悬索桥吊杆损伤的两阶段精细化诊断与性能综合评估方法

This project studies a two-stage approach of precise damage diagnosis and performance assessment for suspension bridge suspender cables from the level of structural components: i.e. the vibration-based damage diagnosis method and the defect reflective echo wave-based damage localization and quantification method of the local damage. Damaged suspender cables can be diagnosed but further performance assessment cannot be conducted based on the first method; the second technique can be used to accurately assess the local damage on the suspender cable, but it is costly and not efficient to be used in large number of suspender cables one by one. This project combines the two techniques and the combination makes best use of their advantages and bypass the disadvantages, and the main contents are listed as follows: (1) to develop a damage feature in time-domain that can indicate changes in responses of suspender cables before and after damage and then extract a damage index; to investigate the sensitivity of the proposed method on damage and the length of suspender cables; to investigate the anti-noise ability; to investigate the influence of temprature change and the effective measure of eliminating the influence; (2) finite element modeling of the suspender cable; to study the optimal sensor placement method of excitation and receiving sensors; to analyse the multiple modes and dispersion characters of the guided wave; to investigate the propagation property under the interreaction of stress, environment and contact effect; to localize and quantify the local damage through analysis of defect reflective echo waves with high level of noise; (3) to assess the performance of the damaged suspender cable based on overall information of the cable and local information of the defect; (4) to validate the proposed method based on experiments of a suspension bridge model. The proposed method in the present project doesn't require a finite element model of the suspension bridge, and it works easily and fast with low cost, which provides a new idea with theoretical and experimental support for accurate damage detection and safety assessment of the suspender cables.

本项目从构件层次研究吊杆的两阶段精细化诊断与性能评估：基于振动信息的损伤诊断和基于损伤回波的局部缺陷定位和定量。前者可快速初判损伤吊杆但难以评估局部缺陷；后者可评估局部缺陷但吊杆根数多致效率低。本项目联合这两种方法使其扬长避短，主要内容有：(1)在时域里构造反映吊杆损伤前后振动响应改变的损伤特征函数进而构建损伤诊断指标；提出方法对损伤和吊杆长度的敏感性研究；抗噪声水平研究；受温度的影响及有效的消除措施研究；(2)吊杆精细化建模；发展激励和接收线圈的优化布置方法；吊杆导波多模态以及频散特性分析；应力、环境、钢丝间接触效应耦合下导波传播特性研究；分析高背景噪声下损伤回波进而对局部缺陷定位和定量；(3)基于损伤吊杆整体信息和局部缺陷信息的性能评估；(4)基于悬索桥模型的试验验证。本法不需悬索桥数值模型、方便快速、成本低廉，为吊杆检测和评估提供了新思路及理论与试验支撑。

本项目研究了悬索桥结构的关键受力构件吊杆等重要基础子结构的损伤诊断、性能分析或评估方法。提出了5种具有损伤敏感性高、无需数值模型、抗噪性强等优点的损伤实时识别(监测)/定期识别(检测)方法，较大程度地解决/减小了损伤识别面临的受噪声干扰大、对数值模型精度依赖大、对损伤不敏感3个局限。基于损伤回波分析对钢杆局部损伤进行了定位和定量。提出了基于长期监测数据的高铁列车-桥-环境作用耦合下高铁桥梁刚性吊杆的振动空间特征、振动特性概率统计特征及其与环境的相关性等长期规律分析方法。基于悬索桥主缆不同施工期的模拟与风洞试验，建立了两种施工方式下悬索桥主缆施工期弛振可能性与其施工进度的关系。本项目为保障悬索桥等大跨桥梁关键构件的诊断、评估与安全运营等提供了理论与方法支撑。