Analysis Of Shear-lag Effect On Steel Box-girder Of Pedestrian Overbridge

The steel box-girder has many advantages such as strong torsional stiffness, high intensity, light deadweight, prefabricate and machining conveniently, short construction period, good integrity, small building height good integrity, succinct and beautiful appearance. With the development of the transportation, steel box-girder are widely used in bridge construction. especially widely used in pedestrian overbridge.Under the action of load, the box-girder bridge may present the phenomenon of shear lag. Overlooking this problem in designing would underestimate the stress and have serious influence on the safety of bridge. Solution methods of shear lag effect of straight concrete box-girder are mentioned in specifications of many countries now, but the researches of shear lag effect of wide flange plate steel box-girder is absent. Our country's current code for design of highway bridge and culvert prescribe the effective width of flange plate of concrete box-girder which of curved steel box-girder is not mentioned. So the research of shear-lag effects of steel box-girder is of vital significance. The meaning of'shear lag effect'was that the bending normal stress near the boundary of wing plate and web plate is bigger than the stress near the midpoint of the wing plate.steel box-girder are widely used in pedestrian overbridge. This thesis take the steel box-girder of pedestrian overbridge as a subject, derived the differential equations of shear-lag effect used energy variational method, then used large general finite element programme ANSYS, take a simple-supported beam as a subject, analysis the shear-lag effect, and compared with the results of energy variational method. It is proved that the research method is feasible. According to the structural characteristics of steel box-girder, create its finite element model, analyzed the width-to-span ratio, section height, slant of web plate, length of section cantilever part, number of compartments of box, diaphragms'distance, structure parameters influence of shear-lag effects. It provides the basis and the technical guidance for this kind of bridge design, to guarantee bridge structure security.