5-71
504.23 Die Stamping Die stamp primary members (including splic e material,
diaphragms and cross frames on curved bridges) in no-stress loc ations. No-stress locations include the ends of girders within the cross-sectional area, we b splice plates in the middle third of the plate height and out side the outermost row of bolt holes and flange splice plate ends between the outermost row of holes and the edge. Use blun t-nose, low-stress dies.
504.24 Camber and Curvature When camber or curvature is requir ed for stringers or
girders, it will be specified on the Plans. Measure and record specified c amber or curvature using the same ordinates show n on the reviewed shop drawings af ter all welding is complete. When no camber or curvature is specified, variations in straightness of rolled shapes, with and without cover plates, shall not exceed the tol erances of AASHTO M 160 (ASTM A 6).
504.25 Heat Cambering and Curving Minor correction of camber o r sweep of welded
plate girders is considered part of ordinary shop fabrication p ractice and does not require an approved procedure, however, use the following guidelines:
1.Notify the QAI prior to beginning heat correction 2. Do not use hammers 3. Have suitable temperature indicating crayons at the work sta tion
4.Do not exceed 1150º F 5. Cool in still air to 600 º F. B elow 600 º F compressed air may be used All cambering and curving operations that are not corrective sh all meet the following: Use a camber/curving procedure reviewed by the Fabrication Engi neer. The procedure shall include:
1.The heating pattern and sequencing of heating 2. Method of support of the member 3. Proposed minimum and maximum base metal temperature 4. Method of heating (fuel, nozzle size, etc.) Clean structural steel to SSPC SP-6 prior to heating. Heat bot h the flanges and the web using two torches (one torch on e ither side of the plate). Do not use restraint or jacking devices unless approved by the Fabrication Engineer. Submit ca lculations showing that the nominal bending stress in the member does not exceed 0.60 F y if restraint or jacking is proposed. The target temperature for all ASTM A709 steel is 1100º F. St eel heated in excess of 1200 F will be subject to rejection. Measure the temperature of th e steel with temperature indicating crayons applied to the heated area 10-15 seconds aft er the torch is removed or with a pyrometer that has been calibrated within the past year. Provide temperature- indicating crayons in increme nts of 50 º F between 1050º F and 1250º F to each torch 5-72 operator. Stop the cambering/curving operation if a torch oper ator fails to demonstrate the proper skill and technique necessary to prevent potential damag e to the steel. Camber stringers and girders using a “V” pattern with a 10-15 d egree included angle that extends the full web depth, less 2 inches at the apex. He at the web first beginning at the apex of the triangle and proceed ing toward the base. Begin hea ting the flange immediately after completion of the web. The Contractor may curve stringers and girders using a combinat ion of line heats applied to the edge of both flanges simultaneously with automatic track torches and "V" heats. "V" heats shall have an included angle of 15-30 degrees and a minim um height of 65% of the flange width. Apply heat to adjacent areas on both flanges sim ultaneously. Perform all cambering and curvi ng in the presence of the QAI. Heating a structural member without the QAI present shall be cause for rejection of the member. Measure and record camber and sweep after the steel has reached ambient tem perature and all stiffeners and connection plates have been welded.
504.26 Welding Qualify welders and Weld Procedure Specificatio ns in accordance with
the most recent edition of the D1.5 Code. Provide a list of qualified welders including process and position to the QAI prior to beginning fabrication. Submit the Weld Procedure Specifications to the Fabrication Engineer for review prior to beginning work. Weld Procedure Specifications previously reviewed and still valid in accordance with the D1.5 Code are acceptable without re-submission.
504.27 Welding Requirements Calibrate welding equipment at the intervals indicated in
the D1.5 Code. Meters shall be accurate within 2% throughout t he range of the WPS. Work done with equipment that is not properly calibrated will be rej ected. Provide copies of the calibration records to the QAI. The QAI can require the Contra ctor to demonstrate the accuracy of the meters at any time. Display a copy of the applicable Weld Procedure Specification a t each welding station. Weld within the parameters of the Weld Procedure Specification. Failure to display a Weld Procedure Specification at the welding station will make all we lding performed at that station subject to rejection. Perform all preheat, welding and postheat in accordance with th e D1.5 Code and this Specification. Provide the appropriate temperature indicating crayons at each workstation to verify preheat. Calibrated digital thermometers may be used with the approval of the Fabrication Engineer instead of temperature indicating crayons.
Source: Maine Standard Specifications for Road and Bridge Construction, 2020 Edition. Pages 363–364 of 817.