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10 OTHER IMPORTANT ERECTION Falsework CONSIDERATIONS Proper placement of the required falsework is essential. Ele- Substructure Alignment vations should be set to account for tolerances and to match shop blocking dimensions. Additional cranes may be used as Horizontal and vertical alignment of the bearings and anchor a substitute for falsework, if necessary or desirable. bolts should be accomplished (by others) before erection begins. Adjustments for any errors in elevation or location should be made at this time. KEY ISSUES FOR A PROPERLY ERECTED BRIDGE In the collective opinion of the fabricators, a properly erected bridge should involve the following: Ground Assembly · The designer should address constructability issues (e.g., When members are to be assembled on the ground, they differential deflection) and keep the design simple. should be properly blocked (in the no-load condition or the · The owner should enforce submittal and approval of an same condition as that used in the shop), pinned, and bolted. erection procedure prepared by the erector. Also, the alignment should be checked before lifting the mem- · The fabricator should understand the geometric features bers in place. One fabricator suggested that the erector obtain and how they affect erection, properly match-mark the records of the actual blocking dimensions recorded in the splice plates, maintain appropriate sweep and camber tol- shop during the shop assembly. erances, consider complexity of the structure when deter- mining shop-assembly method, accurately drill holes, and properly detail the structure. Sequence of Erection The erector should provide an erection procedure that addresses measures that lead to the desired erected structure, The sequence of erection has a great impact on the overall keep the ends of the girders aligned and webs vertical, prop- geometry. Owing to fabrication and erection tolerances erly orient match-marked splice plates, and use qualified erec- and practices, member deflections, and bolting/pinning tors and experienced crews. practices, both horizontal and vertical alignment and the In general, horizontal and vertical alignment verification of stability of the structure are controlled by the sequence of both the substructure and the superstructure at all stages of the the erection of the girders, as well as the attendant cross- process is critical to attaining a well-positioned and erected frames. structure.