Research On Modal Analysis And Application Of Long-span Continuous Rigid-frame Bridge With High Piers Based On Ambient Excitation

Long-span continuous rigid-frame bridge with high piers is widely built in the bridge area because of its own advantages, but some long-span pre-stressed concrete continuous rigid-frame bridge suffered different degrees of disease, these diseases mainly focus on the following two aspects: first, the main cross-beam deflection is too large, the other is the problem of cracking in the box girder. So, there are especially important that construct the structure health monitoring system, real on time monitoring on the bridge under various environmental conditions and realize intelligent assessment. Its need to accurately identify the modal parameters on the process of health monitoring and evaluation with long-span bridges, these parameters (frequency, modal shape, damping ratio) are main parameters that determine the characteristic of dynamic. The traditional model experiments will cause difficulty in the large bridge experiment. Environment excitation-based model experiment methods only need to test the output signal then it can identified the modal,It does not need to excite the structure, so it is more in line with the features of structure experimental in long-span bridge, this thesis aims at the mode analyze and apply of Yesanhe Bridge, a long-span continuous rigid frame bridge with high piers. The main research work is summarized as follows:1. Several modal Parameter identification methods are discussed. The study is focused on NExT/Piek-Peaking(PP), the experimental results shows that the NExT/Piek-Peaking can identify the dominated vibration modes of the bridge.2. Beam units and solid element models of Yesanhe Bridge are established to verify the validity of the models. Then a more Suitable modeling methods and strategies was found from the contrastive analysis.3. Ambient vibration testing of Yesanhe Bridge is discussed. Compared test results with theoretical results showed that the dynamic characteristic of long-span continuous rigid frame bridge with high pier is obvious. The parametric analysis of the bridge found when the pier height of more than 60 m, the first modal shape of the bridge change from the transversal vibration to longitudinal vibration.4. Based on the theory of the modified finite element model, the FE model is modified in terms of ambient vibration test results. The modified results are well agreed with the ambient vibration test results. the module is capable of reflecting dynamic characterize of bridge, It 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 Yesanhe Bridge.5. Updating the finite element model,it found that physical stiffness at the bottom of the pier have great influence on dynamic characteristics of long-Span continuous rigid-frame bridge with high piers, should be taken into account in modeling.