钢箱拱桥斜拉扣挂施工法拆索工序研究

Research on the cable removal procedure of the cable-stayed fastening construction method of the steel box arch bridge

斜拉扣挂体系钢箱拱桥拱肋合龙后需进行拆索工作,拆索时桥梁各构件均会产生应力变化从而影响结构安全性。为探究钢箱拱桥合理的拆索顺序及拆索时可能出现的极限不对称状态,以车田江大桥为实际工程背景,建立有限元模型,分别模拟四种拆索方案对拱肋应力及位移的影响。发现当从拱顶向拱脚依次拆索时,扣索索力的增幅最小;相反,若从拱脚向拱顶依次拆索,则会导致拱肋的竖向位移和应力极值达到最大。因此,从拱顶向拱脚依次拆索的方案最符合实际施工需求。采用Midas/Civil软件对几种极限不对称拆索状态进行模拟,结果表明:扣索、背索的拆除应尽量同步进行,以确保结构稳定。同时,两岸的拆索进度差异以及左右两幅的拆索进度差异都应控制在1束索以内,以减小对桥梁结构的不利影响。

The cable of the cable-stayed buckle-and-hang system needs to be removed after the arch rib is closed.Various changes will occur to the bridge components during cable removal,affecting structural safety.To explore the optimal cable removal sequence for a steel box arch bridge and the possible extreme asymmetric states during cable removal,this study used the Chetianjiang Bridge as a case study.A finite element model was established to calculate the effects of four different cable removal schemes on the arch rib.The results indicate that removing cables sequentially from the vault to the arch foot minimizes the increase in cable force.Conversely,removing cables from the arch foot to the vault results in the maximum vertical displacement and stress extreme values in the arch rib.Therefore,the most suitable sequence for meeting construction requirements is to remove the cables from the top of the vault to the foot of the arch.Using Midas/Civil software,several extreme asymmetric cable removal states are simulated and analyzed.The findings suggest that the removal of the backstay cables should be synchronized as much as possible to ensure structural stability.Additionally,the removal progress of the cables on both sides and the difference in removal progress between the left and right spans should be controlled within one cable bundle to minimize adverse impacts on the bridge structure.