Research On Reasonable Construction State Of Large Span Combined Girder Cable-stayed Bridge

In recent years,China’s transportation industry has developed rapidly,and the combination girder cable-stayed bridges are more and more widely used due to their good force performance and spanning capacity.During the construction of the combined girder cable-stayed bridge,the determination of reasonable construction state is a key issue in the construction control of large-span combined girder cable-stayed bridge.Based on the summary of the structural characteristics of the combined girder cable-stayed bridge and the theoretical and practical achievements of domestic and foreign research,this thesis takes the Chibi Changjiang River Highway Bridge as an example to study the reasonable construction state of the large-span combined girder cable-stayed bridge.The following work was mainly done:(1)The structural characteristics of the combined girder cable-stayed bridge are introduced,and the design calculation theory of the combined girder,the geometric nonlinear calculation theory of the combined girder cable-stayed bridge and the reasonable construction state determination method are reviewed.(2)According to the tensioning characteristics of the cable-stayed bridge of the combined girder cable-stayed bridge,the stress-free cable length value of the cable-stayed bridge is used as the cable-stayed bridge tensioning control parameter,and under the condition that all the cable-stayed wires are tensioned for the last time before the bridge deck is decked after the main girder is assembled,the cable-stayed wire force and the stress of the main girder in the designed bridge state are used as the target,and the stress of the main girder during the construction process is used as the constraint,the method to determine the reasonable construction state of the combined girder cable-stayed bridge is proposed,and the validity of the method is verified by taking the Chibi Changjiang River Highway Bridge as an example.(3)The method of calculating the initial value of unstressed cable length tensioning in first-tension and twice-tension of combined girder cable-stayed bridges is proposed,and the initial value determined by this method can ensure that the stresses in the main girders meet the safety requirements under most working conditions in the construction process,and for the very few conditions that do not meet the stress conditions,the stress can be easily adjusted to meet the requirements by fine-tuning the initial values of the two sheets according to the stress calculation results of the main beam.(4)The feasibility of reducing the number of tensioning times in the construction stage of large-span combined girder cable-stayed bridges was studied by comparing the stress of the main girder and the tensioning force of the cable-stayed bridges in the completed state,and the results showed that the elimination of the last tensioning before the deck pavement after most of the cable-stayed bridges were assembled could also better achieve the design goal.