公铁两用斜拉-悬索协作体系桥结构参数研究

Parametric Study for a Rail-cum-Road Bridge of Combined Cable-Stayed and Suspension System

为探究结构参数对公铁两用斜拉-悬索协作体系桥受力性能的影响,确定结构参数的合理取值,以甬舟铁路西堠门公铁两用大桥为背景,采用MIDAS Civil软件建立该桥杆系有限元模型,计算分析辅助墩、吊跨比、矢跨比及交叉索数量等参数变化对结构竖向刚度、端吊杆活载轴力幅、桥塔弯矩等的影响,提出各结构参数的合理取值建议。结果表明:在边跨设置辅助墩能提高结构的竖向刚度、降低桥塔顺桥向弯矩和端吊杆活载轴力幅;吊跨比越大,结构的竖向刚度越小;矢跨比越大,结构的竖向刚度越大;增加交叉索对数可以降低端吊杆的活载轴力幅,但交叉索数量增至一定数量,端吊杆活载轴力幅值降低趋势趋于稳定;推荐大桥采用边跨设置2个辅助墩、跨中纯悬吊段吊跨比0.3、主缆中跨矢跨比1/6.5、交叉索9对的结构布置。

To study the influence of structural parameters on the mechanical property of the rail-cum-road bridge of combined cable-stayed and suspension system and determine the rational values of structural parameters,the Xihoumen Rail-cum-Road Bridge on Ningbo-Zhoushan Railway was taken as the background project.The beam-column element model of the bridge was built by MIDAS Civil,based on which the influence of variation of parameters,such as auxiliary piers,suspension-to-main span ratio,sag-to-span ratio and number of crossed suspenders and stay cables,on the vertical stiffness of the structure,axial force amplitude of live load on end suspenders and bending moment of towers were calculated and analyzed.Recommendations on rational values of structural parameters are given.The results show that adding auxiliary piers in side spans can enhance the vertical stiffness of the structure,reduce the bending moment of towers along the bridge length and the axial force amplitude of live load on end suspenders.Bigger suspension-to-main span ratio results in smaller vertical stiffness of the structure,while bigger sag-to-span ratio leads to bigger vertical stiffness of the structure.Increasing the number of crossed suspenders and stay cables can reduce the axial force amplitude of live load on end suspenders,but when the number of crossed suspenders and stay cables reaches a critical point,the reduction of axial force amplitude of live load on end suspenders tends to be steady.It is recommended that two auxiliary piers be installed in each side pan,the suspension-to-main span ratio of midspan pure suspended segment draw 0.3,the sag-to-span ratio of central-span main cable be set at 1/6.5,and 9 pairs of crossed suspenders and stay cables be arranged.