of collar plates reinforced joints, doubler plates reinforced joints and unreinforced joints decreased progressively. Thickness of reinforcement plates had an obvious effect on out-of-plane ultimate capacity of SHS X-joints. Thickness of reinforcement plates had no obvious effect on out-of-plane flexural initial stiffness of SHS X-joints when the value of reinforcement plates to chord wall thickness ratio exceeds 1.0. As thickness of reinforcement plates increased, the ductility of reinforced X-joints decreased. The concave and convex deformation of every specimen had good symmetry. The design equations were proposed for collar and doubler plates reinforced SHS X-joints under out-of-plane bending, which were shown to be accurate and reliable.