ABSTRACT
Spars in aircraft wing boxes constitute thin walled shells, providing a load path for vertical shear loading. Well established design rules for the prediction of the initial shear buckling load are extended to cover the cases of compression and in-plane bending, resulting from overall wing bending. A parametric study, performed using an exact strip method and verified by finite element results, for both simply supported and clamped longitudinal edges, shows that the stiffeners effectively provide simple support if their dimensions are made large enough. Using a single plate model for such cases, a simple interaction equation is shown to give accurate and conservative initial buckling predictions for combined loading cases, with some scope for improvement when the stiffener spacing is large.
