Out-of-plane inelastic stability of circular arches under bending moment

In order to create a systematic design method for out of-plane stability of steel arch under the combination of uniform compression and bending,the out-of-plane ultimate strength of circular arch under bending moment is required to be investigated at first.By considering the factors such as arch section types,initial geometric inperfection,residual stresses,rise-to-span ratio,support conditions and end moment ratio,this paper presented design principles for out-of-plane strength of circular arches under bending moment.Firstly,arches under uniform positive bending were studied and stability design curves with normalized arch slenderness for welded I-section,welded box section and hot-rolled pipe section were proposed.Then for arches under non-uniform bending with end moment,two methods of modified normalized slenderness and moment modified coefficient for calculation of the out-of-plane ultimate strength were established,which can be applied in the formulation of design method for arches under the combination of compression and bending.It shows that the stability curve of circular arches under uniform positive bending is similar to that of straight beams.Modified normalized slenderness or moment modified coefficient should be introduced to take account of the effects of moment gradient and negative moment.The results of ultimate strength calculated by the two methods proposed are close to those of FEA.