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Re: Enclosed vs Partially Enclosed

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Yes, your interpretation is correct when openings are relatively evenly distributed around the perimeter of the buildings. Most such buildings would be classified as "enclosed". This is kind of counter-intuitive, especially for a parking garage with lots of opening all around. But, that's how it is.

Ben Yosuefi, SE

-----Original Message-----
From: Brian Hsi <brian.s.hsi(--nospam--at)>
To: seaint <seaint(--nospam--at)>
Sent: Tue, Jul 12, 2011 8:27 am
Subject: Enclosed vs Partially Enclosed

I was hoping that you guys can help me interpret the Partially Enclosed condition in ASCE 7.

I'm looking to concentrate on condition #1.  Based on my interpretation, a typical office building or parking garage, will never be a partially enclosed building.

Condition #1 states: The total area of openings in a wall that receives positive external pressure exceeds the sum of the areas of openings in the balance of the building envelope (walls and roof) by more than 10%.

Let's use a rectangular parking garage for example and place the wind load on the front, long face.  The positive pressure will act on this face, but there will be negative pressure on the sides and leeward face.  In my condition, the front and the leeward (back) face have similar spandrel opening conditions.  The two side faces will also have similar spandrel opening conditions.  Therefore, the front positive face, will never have more opening area than the sum of the side and back faces.

This example would also apply to most typical office buildings in a hurricane prone region without proper wind borne debris protection.

Am I interpreting condition #1 correctly?