Wind Load on an Open structure
Wind Load on an Open structure
(OP)
I am currently looking at an open structure for a project. The problem I am having is with the h/L ratio. Per ASCE 7-05, Figure 6-18B, the minimum h/L ratio is 0.25. My structure has an h/L ratio of approximately 0.16.
I looked through the ASCE 7, and did not find an alternative way to determine the wind loads for the building.
I am considering just ignoring the ratio and proceeding with the analysis, but I was wondering if anyone knew of a "legal" alternate way of doing this analysis, or any other suggestions on this matter.
Thanks
I looked through the ASCE 7, and did not find an alternative way to determine the wind loads for the building.
I am considering just ignoring the ratio and proceeding with the analysis, but I was wondering if anyone knew of a "legal" alternate way of doing this analysis, or any other suggestions on this matter.
Thanks






RE: Wind Load on an Open structure
For a very squat building, there might be some addtional pressures from the wind entering and leaving the open sides. It would be very conservative to assume the ends are solid and add those forces to the Figure 18B forces if that doesn't greatly change your design.
RE: Wind Load on an Open structure
What is frustrating is the ASCE 7-05 gives no parameters of what to do when you DON'T meet the minimum or maximum h/L.
RE: Wind Load on an Open structure
As far as ASCE 7 not having any parameters for your case, you've got to admit it's somewhat unusual.
RE: Wind Load on an Open structure
I do not know what "h" is in your code, but if h/L is about 0.16, I am guessing that "h" is either the height of the sloping roof or the vertical distance from the ground to the middle of the slope.
If you are interested, I could send you some material from the NBC.
Best regards,
BA
RE: Wind Load on an Open structure
RE: Wind Load on an Open structure
The 'h' dimension, per ASCE 7, is the mean roof height...The average of the dimension between the eave height and the top of the peak.
The plan dimensions of the building are 152'x 354'. The eave height is 13' with a gable roof slope of 4/12.
RE: Wind Load on an Open structure
RE: Wind Load on an Open structure
In your case, h = 13 + 152/12 = 25.7' or 7.82m, giving a value of Ce of 0.952, close enough to 1.0.
Hope that helps.
Best regards,
BA
RE: Wind Load on an Open structure
Use 16-8B for 26' at the eaves and 6-11D for the middle 100 ft.
The rational behind this approach is that the greatest turbulence occurs at the eaves.
Just to be safe, I would check using 16-8B for the whole roof and compare it with the above approach to see which produces the greatest horizontal and vertical loads and go with the highest load.
It gets even more complicated if you have a back wall.
Just be glad you didn't have to design this with ASCE 7-02.
Figure 16-8B didn't exist.