Experimental and numerical study on compressive behavior of convex steel box section for arch rib

• Bearing capacity of convex steel section used for arch ribs is obtained.
• Some parameters on the stress–strain relation of convex section are studied.
• Bottom plate has the lowest critical stress among all the stiffened plates.
• A smaller width ratio hardens the post-buckling behavior of convex section.
• Larger RR and smaller γ/γ∗ values reduce the critical stress of cross section.
• Equations of normalized stress–strain relation of convex section are proposed.

The mechanical behavior of a convex steel box section under axial compression is studied using loading test on reduced scale-model and nonlinear FE analysis, taking into consideration initial geometric deflection and residual stress. The actual bearing capacity of the convex steel section used for the arch ribs of the Yongjiang Bridge is obtained. The difference in critical stress among the stiffened plates is revealed. The influence of width ratio η between upper and lower boxes, stiffened plate width–thickness ratio RR and ratio of stiffener’s relative flexural rigidity to its optimum value γ/γ∗ on the normalized stress–strain relation of the section are examined. It is found that the bottom plate has the lowest critical stress among all the stiffened plates in the convex section. A smaller width ratio increases the critical stress of the middle plate and hardens the post-buckling behavior. The effect of width ratio on the normalized stress–strain relation of convex section is so small as to be negligible. RR and γ/γ∗ values influence the critical stress of the convex section and significantly affect the post-buckling behavior. Larger RR and smaller γ/γ∗ values reduce the critical stress of the cross section. Equations representing the normalized stress–strain relation of the convex section under axial compressive loading are proposed as a function of these influential parameters and their validity is demonstrated through numerical analysis.