Dynamic Detection And Model Analysis Of Long-Span Cable-Stayed Bridge

The long-span cable-stayed bridge is one of most competitive power bridges in the modern bridges. It is important to understand their dynamic properties during the inspection, assessment and health monitoring. Structural modal parameters reflect the dynamic properties that can be obtained by either traditional identification techniques of output-based and input-based data or ambient vibration identification techniques. Dynamic testing of civil engineering structures under ambient vibration excitation has many advantages, including no excitation equipment needed, no interruption of structural service and less test time, which is adapted to the real working conditions of civil engineering structures. In terms of ambient vibration testing, as output is measured and real input remains unknown, the modal parameter identification will be techniques of output-based data only. The output-based modal parameter identification is different from traditional techniques of input-based and output-based data and it is now very active in the system identification of engineering structures. The state-of-the-art studies are carried out in this thesis related the theory, algorithm and field case applications of pick-peaking(PP) which is furthest common use, simplicity of operator and snap recognition. The main work and conclusions as follows:1.Several modal parameter identification methods are discussed. The study is focused on pick-peaking(PP). Modal frequency is identified by peak points of self-spectrum and cross-spectrum this article. Fourier spectrum peak value of the mobile and reference stations is used, whose ratios represent modes; And the phases of their cross-spectrum represent orientations of the relative movement. The experimental results of Badong Yangtze River bridge could know that pick-peaking(PP) can identify the dominated vibration modes of the bridge.2. Ambient vibration testing of Badong Yangtze River bridge is discussed. Pick-peaking(PP) has been used to identify the 3-D vibration characteristics. It is demonstrated that the ambient vibration measurements can identify the dominated vibration modes of the bridge.3. The 3-D finite element model of Badong Yangtze River bridge is established. Then the FE model is calibrated in terms of ambient vibration test results. The calibrated results are well agreed with the ambient vibration test results. It is demonstrated the calibrated FE model which reflects the built-up structural dynamic characteristic can be served as a baseline model in the succeeding dynamic response analysis under complicated excitations, long-term health monitoring and structural condition assessment of Badong Yangtze River bridge.4. The model building procedure of the baseline FE model of Badong Yangtze River bridge can provide reference for the model building of homogeneous bridges. It is concluded that the test method of the bridge which can provide favorable reference for safety evaluation of the long-span cable-stayed bridges is very reasonable in terms of good agreement of the calibrated FE model results and ambient vibration test results.