ASCE 7-16 partially open buildings

[UKJim]

Chapter 26 defines "partially open" as the new catch-all for buildings that don't classify as enclosed, partially enclosed, or open. For purposes of internal pressure coefficient, the new partially open classification is treated the same as enclosed. This is numerically consistent with the 2010 version.

However, in chapters 27 and 28, the new partially open classification is not included as one of the classifications covered by the directional or envelope procedures. Unless I am missing something, we are left with no letter-of-the-law way to design a partially open building. Put another way, chapters 27 and 28 specifically state that their provisions apply to open, partially enclosed, and enclosed buildings. There is no mention of partially open, so technically one would have to reach the nonsense conclusion that neither 27 nor 28 can be used on a partially open building.

I believe the right approach is to treat a partially open building as enclosed with regard to the directional and envelope methods for MWFRS design, but this seems to be an enormous hole introduced to the code in 2016.

Have others noticed this?

 

[NITTANYRAY]

I am still using 7-10 so I am not familiar with the Chap. 26 provision.
From experience I have found ASCE 7 to be extremely vague on the treatment of partially open buildings.
After Hurricane Ike went through Ohio in 2008, I observed several buildings of the partially open and three sided variety that did not do well in 70 to 90 mph winds.
One building was a pole barn with a large overhead door. The owners said they saw the door flexing in the wind and when the door collapsed the roof lifted off the building. Obviously that "partially open" building did not perform as well after the door failed and the enclosed building became a partially open building. So I would probably take a more conservative approach on partially open buildings than the code suggests.
In another case a large three sided structure with a monoslope roof was open on the windward side. The roof lifted up moved about 5 feet toward the rear and came crashing down on some RVs that were parked in the building.
A blog on the Simpson Strong-tie web site in 2013 recommends using the .55 internal pressure coefficient as well as the appropriate external coefficients on all three walls and the roof.

As a side note, I now design truck bays in fire stations and EMS facilities using the .55 internal coefficient because it is very likely that the doors may need to be open for a time during a storm with high winds as emergency vehicles respond to calls.

 

[UKJim]

Thanks for the reply. I agree that there is some room for interpretation of what is considered open vs enclosed with regard to openings (doors, windows, etc.). This has been the case for many years and the 2016 edition does not seem to make this any better or worse.

However, "partially open" is a brand new classification that was not included in 2010 and earlier versions of ASCE 7. So the problem I, and probably others, have run into is that the new partially open classification is not addressed in ASCE 7 once you get out of chapter 26 and into the meat of the wind load provisions.

My plan is to treat "partially open" buildings as "enclosed" and drive on. I would just like to have some support for that position ;-)

 

[ajh1]

Nittanyray, I would suggest that both of your examples fall into the "Partially Enclosed" category rather than the new "Partially Open" category. If one wall has the preponderance of openings, then it becomes "Partially Enclosed". The wind will enter through the openings and have no way to escape on the other 3 walls and thus will balloon.
If more than one wall has significant openings, such that whatever wind comes into the interior of the structure through the openings on one wall (assumed the windward) then the wind is assumed to travel back out through the openings on the other 3 walls and thus does not get the ballooning effect you are describing occurred.

 

[UKJim]

The issue still, in 2016 edition, is that there is no treatment of "partially open" outside of chapter 26. Only the legacy classifications (open, enclosed, partially enclosed) are addressed in 27, 28, 29, 30.