Wide Box Girder Bridge Construction Monitoring And Analysis Of Shear Lag Effect

It is easy for the wide box-section bridge construction section occurs lateral deformation in the construction process,makes the linear control more difficulty;the bridge girder section stress biggest state occurred in construction stage,rather than into a phase of the bridge,and it is easy to occur safety accidents under the influence of shear lag effect in the process of construction.Based on the above consideration,this paper takes Fugou County Dongguan Bridge –width is 26.5m' single box five room continuous girder bridge as the background engineering to carry out construction monitoring,research in the change law of shear lag in the construction process at the same time.Main content includes:(1)Use Midas/Civil to build in line with the actual construction state of truss model and the grillage model.Use Midas/Fea to build spatial entity model,analys different models varied,explore the cause of the differences and provide theoretical data support for the construction monitoring.(2)Study the influence of shear lag effect of main girder section in the pouring concrete,tensioned prestressed,bridges closure,system transformation,different steps of construction of main girder stress in roof and floor show different "whole" and "local" shear lag effect at the same time,analys the shear lag effect of the cantilever root section in the whole construction process.The results show that casting concrete makes roof tensile,bottom pressure,after casting roof shear lag effect increased,the bottom shear lag effect weakened;tensioning prestressed makes roof pressure,has less impact on the bottom plate;after prestressed roof shear lag effect weakened,the bottom shear lag effect has little change;closure and system transformation on the influence of shear lag effect affected by the section location;as the construction stage,cantilever root section stress increases,and the shear lag effect is weakened.(3)Carry out the monitoring work of Dongguan Bridge by adaptive control method: through setting of each stage formwork elevation reasonable to control line,ensure the bridge linear smooth in construction process;by comparing the measured stress results after correction and the theory of stress results,ensure the safety of construction process of reasonable girder.Monitoring results shows that the bridge line is relatively smooth,linear control goal;in the process of the construction of main girder is in a state of safe and reliable,After the completion of the construction stress meet specification requirements,and has a certain safety reserve.