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
Source: Maine Standard Specifications for Road and Bridge Construction, 2020 Edition. Pages 363–363 of 817.