Study On Mechanical Characteristics And Closure Deviation Limit Of Long-span Continuous Rigid Frame Bridge In Closure Stage

Continuous rigid frame bridge,which combines the characteristics of continuous beam bridge and T-shaped rigid frame bridge,is a popular and common bridge in China.In the process of cantilever construction of continuous rigid frame bridge,bridge closure is an extremely important stage,which directly affects the internal force state and alignment of the completed bridge,and also affects the safe operation of the bridge in the later stage.In view of the problems of unclear stress and deformation of key sections and unclear closure deviation limit in the process of bridge closure,this paper makes the following research:Analyze the key technologies of each stage in the process of bridge closure,elaborate the role of applying closure counterweight and locking stiff skeleton,and compare the different implementation forms and setting methods of the two technologies.Taking Lingxia bridge as the background,the finite element model of Lingxia bridge is established by Midas civil.The closure process of the bridge is divided into nine working conditions.The load and boundary conditions of each working condition are simulated.This paper analyzes the stress and deformation of the bridge under different working conditions,focusing on the influence of the closure weight and the rigid skeleton,and obtains the stress and deformation characteristics and rules of the bridge under nine working conditions.The stress and deformation of the bridge in the process of side span closure and the bridge in the process of middle span closure are calculated,and the change trend of the stress and deformation of the bridge in the process of side span and middle span closure is clarified.It is pointed out that the most dangerous part of the bridge closure is at the top of the pier,and the most dangerous construction step is to tension the prestressed reinforcement of the closure.Summarize the causes and treatment methods of bridge closure deviation,and deduce the mechanical formula of additional closure weight when the bridge is forced to be closed,so as to calculate the additional closure weight manually in the construction.The closure deviation of the bridge is simulated by setting the pre camber of the bridge in Midas civil.The influence of different closure deviation on the stress and deformation of the bridge under three working conditions with additional closure weight,closure completion and three-year creep,is analyzed.By increasing the closure deviation of the bridge with gradient,the closure deviation limit of the bridge is preliminarily explored.The results show that the closure deviation has more influence on the bridge mid span alignment and stress than on the bridge side span alignment and stress,and the closure deviation mainly affects the bridge mid span and the joint of beam and pier.The maximum allowable closure deviation of the example bridge is68.5mm.At present,there are few studies on the stress analysis and closure deviation limit of bridge closure process.The conclusion of this paper has some reference value for similar projects.