Bending And Torsional Behaviour Analysis Of Multi-room Ribbed Steel Box Girder

With the increasing of strength of steels and alloys, application of thin-walled bar is gradually increasing. The thin-walled bar is widely applied to aviation, aerospace, marine, automotive and other industries, and construction industry is also rapidly increasing application of construction industry. Now thin-walled box structure has been widely used in bridge engineering, marine engineering, high-rise buildings and heavy plant, especially in recent years, the large number of the thin-walled steel box girder is applicated in large span steel bridge.This article starts from the multi-room ribbed steel box girder's two stress performances what are bending and reversing, using the basic assumptions of thin-walled box girder and force method of structural mechanics, first proceeding theoretical deduction, then combining with the finite element analysis, this article discusses the web and stiffener decorating of multi-room ribbed steel box girder, and gives the suitable suggestions, providing certain theoretical basis for practical engineering.In the paper, the main contents are divided into the following points:1. Put forward computation theory analysis of the thin-walled steel box girder, then establish the foundation for the following specific analysis.2. Using theoretical assumptions and force method, infer the bending stress calculation formula. And on this basis,using the calculation of bending shear stress as an example, analysis the number of webs which play the point on the distribution of the bending shear stress, then draw the reasonable proposal about webs' quantity and decorating.3. In this paper, the method of free torsion analysis is similar to the analysis of bending, combining with the assumption of free reverse,the principle of force method and superposition principle, infer calculation expression of multi-room ribbed steel box girder.4. According to torsion, citing a specific example, first use the formula results to describe longitudinal rib on the torsion performance improvement, combine with finite element analysis again, further explain benefits of setting up rib.In this paper, the main conclusions are listed as follows: 1. The longitudinal rib has no impact on bending shear stress, so using the steel box girder which is not decorated rib as a model, adopt the basic assumptions and force method, derive bending shear stress calculation expression that can be used multi-room ribbed steel box girder.2. Webs can take on some shear stress, additional webs can help alleviate shear stress distribution of the roof and floor, thus improve the bending behaviour of steel box girder. And this analysis of the specific example draw the conclusion which is that bending property better is multi-room steel box girder that has uniform layout of the webs and aspect ratio of each room is [1:1,4:3].3. To its torsional analysis, still continue to use force method of structural mechanics, first make up incision, then use the deformation coordination condition in the incision to establish equations, last derive the torsional shear stress calculation formula of multi-room ribbed steel box girder.4. Under the premise of stiffening rib spacing of meeting the standard stipulated, this article suggests that appropriate is even symmetrical put stiffener in steel box girder, and decorate the increasing the web can help to improve the torsional rigidity of the steel box girder, thereby improve the torsion property of steel box girder.