The Shear Lag Effection And Concrete Deformation Research On Construction Stage On Wide Box Girder- Continuous Rigid Frame Bridge

With the development of free way,a single carriageway& single cell box girder is used widely in constructing continuous beam bridges and continuous rigid frame bridges .As the span and flange width become langer and larger ,the shear lag effect gets more and more obvious .Under the background of Chishancun Bridge project,the paper analyses the shear lag effect of the width-flange and thin-wall prestressed concrete continuous box-girder with varying depth under cast-in-place cantilevering construction and service load of pre-stress.Firstly ,the applicability and limitation of current theories and methods analyzing the shear lag effect on a box girder are summariesed and discussed .In order to disclose the essence ,this paper used the ANSYS analysis soft to simulate the actual cantilevering construction on the analysis of consyruction stage,according to the construction control ,which is used to verify the finite element result. According to the up to research work ,several main task are finished and some primary conclusions are inductived as follows:Under the gravitation load and pre-stress ,the shear lag effect of box girder reached maximum at the very beginning .As number of the cantilever segment larger and larger,the value of shear lag coefficient becomes more and more small ,and near a constant because of tone up restriction.Scilicetly ,the shear lag effect isn't obvious ,and the uprightness stress of top walls and bottom walls gets more even.The larger of the width-depth and width-span ratio ,the shear lag effect is more obviously too.But the effecttion of different ventral shield isn't obviouse.Shrinkage is the inherent time-dependent characters of concrete which belongs to a viscoelastic material.It is important to accurately estimate and predict the deformation and long and wide-span bridges with high piers which arise from the effect of shrinkage for engineering design,construction control and construction process. In this paper, the equivalent temperature difference method, using ANSYS simulation software. Will be converted into equivalent temperature contraction, that contraction is equivalent to lowering the deformation temperature to simplify a number of methods, first approximation, taking into account the effects of shrinkage stress, so that greatly simplify the calculation process. Have been more satisfied with the results.Fold the construction has been an extremely complex process and it is closely related key to the success of the whole bridge, so the process of design and construction are particularly concerned about this. Even so, the construction has been completed, we often found in the number of segments, such as the earlier cracks, etc.up to now it is difficult to solve. The design process, therefore the calculation of precision, the construction process in accordance with the intuitive important. In this paper, the use of ANSYS simulation software as well as the causes of cracks are analyzed and put forward relevant proposals. The bridge of similar design and construction will be practical significance in the future.At the same time ,on the basis of the FEA,various factors of the shear lag effect on a box girder ,concrete shrinkage,fold the construction cracks are analysed and some proposal are provided for the related problems in bridge design .In a sense ,the result can be referred in designing box girder bridgers.