自锚式结合梁悬索桥新型先缆后梁施工方法研究

Study of Technique of Erecting Cables Before Constructing Girder for Self-anchored Suspension Bridge

当自锚式结合梁悬索桥跨度较大且跨越通航河流或深谷时,若采用传统方法施工,临时设施多、工期长、造价高,鉴于此,以武汉市江汉六桥(主跨252m的自锚式结合梁悬索桥)为背景,提出一种新型先缆后梁施工方法。该方法在钢梁顶推完后浇筑锚跨混凝土梁,架设主缆,张拉吊索,进行一次体系转换,形成钢梁悬索桥,然后利用主缆的承重能力架设预制桥面板。从施工辅助设施、对通航孔的影响以及结构受力等方面,对新型先缆后梁法与传统先梁后缆法进行对比,采用有限元软件对施工过程和成桥状态受力进行对比分析。结果表明:新型先缆后梁施工方法在施工经济性和安全性上有较大优势;2种方法成桥状态受力有一定差别,但成桥后结构受力均满足要求。江汉六桥采用新型先缆后梁施工方法施工,施工过程及施工完成后,主桥线形、内力均满足要求,且造价较低,验证了该方法的科学性、适用性。

When a self-anchored composite girder suspension bridge has long spans and crosses navigational river or deep valley, the conventional construction method would not be a proper choice, due to the large number of construction equipments, long construction schedule and high costs needed.The Jianghan Six Bridge in Wuhan, a self-anchored composite girder suspension bridge with a main span of 252 m, was taken as the study background to verify a new construction method of erecting cables before the construction of the girder.In this method, the concrete beams in the anchor span were cast after the incremental launching of the steel girder.Then the main cables were installed, the hanger cables were tensioned, and the structure experienced the first system transformation to be a steel girder suspension bridge.The prefabricated bridge slabs were subsequently installed with the support of the main cables.The construction method of erecting the main cables before the construction of the girder was compared with the conventional method from aspects of auxiliary construction facilities used, the influence of the construction on the navigation and the load bearing capacity of the structure.The finite element software was used to carry out comparative analysis of the construction process and load bearing performance of the bridge in the completed bridge state.The results showed that the new construction method of erecting the main cables before the construction of the girder is superior to the conventional method in terms of economy and safety.Although the load bearing capacity of the bridge in the completed bridge state changes due to different construction method chosen, both the methods can ensure that the load bearing capacity of the bridge meet the requirements.The Jianghan Six Bridge was constructed by the method of erecting the main cables before the construction of the girder.When the construction was completed, the geometry and internal forces of the main bridge met the requirements and the construction cost was lower, which proved that the method was scientific and feasible.