The Unbalanced Force Problem Research In The Process Of Main Girder Erection For Long-span Cable-stayed Bridge With Steel Box Girder

Steel box girder cable-stayed bridge has great spanning capacity,simple structure,main girder erection convenient and quick,the advantages of beautiful shape.In the construction of long-span Bridges,it has been widely applied in across the river,sea and so on.Long-span steel box girder cable-stayed bridge girder erection of the cantilever construction method is adopted usually.During girder cantilever construction,double cantilever of unbalanced load has great influence on the internal force of structure.the paper in the engineering background of the Fengdu Yangtze river second bridge in Chongqing,main girder erection is studied the whole process of unbalanced force problem and its effect on the performance of structure.Specific research contents and results are as follows:1)Comparison of the commonly used method of cable-stayed bridge girder erection,analyses the characteristics and applicability of different construction methods,put forward in this paper,relying on the technical characteristics of construction projects.2)This bridge is analyzed using the cause of the imbalance of the bridge crane and the main factors that lead to imbalance,by loading test and structure analysis of the research on the stress of Luffing type bridge crane safety.Analyzes the unbalanced erection procedures,there are side of beam section of side span beam,beam process and a counterweight.In view of the main girder erection process is difficult to fully synchronous hoisting and actual situation,unilateral non ideal lifting tower-beam temporary fixation problem of unbalanced force was analyzed.For the construction of the girder under the condition of unbalanced moment was calculated,analyzed its changing rule.3)The Fengdu Yangtze river second bridge during main girder erection,for mechanical performance of steel box girder,tower-beam temporary fixation construction and the lower beam,researches has carried on the theoretical analysis,field monitoring and comparison show that Main girder during the erection,of the structure stress in the normal control and the security situation.Stress monitoring results and calculation of trend is consistent,deformation monitoring results in good agreement with the calculated value,and for similar cable-stayed bridge girder erection construction provides the reference.4)Bridge structure analysis of finite element software Midas/Civil is adopted to establish the whole bridge construction stage the local stress calculation model and the temporary consolidation model,through the analysis of the structure calculation,studies the beam with the period of erection of tower are the stress of the beam temporary rigid fixity area law and the change of the construction progress,to evaluate its security was analyzed.5)Establishing calculation model of cable-stayed bridge under the pillar and beam entity to girder erection process middle beam deviation and mechanical performance,the top of the tower bottom bending moment as evaluation parameters,considering the during the girder erection remove temporary rigid fixity of reasonable time,safety and rationality of lifting demonstrates the project timing.