The Influence Research Of Continuous Rigid Frame Bridge Stress In Construction Stage

PC continuous rigid frame bridge with its driving a smooth, convenient construction,integral sex is good and other advantages, in the field of bridge engineering to get fastdevelopment, become a kind of commonly used large span bridge. Although the theory ofconstruction and design of long span continuous rigid frame is mature, but at home andabroad in recent years, the statistics of prestressed concrete continuous rigid frame bridgediseases. At home and abroad mainly displays in: common fault of long span continuousrigid frame is gradually increasing loss of prestress, web inclined crack, roof and floorcracks and deformation of main girder serious, such as overall bridge across the middleand lower scratching, carrying capacity is falling and cracking of box girder and otherproblems. The uncertain factors in the construction of (mainly stress of the main girder) onthe impact of these diseases not only single qualitative estimate, need to further study thecausal relationship between them. Closely with the engineering practice, this paper, on thebasis of the cantilever construction stage through the analysis of the theoretical analysis ofmain girder stress state of bridge across the middle and lower scratching, late latecompressive stress reserves and the influence of box girder cracking performance.The main research work includes:①the first acquisition in China more than continuous rigid frame bridge andcontinuous girder of the bridge at construction stage of stress measured data, the analysisof these data discrete, find out the rule of the deviation of measured value with thetheoretical value, to determine the construction phase of the working condition of the maingirder stress deviation;②the second summarizes continuous rigid frame bridge in our country late threecommon problems in the operation stage disease: long-term late downwarping, bridgebearing potential drop across and cracking of concrete box girder. Points out theimportance and necessity of studying these common problems, and the qualitative analysisthe influence factors of these problems;③and then introduces the theory of concrete creep, both bridge long-term deflectionanalysis method, the analysis methods of late compressive stress reserves and box girdercrack mechanism of the model built based on a project, the finite element analysis andcalculation, combining normative research analyzes the continuous rigid frame bridge construction stage stress deviation on the last stage of operating a bridge across the latedeflection, compressive stress in the reserves and the influence of box girder crackingbehavior;④through the analysis and calculation show that the construction stage of stress stateof operation stages is very significant, the impact of three kinds of problem duringconstruction stress decreases, and will accelerate the operation stage of three kinds ofproblems appear, but little influence on the structure of normal use; Bridge constructionstage increases stress deviation, the late late compressive stress reserves increase, reducethe probability of cracking of concrete box girder, more long span of the deflection, stressexceeds a certain limit, but the construction phase will lead to long-term operation stagesconcrete in high stress state, the concrete creep effect significantly, increasing deformationof main girder, adverse to the structure safety.