ASCE7-05 Monoslope Wind Uplift

[kennyb04]

I am using Wind Method #2 for Low-Rise Buildings, 6.5.12.2.2 in ASCE7-05.

My question is regarding the GCpf value for the roof uplift in the transverse direction.

For the longitudinal direction, figure 6-10(cont.) note 7 says to use the Zone 2 load for the front(windward) portion of the building and then Zone 3 for the back half (even though both zones are along the same elevation.)

When you look at the roof load in the transverse direction, I think it is a little unclear since there is not a diagram for a monoslope direction.

I originally thought you would use Zone 2 for the front half and Zone 3 for the back half. Even though our roof is sloping up 0.25/12, it is essentially flat as it is in the longitudinal direction.

However, upon looking at some calcs from another source, it looks like they are using the Zone 2 load for the entire length of the roof with wind applied windward to the monoslope, and then applying wind in the other (leeward) direction of the monoslope they are using Zone 3 for the entire roof.

Any thoughts which way to use?

 

[ash060]

Note 8 in figure 6-10 (cont) covers that situation. So you can use 2.5 times the eave height if it is less than half the direction under consideration.

 

[kennyb04]

So would you agree that using the Zone 2 uplift for the entire roof for one load case is overly conservative and that we are able to reduce the back part of the roof to the Zone 3 loads?

Thanks for the input.

 

[ash060]

Yes the code tells you where to put the zone 2/3 interface