受弯圆弧拱平面外稳定承载力分析

为建立压弯钢拱平面外稳定承载力设计方法，对承受弯矩作用的受弯圆弧拱的稳定承载力进行系统研究，考察弯矩对其面外稳定的影响。采用有限元分析方法，考虑截面形式、初始几何缺陷、残余应力、矢跨比、拱脚条件及端弯矩比例的影响。首先针对均匀正弯矩作用，基于正则化长细比给出了焊接工形截面、焊接箱形截面及热轧圆管截面拱的平面外稳定曲线；之后对于不同比例的端弯矩作用下不均匀受弯情况，提出了平面外稳定承载力计算的等效正则化长细比法和等效弯矩系数法，为压弯圆弧拱设计方法的建立奠定基础。研究表明：采用正则化长细比，均匀正弯矩作用下圆弧拱的平面外稳定系数可采用与直梁类似的平面外稳定曲线；不等端弯矩作用的情况需引入等效正则化长细比或等效弯矩系数，以考虑弯矩梯度和负弯矩作用的影响；提出的两种平面外稳定承载力计算方法与大挠度弹塑性有限元分析结果吻合较好。

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.