ASCE 7-02 wind low rise method 1

[structural01]

Hello.

Is it correct to use roof angle=0 degrees to determine GCpf for wind parallel to ridge? Thanks in advance.

 

[Ron]

No. By definition, a ridge has angle > 0.

 

[structural01]

Ron,
I believe it is correct to use roof angle=0-5 degrees (figure 6-10 p. 56) for determination of GCpf for all wind parallel to ridge. An example p. 59 of the "Guide to the Use of the Wind Load Provisions of ASCE 7-02" shows that my thinking is correct. Anyone else agrees?

 

[structural01]

I forgot to mention that the roof is a gable.

 

[chichuck]

Figure 6-10 Note 7 says to use angle = 0 degrees and also how to locate the boundary between zone 2 and zone 3.


chichuck

 

[structural01]

chichuck.

Yes. That is correct.

Do you agree that if I have 2 Cp for windward and 2 Cp for leeward, I would have 8 load cases?

 

[structural01]

Chichuck,
I forgot to add. The Cp for MWFRS all heights method. Not low rise method.

 

[chichuck]

structural1,

I'm not sure I understand your question. But here's what I think you mean:

For calculating wind loads on roofs, MWFRS using Method 2 (this is not the low-rise method), you can find Cp for the roofs in Figure 6-6. For some of the windward roofs there are listed two Cf coefficients. (Sometimes there are two negative Cf values, other times there are two negative Cf values.) Each of these will actually define two separate load cases; one when combined with internal suction and a second when combined with internal prssure. IF you have a roof geometry where there are also 2 Cf values listed, that would represent two additional load cases (one when combined with internal suctino and a second when combined with internal pressure.) But looking at Figure 6.6, I see no case where there are two Cf values on leeward roofs. (The Cp values in the bottom part of Fig. 6-6 (normal to riddge for theta < 10 and Paralell to ridge for all theta are only for windward perp to ridge.) So your hypothetical case will never come up. I can see only 4 load cases.

Regards,

chichuck