Steel Decking Design 1

[collma]

Help! I am not experienced in designing floor systems using steel decking.

The floor decking will span 5' maximum and will not have a concrete overlay. I will have a 2/3" steel plate covering the decking, but it will not be attached sufficiently to comprise a composite system.

My primary live loading will be from a 13,000lb forklift. With this kind of decking how would you apply the forklift load? Would it be more of a point load over each individual wheel, or applied over the area of the forklift?

How do you calculate web crippling in a steel deck that doesn't have a concrete overlay? I have found several examples using concrete, but none without.

Any help would be greatly appreciated!

 

[ishvaaag]

Assuming you weld connect the plate to the underlaying deck the biggest theoretical problem I see is that your beam will be neither thin steel plate as if only cold formed steel nor structural steel only. In the doubt, going for the as if thin case, or AISI code, a rendition of which is in UBC code should give a safe solution, provisions caring for crippling included.

I did one spreadsheet for deck design and have also at least one worksheets in Mathcad dealing with deck-only designs...AISI I have seen somewhere (maybe the Mathsoft's site itself) makes available mathcad worksheets with which you should be able to deal with any crippling situation at hand.

Respect analysis, and in lack of previous experience I would deal with the forklift load both as area load and wheel loads, since the deck is prone to crippling being relatively thin.

 

[dougantholz]

Collma,
USD publishes some web crippling/maximum deck point load information. It is usually on the inside cover of Modern Steel in the US. In fact is in the latest MS.
Secondly I would ask a question of why are you putting deck, which is not very strong under the steel plate. I would say that the deck does not add anything to your system, so I would just bear the plates on beams.
There's my 2cents

 

[JAE]

Here is the website for USD that dougantholz referred to. You can find the deck tech sheets under the USD page.

http://www.njb-united.com/usd.htm

I would be very careful about allowing such a heavy forklift on a metal deck even with the plate cover. A forklift also loads floors with impact and local crippling/buckling of a deck flange can be devastating. Why no concrete?

 

[collma]

Thank you all for your help with this topic. I found the USD web site very helpful. I may have found a product that will work for this project. I will use the suggestion to analyze the decking using the point and distributed load of the forklift.

I know that the use of steel decking sounds a bit strange for the application, but I wasn't given a choice about the floor structure. I was just told to find a decking product and make it work. The company I work for provides great latitude to the scientists to specify exactly what they want, and leaves it to us structurals to make it happen (no matter how infeasible it is).

Again, thank you for your help.