Structural Steel Erection, Framing, and Alignment
Erection questions test AISC 303 and field judgment. The erector owns means, methods, sequencing, temporary support, and safety; the EOR owns the design. Before erection begins, verify that approved erection drawings are on site, the foundations and anchor rods are within tolerance, and stability is addressed - temporary bracing, guying, and shoring must be designed, not improvised.
Alignment concepts
- Plumbing: columns are brought to plumb and held until the permanent framing and bracing are in place. A common tolerance is 1:500 of the column height between adjacent girts or splices.
- Elevation and alignment: member alignment is checked relative to established column lines and elevations; camber is verified as fabricated, not as an erection defect.
- Dead load connections: certain connections are detailed to be made only after the structure has been plumbed and aligned, allowing the frame to shed construction loads.
- Anchor rods and base plates: verify projection, thread condition, and shim packs; over-tightening or bending anchor rods to close a misfit is a reportable condition.
Know the difference between mill tolerances (permitted variation in the fabricated product) and erection tolerances (permitted variation in the assembled structure). A member at the edge of a mill tolerance may still require adjustment; it does not excuse an out-of-plumb frame beyond erection tolerance. Any correction outside tolerance must go to the EOR before force is applied to the steel.
Traps: the inspector directing the erection crew; assuming temporary bracing is the EOR's design; accepting heat-corrected plumbness without documentation.
Worked example: a 40 ft tall column measures 1 1/4 in. out of plumb. That exceeds 1:500 (about 1 in.), so it is a nonconformance - record conditions, notify the EOR, and do not let the crew "pull it with a come-along" without an approved plan.