沪通长江大桥主航道桥总体设计参数分析

Parametric Analysis of Overall Design of Main Ship Channel Bridge of Hutong Changjiang River Bridge

为研究公铁两用斜拉桥的力学性能,以沪通长江大桥主航道桥[(140+462+1 092+462+140)m双塔斜拉桥]为对象,采用空间板梁单元法建立全桥有限元模型,对边跨支点数量、边中跨比、主梁高跨比和宽跨比、塔梁高跨比等设计参数进行分析。结果表明:边跨设置辅助墩可改善结构受力、提高桥梁整体刚度;边中跨比增大使结构总体刚度减小,活载塔底顺桥向弯矩增大;主梁高度增大可提高结构整体刚度,但提高幅度有限,同时对恒、活载拉索应力的影响也较小;主梁宽度增大使横弯基频增大、竖弯基频减小,扭频先减小后增大而后趋于平稳,结构颤振稳定性提高;塔高增大使结构竖向刚度增大而索塔纵向刚度降低,活载塔底顺桥向弯矩减小,恒、活载拉索应力减小。

To study the mechanical behavior of the rail-cum-road cable-stayed bridge,the main ship channel bridge[a double-pylon cable-stayed bridge with span arrangement（140＋462＋1 092＋462＋140）m）]of the Hutong Changjiang River Bridge was taken as the object,the spatial plate and beam element method was used to set up the finite element model for the whole bridge of the bridge and the design parameters of the side span support numbers,side span-to-central span ratio,depth-to-span and width-to-span ratios of the main girder and the height-to-span ratio of the pylon and main girder were analyzed.The results of the analysis reveal that the arrangement of the auxiliary piers in the side spans can improve the mechanical conditions and integral rigidity of the structure.The increase of the side span-to-central span ratio can cause the integral rigidity of the structure to decrease and the longitudinal bending moment in the pylon footings under the live load to increase.The increase of the depth of the main girder can increase the integral rigidity of the structure,but the amplitude of the increase is limited and the influences of the increase on the stress of the stay cables under the dead and live loads are slight.The increase of the width of the main girder can cause the transverse bending base frequency to increase,the vertical bending base frequency to decrease,the torsional frequency to decrease first,increase then and finally to tend to be stable and can improve the flutter stability of the structure.The increase of the pylon height can cause the vertical rigidity of the structure to increase,the longitudinal rigidity of the pylons to decrease,the longitudinal bending moment in the pylon footings under the live load to decrease and the stress of the stay cables under the dead and live loads also to decrease.