The Wide Concrete Cable-stayed Bridge Box Girder Shear Lag Effect

The box girder has been used widely in bridge engineering due to its Significantadvantages of strong ability to support the positive and negative bending moment, torsionalrigidity, high Cross-section efficiency indicators and excellent structural stability.However,because of the structure characteristics of thin wall and wide flange, box girder takes on theaction of torsion, distortion, warping, etc,which is different from other mechanicalcharacteristics of the open section, ande the shear lag effect of box girder cannot beignored.Shear lag will cause stress concentration in wide flange, it is bound to reduce thereserves ofthe structural safety and even lead to structural damage, if this effect is ignored inthe design and construction process.So this thesis studys the shearlag effect of box girder withsix-cell used in Tuanjie Bridge, which, I think, will have its important engineering value andtheoretic significance.The work this thesis has done is as follows:1.This paper refers to a large number of references, and reviews and analysesby contrastexisting shear lag theories and methods, and pointed out the limitationsand applicableoccasions of the methods refered by this paper, and propose someplace where existing shearlag theory needs to be improved. At last, the significanceand necessity of this thesis are madeclear.2.This paper expounds the loading characteristics of box girder and the concept ofthin-walled box beam shear lag effect.3.This paper expatiated on the cable-stayed bridge structure system and itscharacteristics.4.This paper establishes the finite element models of Tuanjie Bridge by MIDAS/Civilsoftware, and analyzes respectively the shear lag effect of the four kinds of cable-stayedbridge systems of floating system, half floating system, Tower beam consolidation system andrigid frame system in a typical construction stage and with a general section (no transversediaphragm section) and special section (with transverse diaphragm), and has carried on thecontrast analysis.The analysis results show that the shear lag effect of the concrete cable-stayed bridge isprominent, and the shear lag coefficient show obvious zoning characteristic along thelongitudinal direction.