三塔悬索桥中塔适宜刚度

Stiffness Value of the Middle Tower in Triple-tower Suspension Bridges

为了明确三塔悬索桥的中塔刚度取值范围,以主缆与中塔鞍座的抗滑安全系数和加劲梁挠跨比为控制指标,推导了三塔悬索桥中塔刚度上、下限值解析公式,建立有限元模型验证了公式的有效性,最后分析了垂跨比、恒活载比值、跨径等主要设计参数对中塔刚度取值的影响.结果表明:理论值与有限元值符合良好,可在初步设计阶段指导多塔悬索桥的中塔选型;恒活载比值对中塔刚度取值的影响较大,当恒活载比值约大于6. 5时,才存在合适的中塔刚度使三塔悬索桥同时满足结构变形和主缆抗滑的要求;主缆垂跨比主要影响中塔刚度上限值,且对上限值的影响与恒活载比值有关;中塔刚度取值范围随着主跨跨径增大而增大.

To make clear the value range of the central tower stiffness of the triple-tower suspension bridge,with the anti-skid safety factor and the deflection-to-span ratio of the main cable as the control indexes,the expressions for the upper and lower limits of middle tower stiffness of the triple-tower suspension bridges were deduced,so as to obtain the analytical algorithm for an appropriate stiffness of the middle tower.The formulas were verified by finite element models and the results showed good agreement.The formulas can be used to quickly select the type of middle tower for a multi-span suspension bridge at the initial design phase.Effects of major design parameters on the stiffness value of the middle tower were also studied.The research shows that the ratio of the dead load and the live load impose a significant effect on the tower stiffness value,and only when the ratio of the dead load and the live load is greater than 6.5,the middle tower stiffness can simultaneously meet the requirements of structural deformation and skid resistance of the cable.Effect of sag-to-span ratio to the middle tower stiffness depends on the ratio of the dead load and the live load.With the increment of span length,the value range of the middle tower stiffness increases.