Rail Crane Column Brackets

[B16A2]

Is there any possible way to support heavy (100kip reactions) rail cranes, by any means other than dedicated columns located directly under the rail beams? I'm well aware of weld fracture issues, and many manuals say not to bracket above 50kip loads. Just wondering if anyone has overcome this as I have a client wanting to use overlapping high/low rails.

 

[ToadJones]

100 kips is really extending the recommendation of not going over 50 kips.

I guess anything can be designed.

You have two cranes running one over top the other?

 

[B16A2]

Yep, one bay will have overlapping cranes. If I have to use dedicated columns, it will kick the entire lower crane rails in to allow the high columns to pass.

I'm just not sure you can design anything enough to prevent fracture

 

[ToadJones]

Pretty unique situation for such heavy reactions.
most of the time you see a single gantry on the lower level.

I know I would be most comfortable with independent columns or a column right along side the crane shaft for upper crane....of course this would mean very tight side clearances on the lower crane.

 

[ToadJones]

Keep in mind also, that if you use brackets, your reactions should include impact.

 

[B16A2]

Yep, impact and lateral. I'm looking to see if anyone overcame this limitation.

 

[ToadJones]

I have analyzed a runway in the past that had VERY deep brackets. If I had to guess, they were 6'-8' deep. I analyzed them for reactions that were around 60 kips.
In that case I felt comfortable in analyzing them for more than 50 kips.
They were so deep, they were almost hard to consider as brackets.

 

[audeuce02]

Toad,

Were the 6-8' brackets actually fabricated as a bracket, or was it a 6-8' section of beam attached to the columns flange like a column segment?

 

[ToadJones]

welded up plates. They were nearly half the length of the column itself.

 

[hokie66]

I would call Toad's solution a stepped column rather than a bracket. You can look at using a stepped column solution with a gap to allow the lower crane to pass.

 

[B16A2]

I hear what you're saying, but what criteria did you use to justify the welds wouldn't initiate a crack(s) at the top and zip down the column face? More is not always better in the fracture world.

 

[hokie66]

You could use a separate column for the lower crane, then step the building column at the upper crane, so that the crane is supported over the inside flange of the building column. Then provide a bracket on the outside to support the roof. Thus no crane is supported on a bracket...just the building frame is offset outward at the top. The crane bridges would have different spans.

 

[ToadJones]

Hokie-
I wasn't really a stepped column in the classical sense of a step-column.
It literally was a giant bracket....but I guess once a bracket gets that big, it can be view a little differently.

I guess I had no criteria and I'm not sure one exists.
It was not a new design and the capacity increase was not a large percentage.

Is his a new building?
Is there no room for extra columns?

I'd advise the owner than it is in his best interest to avoid brackets.

Is there a particular fracture issue that is of concern for the welds?
I'm thinking that with very large brackets, the weld stresses would be low?

 

[MikeHalloran]

Could the 'inner' crane be a gantry, running on rails in the floor?



Mike Halloran
Pembroke Pines, FL, USA