【作者】 雷小华；

【导师】 陈伟民；

【作者基本信息】 重庆大学 ， 光学工程， 2008， 博士

【摘要】 桥梁结构在服役期间受到各种因素的影响,其可靠性不断下降可能导致结构安全问题甚至桥毁人亡的重大灾害事故,使桥梁结构状态的安全监测一直受到学术界和工程界的高度重视。世界各国皆投入巨资进行研究,取得了一定成果并在各种特大型桥梁陆续试用。但桥梁结构状态监测技术仍然是一个未成熟、正在发展的新技术。而世界上桥梁种类繁多、结构各异,桥梁结构状态监测技术还存在众多亟待解决的科学与技术问题。其中,能较全面反映桥梁结构性能退化与失效的关键参数——变形/位移,是桥梁结构状态监测领域众多亟待解决的科学与技术问题的重要研究热点之一。大跨径拱桥结构外形美观、跨径大,在桥梁世界中占有一席之地。但它结构特殊、受力关系复杂、施工工艺难度大,导致其成为国内外桥梁重大垮塌事件的主要桥型之一。其次,大跨径拱桥其特殊的拱、梁组合结构,使得变形呈现多维度特点,迄今为止还没有一种较为理想的监测方法能够满足这一类桥梁变形/位移监测要求。因此,针对大跨径拱桥多维变形/位移监测技术展开研究,解决其关键技术问题,对于大型桥梁结构状态监测的整体技术发展具有重要的科学价值与应用前景。鉴于此,结合重庆市科技攻关项目重大专项“菜园坝大桥运行状态监测与健康诊断系统研究”,根据大跨径拱桥的结构受力与变形特点,提出了基于光电全站仪和光电式连通管的多维位移组合监测方法。研究了光电自动全站仪在主拱三维变形监测中存在的基准漂移问题与光电式连通管监测主梁的一维静态及准静态变形存在的液位振荡问题。从数学模型与监测系统两个方面进行了相互印证,最后将取得的研究成果实际应用于重庆菜园坝大桥。具体研究内容如下:①以大跨径系杆拱桥为代表,对大跨径拱桥桥拱和主梁等关键部位的结构受力与变形特点进行了分析;结合重庆菜园坝长江大桥的特点,提出了采用光电自动全站仪对桥拱进行三维静态位移变形监测、采用光电式连通管系统对梁体进行一维静态与准静态位移监测的多维位移变形监测的光电组合方法;还提出了利用轻轨列车的自重长期进行桥梁固定荷载条件下的位移监测思路。②为了避免光电全站仪在主拱圈三维位移监测中因通视限制导致的测量基准漂移,建立了全站仪基准漂移的三维模型,分析了全站仪基准漂移及其对观测点精度的影响;提出了采用两台或多台全站仪相互观测,继而实现全站仪基准漂移补偿观测的新方法。结合补偿观测方法的特点,研究了补偿大气条件对变形点观测精度影响的方法。还设计了适当的自动防护装置,使其能够在测量时自动打开,未测量时关闭,有效的防止雨水、粉尘等对棱镜镜头的污染。③为了突破原始连通管挠度监测方法的完全静态监测瓶颈,针对利用光电式连通管方法监测主梁挠度/线形的问题,分析了液位基准对监测精度的影响,重点研究了轻轨或火车等重载通过大跨径拱桥形成的准静态位移测量过程,建立了多连通管内液体振荡的力学模型,分析了液位振荡的内在规律,提出了改进的小波阈值去噪方法对含有液位振荡的位移信号进行滤波,以消除液位振荡对准静态位移测量的影响,并通过仿真计算证明了该方法的可行性。④为了满足大跨径拱桥多点、同步位移/线形监测要求,分析了连通管式光电液位传感器的信号变异问题,改善了硬件响应速度、采集频率;研制出了适用于桥梁静态与准静态位移测量的传感器,将连通管式静态挠度传感器拓展到了准静态测量范围。⑤分别构建了全站仪三维监测、光电式连通管一维位移监测两大物理模拟实验验证系统。通过系列实验,证明了全站仪基准传递及补偿观测方案可行,光电式连通管位移测量系统能够满足轻轨通过桥梁过程中的准静态位移测量要求。⑥将研究成果实际应用于重庆菜园坝长江大桥的荷载实验,获得了满意的数据,为重庆菜园坝长江大桥顺利通车提供了关键数据,且全站仪和连通管系统位移监测结果能够相互验证,达到预期目标。更多还原

