Crane support systems

[enfsgi]

Looking at a crane system independant from the building structure. No clearance to brace overhead from runway to runway so columns will be cantilevered to resist horizontal forces perpendicular to runway. Is the bridge and the trolley mechanism strong enough such that the horizontal forces perpendicular to rail will be shared across the bridge to columns on both sides? Equal sharing?

 

[bpstruct]

I'm assuming you don't feel comfortable tying back into the building framing/roof diaphragm? IBC allows a reduction in the wind load (if using allowable stress design) when combining with crane loads. The 20% required lateral load might be less than 50% of the calculated wind load...you MIGHT be able to justify the additional diaphragm shear induced in the roof diaphragm. I would study the crane load section in the IBC before making any assumptions though. And I would want to feel pretty good about the building too. If it is a metal building, I would use extreme caution.

Just my opinion, but I wouldn't want to count on the bridge alone.

 

[enfsgi]

Thanks for the quick response. Existing structure is PEMB designed as a warehouse, no accounting for crane. Owner has instructed that crane be independant of building. Found other posts on the sharing or lack thereof of the horizontal force accross the bridge. Will apply load without sharing at this stage.

 

[spats]

I would definitely NOT simply cantilever a plain steel column... will likely be way too much movement. If you've ever seen exterior bridge cranes the columns are buttressed with a leaning column and the two are laced together, forming a vertical truss that is wider at the bottom. Besides, the lateral load will simply roll the runway beam over if it's just sitting on top of a column. You would have to put an extension to the side of the column in order to brace the top of the runway beam.

In answer to the columns sharing the horizontal force - yes, equally shared if same stiffness each side. The horizontal load is 20% of the lifted load plus the weight of the trolley, including all accessories.

 

[bpstruct]

I agree with spats. I would want to stabilize those columns somehow.

 

[enfsgi]

Plan on an extension to which we can brace the top of the runway. I do not like the cantilevered column either, but not sure of alternatives. Have preliminary design with column taking all load (no sharing). Large column to resist moment and limit deflection to h/400. With sharing should be conservative. thanks for input.

 

[Sawbux]

Check Gorbel.com They have freestanding crane systems for the smaller capacity cranes. Maybe you can get one off-the-shelf.

 

[paddingtongreen]

I had one similar to this. I was able to brace the end bays and run horizontal trusses to stabilize the tops of the interior columns. It's not ideal but we could control the lateral displacement.

Michael.
Timing has a lot to do with the outcome of a rain dance.