Capacity of Steel Deck

[canstruct]

Hi Everybody,

I am designing structure for mechanical units which is located above grade level. Spans are large and we need to provide composite steel deck. Requirement is to place mechanical units having some sort of moving load and the some area should have a capacity of resisting live load of 12.6kPa(Unfactored). I see the manuals for deck design which have some limiting capacity of factored load max upto 20 kPa. If i need to design steel deck with concrete for more than this loading, what i have to do. Sometimes in mechanical units supporting at intermediate levels we cannot provide separate steel framing, instead we are providing house keeping pad to support it.

Appreciate for help in this matter.
Atif

 

[msquared48]

In lieu of a solution from the manufacturer, you might consider using the deck only as a form deck, and designing the slab to take the total load.

Mike McCann
McCann Engineering

 

[canstruct]

Thanks Mike,

Is there any criteria for average slab thickness to use, e.g if i have a 3". steel deck with 4" concrete, Can i assume 4+3/2=5.5" th. slab safely. As the rib width of the deck is small as in the case of 3" deck as compared to 1.5" deck, loads are more concentrated in the support zone, do we need to check some stresses there or we can based on reduced average slab thickness or average thickness works well.

 

[shin25]

The load normally will be distributed on a larger area than the actual foot print of the mechanical unit.

 

[DTGT2002]

Contact the engineering department of the brand of deck you intend to specify. I have found the Vulcraft engineering department remarkably helpful in many atypical situations. I have reliably used Vulcraft decking as a form for 12" and 24" slabs in the past. You can use the tabular data for other thickness slabs to get a feel for how much concrete is displaced by the decking, though I typically design for the full depth when determining my self dead weight of concrete.

I would either use the tables, as most decking providers have loading for 4" slabs, or use the full nominal depth. You could also use the tables for thicknesses shown and add the additional load if your slab must be thicker. However, when using slabs thicker than those listed, you must verify the loading will not exceed the web crippling capacity of the deck. Vulcraft can provide further info to help you with their product.

Best of luck,

Daniel Toon

 

[civilperson]

Do not forget the snow/rain loads if this deck is exterior.

 

[canstruct]

Thanks Guys,

I appreciate your support. Canam is the larger deck supplier herein Canada. I will contact them regarding this matter to support loading more than that specified in their tables we have. Like if we can provide WWF in concrete, it should certainly have more load carrying capacity except the web crippling of the deck as you mentioned.