Finite Element Analysis On Shear Lag Effect Of Box Girders With Special Supports

The application of thin-walled box girder of skew support is more and more widely with the development of traffic cause in the high grade line and the construction of urban elevated road. It is the direction of the need to skew box girder bridge abutment and bridge axis layout in order to adapt to the surrounding environment of restrictions or to adapt to the line. The box girder’s shear lag effect is very significant due to the complexity of spatial crinkle and reverse’s coupling is more noticeable. The domestic and foreign scholars study of box beam shear lag effect did a lot of work, but they are mostly in the management of orthogonal thin-walled box girder, the study of the shear lag effect of box girder for special supporting is not a lot.This paper concentrated load and symmetrical load and eccentric load and uniformly distributed load conditions, analyzes the special bearing under the rule of shear lag effect in oblique angle change and oblique angle to the appropriate section of the impact of stress. The shear lag effect of box girder under the special support analysis, using the large general finite element software ANSYS to analyze the shear lag effect of some cross section. Because this model of bridge pier is not orthogonal to the beam axis, but the existence of oblique angle, this is bound to affect the box girder stress and shear lag effect, we can draw on the control box girder section stress and some regularity of shear lag effect through analysis. The main research results in this paper are as follows:(1) The stress of the box girder under special bearing is more complicated relative to the orthogonal bridge. In concentrated load and symmetrical load and under the action of eccentric loading, the study section stress is decreased with the increase of oblique angle, the oblique angle, the greater, the attenuation rate it will speed up.(2) Through the effect of load, can be found in the near the load, web and roof joint, web plate and bottom plate joint, and the point of the shear lag effect is very obvious. This is due to the load and the stress of the bearing is bigger, affect the surrounding section stress distribution, thus causing the shear lag effect of outstanding, this needs to be in real full consideration in the design of Bridges.(3) Because of the existence of skew angle on some section of the flange plate, both the tensile stress exists, as well as compressive stress exists, that is to say, in the same flange plate tensile compressive stress at the same time, the stress is very complicated.(4) Under the action of concentrated load and symmetrical load and eccentric loading, the special support of box girder section stress distribution is not symmetrical. This is mainly due to the special bearing, in addition to bending shear lag of box girder and warp and restraint torsional buckling.(5) The shear lag effect of the flange plate of the roof strengthening phenomenon under eccentric load. This is different from the general situation of a feature of the box girder space, special bearing and mechanical load position.(6) Under different oblique angle, the section on the shear lag effect will exist. When? ?30?, on the influence of each control section is not very big, so the changes within 30 ° to each control cross section of shear lag effect can be ignored. When ? ?30?, as the change of oblique angle of shear lag effect is obvious, the shear lag effect can’t be ignored.