【Abstract】 Influenced by long-term fatigue and other occasional damage during their service period, the structural reliability of bridge will be declined, and which will result in potential security problems. Therefore, more and more attention was paid on the structural health monitoring of bridge. As a result, some bridge structural health monitoring with modern sensing systems were developed and implemented on some long-span bridges and some interesting results were obtained; however, the state of art in structural health monitoring system is far behind the diversiform needs of bridges. So there are still some key problems for health monitoring of bridges need to further research. Among them, an important prarameter-displacement/deformation (which can indicate status of bridges) is one of the research hotspot.Arch bridges are famous for its reasonable structure, good looking, easy to achieve long span, but it is very hard to set up their mechanical model, because of their complicate structure, and then structural health monitoring for arch bridges becomes a big problem. Among all bridge collapse disasters in China’s mainland, one third were happened on arch bridges, because the absence of inner structural/safety information during their service time. In an arch bridge, the arch and the girders are the key components to endure internal force, and their strain condition could be showed as their global deformation. If the deformation is in normal range, the inner force of the arch and girders should also be in the normal range; correspondingly, a out-range deformation usually represents an abnormal force on these components, and which will lead to bridge damage. From this point of view, displacement or deformation can be used as a key parameter to evaluate health status of arch bridges. The arch bridge has very complicated 3D deformation, because it is a large combination structure with one main arch and hundreds of support girders and beams. Real-time, high accuracy and large measurement range 3D deformation monitoring is a new challenge to current deformation measurement technology, but it is a very important science and engineering problem deserves careful study.The main contents of this dissertation are stated in detail as following:①Mechanics prosperities of arch and girder of Caiyuanba Yangtze River Bridge were analyzed. A method for multi-dimensions displacement monitoring of long-span arch bridges based on combination measurement technology is proposed. The main idea is: a total station system was adopted used to monitoring the three-dimension deformation of the arch; and a connected pipes system was used to detect vertical displacement direction for girder. Some key problems for these two measurement technique were studied.②For displacement deformation monitoring in three-dimensions of arch, the most important error reason is the shift of total station. A three dimensions movement model of instrument base was set up, according to measurement principle of total station. Coordinates of deformation points are calculated. Methods to calculate the instrument base shift were proposed based on the analysis instrument base movement properties. Furthermore, the influence of atmosphere refraction was analyzed, methods to address this problem were also proposed. At last, an automatic protection device was designed for prisms, and it can open automatically during measurement and close in other times.③For vertical displacement monitoring of girder, measuring precision and liquid fluctuation in connected pipes are the key problems need to be studied. Mathematics model of liquid flow based on multi-channels connected pipes was set up with hydromechanics knowledge. Properties of liquid fluctuation in time domain were analyized. According to properties of liquid fluctuation, a wavelet threshold algorithm was proposed to eliminate the fluctuation noise.④Signal distortion of opto-electronic liquid sensor was analyized, and corresponding measurement software was analyzed in detail, the liquid sensor which can be used to measuring displacement signal in static state and in low frequency dynamic state together are developed.⑤Lots of experiments were designed and carried out to demonstrate the validity of our combination measurement technique for arch bridges. A series of experimental results with two Leica TC 405 total stations show that, a three dimensions movement model of instrument base is correct and the improved measurement method to compensate movement of total station is feasible. For connected pipes system, experiments results showed that the static accuracy and quasi-dynamic accuracy of opto-electronic liquid sensor 0.1mm and 0.25mm respectively. A series experiments results for connected pipes system showed, connected pipes system is suitable to measure static displacement and very low frequency dynamic displacement at the same time. With improved wavelet threshold algorithm, the measurement error is less than 4mm for a ten minutes continuous time.⑥At last, total station and connected pipes system are applied on Chongqing Caiyuanba Arch Bridge spans across the Yangtze River. The on site load experiment results also demonstrated the feasibility of multi-dimensional deformation measurement by the combination of total station technique and connected pipes system. The method to compensate total station instrument base shift was also verified by the load experiments. The experimental data also showed that the displacement measurement with connected pipes system has very good accuracy. A mutual proved analysis between the vertical displacement measured by total station and connected pipes, and it raise the reliability of the data.更多还原