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Re: Open Building with Gable using ASCE

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Tripp Howard wrote:

. > You can get Cf for this condition from Army TM 5-809-1, Chpt. 5 "Wind 
. > Loads". It gives Cf for arched and gabled roofs on open sheds.  I printed 
. > out a copy from the web a while back, but can't seem to find it on the 
. > web now. I think the manual has been discontinued/superceded by another 
. > military manual.
 
. > Anyway, if you can find a copy, here is basically what it says.  For a 
. > roof slope of 30-deg or less, Cf = +0.60 on windward slope (acts inward) 
. > and -0.60 on leeward slope (acts outward). For roof slope greater than 
. > 30-deg, Cf = +0.80 windward, and -0.80 leeward.
 
. > Hope that helps.  This is the only recommendation I have ever beeen able 
. > to find.  Let me know if you find anything else.
 
. > Tripp Howard, P.E.

Tripp,

Something doesn't seem right here.  The gabled roof should act as an airfoil, 
resulting in a net uplift.

IIRC, 30 deg. is the slope where wind on the windward roof changes from 
suction to pressure.

ASCE Transactions, Vol. 126, shows Csub(pe):

Surface:         A     B     C     D
30 deg slope   +0.6  -1.0  -0.5  -0.9
w/stored matl  +0.1  +0.8  -0.7  +0.9

10 deg slope   -1.0  +0.3  -0.5  +0.2
w/stored matl  -1.3  +0.8  -0.6  +0.7

where:   A is the top windward surface
         B is the inside windward surface
         C is the top leeward surface
         D is the inside leeward surface

A. Roger Turk, P.E.(Structural)
Tucson, Arizona

Rich Lewis wrote:

. > I have a gable shaped roof maintenance shed with a 3:12 roof pitch. The
. > shed is open, no side walls. I am looking at Table 6-1 on page 16 and
. > there is a column for "Open Buildings and other structures". The Cf
. > value is obtained form Tables 6-6 to 6-10 (pgs. 32-33). There is not a
. > table for a gable style roof. There is one for a monslope roof.

. > What Cf value do I use if I have a gable roof of an open building?

. > Thanks.

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