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6 CHAPTER TWO OWNER-SPECIFIED OR PREFERRED PRACTICES Owner-specified or preferred practices related to steel bridge actual deflections and rotations owing to structure complexity. erection were reported in the questionnaires and follow-up These methods ranged from three-dimensional, finite-element telephone interviews. These practices are categorized by analysis through simple one-dimensional, line-girder analysis. design, fabrication, or erection. This range represents a tremendous variation in analytical sophistication and accuracy in capturing system behavior. DESIGN The state DOT respondents expressed varying opinions Flange Dimension Requirements that the impact of the sophistication of the analysis method on erection procedures varied from minimal to total impact. Owners restrict flange dimensions to limit unwieldy flexibil- ity during handling and distortion after welding. Only one owner, Maine, restricts the width-to-thickness ratio (b/t) of FABRICATION flanges to between 12 and 20, with a preferred ratio of 16. Shop-Assembly Methods Three owners limit the width of the flange to a minimum of 300 mm (12 in.). These owners also limit the thickness to a The AASHTO/National Steel Bridge Alliance Steel Bridge minimum of either 19 or 22 mm (3/4 to 7/8 in.). Kansas has Fabrication Guide Specification allows either full girder or minimum flange dimensions that are a function of span progressive girder assembly (2). A review of specifications length. Texas, although having no requirements, presents submitted in response to the questionnaire shows that seven some preferences on the National Steel Bridge Alliance owners require full girder assembly unless contract docu- website ( ments specify otherwise. Fourteen owners and the AASHTO 2000.doc). Although Washington State has no specific lim- LRFD Bridge Construction Specifications (3) either specify its, officials there believe that some in-house guidelines and or allow progressive girder assembly as a first choice. Five AASHTO specifications would be helpful. It should be of the owners apparently have no shop-assembly require- noted that in Section 6 of the AASHTO LRFD Bridge Design ments, as no such provisions appear in their specifications. Specifications (1), an upper bound of 12 is placed on b/t for tension and compression flanges. There are various requirements for progressive girder assembly, whether first choice or an option to full assem- Member Length-to-Flange Width Ratio (L/b) bly. They range from minimal numbers of girders (two or three) or spans (one or two) per assembly to no specified Two owners require that L/b for compression members be less minimums at all. than 85. Minnesota requires an L/b ratio of between 80 and 85. Maine prefers that L/b for welded beams not exceed 90, but up to 110 may be used if economy dictates. Again, Texas pre- Alternate Shop-Assembly Methods Allowed sents some recommendations on its website. Most owners allow alternate shop-assembly methods. Vari- ous additional requirements noted were: In-House Steel Specialist or Advisory Group Must be approved, Fifteen owners have a steel specialist or advisory group within Should be equal or better than specified methods, their organization that reviews and provides assistance to Should be based on fabricators' performance, designers developing steel bridge plans. Must give credit based on cost differential, Used only if stresses and tolerances are within design Analysis Methods for Complex Structures limits, Must be in writing, A wide range of computer software and analysis methods were Must meet minimum specifications, reported as being employed when there were concerns about Only be considered if framing is simple,