Need Help/ Opinion of Classification of Structure (Porch Addition) Based on ASCE 7-10 or ASCE7-16

[WTT1]

Hello,

Can you all give me your thoughts on this. I'm struggling to put this one in a classification. I have not used ASCE 7 very much at all.

The front opening is 10*10, the side opening is 5*10. Porch is 10*10, Roof line is 10*16 (on the angle). It has a full back wall, full left wall, and half 3/4 right wall.

 

[Respawn]

Classification for wind?

 

[Ron247]

You need to better clarify what you are trying to determine.

 

[WTT1]

@Ron247 @Respawn

Sorry, yes. Classification for wind. I ended up using 7-16 and choosing “Partially open”.

I looked at it from each cardinal direction following asce 7 and I couldn’t get the porch structure to meet any of the other classifications (from every direction at least).

It seems like this could get really nasty if each cardinal direction is allowed to have a different enclosure classification.

Can you all comment on that and the remainder below.

I’m not certain this is the correct way to do it or not.

It also confused me that the loads were stronger when using “open” than they were when using “partially open.” That really made no sense to me but maybe there is a logical reason I am missing.

I can provide calcs if necessary.- for now I would like to understand the theory/ generalities.

Thank you all!!

 

[Ron247]

For a better initial understanding, read the formulas in the Table using the actual definition of the variables rather than the variables themselves. For example, Partially Enclosed reads that "Area of holes with positive pressure (air coming in) is greater than Area of all other holes (places for air to get out)". More air coming in than can get out therefore has higher internal coefficients (.55).



They are mostly looking at air getting inside a building and then what allows it to escape. It only addresses your "internal pressure". It is also more concerned with windows and doors blowing out. That is why it refers to glazing so much. If you are concerned about the internal coefficients at the porch, treat it like a small structure, it won't be open or enclosed.

 

[DanKile]

Exposure is done based on each cardinal direction. Enclosure is done based on building surface area. You should find a copy of "Guide to the Use of the Wind Load Provisions of ASCE 7" to be highly informative.

Just looking at that porch says its partially enclosed.

 

[WTT1]

For a better initial understanding, read the formulas in the Table using the actual definition of the variables rather than the variables themselves. For example, Partially Enclosed reads that "Area of holes with positive pressure (air coming in) is greater than Area of all other holes (places for air to get out)". More air coming in than can get out therefore has higher internal coefficients (.55).


View attachment 10021
They are mostly looking at air getting inside a building and then what allows it to escape. It only addresses your "internal pressure". It is also more concerned with windows and doors blowing out. That is why it refers to glazing so much. If you are concerned about the internal coefficients at the porch, treat it like a small structure, it won't be open or enclosed.

I follow you on this from a practicality standpoint. When I start applying the formulas, it sees awfully easy to not meet any of the classifications from all directions. Which if I am doing this correctly, automatically kicks you into “partially open”.

 

[WTT1]

Exposure is done based on each cardinal direction. Enclosure is done based on building surface area. You should find a copy of "Guide to the Use of the Wind Load Provisions of ASCE 7" to be highly informative.

Just looking at that porch says its partially enclosed.

Thank you for that guide name. I didn’t even know that existed.

I have a spreadsheet that has each cardinal direction in it and it failed the criteria for partially enclosed from every direction but 1 I believe (I don’t have it near me to look at at the moment).—this is only true if I was applying it correctly of course.

If I understand, it would definitely be the more conservative approach to use the “partially enclosed” due to the .55 vs .18.

 

[DanKile]

It only takes one wall to make the building partially enclosed.

 

[WTT1]

I may as well ask this also while we’re on the same subject. What enclosure classification would a ledger attached deck have on the back of a house.

I think I chose open with obstructed flow for 7-10- maybe I should’ve chose partially enclosed however. But to me this has a hole in it also, pun intended. The back wall of the house that the ledger is attached to doesn’t allow free flow air. I chose partially open for ASCE 7-16 because of what I found in the attached.

