拉索损伤下大跨径斜拉桥易损性分析

Vulnerability evaluation of cable stayed bridge considering cable damage

为研究拉索不同程度损伤下的大跨径斜拉桥易损性,以四川合江长江二桥为工程背景,结合有限元数值分析方法对结构进行力学性能分析,选取全桥7对有代表性的斜拉索,分析拉索、桥塔与主梁在拉索不同程度损伤下的力学性能变化,揭示了斜拉索应力安全系数、桥塔应力安全系数以及主梁屈曲安全系数和主梁应力安全系数在拉索不同损伤工况下的变化规律。基于有限元计算结果,采用交叉效率数据包络分析方法对拉索损伤工况下的斜拉桥易损性进行分析,并以各拉索在不同损伤程度下的截面面积以及等效弹性模量作为投入参数,上述4类安全系数作为产出参数。此外,为体现评估重点并考虑各项参数差异过大对评估结果产生的不利影响,将熵权层次分析法与交叉效率数据包络分析法结合并加以改进,通过综合决策和原始数据评价计算获得4类安全系数分项权重,从而确定易损拉索的位置。研究结果表明:长索损伤后引起的拉索应力、主梁弯矩及桥塔位移的变化幅值更明显;随着损伤拉索长度的增加,安全系数下降幅值明显增大,边墩拉索和中跨跨中拉索对维持结构整体性能有重要作用;结构对中跨拉索损伤敏感性高于边跨拉索损伤,长索损伤易损性高于短索。该研究可为服役斜拉桥重点区域监测和结构安全性评定提供科学依据和参考。

The vulnerability of long-span cable-stayed bridges under different degrees of cable damage was investigated based on the Second Hejiang Yangtze River Bridge in Sichuan Province. Finite element(FE) method was used to analyze the mechanical performance of structures. Seven pairs of representative cables of the entire bridge were selected to investigate the mechanical performance changes of cables, pylons, and main beams under various levels of cable damage. The variation laws of cable stress safety factor, bridge pylon stress safety factor, buckling and stress safety factors of main beam under different damage degrees were revealed. Based on the results of FE method, the cross-efficiency data envelope analysis method was used to determine the location of vulnerable cables. The cable section area and equivalent elastic modulus were regarded as the model input parameters and the four safety factors as output parameters. Combined with the entropy analytic hierarchy process method, the partial weights of the four safety factors can be obtained by decision-making and raw data evaluation, which can reflect the evaluation focus and weaken the adverse impact induced by the difference between different type values. The results show that long cable damage leads to more obvious variation amplitude of cable stress, main girder bending moment and pylon displacement. With the increase of the length of the damaged cable, the reduction of safety factor increases significantly. The cables near the side pier and middle span have a significant effect on the structural performance. The sensitivity of structure to mid span cable damage was higher than that of side span cable damage, and the damage vulnerability of long cable was higher than that of short cable. It can provide a reference for the critical areas monitoring of cable-stayed bridges. 1 tab, 11 figs, 23 refs.