C&C Wind Loads
C&C Wind Loads
(OP)
The wind directionality with C&C wind loads is not made clear in the ASCE 7-10 however per the SEAW's Handbook for Wind Design the directionality should be considered when combining zones to determine the applied loads.
For a typical truss (interior) in a gable roof (4/12 pitch) I get the following:

My question is what to do with the overhang pressure on the leeward side? The standard does not mention whether overhang pressure are to only be applied to windward overhangs so I am assuming that it would also apply to an overhang on the leeward side but somehow this seems slightly counter-intuitive.
For a typical truss (interior) in a gable roof (4/12 pitch) I get the following:

My question is what to do with the overhang pressure on the leeward side? The standard does not mention whether overhang pressure are to only be applied to windward overhangs so I am assuming that it would also apply to an overhang on the leeward side but somehow this seems slightly counter-intuitive.
A confused student is a good student.
Nathaniel P. Wilkerson, PE
www.medeek.com






RE: C&C Wind Loads
this makes sense as it can't push up under the overhang from the leeward side. I would apply regular negative pressure
RE: C&C Wind Loads
Agreed, that is why I question my diagram above. However, I can't find any verbiage in Ch. 30 that applies the C&C overhang wind loads only to the windward side hence my uncertainty and bringing this question to the board.
The funny thing is that I've managed to get my hands on some load cases from Mitek and Alpine software. One applies the overhang pressures at both windward and leeward overhangs and the other does not, so I'm not the only one confused here.
A confused student is a good student.
Nathaniel P. Wilkerson, PE
www.medeek.com
RE: C&C Wind Loads
A confused student is a good student.
Nathaniel P. Wilkerson, PE
www.medeek.com
RE: C&C Wind Loads
When it flows parallel to the ridge I don't see any mechanism to cause it to flow up into the eaves. So I'm gonna say no.
RE: C&C Wind Loads
Without an overhang there are just zone 2 and zone 1 pressures, overhangs tend to complicate things.
A confused student is a good student.
Nathaniel P. Wilkerson, PE
www.medeek.com
RE: C&C Wind Loads
Should there be one other load case where both the windward and leeward side have the positive C&C pressure applied? My thinking is that the positive pressure would only be ever applied to the windward side of the roof but I don't want to mistakenly eliminate a load case from my analysis.
A confused student is a good student.
Nathaniel P. Wilkerson, PE
www.medeek.com
RE: C&C Wind Loads
http://design.medeek.com/resources/wind/WIND_ANALY...
PDF preview here:
http://design.medeek.com/resources/wind/WIND_ANALY...
The C&C spreadsheet for the corresponding open building is at:
http://design.medeek.com/resources/wind/WIND_ANALY...
PDF preview here:
http://design.medeek.com/resources/wind/WIND_ANALY...
A confused student is a good student.
Nathaniel P. Wilkerson, PE
www.medeek.com