I am currently calculating wind loads for an insulated metal panel assembly and had a few questions regarding the effective wind area. The IMPs are fastened (concealed fastening) at every girt/purlin location and every width of the panel and acts as one composite when installed.

In the Chapter 6 wind load commentaries of ASCE7, it states: "For a cladding panel, the effictive wind area may be equal to the total area of the panel. For a cladding fastener, the effctive wind area is the area of cladding secured by a single fastener."

Say I am using a 3' wide wall panel that is 30' long fastened to girts 5' o.c. Do I:

a) Take the effective wind area of the panel (30' x 3') to determine the wind load. Use that wind load and apply it to the tributary area of each fastening location to determine number of fasteners required at each location, or

b) Take the tributary area of each fastening location as my effective wind area to determine the wind load? If this is the case, there will be two different loads in the corner zone - one with a full tributary area and the edge panel with half the tributary area. Why would these areas see different loads if the wind is uniform and acting onto the full panel assembly as a whole?

c) Use the full panel length to calculated the effective wind area when determining whether the panel itself would fail (not fastening) or do I take the span length (girt to girt) to determine the effective wind area?

The code seems open to interpretation when it talks about the single fastener effective wind area and I am not sure which way to design the panels. Any insight would be great. Thanks and I appreciate the help.

2. I just searched Chapter 6 and was unable to find "For a cladding panel, the effictive wind area may be equal to the total area of the panel. For a cladding fastener, the effctive wind area is the area of cladding secured by a single fastener."

I do know that for design pressure on all buildings and other structures shall be based on the highest winds loads for any direction at the site.

Dissecting your statement "For a cladding panel, the effective wind area may be equal to the total area of the panel." - makes sense as the total area is what matters.

"For a cladding fastener, the effective wind area is the area of cladding secured by a single fastener." This is reasonable as well as the wind loading applied to the fastener can only be that area related to the fastener. Basically I would think for a robust design, one would determine the fastener with the highest loading and run the numbers.

Though! I would lean toward your interpretation given by "a" "Take the effective wind area of the panel (30' x 3') to determine the wind load. Use that wind load and apply it to the tributary area of each fastening location to determine number of fasteners required at each location".

This is a practical interpretation as determining which fastener sees the most wind loading would likely prove to be a fruitless pursuit.

Also, I suggest you find somebody whom has an approved wind design experience to answer your question definitely

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