Design expression for web shear buckling of box sections by accounting for flange restraints

• Is proposed new analytical expression for shear buckling stress of box sections.
• Significant cost savings result by using the design expression.
• Design codes predictions may vary by up to 40% by ignoring the rotational restraints.

This paper presents a new analytical expression for computing the web shear buckling stress with partial flange rotational restraints. The derived expression is suitable to be used in practice for hand calculation and avoids excessive efforts required to perform numerical analysis using finite element or finite strip methods. The material savings resulting from using the proposed design expression are also illustrated. Current design provisions ignore the flange rotational restraints effect in determining the web shear buckling stress for box sections. A comparison is made with AISI, CSA-S16, Eurocode 3 and AASHTO provisions for the limiting conditions. It is also shown that the shear buckling stress may vary by 40% with the current design expressions. Numerical validation of the proposed expression with semi-analytical finite strip method is also presented. The influence of the flange geometric properties on the web buckling stress is also highlighted.