The Study On Difficulties For Construction Control Of Long Span Continuous Rigid Frame Bridge

Long-span continuous rigid frame bridge is a common bridge structure system in China,most of the long-span continuous rigid frame bridge adopts the hanging basket-situ cantilever construction method,the line of structure are greatly influenced by uncertain factors in the construction process.Influenced by various factors,the line of bridge is not smooth and needed to be adjusted.There are still many difficulties in construction control of continuous rigid frame bridge.This paper based on 81.8m+150m+81.8m prestressed concrete continuous rigid frame bridge monitoring project in Guizhou mountain area and the main contents as follow:(1)Adopting the existing continuous rigid frame bridge monitoring strategy,the alignment of the bridge deck to the design alignment will take a long time as the shrinkage and creep of concrete,and there is a certain contradiction between the early alignment and the late alignment of the continuous rigid frame bridge.For the problem of bridge deck alignment adjustment,this paper points out the deficiency of existing bridge deck alignment adjustment control methods,and puts forward two kinds of bridge deck alignment control forms based on the route design specification.Adopting the static analysis method to analyze the influence of different bridge deck alignment adjustment forms on bridge structure.The results show that the overall linear control is feasible.(2)During the construction process,the actual construction period arrangement is often inconsistent with the established construction period arrangement.The article analyzes the influence of the construction period of beam segment and the influence of different construction stopping positions and different construction stopping times to the line control for long-span continuous rigid frame bridge.The research shows that the maximum cantilever state lockout has great influence on the alignment of bridge.Shutdown for 30 days in the longest cantilevered stage,the down deflection value of Maximum cantilever end over 1/2 criterion value.According to different situations,the countermeasures of continuous rigid frame linear control are proposed.(3)For two different construction methods of hanging basket and hanger,this paper analyzes the influence of the two construction methods on the linear control of long span continuous rigid frame bridge.The research result shows that the influence of the hanging baskets for the closure segment on the alignment of bridges cannot be ignored.When the hanging baskets are used to construct the closure of the long span continuous rigid frame bridge,the choice of removing the hanging baskets moment should be reasonably arranged.And according to the research results,several countermeasures are proposed to the closure construction scheme is inconsistent with the design scheme(4)The hanging basket is an important equipment for cantilever cast-in-situ construction.But at present,the method of hanging basket template adjustment is time-consuming and laborious.In this paper,a new device is put forward about the elevation adjustment and the mechanical properties is analyzed.The research result shows that the device is safe and reliable,and can effectively improve the adjustment speed of hanging basket.