| As box girder has satisfying Structure performance, it's widely used both here and abroad. The theory holds true for the primary beam is no more applicable to bedding box girder. Because the basic assumption of the theory for the primary beam is plane deformation assumption, and the influence of shear deformation is not taken into account, so the bending stress is equally distributed along the beam width. But the bending stress in the box girder is not equally distributed due to the shear deformation. This phenomenon is called the shear lag effect.The research on the shear-lag effect in the simple-supported steel box-girder was made in this paper. The first of all, the definition of shear-lag effect, analytical theories and methods were expatiated, and then, based on the characteristics the stress distribution and shear lag effect of the steel box girder was studied thoroughly by three methods including the model test, the 3-D finite element theory and the principle of minimum potential energy. The paper emphasized on the model test studies of the shear lag by exerting different composite load on two steel box girder models. The influence of many factors such as setting the spacer bar, the transverse acting location of external load and longitudinal changes on the shear-lag effect of the steel box girder was analyzed, and the change rule of the shear-lag effect under different load was confirmed on. After that, using 3-D finite element method the simulation calculation for the model had been carried out, the results was compared with that of the test. Generally speaking, the results show that the finite element method accurately simulate the shear-lag effect of the simple-supported steel box girder.The research on the shear-lag effect in the steel box girder will be helpful for understanding the bending mechanism and the calculation of ultimate bearing capacity of steel box girder, and also distribute the far-ranging study and building of the same type box-girder bridge in China.
|
PDF Full Text Request