In-situ Monitoring Investigfations For Wind Field And Vortex-induced Vibrations Of Stayed Cables In A Large-span Cable Stayed Bridge

For nearly half a century, cable-stayed bridge has been widely used as a kind ofnew bridge structure form, because of its excellent mechanical properties and goodconstruction effect. With the increase of the span of cable-stayed bridge, cablebecomes longer, lighter and softer. Therefore, cable becomes more sensitive to windload. Wind load becomes the main control load for the design of large-span cables.In recent decades, engineers have done a series of effective research on themultimodal vortex-induced vibration of cables. Common methods include thefollowing three ways: setting up mechanics models to carry on the theoreticalderivation, testing scale models of cables in the wind tunnel test, the technology ofCFD numerical simulation. With the continuous development of bridge healthmonitoring technology, the sources of loads and the structure responses can bereal-time monitored by building up the health monitoring system of bridge structural.The characteristics of wind field and the multimodal vortex-induced vibration ofcables can be studied. In this thesis, the main research content includes thefollowing:(1) The health monitoring system of bridge structural is builded up for JinTangBridge by the existing health monitoring technologies. The wind loads and vibrationresponse of cable of JinTang Bridge are monitored by the ultrasonic anemometersinstalled at the bridge deck and single-way accelerometer installed at cables. It isimportant to ensure the integrity, the validity and the reliability of the monitoringdata.(2) The wind field characteristics of JinTang Bridge are analyzed. Bridgeslocate in the atmospheric boundary layer. The statistical properties of atmosphericboundary layer wind field are random. In this thesis, the statistical parametersanalyzed include: the probability distribution of average wind speed and winddirection angle; the turbulence of free stream wind field; the power spectrum and theturbulence integral scale of free stream wind field; the gust factor of fluctuatingwind field and so on.(3) For JinTang Bridge, the characteristics of the multimodal vortex-inducedvibration of cables are studied by time domain method and frequency domainmethod. The vibration response level and frequency characteristics of cables areanalyzed. The factors influenced the multimodal vortex-induced vibration of cablesof are discussed. The correlations between the multimodal vortex-induced vibrationof cables and the fluctuating wind field are taked into account. Meanwhile, the wind tunnel tests based on the TMD controlling the multimodal vortex-induced vibrationof cables are carried out.