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7 If requirements are generally upheld for complex Pick points and reactions at pick points for all girder geometries, sections; If it makes sense, Temporary support points to be used during all stages Provided that an unsatisfactory product will be cor- and loading conditions, and reactions for which support rected by the fabricator, and towers should be designed at all of these points; If the fabricator assumes full responsibility for the Deflections to be expected in all girders under all con- procedures. ditions of temporary support and under all anticipated loading conditions; and Direction pertaining to the connection of diaphragms to Oversized Holes ensure stability during all temporary conditions. Sixteen owners allow oversized or slotted holes under some The opinions of the respondents on the value of erection circumstances to facilitate fit-up of diaphragms or cross- procedures provided by the designer ranged from "a positive frames. Another allows only vertical slots to permit differ- effect" to "a waste of time and money." ential movement between girders during deck pour (staged construction or bridge widening, not staged deck placement). A smaller majority of the owners (17 of 32) require the Ten owners prohibit the use of oversized holes. erector to submit an analysis and erection procedure whether or not the procedure was performed by the designer. The com- ments of individual respondents suggest that their require- Load Condition for Detailing Crossframes ments are not as rigorous, stating that the submitted erection procedures were for information only or record purposes, or Three owners indicated a need to research the appropriate both; required, but many times not actually submitted; and condition at which to detail crossframes: no-load, dead-load, not necessarily based on analysis. A few of the remaining or full-load condition. One owner is developing a set of spe- owners stated that the erector may be required to submit erec- cial provisions dealing with this issue. Another owner volun- tion procedures if specified in the special provisions or con- teered that it requires crossframes to fit in the no-load condition tract plans. (now a standard note on design drawing) for curved girder bridges, and in the steel-only dead-load condition for straight Nineteen owners reported that they provide some sort of bridges. review (ranging from casual to thorough) of the erection pro- cedures if submitted by the erector, but they apparently do not go so far as to approve the procedures. Among those owners ERECTION that stated that they did not review the procedures, the fol- lowing comments were added: "contractor's responsibility," Erection Procedures "would if requested," and "stay out of approval or checking." The vast majority of responding owners (27 of 32) do not require the designers to provide an erection procedure for com- Preferred Field Connection Practices plex structures. The other five owners specifically require the designer to provide an erection procedure as a part of the con- Seven owners expressed a preference for field connection tract drawings. On the basis of its experiences with severe practices that lead to good final geometry. Shop assembly, problems with erection of curved girders, one owner noted good field inspection, verification of shop and field measure- the following among its standard procedures: ments, and use of experienced personnel are the most cited preferred practices. Texas uniquely indicated that bolting or When designing curved girder structures, designers must inves- welding of field connections work equally well when prop- tigate all temporary and permanent loading conditions, includ- erly executed. Oklahoma indicated a preference for direct ing loading from wet concrete in the deck pour, for all stages of construction. Future decking must also be considered as a sepa- tension indicators to aid inspection of bolted connections. rate loading condition. Diaphragms must be designed as full load carrying members. A three-dimensional analysis representing the structure as a whole and as it will exist during all intermedi- ate stages and under all construction loading is essential to accu- Proven Methods for Erecting Complex Structures rately predict stresses and deflections in all girders and dia- phragms and must be performed by the Designer. Eighteen owners reported that temporary supports and/or bracing have proved valuable in erecting complex struc- The designer is responsible for ensuring that the structure tures. Launching of girders, particularly box girders, was is constructible and that it will be stable during all stages and cited by three owners as a proven method. Four owners under all loading conditions. To achieve this end, the designer believed that full shop assembly is useful in ensuring more must supply basic erection data on the contract plans. This easily erected complex structures. Several owners cited novel information must include, but is not limited to, the following: methods for erecting unique complex structures. For curved

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8 box girders, one owner prefers only one bearing at a support bolts; a maximum of 15% pins and sufficient bolts to keep for a single box. pieces together; and 25% bolts with the number of pins deter- mined by the engineer. Pinning and Bolting Procedures Because the pins are important in setting the geometry, the stage at which the pins are removed (before or after bolts Inadequate pinning and bolting practices, including field ver- are tightened) may have an impact on the geometry. Three ification of horizontal and vertical alignment, were reported owners specify that all holes not containing pins be filled to be the cause of a number of problems. Conversely, many respondents listed good pinning and bolting practices as with tightened bolts before removing the pins. Two owners essential to achieving an effective erected structure. specify that all the holes be filled with snug-tight bolts, whereas one other owner specifies that all holes be filled with The use of pins during the erection of the structure is an finger-tight bolts. important concern because the pins are very nearly the same diameter as the drilled or reamed hole. This situation allows Twelve owners' specifications reflect several varying very little movement, and consequently it is critical in setting requirements as to when the bolts should be tightened. The the final geometry of the structure. The AASHTO specifica- major difference seems to be whether they should be tight- tions and seven owners require an initial minimum require- ened after full girder lines, at full structure, or as part of the ment of 25% pins and 25% bolts in each connection. Nine structure has been erected, and if the horizontal and vertical owners cited an initial minimum requirement of 50% of the alignments require verification. holes filled with pins or bolts. Individual owners specified various requirements: at least two pins in extreme hole loca- Several owners reported problems with field inspections tions; pins in extreme corners of splices; eight pins in each and verification procedures. Problems ranged from inexperi- flange and web splice; 33% pins; a minimum of four pins; a ence and failure to inspect to failure of inspectors or project preference for 25% pins, 15% pins, 50% pins, and 50% bolts engineers to require the contractor to follow the approved in main splices; 50% pins and 50% bolts; adequate pins and erection procedures.