中承式钢管混凝土拱桥拱肋关键参数影响分析

Key Parameter Influence Analysis of Half-Through Concrete-Filled Steel Tubular Arch Bridge

为寻求钢管混凝土拱桥拱肋关键参数的合理取值,分析拱肋关键参数对钢管混凝土拱桥结构力学行为、桥梁景观和工程造价等方面的影响。以净跨径360 m中承式钢管混凝土拱桥为背景,结合既有经验,以矢跨比系数(矢跨比倒数)、拱轴系数和主管管径为单因子变量建立17个主桥有限元模型,研究恒载作用下各关键参数对主拱内力、变形和稳定性等的影响规律。结果表明:随着矢跨比系数增大(矢跨比减小),拱肋的竖向刚度减小,弦管轴力和拱脚水平推力增大,关键截面偏心距标准差呈波浪形变化,主拱稳定系数先增大后减小;上弦管拱顶处轴力对矢跨比系数的敏感性高于拱脚处,下弦管相反。随着拱轴系数的增大,关键截面偏心距标准差先减小后增大,拱肋成拱后马鞍形效应越突出;拱脚截面、L/4(L为主拱跨径)截面和拱顶截面弦管轴力对拱轴系数敏感性较高,L/8截面和3 L/8截面的较低。管径为1~1.2 m时关键截面偏心距标准差基本相同,随着主管管径增大,主拱稳定系数增大。背景桥梁矢跨比、拱轴系数和主管管径分别取1/4.0、1.55、1.2 m时可兼顾景观、受力和经济性。

In this paper,the rational values of key parameters of the concrete-filled steel tubular(CFST)arch rib are studied,and the influence of key arch rib parameters on the mechanical properties of the CSFT arch bridge,bridge landscaping and engineering costs is analyzed.Based on an existing half-through CSFT arch bridge with a net span length of 360 m,17 finite element models of the main bridge were developed,in accordance with the existing experience,using the rise-to-span ratio coefficient(derivative of rise-to-span ratio),arch axis coefficient and diameters of chord tubes as the single-factor variables.The influence of key parameters on the internal forces,deformation and stability of arch ribs under dead loads were studied.It is shown that as the rise-to-span ratio coefficient increases(rise-to-span ratio decreases),the vertical stiffness of the arch rib is reduced,axial forces of the chord tubes and the horizontal thrusts of the arch springings increase.The standard deviation of key cross-sectional eccentricity reveals waving variation,and the stability coefficient of main arch reverses after an increase.The impact of axial force at arch-crown chord tube is more sensitive to the rise-to-span ratio coefficient than that at the arch-springing chord.And the situation for the lower chord is the opposite.As the arch axis coefficient increases,the standard deviation of key cross-sectional eccentricity shows sign of from decreasing to increasing,and after completion,the saddle effect of the arch rib becomes more significant.Compared with the L/8 and 3 L/8 cross-sections(L refers to the span of arch),the chord tube axial forces at the arch springing cross-section,L/4 cross-section and the arch crown cross-section are more sensitive to the arch axis coefficient.When the chord tube is 1 to 1.2 m in diameter,the standard deviation of key cross-sectional eccentricity is basically the same.As the diameter of the chord tube increases,the stability coefficient of the main arch rises.For the case bridge,when the rise-to-span ratio,arch axis coefficient and chord tube diameter are set at 1/4.0,1.55 and 1.2 m,respectively,a balance between the landscaping,load bearing performance and economy can be achieved.