斜拉桥监测索力的时空评估方法

Temporal and spatial evaluation method of monitoring cable forces for cable-stayed bridge

摘要:

为更准确地反映监测索力的综合状态，提出一种考虑索力时间和空间特征的评估方法.借鉴桥梁风险矩阵决策方法，将时间指标和空间指标置于一个矩阵中进行评估决策.时空评估等级分为四级，分别为蓝色Ⅰ级、黄色Ⅱ级、橙色Ⅲ级和红色Ⅳ级.时间指标同时考虑索力变化速率和变化幅度，其中，索力变化速率通过时间序列分析得到，变化幅度通过索力变化率绝对值计算得到.空间指标主要反映由偏载、单索损伤等因素造成的斜拉桥两侧索力的偏差程度，采用Canberra距离表征.以南京长江三桥7 a监测数据为例，对20根长索进行索力时间和空间的综合评估，得到群索评估表和评估等级分布图.结果表明：监测索力符合时间序列特性，可采用一元线性回归模型提取趋势项；斜拉索的时空评估等级在Ⅱ级及以上，主要原因有索力变化趋势过快和上下游索力差异较大.评估分布图为斜拉索的人工检查提供更有针对性的指导.

Abstract:

To investigate the comprehensive state of cable forces, an evaluation method considering the temporal and spatial characteristics of the cable forces was proposed. Using the bridge risk matrix decision-making method, the time index and spatial index were taken into a matrix for evaluation and policy decision. The spatial and temporal evaluation levels are divided into four levels: blue grade Ⅰ, yellow grade Ⅱ, orange grade Ⅲ and red grade Ⅳ. Time index considers both the change rate and the amplitude of the cable forces, in which the change rate of cable force was obtained by time series analysis, and the amplitude of cable force was obtained by absolute value of change rate of cable force. Spatial index mainly reflects the deviation degree of cable forces on both sides of cable-stayed bridge caused by unbalance loading and single cable damage, and was characterized by Canberra distance. Taking 7 years of monitoring data from Nanjing No.3 Yangtze River Bridge as an example, twenty long stay cables were evaluated by the temporal and spatial comprehensive evaluation method. The group cables evaluation grade table and evaluation grade distribution map were formed. Results show that monitoring cable forces conform to time series characteristics, and a linear regression model can be used to extract trend terms. The temporal and spatial evaluation levels of the cables are grade Ⅱ and above, and the main reasons are excessively fast change rate of cable force and great differences between the upstream and downstream cable forces. The evaluation distribution map provides more targeted guidance for the manual inspection of stay cables.