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Effective Wind Area ASCE-7-05

Effective Wind Area ASCE-7-05

Effective Wind Area ASCE-7-05

I am new to the ASCE-7-05 code book. I need assistance in determining big "A" for effective wind area.

Say I have a residence that is 10' wide, 20' long and 10' high to plate. What would "A" be for this? Basically I'm confused as to the description and how it's calculated.

RE: Effective Wind Area ASCE-7-05

The "effective wind area", "A" is defined in section 6.2 of ASCE7-05. It is only used to calculate the Components & Cladding pressure. Essentially, the code tells you that the smaller the effective wind area actually is, the larger the wind pressure will be (for that area).
Note that the minimum "A" need not be less than the span length (of the member) times 1/3 of the span length, or L squared divided by 3.

RE: Effective Wind Area ASCE-7-05

The length component of the large "A" is determined by the calculation of the small "a" from note 10 at the bottom of Figure 6-2 (Method 1).  The distance along the wall for "A" is then "2a".  You can see similar application of "a" in the other figures following too.

Hope this helps.

Mike McCann
McCann Engineering

RE: Effective Wind Area ASCE-7-05

msquared48 defined "Zone A" for use on MWFRS in Method 1.
In my previous post I defined effective wind area, A for use in Components & Cladding forces. They are both correct.
If you think that is confusing, wait until you get to Load Case A & B for use in Figures 6-18A through D.
The folks that brought us the wind load provisions of ASCE 7 did not make it easy to use.

Good Luck

RE: Effective Wind Area ASCE-7-05

Thank you all for replying. This has helped.

Since I'm really familiar with UBC97 and now that our county has adopted CBC 06 and ASCE-7-05, I'm a little behind the curve.

Is there a good publication that can help me use the various new code books with examples?

I would like to use this publication with the new analysis software from Daniel Li (Engineering-International).

I'm just having a little trouble interpreting the new code book and plugging in the right values of my software.

Thanks again to all!

RE: Effective Wind Area ASCE-7-05

The Structural Engineers Association of Washington with the Applied Technology Council published a 3 volume set which has two volumes (SEAW/ATC 60) on the Commentary on Wind Load Provisions and the third volume (SEAW RSM-03) is a Handbook of a Rapid-Solutions Methodology for Wind Design. These volumes are based on ASCE 7-02 & the 2003 IBC. They are in the process of being revised to follow ASCE 7-05 & the 2006 IBC. check with www.ATCouncil.org to see when the new set will be available.
I think that the California Division of the State Architect has published a Wind Load Determination-Alternate Method (IR 16-7) that is very similar to the old UBC wind load design procedure. I think that you can find it on the Internet. I don't know how this fits with the CBC and Counties adoption process.

RE: Effective Wind Area ASCE-7-05

Is the minimum effective area defined in Section 6.2 valid for the Simplified Procedure? All of the charts referred to in the definition are to be used in the Analytical Procedure. Or is the effective area determined from the Zones in Figure 6-3 for the Simplified Procedure? If the effective area is greater than 100 sq ft, is 100 sq ft then the maximum effective area?

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