双缆多塔悬索桥主缆垂跨比的合理取值

Reasonable Value of Sag-span Ratio of Main Cable in Double-cable Multi-pylon Suspension Bridge

为了明确双缆多塔悬索桥主缆垂跨比的合理取值,为结构设计提供依据,以主缆与中塔鞍座的抗滑安全系数和加劲梁挠度为控制指标,拟定满足主缆抗滑及结构变形要求的三塔两跨悬索桥设计参数,建立双缆及传统多塔悬索桥有限元模型,分析双缆体系主缆垂跨比对结构变形、主缆抗滑稳定性及主缆用钢量的影响。结果表明:双缆体系的结构刚度主要取决于主缆垂跨比而非中塔刚度,结构变形随着上缆垂度的减小和下缆垂度的增大而减小;主缆抗滑安全系数随着桥塔刚度的增大而减小,随着下缆垂度的增大而减小;上缆垂度对抗滑安全系数的影响与桥塔刚度有关,桥塔刚度较小时,主缆抗滑安全系数随着上缆垂跨比的增大而增大,桥塔刚度较大并且下缆垂跨比较小时,随着上缆垂跨比的增大,主缆抗滑安全系数先增大后减小;与传统悬索桥体系相比,双缆多塔悬索桥加劲梁变形和主缆抗滑稳定性受桥塔刚度的影响较小,桥塔刚度的可行性范围远大于传统多跨悬索桥。双缆体系悬索桥主缆用钢量与传统体系用钢量基本一致,主缆用钢量随着上、下缆垂度的增大而减小;下缆垂跨比适宜取值为1/8~1/6,上缆垂跨比适宜取值为1/14~1/11,当桥塔刚度较小时,应增大上下缆垂度差值。

In order to determine the reasonable value of main cable sag-span ratio of double-cable multi-pylon suspension bridge,and provide the basis for structural design,taking the antiskid safety factors of the main cable and the saddle of the central pylon and the deflection of the stiffening girder as the control indicators,the design parameters of 3-pylon 2-span suspension bridge that meet the requirements of the main cable anti-skid and structural deformation are determined,the finite element models of a double-cable and traditional multi-pylon suspension bridge are established,and the influences of sag-span ratio of main cable of double-cable system on the structural deformation,the anti-sliding stability of the main cable and the steel amount of the main cable are analyzed.The result reveals that(1)The structural stiffness of the double-cable system is mainly determined by the sag-span ratio of main cable rather than the stiffness of middle pylon,and the structural deformation decreases with the decrease of the sag of the top cable and the increase of the sag of the bottom cable.(2)The influence of the top cable sag on the antiskid safety factor is related to the pylon stiffness.When the pylon stiffness is smaller,the antiskid safety factor of the main cable increases with the increase of the sag-span ratio of top cable,while the stiffness of bridge pylon is larger and the sag-span ratio of bottom cable is smaller,the antiskid safety factor of main cable first increases and then decreases with the increase of the sag-span ratio of top cable.(3)Compared with the traditional suspension bridge,the deformation of the stiffening girder and the antiskid stability of the main cable of the bridge are less affected by the stiffness of the pylon,and the feasibility range of the pylon stiffness is much larger than that of the traditional multi-span suspension bridge.(4)The steel consumption of the double-cable suspension bridge is basically the same as the traditional cable system,the steel consumption of the main cable decreases with the increase of the sags of the top and bottom cables.(5)The appropriate sag span ratio of the bottom cable is 1/8-1/6,and that of the top cable is 1/14-1/11.When the stiffness of the pylon is smaller,the difference in sag between the top and bottom cables should be increased.