The Analysis Of Shear Lag Effects For Single Cell Box Beam

In modern bridge structure, the box-section beam has been widely used in allkinds of bridges due to its good structural performance.Box section which can adoptto the structure construction and construction requirements more better,has been usedin various forms of prestressed concrete bridges particularly. With the continuousimprovement of concrete material properties and prestress technology, single cell boxsection becomes mainstream. However, the stress distribution of wide and thin singlecell box girder does not meet the plane section assumption when under the verticalloads,sterss becomes more asymmetrical along transverse distribution.Suchinhomogeneity must be considered in design calculation and construction controlunder the circumstance of the increasing bridge span and the decreasing safty margin.An accurate analysis of the shear lag problem in the construction stage and usingstage means important theoretical significance and engineering value.The main work accomplished in this paper are:(1)The concept of box beam shear lag effect and its adverse effects on thestructure are stated,summarized various research theories and methods which hadsloved the shear lag problem, and commented the applicability, limitations and futureresearch and development direction of these various research theories andmethods.Put forward the main work of this thesis.(2)The stress fomular has been obtained based on the three-pole analogymethod,and combined with the superposition principle and the equivalent simply-supported beam method to solve the shear lag effect in continuous box girderrespectively.(3)By using ANSYS finite element method, established a space finite elementmode of weishui bridge considering the whole construction process for calculating thesheer lag effcet of single cell box girder, and presented the result of ANSYSsimulation analysis and engineering test data for comparative analysis.(4)Take simply-supported and continuous straight box girder with single cell boxconstant section for instance to systematically discuss the influence of sheer lag effecton box girder caused by such parameters:load forms,span to width ratio,thickness towidth ratio,webs inclilation, diaphragm setting.And obtained some significant lawsand conclutions. (5) Take simply-supported and continuous straight box girder with single cellbox constant section and curved box girder with single cell box constant section forinstance to systematically discuss the influence of sheer lag effect on box girdercaused by such parameters:load forms,span to width ratio,thickness to widthratio,webs inclilation, diaphragm setting.And obtained some significant laws andconclutions.