The Dalian North Bridge, opened to traffic in 1987, is a three-span simply-supported steel truss girder suspension bridge with a main span of 133 m.The main cables are anchored by gravity anchors.The inspection conducted in 2015 showed that severe downwarping occurred in the bridge deck alongside with other deteriorations, including the offsetting of main cable saddles and splay saddles.Based on the characteristics of the deteriorations and the related causes, a scheme, incorporating structural de-loading, main cable tensioning and hanger cables replacement, was proposed.To study the rationality of the scheme and further optimize the scheme, the finite element model of the overall bridge was established, to calculate and analyze the structural de-loading modes as well as the effects of main cable tensioning amounts on the bridge deck geometry, structural internal forces and the gravity stiffness of the main cables.According to the calculation, the overall bridge should be de-loaded by 5 kN/m and the main cables be tensioned by 100 mm, along with the hanger cable replacement to make the bridge deck reach its ideal alignment.The scheme after optimization can effectively reduce the downwarping deterioration of the bridge deck, improve the load bearing condition of the structure and enhance the load bearing capacity of the overall bridge.%大连北大桥为主跨133 m的三跨简支钢桁架重力式地锚悬索桥,1987年建成通车,2015年检测发现该桥桥面出现严重的下挠,并伴随有主索鞍、散索鞍偏位等病害.基于病害及其产生原因,提出结构减载、主缆张拉及吊索更换的方案.为研究该方案的合理性并进一步进行方案优化,采用有限元软件建立全桥模型,计算分析结构减载方式、主缆张拉量对桥面线形、结构内力、主缆重力刚度的作用效应.结果表明:优化后的方案为全桥减载5 kN/m、主缆张拉100 mm,结合吊索更换使桥面达到理想线形;优化后的维修方案可以有效地消除桥面的下挠病害,改善结构受力状况,提高全桥的承载力.
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