基于非接触振型测试及压电阻抗技术的桥梁索结构状态识别

There are huge number of existing bridges consists of stay cable, suspender, tied cable or prestressed tendons, which however are facing the challenges of severe damage, cable replacement and possible collapse of bridge. To meet the requirement of the structural safety of cable structure during the service life, the study places emphases on the condition identification of cable structure considering complex boundary condition. The study proposes the theories for dynamic modeling of cable structure under complex boundary condition such as elastic end condition, multi dampers or intermediate supports and its explicit solution for cable force. An innovative modal shape based method independent of boundary condition is proposed for the tension estimation of tied cable with multi intermediate supports and stay cable with multi dampers, which in some sense avoids the difficulties in dynamic modeling and explicit solution of the cable structure with complex end conditions, moreover,an innovative non-contact photogrammetry-based technologies are employed to identify the mode shape of the cable for further estimation of the cable force; A PZT impedance-based method is presented to measure the tension of the prestressed tendons by constructing the relationship between the tension and the PZT impedance; The numerical simulation, three experimental model tests and the field tests on three cable-stayed bridges and an arch bridge with tied cables are conducted to establish a condition identification method for bridge cable structures such as stay cable, suspender, tied cable, and prestressed tendon under complex boundary condition. The objective of the study is to remedy the shortage in tension force measurement and evaluation of cable structure, and to improve the structural safety and durability of the cable system.

我国服役的索结构桥梁数量庞大，索结构的损伤、破断、更换以及由此造成的安全问题尤为突出。本项目紧密结合索结构桥梁服役期对运营安全的迫切需求，旨在建立考虑复杂边界条件的索结构状态识别理论。研究具弹性边界、设置多个减振阻尼器、带多个中间支撑等复杂边界条件的索结构动力学建模与索力的显式求解；提出独立于边界条件，基于模态振型信息的索结构状态识别方法，避免了复杂索结构建模及索力显式求解的困难，并发展基于非接触摄影测量技术的模态识别技术；针对运营期预应力测试方法的不足，通过建立张力与压电阻抗之间的定量关系，提出了基于压电陶瓷（PZT）阻抗分析技术的预应力测试方法。通过仿真实验、室内模型试验与现场实桥试验，建立涵盖桥梁工程中斜拉索、吊杆、系杆、预应力筋等重要构件在复杂边界条件下的状态识别理论与方法。这对于弥补现有桥梁索结构状态识别方法的不足，提高索结构的安全耐久性能，具有重要的科学意义与工程实用价值。

为建立考虑复杂边界条件的索结构状态识别理论，本项目主要开展了以下三个方面的工作：（1）研究具复杂边界条件的索结构动力学建模与索力的显式求解。建立了考虑抗弯刚度（模型A）与不考虑抗弯刚度（模型B）的两种拉索-双阻尼系统模型，构造了相应的无量纲参数，分析了各参数对模型A动力特性的影响，并对模型A与模型B在索力识别方面的适用范围进行说明；建立了拉索-单阻尼以及拉索-单支撑系统模型，引入奇异摄动相关理论对所建立模型的动力学方程进行求解，构造了相应的无量纲参数，分析了各参数对两种模型动力特性的影响，验证了奇异摄动理论在求解动力学方程方面的有效性，为频率法索力识别理论提供了一种求解方式上的选择；建立了拉索-多支撑系统模型（亦可退化为拉索-单支撑、拉索-双支撑等系统），结合动力刚度法与PSO算法提出了具有多个支撑的索结构的张力识别方法，验证了这一组合方法进行索力识别的有效性。（2）研究基于索结构模态信息的索力识别理论，该方法不必考虑拉索的复杂边界条件。应用数字图像相关（Digital Image Correlation, DIC）技术，实现了基于整像素算法FTCC及亚像素匹配算法IC-GN的视频多点位移实时测试程序，通过频域分离技术（FDD）获得索结构的模态及驻点信息，然后选择任意两驻点间的索段建立等效模型（单跨受拉铰接梁），最后根据等效模型的张力计算公式求得索力。基于索结构模态信息的索力识别方法已在室内实验以及实桥实验中得到应用，测试精度完全可满足工程要求。（3）研究了基于压电阻抗技术的预应力筋张力识别的可行性。通过实验建立了压电阻抗与预应力筋张力大小之间的关系，但这一关系受PZT压电陶瓷片粘贴位置、粘贴质量、预应力筋锚固条件等各种因素影响，需要事先进行标定，而且对于高应力状态下的索力变化，压电阻抗对之并不敏感，对于实际工程有一定应用困难。