三塔以上悬索桥关键力学行为及结构成立特征

Key mechanical behaviors and structural establishment characteristics of suspension bridge with more than three pylons

为探究三塔以上悬索桥在不同跨径及桥塔数目时的力学行为和成立特征,建立了主跨径为500~1500 m、桥塔数目为3~8的24个悬索桥计算模型,明确了竖向刚度及主缆抗滑的最不利简化布载模式,分析了汽车荷载和温度荷载作用、结构振型基频以及颤振临界风速,探讨了中塔纵向刚度对结构成立特征的影响.结果表明:单主跨及单侧简化满载可分别用于最不利竖向挠度及抗滑安全分析;加劲梁竖向挠度仅在桥塔数目由3增至4时存在明显跃升;抗滑安全性对桥塔数目变化不敏感,但随主跨径的增加而显著提高;加劲梁温致纵向变形较大,可通过优化塔梁约束体系加以解决;桥塔数目奇偶性影响结构正/反对称横弯的次序,主跨径增加会导致各振型基频及颤振临界风速显著减小;三塔以上悬索桥中塔效应更为突出,缆鞍间摩擦系数取值为0.3时结构成立空间大幅增加.

To investigate the mechanical behaviors and establishment characteristics of suspension bridges with more than three pylons(SBMTP)for different spans and different numbers of pylons,24 calculation models for the suspension bridge with the main span of 500 to 1500 m and the pylon number of 3 to 8 were built.The most unfavorable simplified loading modes of the vertical stiffness and the anti-slip of the main cable were clarified.The actions of the vehicle and temperature loads,the structural modal shapes and fundamental frequencies,and the flutter critical wind speeds were analyzed.The effects of the longitudinal stiffness of the mid-pylon on the structural establishment characteristics were discussed.The results show that the most unfavorable vertical deflection and anti-slip safety can be analyzed according to the simplified full-loading on single main span and single side,respectively.The vertical deflection of the stiffening girder grows significantly only when the pylon number increases from 3 to 4.The anti-slip safety of the main cable is not sensitive to the number of the pylons,but increases significantly with the increase of the main span.The temperature-induced longitudinal deformation of the stiffening girder is large,which can be solved by optimizing the pylon-girder restraint system.The parity of the pylon number affects the order of symmetric and anti-symmetric lateral bending.Increasing the main span can reduce the fundamental frequency of each modal shape and the flutter critical wind speed.The mid-pylon effect of the SBMTP is more prominent.When the cable-saddle friction coefficient is taken as 0.3,the structural establishment scope can be significantly increased.