斜靠式钢管混凝土异形拱桥非线性稳定分析

Nonlinear stability analysis of the CFST double X-arch bridge

斜靠式拱桥是在无风撑拱桥基础上发展起来的一种新型拱桥结构型式.针对此类钢管混凝土异形拱桥的特点对其非线性稳定求解机理和方法进行了分析介绍,以一座拟建的大跨径斜靠式拱桥为例,采用通用程序ANSYS建立该桥的空间有限元计算模型,分工况对其成桥状态进行了线弹性、几何非线性和双重非线性稳定分析计算.同时分析了其主要结构参数(矢跨比、斜拱倾角、横撑数量及位置)对非线性稳定性的影响.计算分析发现:斜靠式拱桥的失稳形式一般表现为面外拱肋侧倾失稳;几何非线性对斜靠式拱桥稳定极限承载力影响较小,要准确的分析其稳定极限承载力必须采用双重非线性的分析方法;横向静风和桥上荷载分布对结构稳定有一定影响而对结构变形影响显著;结构稳定性与矢跨比和斜拱倾角增加均成正比,靠近拱脚和L/4处横撑对结构稳定性影响较大.

Double X-arch bridge is a new type of arch bridge,developed on the basis of arch bridge structure with no brace.After analyzing and introducing the characteristics of double X-arch bridge,it presents the nonlinear stability analysis mechanism and solving method for this type of special-shaped arch bridge.An ANSYS finite element spatial analysis model is presented based on a long-span double X-arch bridge which is being constructed.Using different types of the operating mode,the stability analysis for the bridge considering the linear,the geometrical nonlinear and the double nonlinear （geometric and material） are presented,and the instability characteristics described.Furthermore,the key structural parameters （the ratio of rise to span,the rake angle of the inclined arch,the number and location of transverse） are proposed for analyzing their influence on structural stability.The results show that the buckling mode of double X-arch bridge is out-of-plane buckling;that the geometrical nonlinear has not a lot effect for the ultimate carrying capacity on the stability of the bridge;that only the material and geometrical nonlinear analysis can assess the bridge’s ultimate carrying capacity for stability accurately;that the transverse wind load and the load distribute on the bridge deck have some influence on the stability and significant effect on the deformation of this type of bridge;that the structural stability will increase with the addition of the rise-span ratio and skew angle of the inclined arch;and that the brace near the arch springer and L/4 section have large effect on the structural stability.