Flexural-Torsional Stability of Curved Beams

General fourth order coupled differential equations are presented to determine the elastic buckling loads of in-plane as well as out-of-plane buckling modes of spatial thin-walled curved beams. Included are the warping contribution to the buckling loads, and the effects of antisymmetry of cross-section (found to be significant). The governing differential equations are based on the variational principle. Critical load formulas are given for a few special combinations of loadings and boundary condition. Comparative studies were made and possible sources of discrepancies were traced.