基于桥梁挠度监测的斜拉桥拉索损伤识别预测函数法研究

Stay cables are the key tension members for a calbe-stayed bridge. Up to now, the damage of stay cables are primary in the diseases of cable-stayed bridges. How to master the cable damages in time and scientifically assess the health state of cables has an important theoretical significance and practical utility to guarantee the operation safety of a stayed-cable bridge. In this project, a new damage identification method for cables of calbe-stayed bridges based on deflection monitoring will be researched. The main research contents include: (1) to simulate and calculate the tension of cables and the deflection of the girder when cables of the cable-stayed bridges are in good or damaged condition under a variety of loads (including temperature and wind), to analyse the change rule of the deflection of the girder and the cable force with the variation of ambient temperature, wind, vehicle loads and the damage of cables, and to study the sensibility of the deflection on the damage of cables; ⑵ with support vector machine, to establish the predictive function whose independent variables are deflections of the girder, the ambient temperature and the loads, and dependent variables are the tension of cables; (3) to propose the judgment standard and methods for identifying whether stay-cables are damaged, and detecting the damage location and degree of cables, based on the deflection monitoring data of calbe-stayed bridges; (4) a cable-stayed bridge model test, to verify whether the stay cable damage identification method is effective. A new economic, practical and operability strong damage identification method can be provided for cable-stayed bridges management and maintain department to detect the cable damage, and judge which cable needs to be changed timely and accurately in this study. This method has extensive applied foreground.

对于斜拉桥而言，拉索是关键受力构件。在迄今发现的斜拉桥病害中，拉索出现损伤的病害占绝大部分。如何实时掌握斜拉索病害损伤，科学评估拉索健康状态，对保证斜拉桥运营安全具有重要的理论意义和实用价值。本项目拟研究一种基于桥梁挠度监测的斜拉桥拉索损伤识别新方法，主要研究内容包括：⑴模拟计算斜拉桥拉索损伤前后在多种荷载（含温度、风）工况下梁体挠度及索力，分析梁体挠度和索力随环境温度、风、车辆荷载、拉索损伤情况而变化的规律以及挠度对拉索损伤的敏感性；⑵采用支持向量机构建以实测梁体挠度、环境温度、风、车辆荷载为自变量，索力为因变量的预测函数；⑶提出基于梁体挠度监测数据识别斜拉索是否损伤、损伤位置和损伤程度的判决标准和方法；⑷斜拉桥模型试验，验证拉索损伤识别方法的有效性。本项目研究可为斜拉桥管理和养护部门及时、准确识别斜拉索损伤，决定是否需要换索提供一种经济、实用、可操作性强的新方法，具有广阔的应用前景。

对于斜拉桥而言，拉索是其关键受力构件。在迄今发现的斜拉桥病害中，拉索出现损伤的病害占绝大部分。准确识别拉索病害损伤，实时掌握拉索病害损伤发展变化情况，科学评估拉索健康状态，对保证斜拉桥运营安全具有重要的理论意义和实用价值。这也是工程界关注的重点和难点问题之一。.本项目研究了一种基于桥梁挠度监测的斜拉桥拉索损伤识别新方法。主要研究内容包括：⑴模拟计算斜拉桥拉索损伤前后在不同环境温度、不同荷载工况下梁体的挠度和索力，分析梁体挠度和索力随环境温度、车辆荷载和拉索损伤变化而变化的规律以及挠度对拉索损伤的敏感性；⑵采用最小二乘支持向量回归机（LS-SVR）构建以实测环境温度、车辆荷载为自变量梁体挠度为因变量的预测函数，并研究确定采用预测函数法进行桥梁健康状态评估的两级安全预警标准；⑶研究并提出基于梁体挠度监测数据识别拉索是否损伤、损伤位置和损伤程度的识别指标和方法；⑷斜拉索模型试验和武汉月湖桥（独塔斜拉桥）挠度监测与安全评估试验，验证拉索损伤识别方法的有效性。四项创新性成果：⑴模拟分析结果表明，斜拉桥在不同荷载工况下梁体挠度分布曲线在对应于损伤索锚固点处挠度变化幅度最大，临近拉索锚固点处挠度也均有明显增大，并且损伤索锚固点处的挠度随损伤程度增大而增大；⑵建立了基于挠度监测的桥梁结构健康状态评估预测函数法，提出了确定预测函数法中两级预警标准的方法，可实现桥梁结构健康状态的快速评估；⑶以各拉索锚固点处梁体挠度的最大改变率作为拉索损伤识别指标，采用SVM建立了损伤位置和程度识别模型，可准确识别出发生损伤的拉索位置和损伤程度，并具有良好的抗噪和泛化能力；⑷提出了一种通过测定斜拉索的垂度来确定索力的新方法—垂度法，并通过拉索模型试验验证了垂度法测索力的有效性和可行性。.本项目研究成果可为斜拉桥管养部门及时、准确识别拉索损伤，决定哪根索需要更换提供一种可靠且经济、实用、可操作性强的新方法，具有广阔的应用前景。