多塔悬索桥主缆与鞍座抗滑解析计算方法

Analytic Method for Calculating Anti-slip Safety Factor Between Main Cable and Saddle in Multi-tower Suspension Bridge

为指导多塔悬索桥初步设计时参数取值,提出了一种多塔悬索桥中塔主缆与鞍座抗滑安全系数的解析计算方法。将主缆在纵桥向等效为一系列弹簧,通过研究最不利加载工况下活载引起的桥塔两侧主缆内力变化,给出了鞍座两侧主缆松紧比的解析公式,并据此求得主缆抗滑安全系数。建立四塔及五塔有限元模型对提出的公式进行了验证,给出了通过恒活载比值、主缆垂跨比确定桥塔刚度上限的图表,分析了桥塔刚度、恒活载比值以及主缆垂跨比等设计参数对主缆抗滑安全性的影响。结果表明:采用提出的公式计算主缆鞍座抗滑安全系数精度较高;活载与恒载比值、塔缆刚度比值对抗滑稳定性影响较大,垂跨比对于主缆抗滑的影响取决于桥塔刚度。

In order to guide the preliminary design of multi-tower suspension bridge in selecting parameter values,an analytic method for calculating safety factor of main cable slip on saddle was proposed.The main cables were equivalent to a series of springs in longitudinal direction.Analytic formula was deduced for calculating ratio of cable tension on both sides of the tower through investigating the internal force change of the main cable brought by live load under the most unfavorable load case,so the anti-slip safety factor of main cable can be obtained.The FE models of suspension bridges with four towers and five towers were established to verify the proposed formula.Some charts used for determining upper limit of stiffness of the bridge tower were given through sag-to-span ratio and ratio of live load to dead load.The influences of tower rigidity,sag-to-span ratio as well as ratio of live load to dead load on cable sliding stability were analyzed.The results show that the proposed method has a satisfied accuracy in calculating antislip safety factor of main cable on saddle,the ratio of live load to dead load and ratio of tower rigidity to cable stiffness have great influence on anti-slip stability of the main cable,and the effect of sag-to-span ratio on cable sliding depends on the tower rigidity.