Stability Analysis And Safety Evaluation Of The Tower In The Whole Hoisting Construction Of Large Span Ratio Steel Box Arch Bridge

With the increasing diversity of the bridge structure, various types of bridges are becoming more and more important in social life.In the history of the bridge, steel arch bridge has always been an important kind of bridge, steel arch bridge's beauty and practicality has been loved by the people.The construction method of steel arch bridge includes: support method, cable hoisting method, rotation construction method and arch rib integral hoisting method etc,especially the arch rib integrally hoisting construction method has the advantages of short construction period, reduce the risk of aerial work, influence of shipping is very small, so more and more bridges are constructed using this method. When the arch rib integral lifting method is used, it is obvious need to use a structure for lifting arch rib. Guarantee the stability of the high tower is a prerequisite for the construction safety, so study on the stability of tower in the rib hoisting process has practical significance.This paper firstly describes the support research status in the domestic and foreign, and the main research content and the practical significance of the research.Then according to the requirements of the design information, established a finite element model of the tower structure, selected the suitable sling and wind resistance cables, determined the hanging point position and tower placement and treatment of arch foot.Because the finite element model is less accurate than the model in the actual engineering, therefore, it is necessary to modify the finite element model so that which is more close to the actual engineering situation.First determine the BP neural network method is used to modify the finite element model, but due to the BP algorithm has some limitations, such as easy to fall into the local minimum problem,so consider the genetic algorithm is used to optimize the BP neural network,and GABP neural network is formed, then use the MATLAB software to program.After the finite element model was modified by the GABP neural network, the training samples and test samples of neural network are selected,compared the frequency of the model correction before and after, It is found that the finite element model modified by the GABP network is more close to the experimental results than the uncorrected finite element model, and used the Modal confidence criterion MAC value verified the feasibility of the GABP network modified finite element model.Finally, according to the modified finite element model, the slings and the towerstress were studied in the arch rib turning stage and the arch rib lifting stage. The study found that the slings and the tower can meet the bearing capacity requirements in the whole arch rib hoisting stage.We also calculated the stability safety factor K of the tower structure at the arch rib lifting stage and overturning stage, the K value is within the range of security, it is proved that the tower can meet stability requirements.The cable stress and maximum displacement support were verified through experiment, this paper proves the accuracy of the results of finite element analysis.