一种减少多塔悬索桥塔顶不平衡力的方法

An effective method to reduce the unbalanced force on top of towers of multi-tower suspension bridges

针对多塔悬索桥塔顶不平衡力过大、刚度下降、塔底弯矩及剪力明显增大等缺陷,本文提出一种新的解决方法。通过新增凸杆、斜腹杆及带节点板索夹等构件,形成新的悬索结构体系,其结构布置为:凸杆以塔为中心对称布置,与梁连接后作为桁架的下弦杆;主缆承担全部恒载后获得重力刚度,作为上弦杆;通过斜腹杆将上下弦杆连接形成桁式结构以抵御活载。该结构的承载理念是以传统悬索桥结构形式承担恒载,以桁架结构形式承担活载,既保留了传统结构承载力大的优点,又具有桁式结构刚度大的优点,从而有效减少结构的变形及不平衡力。本文以主跨为1 020 m的三塔双跨双线铁路桥为例,通过有限元方法分析表明:在用钢量同等或增加不多的前提下,多塔悬索桥的塔顶不平衡力大幅度减少,结构刚度明显提高,因此其特别适用于高铁或重载铁路桥梁。

In view of the defects of multi-tower suspension bridges, such as excessive unbalanced force at the top of tower, decreasedstiffness, obvious increase of bending moment and shear force at the bottom of tower and so on, a new method is proposed to solve them.In this method, the new suspension structure system is formed by adding convexbars, diagonal web members and cable clamps with gusset plates.The structural arrangement is as follows: the convex bars are used as the lower chords when they are symmetrically arranged with the towers as the center after connecting with the girder;the main cable is used as the top chord when it obtains gravity stiffness after bearing all the dead load;the upper and lower chords are connected by diagonal web members to form a truss structure to resist the live loads.The bearing concept of the structure is that the traditional suspension bridge is used to bear the dead loads and the truss structure is used to bear the live loads.It not only retains the advantages of the traditional structure with large bearing capacity, but also has the advantages of truss structure with large stiffness, so as to effectively reduce the deformation and unbalanced force of the structure.Taking the three-tower double-pan double-track railway bridge with main span of 1 020 m as an example, the finite element analysis shows that under the premise of the same or little increase of steel consumption, the unbalanced forces on the top of the towers of the multi-tower suspension bridge are greatly reduced and the structural rigidity is obviously improved, so it is especially suitable for high-speed railway or heavy-duty railway bridges.