Study On Construction Control And Temperature Field Effect Of Intercity Railway Continuous Girder Bridge

With the social progress and rapid economic development,the development of prestressed concrete continuous beam bridges has also achieved brilliant achievements.For continuous beam bridges crossing rivers,deep valleys,etc.,it is most convenient to use the hanging cantilever pouring method.However,using the hanging cantilever construction method,the linearity and stress of the structure will continuously change during the construction of the continuous beam bridge.Therefore,in order to ensure that the bridge shape and stress meet the design requirements under the construction state and the completed state,it is necessary to monitor the construction of the bridge using the hanging cantilever method.However,during the construction and completion of the bridge,cracks will be found,and the main reason for the cracks is temperature stress.Engineering case studies show that there are many factors that affect the construction control of prestressed concrete continuous beam bridges,among which the temperature difference of sunlight has a great influence on the deflection and stress during construction.For different regional environments and climatic conditions,the deflections and stresses calculated using different temperature gradient models are also very different.Therefore,field temperature field tests and theoretical research work must be performed to obtain the temperature field distribution law of prestressed concrete continuous beam bridges suitable for a certain area of our country and its influence on line shape and stress.It can supplement and guide the design and provide specifications.More accurate construction vertical mold elevation and reasonable concrete pouring timing ensure bridge construction quality and construction safety.This paper takes the construction monitoring project of the(50+80+50)m continuous girder bridge across Century Avenue as the engineering background for the Hangxute Bridge,and studies the construction control and temperature field effects of the railway prestressed concrete continuous girder bridge.The main contents are as follows:(1)First,the domestic and foreign research status of construction control technology for prestressed concrete continuous beam bridges and the domestic and foreign research status of temperature effects of concrete structures are introduced(2)The application of the cantilever construction control theory of the prestressed concrete continuous beam bridge in the entire construction control process and the theory of concrete temperature effect are briefly summarized.(3)Based on the construction monitoring project of the continuous beam bridge across the Century Avenue of the Hangxu Bridge,a finite element simulation calculation model was established.During the construction process,the field measured data was basically consistent with the theoretical calculated deflection value;the relative elevation errors at the ends of the mid-span closure section It is 7mm,and the height difference between the bridge linear shape and the designed linear shape is controlled within 10mm,which meets the specification error requirements.In terms of structural force monitoring,the actual measured stresses of the box girder top and bottom plates are less than the allowable stresses of the concrete.During the construction,the structural safety of the bridge structure is guaranteed,that is,the effect of the bridge construction monitoring can well meet the design requirements.(4)Through the comparison of the two closure schemes,the accumulated deformation and compressive stress of the bottom plate of the optimized closure scheme are not much different from the data of the original design scheme,so that the ideal line shape after the completion of the bridge meets the design requirements;it can guarantee the mid-span The bridge structure after closure prestressed tensioning is safe;the construction period is shortened and the construction progress is accelerated.(5)The temperature field distribution of the box girder was measured in the cantilever construction stage and the bridge state by embedding the temperature sensor,and the vertical temperature gradient function of the box girder of the bridge was fitted by the exponential function curve Ty=19e-2y?Ty=7e-3y.(6)The finite element analysis software FEA is used to analyze and analyze the influence of the temperature difference of the prestressed concrete continuous beam bridge on the line shape and internal force of the prestressed concrete continuous beam bridge during cantilever construction and under bridge formation state through modeling calculations.It shows that the maximum vertical displacement of the cantilever box girder at the end of block 9 is 17.4mm,and the measured value is 15.2mm.The maximum temperature difference between sunlight and 16:00 is reached.The main tensile stress of the box girder section top plate is reached by the stress generated by temperature load.When the pressure is 2.2 MPa,the influence of the temperature difference of sunlight in the bridge state is much smaller than that in the cantilever construction stage.