Steel Erection Tolerances

[tw]

An owner has a recently erected pair of crane rail beams for an underhung crane. The beams were not erected to CMAA specs but were erected under AISC 1989 specs (job originally commenced in 1992). The owner has since had the beams surveyed by a crane service group & found that the beams do not meet CMAA tolerances & has asked us to tell him if the beams meet AISC tolerance specs. Reading section 7 of the Code of Standard Practice for Steel Bldgs makes this look like a complicated task. Does anybody have any experience in this and/or have any advice for how to go about this.

 

[jrmack]

You are right. The Crane Manufactuer's Association (and also the elevator manufacturer's requirements), are more stringent than the AISC for building tolerances. The support beams can end up being eccentric without the capacity to support the loads. Some means of adjustment in the case of crane rails must allowed for in the design.