The Allowable Deviation of Assembly Dimension in Steel Bridge Manufacturing Specification

Bridges will bear frequent dynamic loads after being put into operation, which is different from the general building structure. For steel bridge, compared with reinforced concrete bridge, it also has some special performance requirements, such as higher standard requirements for the geometric accuracy and welding quality of steel bridge bar or steel beam (steel tower) section. The reasonable allowable deviation requirement of steel beam assembly size is particularly important to ensure the dimensional accuracy, convenient production and quality of finished products. However, in the current industry norms, local norms or manufacturing rules of the project, the allowable deviation of assembly size given is often not scientific and reasonable, and it is difficult to meet or match the allowable deviation of the final basic size of the finished product.
Based on the analysis of steel bridge manufacture assembly size with the current situation of allowable deviation in the specification, it expounded the steel bridge assembly dimensions determine the allowable deviation of basis and related examples:1)the height of the steel truss girder lord bar assembly tolerance requirements, Standard of Railway Steel Bridge Manufacture(Q/CR 9211-2015) is more rational and comprehensive; 2)the allowable deviation requirements of bridge steel tower segment assembly. In general manufacturing and acceptance specifications, it is unreasonable to adopt the allowable deviation of steel tower segment assembly consistent with the allowable deviation of the basic size of the finished product; 3)the allowable deviation of steel box girder segment assembly size is not distinguishable between the allowable deviation of the final basic size of the girder segment and the allowable deviation of the assembly size in the current industry standard, local standard or the manufacturing acceptance rule of steel box girder project. It is unreasonable to require that the allowable deviation between the two is basically the same. Then, the paper introduced the making steel component assembly dimension deviation should be allowed the problems:1)assembly of allowable deviation for the part of the steel girder structure analysis, such as:steel tower, steel box girder segment, due to the manufacturing process, influencing factors, should not put the finished product basic size deviation and assembly size allowed allowable deviation as a consistent or near; 2)How to determine the assembly allowable deviation of complex steel beam members should be determined according to the allowable deviation of the basic size of the finished product combined with its structural characteristics and manufacturing technology; 3)to develop the basic size of the steel girder components allowed deviation should be scientific and reasonable, such as:large steel box girder width tolerance requirements were too strict was meaningless, should be combined with the specific structural characteristics of the steel girder components, the importance of the point of the degree of development.
Finally it drew the conclusion:the basic dimension tolerance to determine the scientific and reasonable steel components was of great significance, the assembly tolerance was closely related to the manufacturing process, should be determined by the factory according to the basic allowable deviation of steel components, combining with the characteristics of structure, welding shrinkage factors such as given on process, specification, just set forth some basic requirements for the assembly process.