underhung hoist rail - lateral loads

[enfsgi]

Underhung hoist or bridge crane. The rail is supported at the top flange. There are no other supports. The required horizontal force is applied at the bottom flange. As such it either bends the web or puts the section in torsion. But the supports being at the top rail only do not give much, if any resistance to the torsion. How is this accounted for in normal practice?

 

[MikeHalloran]

Let the web bend. ... and act like a pendulum or hanger, to convert transverse loads into vertical loads.

Overhung bridge cranes' rails are set up with some slack in the transverse direction, so as not to bind the truck wheel flanges on the rails. With proper geometry, the flanges will self-center between the rails, so the rails and the runway beams don't have to be perfectly straight, or placed in their exact ideal position laterally.

By contrast, for underhung cranes, extra care is required to hang the runway I-beams at exactly the correct distance from each other, because the bridge beam has no axial compliance. I.e., any errors in 'track' at the top of the runway beams will make it necessary for their webs to flex laterally as the crane beam passes.



Mike Halloran
Pembroke Pines, FL, USA

 

[amec2004]

I would put the half depth stiffener paltes at 12" c/c to increase the web flexure resistance.

I have some interesting photos at

http://civilbay.com/download/Stiffener-Plate-Help-Beam-Web-Local-Bending.pdf

Hey, you don’t want to see your underhung crane beam behaving like this huh ?

anchor bolt design per ACI 318-11 crane beam design

http://www.civilbay.com