Analysis And Study Of Box Girder’s Shear Lag Effect

With the increasing of the bridge’s span and width, the research of box girder’sperformance is increasingly in attention by scientific and technological workers, andthe study on shear lag effect has become one of the key points. Because the existing ofthe shear lag effect may causes the local stress concentrate in the box girder section,which will lead to the box girder cracks and partial destruction. And in some cases thedeflection change of the bridge may happen because of the shear lag effect, which willaffect the use of the bridge or lead to the destroy of the bridge. So the shear lag effectresearch of the box girder is not only the needs of box girder theory development,which also has the important practical significance and practical value. This papermainly rely on the background of the space mechanics analysis about acontinuous-rigid frame combination bridge Cai Jia-gou bridge, the follow analysis arein progress:①Basic mechanical characteristics and the basic concepts of shear lag effect areintroduced, summarizing the present situation of research on shear lag effect on energyvariation method and the FEM method at home and aboard.②The theory analysis is carried out with energy variation method, and thedifferential equation and natural boundary condition are obtained of the shear lag effectin different load cases. Then the theory and FEM comparison analysis are carried out forthe supported beam and cantilever beam, which get the consistent change law of theshear lag effect.③Relying on the background of the FEM analysis about a continuous-rigid framecombination bridge Cai Jia-gou bridge, the control sections are located in the area ofpositive bending moment and the area of negative bending moment, and the stress andshear lag change situations of the box girder’s top and bottom plate are analyzed withthe different load positions.④Relying on the background of the space solid FEM modal about acontinuous-rigid frame combination bridge Cai Jia-gou bridge, with the load cases ofself-weight, secondary dead load, pre-stressed load and dead load (self-weight+secondary dead load+pre-stressed load), the shear lag coefficient and distribution ofthis bridge are obtained.