ASCE 7 wind?

[SteelPE]

This question is in regard to a building being enclosed, partially enclosed and open in relation to ASCE 7.

If I have a square structure that has a gross area of each wall = 10,000 square feet with each wall having 2,000 square feet of openings in each side. This building would not fall under the partially enclosed section of the code because Ao < 1.1Aoi. However, the building would not be classified as open either since Ao<0.8Ag. So does that mean that the building would be considered enclosed?

The codes says that an enclosed building is any structure that does not fall under the partially enclosed or open definitions so therefore it must be defined as enclosed.

Also, how would interior stud walls effect the calculation of Aoi? If you have stud walls that run from floor to ceiling, I would think that you wouldn’t be allowed to use the area of openings enclosed by the stud walls. Now, if the stud wall comes within 4’ of the roof because of a suspended ceiling, how would that effect the calculation of Aoi?

 

[Den32]

Yes, your explanation seems accurate.

Remember that the Code is MINIMUM provisions. As Engineer you can always make a judgement increasing requirement, such as saying it is 'partially enclosed'. I have bumped buildings to 'partially enclosed' even if they didn't meet the requirement.

'Open' designation is useless in my opinion, since it sets GCpi = 0.0. Look at new tables for Open Canopies and Structures, and compare to a similar roof using the 'open' GCpi=0.0.

Not sure of your second question regaring interior studs. Again, the Code is very generic and can't cover all case for all buildings. So, engineering judgement would rule here unless ASCE provisions or commentary specifically address. I wouldn't see how the interior studs affect Aoi?

 

[ron9876]

Yes enclosed to your first question. The second question I agree with Den32

 

[msquared48]

As a side point, if I understnd your model correctly, and outside of the code requirements here, I would design the interior studs for the same wind force as seen by the outside walls due to the presencde of the exterior openings, and not the 5 psf minimum.

Mike McCann
MMC Engineering
Motto: KISS
Motivation: Don't ask

 

[Den32]

Oh, ok, I see what Mike is saying.

Yes, if you have 'interior' studs that can receive direct wind load (due to openings in exterior) you should design for exterior wind loads (depending on how far in from the exterior cladding they are).

Note, for enclosed, GCpi = 0.55 so the interior stud pressure would likely be more than 5 psf.

Also, if you say the top of wall stops 4' from ceiling, make sure you take the top of wall bracing into account, else contractor will likely just kick it every 6 feet or so, which may not work.

 

[SteelPE]

I understand that you would have to design the interior studs differently. In fact the wind pressures would be extremely high. Making the stud design and detailing very difficult.

However, the question is more in regards to how the interior studs effect the calculations for Aoi. If there are no interior studs the calculation is straight forward. Add in partial height partition walls (the kind where the framing stops just above the ceiling) and it gets kid of murky on how to perform the calculation.

In looking at my particular project, what i don't like is the fact that I can play around with the opening sizes to move my building from partially enclosed to enclosed. That is if I have a square structure with each side having 10,000 square feet.

Side 1 = 2,000 square feet of openings
Side 2 3 and 4 = 400 square feet of openings

The building would be partially enclosed Ao = 1.667Aoi

However I could change the opening sizes around to:

Side 1 = 2000 square feet
Side 2 3 and 4 = 607 square feet

Now Ao = 1.098 Aoi and the building would be considered enclosed. I can change to openings to any value that would give me Ao < 1.1Aoi.

This just seems confusing to me.

 

[neffers]

Den32,

I think the GCpi for an "Enclosed" building is +/-0.18 and not +/-0.55 which I believe is for a "Partially Enclosed" building.

Neffers

 

[Den32]

yes, neffers a type-o, thanks. should say partially enclosed GCpi=0.55

SteelPE,
Again, engineering judgement. Code provisions are minimum requirements, so as long as your calcs meet (or exceed) Code, you did due diligence. However, don't forget common sense and your experience on how things really work.

Internal wind pressure coefficient, GCpi, basically effects C&C component design (GCp + GCPi)

It is difficult to go much further based on verbal description and info. good luck.

 

[a2mfk]

When in doubt, go bigger and stronger. That will almost never get you in trouble. I agree with Den32, it may not fit the few definitions in the code, it is up to you.

In determining open/enclosed/partial I would ignore anything inside the building shell in general. But if you had a full height wall dividing a structure into two buildings, say a hangar with two big openings on each end with a demising wall, then I would say that is like two separate structures, with an opening in the front and three solid walls. Maybe that is sort of your case, why not provide a plan sketch or two if you are still no the fence?

You also should think that they may gut the building at some point unless you have some very special and good notes on your drawings for CYA, so if you are trying to use an interior wall as a way to justify enclosed, then be ready for someone down the line to knock it down.

 

[SteelPE]

a2mfk

I am not trying to use the interior walls to justify whether the building is enclosed. If you look at the equations to determine if the building is enclosed or partially enclosed you need to provide a certain amount of openings in the remaining portions of the building to make sure Ao < 1.1 Aoi. Providing a wall that cuts the building in two would hurt you if you had windows on the other side of the wall that brought the ration of Ao/Aoi to under 1.1.

Unfortunately I am just trying to help somebody out in my office with this determination so therefore it is not my decision.