Steel deck span condition
Steel deck span condition
(OP)
Steel roof and floor deck capacities are typically presented as a function of span condition. Most calculations I've seen assume a 3 span condition to get the most out of the deck; however, if you don't have supports in multiples of 4, wouldn't you be required to design some of the deck to a double or single span condition? When that is the case, how do you convey this in the contract documents?






RE: Steel deck span condition
You should design the metal deck for all applicable conditions. If you have simple-span conditions, then "Yes", design it for simple-span.
The contract documents should provide an explicit framing plan that would show all span conditions for the metal deck to be furnished.
If you feel that either your spec book or your General Structural Notes sheet does not provide sufficient information to draw necessary attention to what you want understood, i will often provide an additional note or specification within a box, near enough to the framing plan to clarify a special condition.
Is there something else you wish to convey that i may not have covered?
RE: Steel deck span condition
On occasion, I've specified three span for the first sheet installed from the edge of the roof and two span elsewhere. Usually, I'm wanting the three span for a governing condition that includes snow drift.
I like to debate structural engineering theory -- a lot. If I challenge you on something, know that I'm doing so because I respect your opinion enough to either change it or adopt it.
RE: Steel deck span condition
RE: Steel deck span condition
RE: Steel deck span condition
Of course single span is conservative.
Two spans, less conservative.
Three spans represents the best (most optimistic) case. Three spans was considered representative of any additional number of spans, say 4, 5, 6, or more. Precise (hand) calculations for 4 or more spans was not considered necessary for engineering purposes - 3 span numbers were good enough. This is not an unreasonable assumption - compare shear & moment results of 3 span and 4 span conditions - not much difference.
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RE: Steel deck span condition
RE: Steel deck span condition
Near the framing plan, I typically show only the deck profile, with a simple spec, (i.e. 1.5B22), with number of fasteners and layout.
With a satisfactory framing plan, it should be understood that i/we/the engineer has (at least) considered all scenarios when providing the depth, profile and gage.
RE: Steel deck span condition
RE: Steel deck span condition