Constructional Moniotoring And Shear Lag Effects Of Prestressed Concrete Continuous Girder

In the recent years, with the development of highspeed railway and highway construction, wide span single beam single box room more and more applied to the construction of prestressed continuous girder bridges,continuous rigid frame bridge. And the increase of bridge spans and flange width shear lag effect is more and more obvious. All of this cannot be ignored.This paper is based on the engineering background of BOLN passenger dedicated Jinping bridge bovine valley river, and combined variable height of continuous rigid frame bridge cantilever pouring construction method to study the stages in the process of construction in the dead load and prestressing effect they the shear lag effect. During construction phase analysis, this paper uses ANSYS and MIDAS software to imitate cantilever construction process and monitor he whole process to put forward some theory and suggestions about control and design continuous beam. In the process of construction, gravitational constant load under the action of the wide span ratio,the greater the did not exert transverse prestress, shear lag effect more apparent,However, web thickness changes on the effect is not obvious.under the effect of gravity and prestress, the cantilever construction segment in its just pouring shear lag effect is the largest.with the increase of casting section,the sheer lag effect of diminishing. Cantilever construction in the process of system transformation, each section stress and the change of shear lag is more complex. The shear lag effect change tiny. It has a negative shear lag effect on the roof but shear lag effect on both sides of the flange plate is obvious.Side span section stress and the shear lag in the process of the first three basic has no obvious change.After side span closed,Compressive stress decreases. But the negative shear lag effect increased. During the construction, with the changing of the structure of the continuous girder bridge and loading state, structural internal force and deformation change constantly. Through the practical field monitoring data, we know that the main beam deflection is lager in the process of continuous girder bridge cantilever pouring construction. Because the design parameters and the practical engineering parameter are not the same, so the actual structure of each state may not meet the design value. According to the measured values of structure during the construction of main design parameters for evaluation, we should revise design value gradually, given to the construction of the deflection theory of expectations again, remove the main part of the theoretical value which isn’t consistent with the measured values, and use certain methods and means to control structure deformation and stress to ensure the implementation of the construction safe and accurate.On the basis of the finite element analysis, I calculate and analyse cross section geometric factors, prestressed factors and system change of the beam shear lag effect in the process of construction, and I put forward some suggestions about the related problems which exist in construction process and design. The results of the study has certain research value on the design of the box girder brigde.