双塔钢桁斜拉桥结构强健性计算方法

Calculating method of structural robustness of double-tower cable-stayed bridge with steel truss girder

为了确保双塔钢桁斜拉桥的结构强健性,依托新疆果子沟大桥,基于现场结构试验,开发了全方位多点温度补偿系统,测量了特定加载工况下钢桁主梁应变、挠度与斜拉索索力增量,确定了钢桁主梁与斜拉索重要构件的具体位置;基于试验结果,借鉴广义结构刚度理论,采用桥梁结构有限元模型分析了斜拉桥弦杆与斜拉索的重要性系数,研究了桥梁最不利破坏模型。研究结果表明:各工况下钢桁主梁应变实测数据规律性较好,钢桁主梁应变与挠度的实测值与理论计算值的比值小于1.0,表明主梁承载能力与抗变形能力符合设计要求,具有足够的安全储备;主梁在各工况下的最大挠度均发生在中跨跨中,达到237mm,具有较强抗变形能力;斜拉索索力增量实测值与理论计算值的比值小于1.0,表明斜拉索具有一定的安全储备;钢桁主梁控制截面处弦杆与特定斜拉索为重要性系数较高的构件,斜拉索的重要性系数大于弦杆的重要性系数,其中弦杆的重要性系数分布集中于主塔附近与中跨跨中;通过斜拉索重要性系数的分布可知单根斜拉索的破损不会造成整体结构的坍塌,但多于2根斜拉索失效可能会导致整体结构的连续倒塌;主跨最长斜拉索和中跨跨中、边跨支座处与靠近主塔处弦杆失效对于整体结构较为不利。

In order to ensure the structural robustness of double-tower cable-stayed bridge with steel truss girder,all-round multipoint temperature compensation system was developed based on the Xinjiang Guozigou Bridge and field structure test.The strain,deflection and cable force increment of steel truss girder were measured under specific loading conditions,and the specific locations of important components of steel truss girder and stay cables were determined.Based on the experimental result and the generalized structural stiffness theory,the robustness importance factors of cables and chords were analyzed by using the finite element model of bridge structure,and the most critical failure model of cable-stayed bridge was studied.Study result shows that the regularities of the measured data of steel truss girder strain under various working conditions are good,and the ratios of measured and theoretical values of strain and deflection are less than 1.0,so the bearing capacity and anti-deformability of steel truss girder meet the design requirements,and the girder has sufficient safety reserve.The maximum deflection of the girder under eachloading case is at the middle of main span and can reach to 237 mm,so the girder has strong antideformability.Because the ratios of the measured increments of cable force and theoretical values are less than 1.0,the stay cables have safety reserve to a certain extent.The chords at control sections and the specific stay cables of the girder have higher importance factors,the factors of stay cables are larger than the values of the chords,and the importance factor distributions of the chords concentrate in the middle of main span and nearby areas of main pylons.According to the distributions of importance factors of stay cables,the damage of single stay cable can causes the collapse of overall structure,and the failures of more than two stay cables will result in the progressive collapse of entire structure.The failures of the longest stay cable of main span and the chords at its middle,as well as the chords at the supports of side spans and near the main towers,are more adverse to the entire bridge.