Crane Building Sway

[JLNJ]

We have a 50' tall x 100' wide single slope PEMB with a 40 ton crane. The crane will be tied to the building but will have its own columns. The use of the crane is such that I'm calling it a service class D. Seismic is not an issue.

What sway do you all allow for such a building? Would you use a tighter sway criteria for a class D or E building than a class A or B? It is makes any difference, this is a design build project.

The PEMB guy is of course suggesting H/60 but this (10"!) seems a bit too loose for me. AISC, CMAA, MBMA all seem to dance around the lateral sway question without directly addressing it. I'm thinking H/100 for wind and H/180 for crane-induced loads.

Anybody have strong feelings on this one?

 

[Ron]

Keep the sway from the crane loads as low as practicable, since these are repetitive loads. As noted in AISC, ASCE 7 and MBMA, the lateral load on the structure should be at least 20% of the crane + crane load, applied at the top.

h/180 is still a lot of movement for a repetitive load. I seem to recall a requirement in MBMA of 1/300, but looking through my MBMA manual, I couldn't find it again. Check their crane manual...it might help.

Due to the repetitive nature of the loading, you might want to keep the lateral deflection to a point that would allow unlimited repetition (generally about 5000 psi for mild steel).

 

[weab]

Don't have it with me. Does AISC design guide for industrial buildings (design guide #7?) say anything on this matter?

 

[JLNJ]

Design Guide 7:

Pendant Operated : H/100 based on 10 year winds or crane.

Cab Operated: H/240 less than 2", 10 year wind or crane.
(This might be for the sake of the guy in the cab.)

 

[weab]

I would be OK using AISC recommendation, but I'd check to see if you have a fatigue problem elsewhere in the building. Find maximum deflection to keep down stresses to eliminate fatigue issues. If fatigue is not a problem, then this is just a comfort issue.

In general I'd say this. If the building is industrial, don't worry about it. If open to public or usually occupied, use allowable deflection for that type of building.

I hope this is helpful.

 

[bdSE]

I've recently been looking into this same issue and found some guidance from a Canadian publication that seems to cover a lot of the great crane design questions.

"Crane-Supporting Steel Structures"
Design Guide, Second Edition
R.A. MacCrimmon
Canadian Institute of Steel Construction

I was able to download a Draft Version on-line for reference.

In table 4.1 there is a whole host of guidelines for design and construction based on your crane type. Typically the service class D crane will have tighter criteria than the class A's. Here's a quote about the building frame sway...

"Building frame lateral deflection at runway beam level from unfactored crane loads or from the unfactored 1-in-10 year wind load should not exceed the specified fractions of the height from column base plate or 50mm (2"), whichever is less." For a Class D crane.... 1/400.

Well, there you go.

This resource has a lot of great information regarding the design of these structures, I recommend you find a way to get a copy.

 

[JLNJ]

Great resource. CISC has it as a free download.

 

[unclesyd]

A version.

http://www.sigi.ca/engineering/documents/cisc_crane_support_steel.pdf

The latest version

http://www.cisc-icca.ca/publications/technical/design/craneguide/

A good list of references.

http://www.aisc.org/assets/0/544/550/0aa88e48-307d-492c-a916-a9da0013d202.pdf

 

[ToadJones]

Keep in mind this criteria are from the runway height, not the building height.
Also, the effects of sway can be mitigated to some degree by load sharing between columns via bottom chord bracing in the trusses,horizontal bracing in the roof beams or a diaphragm.

Analyzing just a single 2D frame can be misleading unless spring supports are used.

 

[ToadJones]

Also, it is H/100, but 1" maximum at the runway elevation.
Anymore than that and you'll probably have severe runway alignment problems.