带L形横撑的大跨CFST桁式拱桥稳定性分析

为研究新型L形横撑在大跨度钢管混凝土(CFST)桁式拱桥稳定中的有效性，以合江三桥为工程背景，采用数值计算和理论分析相结合的方式对其受力性能和稳定性进行比较分析，并利用正交试验和方差分析方法对L形横撑在大跨度CFST桁式拱桥稳定中的显著性进行了检验。结果表明：①对于L形拓扑横撑类型，当K形斜撑设置在主拱肋上弦且靠近拱脚一侧时，主拱的稳定性最好；②与常用的K形、X形和米字形横撑相比，L形横撑对主拱最大轴力、最大面内弯矩、最大面外弯矩、最大应力和竖向变形的影响均较小，仅对主拱水平变形有一定影响；③当各参数在合理的取值范围内时，使用L形横撑代替常用的K形、X形或米字形横撑，不会显著降低大跨度CFST桁式拱桥的分支点和极值点稳定性，工程师在该类拱桥的稳定设计中可以放心选用。

Stability analysis of long-span CFST truss arch bridges with L-shaped bracings

 In order to study the effectiveness of L-shaped bracings in stability of long-span CFST truss arch bridges, the mechanical behavior and the stability of long-span CFST truss arch bridges are analyzed and compared through theoretical analysis and numerical calculation based on Hejiang River Third Bridge. In addition, the significance of L-shaped bracings in the stability of truss arch bridge is checked by orthogonal test and multi-factor variance analysis methods. The results show that (1) for the topology optimization types of L-shaped bracings, the main arch has the best stability when the K-shaped diagonal bracing is set at the top chord of main arch rib and close to arch foot; (2) compared with the K-shaped, X-shaped or double-cross-shaped bracings, the L-shaped bracings may have less influences on the maximum value of axial force, in-plane bending moment, out-of-plane bending moment, stress and the vertical deformation of the main arch, but they may affect the horizontal deformation of the main arch to some extent. (3) When the parameters are within the reasonable ranges, the replacement of K-shaped, X-shaped or double-cross-shaped bracings with the L-shaped bracings may not significantly reduce the stability of bifurcation buckling and the extreme-value point of the long-span CFST truss arch bridges. Hence, the L-shaped bracings can be chosen by engineers in the stability design of such arch bridges without no special emphasis.