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RE: Light composite beams

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If you are trying to achieve composite action, you need at least 2" of topping over the deck per AISC.
Jason Emoto

From: Michael Hemstad [mailto:mhemstad(--nospam--at)]
Sent: Tuesday, December 12, 2006 12:03 PM
To: seaint(--nospam--at)
Subject: Light composite beams

I have a retrofit situation where I am limited in both headroom and weight.  I am adding an exterior terrace above an existing roof.  The headroom is limited by our friends at the Historic Preservation office insisting on the new construction (actually, the roof of the restaurant one bay behind it) remaining below the sightline over the existing parapet as seen from the street.  The load is limited by the capacity of the existing structure to carry it.
I currently have light stringers (W10x17) spaced at 6 feet, carrying a 1 1/2 inch composite deck with 1 1/2 inch topping (3 inch total).  My deflection under pavers and live load is about L/450.
Is this a reasonable solution?  There isn't a lot of room for studs; can I get 2 1/2 long studs?  Alternatively, I could use a slightly heavier W8 with a 4 inch deck (1 1/2 + 2 1/2) and still make deflection work out.  This is slightly heavier and slightly more expensive, but I know the studs will fit.
Any thoughts?
Mike Hemstad

Michael Hemstad, P.E.
Meyer, Borgman and Johnson, Inc.
12 South Sixth Street
Suite 810
Minneapolis, MN 55402
(612) 338-0713 (main)
(612) 604-3621 (direct)
(612) 337-5325 (fax)