悬索桥主缆初张力对成桥结构性能的影响

天津富民桥为单塔空间索面自锚式悬索桥,其主跨主缆由塔顶中点向两侧对称张开至桥面梁端两侧的锚碇,呈空间曲面状态。运用通用有限元分析软件ANSYS,对天津富民桥进行3种不同主缆空缆初张力条件下成桥过程的模拟计算,研究空间索面悬索桥主缆初张力对成桥结构性能的影响。研究结果表明:成桥时,主缆初张力越小,在结构自重作用下主梁底部应力、主缆张力也越小、主塔应力与锚碇应力也越小,主缆初张力的大小对成桥时吊索索力的大小及分布没有明显影响;在活荷载作用下,主缆初张力越小,悬索桥结构体系产生的主缆张力增量则越大,吊索索力增量也越大,即更多的荷载通过吊索传递到主缆,相应地主梁承担的荷载较小,主梁挠度、梁底纵桥向应力随主缆初张力的减小而变小。总之,主缆初张力越小,悬索桥结构体系的性能越佳。

Influence on the Performance of the Completion Structure by the Initial Tension of the Main Cable of the Suspension Bridge

Tianjin Fumin Bridge is a single-tower space cable plane and self-anchored suspension bridge.The main cables of the main span extend symmetrically at both sides from the midpoint of the tower top to the anchorage at beam ends on bridge deck,forming a spatial curved plane.Finite element analysis software ANSYS is employed to simulate the completion process of Tianjin Fumin Bridge under three different initial tension of the free cable.The influence is studied on the performance of the completion structure by the initial tension of the main cable of the suspension bridge with space cable plane.Research results show that upon the completion of the bridge,the less the initial tension of the main cable is,the smaller the stress at the bottom of the main girder and the tension of the main cable will be under the dead load of the structure.The stress of the main tower and the anchorage stress will be smaller too.The initial tension of the main cable has no distinct influence on the force and the distribution of the suspended cables upon the completion of the bridge.Under live load,the smaller is the initial tension of the main cable,the larger will be the increment of the main cable tension produced by suspension bridge architecture.The larger the increment of the suspended cable force will be too.That is to say,further load is transferred to the main cable through the suspended cable.Accordingly,the main cable bears smaller load,the deflection of the main cable and the vertical stress at the girder bottom will decrease along with the decrease of the initial tension of the main cable.In conclusion,the smaller the initial tension of the main cable is,the better the performance of the suspension bridge architecture will be.