基于群索索力域的斜拉桥结构性能状况评估

针对目前依据单根斜拉索索力值变化评估斜拉桥运营健康状态的不足,提出一种基于群索索力域映射斜拉桥性能状况的方法。该方法基于蒙特卡罗法模拟获得斜拉桥群索索力域,在实测索力与群索索力域间做相异度最小寻值,根据桥梁结构不同的极限状态定义评估阈值。以国内某已建24年的大跨径预应力混凝土斜拉桥为工程实例,基于近6年(2013~2018年)实测索力数据,依照提出的新评估方法与传统评估方法对主梁结构性能状态进行评估。结果表明:传统评估方法仅得出2013年单根索力变化幅值超限的结论;新评估方法得出2013年、2018年主梁跨中截面存在消压风险,需要持续跟踪关注。该方法可定量、直观地分析评估群索索力变化对桥梁结构受力状况的影响,为桥梁的科学管养决策提供依据。

Evaluation of Structural Performance of Cable-Stayed Bridge Based on Threshold Cable Forces of Grouped Cables

The way of comparing the variation of cable forces of individual stay cables to evaluate health condition of cable-stayed bridge in service still has disadvantages.In this case,an evaluating method based on the threshold cable forces of grouped cables to reflect the working condition of the cable-stayed bridge is proposed.The method can be used to gain the threshold values of cables forces of grouped stay cables based on the Monte Carlo simulation,find out the minimum dissimilarity degree between the measured cable forces and the threshold values of grouped stay cables,and evaluate the threshold values in accordance with the different ultimate limit states of the bridge structure.A long-span prestressed concrete girder cable-stayed bridge that has been in service for 24 years was taken as the background bridge.Based on the measured cable force data over recent six years(2013-2018),the structural condition of the main girder was evaluated using the proposed method and the traditional evaluation method.When the traditional method is used,the conclusion drawn is that the variation range of the cable forces of individual stay cables in 2013 exceeds the limit.When the proposed method is used,the results show that the midspan cross section of main girder faced decompression risk in 2013 and 2018,which demands continuous observation.The method can quantitatively and directly analyze and evaluate the effect of cable forces variation of grouped stay cables on the load bearing condition of the bridge structure,which can provide data support for the scientific maintenance of bridges.