大跨径混合梁斜拉桥全桥更换斜拉索顺序的研究

Research on the Cables Replacement Sequence of Long Span Cable-stayed Bridge with Hybrid Girder

为研究混合梁斜拉桥斜拉索更换对桥梁结构内力和位移的影响,找到大跨径混合梁斜拉桥的最优换索顺序,本研究以主跨为360 m的广州鹤洞大桥换索工程为依托,以节省工期,确保换索过程结构安全为目标,开展组合式换索顺序的研究。首先建立了全桥精细化有限元模型,确定了桥梁换索前的基准状态,并验证了其正确性;然后根据已确定的由长索到短索的换索原则,以一次对称更换单塔同一索号的一对索为基础方案,进行施工过程仿真分析,在此基础上提出了一种将全桥斜拉索按照长索区、中长索区及短索区分类的优化思路;最后在各索区选取典型索为研究对象,采用增量法对比分析了不同卸索方案下结构关键参数的变化情况。在兼顾施工难度、双塔相互影响等因素影响的前提下,确定了全桥组合式换索顺序的建议方案:长索区按基础方案执行,中长索区优化为双塔反对称一次更换4根斜拉索方案,短索区优化为全桥一次更换同一索号的8根斜拉索方案。由此全桥换索循环由基础方案的72次优化为32次,确保了桥梁换索过程中的结构安全,并大大缩短了工期。

In order to study the influence of cable replacement on structural internal force and displacement of hybrid girder cable-stayed bridge,and to find the optimal replacement sequence of cable-stayed cables of long span cable-stayed bridge,in the paper,based on the cables replacement project of Guangzhou Hedong Bridge with 360 m in main span length,and aiming to save time and ensure the structural safety of cable replacement process,the combined cable replacement sequence is studied.Firstly,a refined finite element model of the bridge is established,and the reference state of the bridge before cable replacement is determined,and its correctness is verified.Secondly,according to the confirmed principle of cable replacement from long cable to short cable,the construction process simulation analysis is carried out based on a symmetrical replacement of a pair of cables with the same cable number in a single tower.On this basis,a kind of classification optimization idea is proposed that all stay cables of the bridge are classified into long cable area,middle and long cable area and short cable area.Finally,taking typical cables in each cable area as objects,the increment method is used to compare and analyze the changes of key structural parameters and adjacent cable forces under different cable unloading schemes.Considering the factors such as construction difficulty and mutual influence of the two towers,the suggested scheme of combined cable replacement sequence of the whole bridge is determined as follows:the long cable area is implemented according to the basic scheme.The middle and long cable area is optimized to antisymmetrically replace four stay cables at a time for the two towers,and the short cable area is optimized to replace eight stay cables of the same cable number at a time for the whole bridge.Therefore,cable replacement cycle of the bridge is optimized to 32 times from 72 times in the basic scheme,and the construction duration can be greatly shortened.