A mathematical and experimental investigation is made of the stresses resulting from the flexure of curved beams of I- and box-section. It is shown that the flanges, if unsupported, distort under the influence of radial stress-components, and are less effective in carrying the circumferential bending stresses than would appear from ordinary methods of calculation. The distortion is accompanied by transverse bending stresses which, in certain circumstances, may be of greater magnitude than the circumferential stresses, and which at the inner radius combine with the circumferential stresses to introduce critical stress conditions. The distortion effects may be limited by using thick, narrow flanges, by ample fillets between the flanges and the webs, by radial gussets and by suitable disposition of the webs in box-sections. Formulae and charts for the estimation of stresses are presented in convenient form for design purposes.