What would be the proper selection for this situation also. While we’re here talking about the other.

I did all of my calcs for this in the same spreadsheet. Chose “open” bc it felt right and I was working with asce 7-10 (for the deck) that doesn’t have the “partially open” category. If we were going off of the knowledge circa 2010. Would this be appropriate? What would be proper selection for asce 7-16?

 

[WTT1]

It only takes one wall to make the building partially enclosed.

Ahh I had no clue. So if 1 direction of the enclosure classification is “true” for partially enclosed- using their provided formulas for classification. The structure becomes partially enclosed?

Is this because, it produces the most conservative results using the .55 figure? Or that’s not the reason at all?

Also I’m in the process of getting the book you suggested.

 

[DanKile]

"Open" and "Partially Enclosed" have used the same formula for a very long time. So "open" in 7-10 and 7-16 are the same. Before 7-16 "Enclosed" was the catch all enclosure classification. This was a point of confusion for many (How is this building enclosed when I can see though it?). In 7-16 they added "Partially Open" to be the catch all and took the minimum opening size from "Partially Enclosed" to define "Enclosed".

The deck could be viewed as a "building" with three open walls. For simplicity, the "roof" could be considered solid. You may be able to use the permeability of the "roof" for the actual loads.

Ahh I had no clue. So if 1 direction of the enclosure classification is “true” for partially enclosed- using their provided formulas for classification. The structure becomes partially enclosed?

Its in the definition of "Partially Enclosed".

BUILDING, PARTIALLY ENCLOSED: A building that complies with both of the following conditions:

1. 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%.

2. Total area of openings in a wall that receives positive external pressure exceeds 4 ft2 (0.37 m2) or 1% of the area of that wall, whichever is smaller, and the percentage of openings in the balance of the building envelope does not exceed 20%.

"Open" and "Enclosed" are defined for the whole building not each wall.

 

[WTT1]

Its in the definition of "Partially Enclosed".

I follow you now I believe. But by this concept. Does the deck also fall under “partially enclosed”. ASCE 7-16. I hope not, the attachment is a structure that I would say is pretty much like my deck situation and they classified it as “partially open”.

Also, thank you for being helpful and not being a butt. lol. I’m just trying to learn and reason things out.

 

[DanKile]

With buildings that are open on three sides it depends on the geometry of the building whether it will be "partially enclosed" or "partially open" and I just have to calc it.

 

[WTT1]

I

With buildings that are open on three sides it depends on the geometry of the building whether it will be "partially enclosed" or "partially open" and I just have to calc it.

I follow you. I may post my spreadsheet here tomorrow where I did all of this.

I think my calculations are correct. I just don’t think I understand how to interpret them.

The deck I was working on was 14 feet out from the house and 20’ wide (parallel to the house). The right side of the deck has a 6’ exterior wall that comes out from the back wall of the house (so 8’ of the 14 on the right side is all that is open to air flow). Left and front sides are normal (fully open). 9’ mean height. Back of deck is up against the house.

For now I have the deck classified as “partially open”

 

[WTT1]

@DanKile

Here is the spreadsheet I made (attached)-- with screenshot below. It is not polished at all. But I'm hoping it will be helpful for discussion if I am doing something wrong.

I ended up getting "Partially Open" for every instance. The 2 decks and the original conversation about the Porch with the virtual photos.

I remember, you had said, you were pretty sure, just from looking at it that the porch was "partially enclosed"

Can you look at the below and tell me where I am going wrong on my application of this if I am not doing this correctly?

On the partially closed, since the process is a little more involved for it. I calculated check one and if it was yes, I went on to check 2 for the offending wall/direction. If either check 2a or 2b were no. I went on and labeled "partially open" (since enclosed and partially enclosed share check of min(4 sqft and .01*Agi).

I followed example 1b (I tried to at least) from "wind design manual, based on the ibc 2018 and asce 7-16" that you referenced earlier.

Thank you for any guidance you can give me.