六广河特大桥施工过程张拉索力优化分析

Optimization and Analysis of Tensioned Stay Cable Forces in Construction of Liuguang River Bridge

为保证平行钢绞线斜拉索的张拉精度及锚固性能,并提高张拉效率,以跨径为(242+580+242)m双塔双索面叠合梁斜拉桥——六广河特大桥为例,对斜拉索张拉方案进行优化。原方案以消除结构自重为主,兼顾结构受力,但需反复微调,耗时长且不利于锚固安全;优化方案提高了第二次张拉的索力值,减小当前节段湿接缝压应力储备,以控制下一节段钢主梁拼装时当前节段桥面板及湿接缝应力不超限为目标,并将第三次张拉调整时的单根张拉法改为大吨位千斤顶整体张拉。有限元计算及实施效果显示:采用优化后的张拉方案,施工过程及成桥后主梁应力及线形、斜拉索索力及桥塔偏位均满足规范要求,相对于原方案工期提前40d。

To ensure the tensioning accuracy and anchoring perform ance of the parallel steelstrand stay cables and to im prove the tensioning efficiency, the Liuguang River B ridge, a com positegirder cable-stayed bridge w ith double pylons, double cable planes and w ith span arrangem ent（242 ＋ 580 ＋ 242） m , was cited as an exam ple and the schem e for tensioning of the stay cables ofthe bridge w as optim ized. In the original schem e for tensioning of the cables, the dead w eight ofthe structure w as rem oved m ainly w hile at the sam e tim e, the force conditions of the structurew ere considered. T he schem e required the repeated fine adjustm ent of the cables, was tim e-consuming and w as even not advantageous to the anchoring safety. In the optim ized schem e, the forcevalues of the cables to be tensioned for the second tim e w ere raised and the com pressive stress reservationof the w et joint of the present segm ent w as reduced. T he controlling of the deck slab andw et joint stresses of the present segm ent w ithin the lim it range at the tim e the successive segm entof the steel m ain girder w as being assem bled w as taken as the target and the single cable tensioningm ethod at the tim e the cables w ere tensioned and adjusted for the third tim e w as accordinglychanged into the heavy load integrally tensioning. T he finite elem ent calculation and the im plem entationeffect of the optim ized schem e show s th at w ith the optim ized schem e, the stresses and geometric shapes of the m ain girder in the construction and of the com pleted bridge, the cable forcesand the pylon offsetting can all m eet the relevant requirem ents in the codes. Com pared to the originalschem e, 40d of the construction tim e schedule was shortened.