The stress distribution in a swept-back box-beam with perpendicular ribs

Abstract

A solution is obtained for the distribution of internal load in a swept-back box-beam of rectangular cross-section under any system of external loading. The theory, based upon strain energy, is considered exact when the ribs are perpendicular to the spars and when the spanwise bending loads are taken by the spar booms. The general solution for encastre root conditions is given. Extensions of the method to cover root flexibility and cut-outs in the top or bottom skins are discussed. A numerical example of a simple two-spar box is investigated for a range of sweepback angle of 0 deg. to 40 deg. for an encastre root condition. The analysis shows that appreciable redistributions of load in the box, compared with the unswept box, are obtained when either torque or bending moment is applied to the beam.