Richard D
Well-known member
Wanting to use a chainfall and trolley on either a 16' or 30' span. What weight can I support?
Doing a set of quick calculations assuming a maximum allowable bending stress of 12ksi (3x factor of safety based off standard A36 structural steel,) give a load capacity of about 6900 lbs at 16' span and 3700 lbs at a 30' span. That being said, for long spans, especially the 30' I would never trust these numbers. The calculations assume everything is always perfectly upright and in plane. On a long thin beam, often buckling will be the method of failure rather than simple bending to the point of failure.
Also, these calculations are assuming that the the beam flange can handle the load. In practice "W" section beams are not desired for lifting from especially from a trolley or beam clamp. These devices load the beam on the far outside edge of the flange, which can cause the flange to yield far before the beam fails in bending. An "S" section beam with a narrower and thicker flange would be more suitable.