Crane Support

[SperlingPE]

I am in the pre-design stages of a wood frame building w/ wood trusses at the roof. There is to be a 2 ton capacity bridge crane running the length of the building. The runway beam at one side will be supported by the trusses. The other runway beam will be supported off of steel columns.

Has anyone run into this design problem?
I am in contact with the truss supplier to help coordinate any requirements.
How did you support the runway beam?
How did you brace the runway beam for the lateral loads?
Was deflection an issue?

 

[vandede427]

I really don't think I'd support a bridge crane off of wood trusses, even for a small load like 2 tons.

Maybe if it was a monorail crane where the crane hung from a beam's bottom flange, but to get a top flange bearing bridge crane to hang from wood trusses just doesn't even sound doable let alone a good idea.

 

[SperlingPE]

vandede427

I share your concerns and I have shared my concerns with the architect and owner.
At this point I want to make sure that I am considering all aspects of this design problem, before putting the brakes on or moving forward.

Any information that anyone has would be helpful.

 

[271828]

How would you address cyclical loads on a wood connection or member? I'm not a wood expert, but I don't remember seeing anything about that in the NDS. Can you push them to provide steel supports for the crane itself?

 

[spats]

Obviously, the bridge is underhung, otherwise it can't possibly work.

My advise... don't do it. I would never hang a crane from pre-engineered wood trusses, no matter how small.

 

[beton1]

In addition to the good points already raised: I would contact the truss supplier to get their input. It may reinforce/help you convince the client against this idea. The thought of even a light load on two different support systems, especially with one being wood, raises concerns.

 

[msquared48]

Usually the deflection limitations are L/600 to L/1000. If the wood truss can handle it, I think it can be done. It's true that it is not the norm, but what is nowadays?

Mike McCann
MMC Engineering

 

[sundale]

In addition to gravity loads and fatique concerns, your truss heel will have to take the crane braking forces in the transverse and longitudinal direction. Consider a 1.0C + 0.5W load combo occuring at the truss heels and the associated blocking, strapping and nailing to deal with this...

A 4 kip bridge crane supported like this on one side only seems like a VERY questionable load path to me. I would politely poo poo this "idea" with the owner and architect or try and talk them into a smaller self supported gantry crane.

 

[FLCraneBuilder]

Perhaps a bit late in reply - but

We have done this in the past - by using a steel truss in between each wood truss - the steel truss carries the crane loads and the wood trusses are there for roof support.
The steel truss had a 2x6 "nailer" on top to fasten the plywood sheathing to it.

we were dealing with 25,000# crane load, so we put the steel trusses on 14' centers, with your 2 ton crane, you might want to go with 20 to 25' centers -