ASCE 7-02 Wind Load Enclosure Type Opinion

[StructuralEd]

In working out wind loads based on ASCE 7-02, I am trying to determine what defines "Partially Enclosed" per the code.

I understand the formulas and guidelines in the code, but are overhead doors considered openings when they would generally not be left open? Also, what about windows and glazed curtainwall?

Most work is in Connecticut and generally in the 80-95 mph wind zones, primarily not directly on the coast but in the center of the state, which of course is an ocean soundfront state.

Do the doors and windows count in the enclosed/partially enclosed consideration, or is that about permanant openings?

 

[csd72]

The wind cant tell the difference between a door that is accidentally left open and a permanent opening!

I believe most houses are designed as partially enclosed, although I would always design a garage door as an opening. Small openings have much lesser effect than large openings.

Coastal Connecticut is deemed as a hurricane prone region and therefore there is a clause in the code that specifies that all glass openings are to be impact resistant or treated as openings (1609.4 in the CT code). Away from the coast, I dont think this applies.

 

[structuralaggie]

In my environmental loads class, my professor said to always design as partially enclosed unless you have really good justification otherwise, like there are no doors or windows. This may be a blanket statement that is not always true, but the partially enclosed bit only affects components and cladding anyway. The main wind force resisting system should not be affected by your choice of enclosed vs. partially enclosed.

 

[nutte]

structuralaggie - The MWFRS will be affected by the enclosure type if the internal pressures don't cancel each other out, like if you have an expansion joint in the building or something similar that causes the MWFRS to see both external and internal pressures.

 

[grandcasita]

If the overhead doors are not rated for the full wind, consider them open. You are designing for maximal wind, and anything that will become open in the wind should be counted as open... that is, unless it reduces your wind load, then count it as closed. (Murphy says that the wind will break things which increase the forces and not those things which reduce them.)

Having done some damage assessment for wind storms, I have seen that you will always get to "partially enclosed" before you get "open" due to failures. Three examples from Hurricane Charlie (out of many): 1) a commercial building of moderate size had one overhead door fail, leading to the failure of the entire standing seam roof. 2) A small warehouse had an overhead door fail which resulted in rupture of fiberglass skylight panels in the roof and failure of the overhead door on the opposite side (one blown in, the other blown completely out.) 3)A glass storefront on a small strip center buckled at mid height (where the brick veneer terminated) allowing the internal pressure to cause failure of corrugated roof panels.

 

[StructuralEd]

The consensus is Partially Enclosed.
I was leaning that way myself.

 

[StructuralEd]

Here is an interesting thing:
I took a look at both enclosed and partially enclosed numbers for a building, and the enclosed appears to give larger overall (main system) lateral wind loading than partially open. I am thinking it prudent to use the "closed door" numbers which appear to control for the main lateral load resisting system.

The partially open gives higher component loadings though, so it looks like using both conditions is in order.

 

[structuralaggie]

I don't think you should get higher numbers for the MWFRS with either. The internal pressures cancel each other out after about 10 pages of calculations and wind up being the same. As I stated earlier, this is probably a really general statement that may not always be correct, but it has always happened that way for me. The partially enclosed will definitely give you larger loads on components and cladding, so I would say to always use it for that.

 

[grandcasita]

To get the right answer, use the right calculation, not the expedient one. And while the wind code covers a lot of pages in the book, it is really not that difficult to use. Everyone complains about it, but it is really pretty straight forward.