Supporting a Monorail Crane

[GalileoG]

I am trying to support a 10 ton monorail crane off the roof framing system of a new building. The roof framing system consists of steel beams running in one direction and OWSJ running perpendicular to the steel beams. There is about a 6" elevation difference between the underside of steel beams and the underside of the OWSJ, where the former is lower. The monorail track is only 15' feet long. I can not support the crane on any new columns because the floor area around the crane needs to be clear/open. The monorail will only be used once every few weeks and therefore fatigue is not a concern.

I have designed overhead crane support before (never a monorail though) where the runway beam would transfer load to the frame in bearing. I am aware of several framing arrangements to support this monorail off the roof framing system, but these rely on connections that are permanently in tension, and this concerns me.

One other method of transfer would be through shear - I am thinking about a very deep beam at the start and end of the track, running perpendicular and connected in shear to the web of the main roof beams. This cross beam would have to be copped, where the underside would be a full 20" below the underside of the main roof beams. Then, I would have the 20" deep runway beam running between the cross beams and connected in shear to the web of the cross beam. I would also have some kind of horizontal bracing arrangement. I'm not completely happy with this option because it requires a very deep beam which may not be readily available - and I'm not even how transferring load through shear would be any better than tension, but my gut tells me otherwise.

What other, cleaner and better options would you suggest? Thanks in advance.

 

[msquared48]

A sketch of the situation would help here.

Mike McCann
MMC Engineering

http://mmcengineering.tripod.com

 

[hokie66]

I suggest that your prejudice against tension is misplaced. Underslung monorails invariably depend on tension connections. A 10 ton monorail is not to be taken lightly. Check the roof beams...that may be a problem, and design the hangers, each to take the whole load.

 

[TLycan]

As I understand the Monorail will run perpendicular to the OWSJ. This Means,as you mentioned, you will have to add two cross beams or more depending on the span . As for connection in tension this is a normal case in monorail. Now in the case of the horizontal force in the direction of the monorail beam, the frame action of main beams and columns will take this load. for the horizontal load perpendicular to the monorail, the force is carried by the horizontal bracing between frames if exists. yet, the added cross beams should be at the location of the panel points of the horizontal bracing.
please not that the design of the monorail beam is some what different from the over head crane track girder

 

[MikeHalloran]

You'll be using nearly as much steel as it would take to put a bridge crane in there. The added areal coverage of a bridge crane may or may not be of value to the owner.

If they're going to be picking up loads that are not guaranteed to be perfectly centered under the monorail, that would put lateral loads on the roof beams. If the roof beams have enough lateral bracing to endure that, and enough vertical capacity to allow roaching on a big crane in some arbitrary location, the owner might be really pissed about the extra roof beam capacity he paid for, or (very remote possibility) grateful for a structural engineer's foresight. ;-)




Mike Halloran
Pembroke Pines, FL, USA