Research On Relationship About The Capacity Of Steel Box Girder Under Combined Bending And Torsion

Because of its good features of structure and mechanical properties, box girder was getting widely used in the modern architectural engineering and bridge engineering. Box girder’s structural characteristics include the contour smoothly artistic, smaller section and economical use of space. Box girder’s mechanical properties are mainly for its good bending stiffness and torsional stiffness.The object this paper worked on was box girder with eccentric concentrated load on flange while its two sides are simply-supported. Consider of the local deformation is maybe too large to influent the elastic-plastic capacity of box girder when there is a concentrated load on its upper flange.In this paper, the article set a diaphragm plate in the middle of the girder as it’s frequently used in engineering practice. On the basis of theoretical analysis, the article simulated and analysed box girder model by ANSYS program. The actual steel material nonlinearity, the axial load large deformation effect and the initial defects factors that exist in actual engineering components were considered. Before the analysis the article set up different lateral bracings on the models to observe their influence to the ultimate bearing capacity of box girders under bending and twisting. After comparative analysis we find that the lateral bracing makes little contribution to the bearing capacity of the steel box girder.Then this paper studied on the elastic-plastic load deformation characteristics of box girders within a certain scope of span and section. The change of the span ,the change of ratio of height to thickness and flakiness ratio and the change of section size is all considered in the analysis. After that the article summarized the change rule of deformation characteristic curves when these factors changed.Finally the article made comparative analysis of the various box girder bending-torsional related curve model. In considering all the analysis results above , the article make out a relevant control equation of bending-torsional bearing capacity of box girders with simply-supported and midspan concentrated load . Then the paper pointed out the suggestion use scope of the equation.This equation has certain engineering significance for engineering design and standard revision reference.