ASCE 7-02 Wind Calcs - Method 2: All Heights Method
ASCE 7-02 Wind Calcs - Method 2: All Heights Method
(OP)
Hi,
What are the values of Cp that I can use to analyze the leeward roof (wind direction parallel to ridge) for method 2 MWFRS? Figure 6-6 does not have a table under the leeward column... I'm a structural engineer intern, and this is the first time I've encountered something like this.
Oh, and fyi... h/L < 0.5 with horizontal distance from windward edge between h/2 and h.
Thanks!
What are the values of Cp that I can use to analyze the leeward roof (wind direction parallel to ridge) for method 2 MWFRS? Figure 6-6 does not have a table under the leeward column... I'm a structural engineer intern, and this is the first time I've encountered something like this.
Oh, and fyi... h/L < 0.5 with horizontal distance from windward edge between h/2 and h.
Thanks!






RE: ASCE 7-02 Wind Calcs - Method 2: All Heights Method
RE: ASCE 7-02 Wind Calcs - Method 2: All Heights Method
Thanks for your reply... but what I was asking was, what values of Cp can I use for the leeward roof. I know the windward roof values are given but I'm not sure what to use for the leeward roof.
RE: ASCE 7-02 Wind Calcs - Method 2: All Heights Method
RE: ASCE 7-02 Wind Calcs - Method 2: All Heights Method
RE: ASCE 7-02 Wind Calcs - Method 2: All Heights Method
You are correct in that leeward is a relative term in this case.
RE: ASCE 7-02 Wind Calcs - Method 2: All Heights Method
Thanks for the reply. I don't see why there wouldn't be a leeward side, regardless of wind direction? I don't understand why they don't have the Cp values for leeward direction on the roof for wind blowing parallel to the ridge.
RE: ASCE 7-02 Wind Calcs - Method 2: All Heights Method
RE: ASCE 7-02 Wind Calcs - Method 2: All Heights Method
So, if the total horizontal distance from the windward edge is h and the roof is symmetric (equal area on both halves), then the windward and leeward roof pressures will cancel out? Or, do I calculate for the worst combination (i.e. use -0.9 for windward half, -0.18 for leeward half or vice versa)?
RE: ASCE 7-02 Wind Calcs - Method 2: All Heights Method
RE: ASCE 7-02 Wind Calcs - Method 2: All Heights Method
So would that mean the wind pressure parallel to the ridge would only have one value? Wind pressure normal to the ridge had two values to calculate the total pressure, but the parallel direction has only one pressure acting on it?
RE: ASCE 7-02 Wind Calcs - Method 2: All Heights Method
RE: ASCE 7-02 Wind Calcs - Method 2: All Heights Method
RE: ASCE 7-02 Wind Calcs - Method 2: All Heights Method
RE: ASCE 7-02 Wind Calcs - Method 2: All Heights Method
But just to confirm that I understand this correctly. Horizontal distance from windward edge is the length of the building in parallel direction (based on ASCE notes "L"). Since leeward does not exist, we would analyze roof for the same pressure acting on whole roof and select Cp base on total length of the roof that is parallel to the wind direction. Is that correct?
RE: ASCE 7-02 Wind Calcs - Method 2: All Heights Method
RE: ASCE 7-02 Wind Calcs - Method 2: All Heights Method
what you are saying is that you should divide the roof into sections. so that is different from what Ron was saying on having one pressure on the whole roof. I guess that would make more sense since bigger value are closer to the windward side, and if you would analyze based on whole length then you would have lower value that would not represent condition of whole roof.
Im trying to get this correct since as you can see, everyone is comming up with different interpretation of the code.
RE: ASCE 7-02 Wind Calcs - Method 2: All Heights Method
RE: ASCE 7-02 Wind Calcs - Method 2: All Heights Method
RE: ASCE 7-02 Wind Calcs - Method 2: All Heights Method
I have ratio h/L=0.87, values that are givien in the table are for h/L<0.5 or h/L>1. So Im in between and what now?
RE: ASCE 7-02 Wind Calcs - Method 2: All Heights Method
I have new question regarding Cp for roof in wind direction normal to ridge for 0 degree angle and for wind parallel to rige.
I have ratio h/L=0.8, values that are givien in the table are for h/L<0.5 or h/L>1.
What does one do in this case?
RE: ASCE 7-02 Wind Calcs - Method 2: All Heights Method