Dynamic Characteristics And Seismic Response Analysis Of Chongqing Fuling Wujiang Large Span Bridge During Its Construction Stage

During the construction process of cable-stayed bridge, due to various kinds offactors including the small structure stiffness, large dynamic response, poor stabilityand continuously changing structure system in the cable-stayed bridge, a dangerousstate may occur in the construction stage, which is even worse than that of the finishedbridge; Besides, due to the large construction cycle of the large-span bridge, andfrequent earthquake disaster in the world, the bridges are being built may be sufferedfrom those disasters, for example, Akashi Kaikyo Bridge in Japan, Ai Zhai greatsuspension bridge in China, etc. Wu Jiang great bridge locates in the earthquake-proneareas, the structure form of a higher lower pylon column and the unique constructionmethod of pylon and beam synchronous construction are used in this bridge, hence, itis essential to carry out a detailed dynamic analysis for the cable-stayed bridge in theconstruction stage, and some suitable measurements are need to be taken to ensurestructure safety based on its characteristics. At present, researches on the dynamiccharacteristics about the cable-stayed bridge mostly aim at the finished bridge state,which are lack of an overall and systematic study. Thus, the jobs have been done areas follows:Firstly, the analytical method and numerical solution of dynamic problem of thecable-stayed bridge are summarized, on this basis, under the background of Wu Jianggreat bridge, its spatial finite element dynamic model is built by MIDAS/Civil, adetailed analysis about dynamic characteristics of its finished state is done, which laida good foundation of comparison and analysis on the dynamic characteristic of theconstruction process.Secondly, the dynamic analysis of the whole construction process of Wu Jianggreat bridge is carried out, the rules of natural vibration characteristics changes asconstruction progress are revealed, the effect of factors such as travelers quality,unbalance load and synchronous construction of pylon and beam to the dynamiccharacteristic, and the changing features of dynamic characteristic before and after theconstraint condition changes including auxiliary pier and transition pier supporterection are studied emphatically in this thesis.Thirdly, the amplification function of the moment at the bottom of the tower andthe displacement of the beam end caused by the temporary moving load and impact load at the state of maximum double cantilever are studied, a horizontal impact actionloading mode of sinusoidal loading is put forward, which is better than loadingconcentrated load suddenly. The results show that the dynamic amplification factorresulting from moving load and impact load is a bit bigger than that in thespecification.Fourthly, the dynamic characteristics affected by the cable tower types of WuJiang great bridge is studied by using comparative analysis. The results show thatcomparing to the ordinary H-type tower, lateral stiffness can be improved by thespecial-shaped tower, the anti-twisted abilities of the girder and the tower can beenhanced, and it is good to wind-resistant in the construction stage.Finally, response spectrum method is used to calculate the seismic response ofthe bridge under the maximum cantilever state and the completed state. Difference andrelation of the seismic response under these two state can be achieved, which isvalidated by the time domain analysis comparison method.