metal building wind load (open on 2 sides)

[labeattie]

Hi all,

I am having trouble figuring out how to get started on finding the wind loads (from ASCE 7-10) for a metal building open on 2 sides. The configuration looks something like the picture from Google that I've attached. The diagonal cases seem particularly weird, and I wasn't sure how to treat the enclosure classification. I was wondering if anyone could give me some tips on starting this. For my (very) preliminary design, I'm planning on considering only the horizontal direction and treating the building as if it were enclosed. I know I will need to consider internal pressures and uplift forces, and was hoping for a few tips. Thanks!

http://files.engineering.com/getfil...-8912-4291-bc6c-6556cfdf2d87&file=mtlbldg.png

 

[JAE]

According to my calcs that type of building should be considered Enclosed per ASCE 7-10.
Go through the calculations from section 26.2.


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[labeattie]

Does something like this seem plausible?

 

[labeattie]

Thanks JAE. I do think that diagonal wind on the inside of building will create a greater force than that same wind on the exterior, as it can't escape by flowing over the roof. From my limited understanding, I think that is what the Cpi coefficient tries to account for, so I threw that into that pressure. Perhaps I should use the .18 for enclosed buildings rather than the .55 for partially enclosed? Or am I just way off or senselessly complicating this? Thanks!

 

[JAE]

I'd use the 0.18. The partially enclosed provision, using 0.55, is for cases where a building has a significant opening on one side where the building sort of acts like a scoop or pocket where wind flow would try to blow the building up like a balloon. In your case, your "balloon" is open at two ends so blow as hard as you like and you won't inflate the balloon.



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[labeattie]

Gotcha. Thank you for the advice. I appreciate it.

 

[SAIL3]

Not knowing the dimensions of the bldg or what is being stored in it, I would certainly investigate the following.
WIND PERPENDICULAR TO OPENING
Depending on the dimensions of the bldg, I could see the windward wall coming close to acting similar to freestanding signs(Cd=2.0 approx) and leeward wall with Cd=0.6.
For roof I would use the myriad examples found in the ASCE code w/o internal press.

WIND PARALLEL TO OPENING.
EMPTY CONDITION: Depending on the length of the bldg ,I could envision boundary layer buildup that would have a choking effect on the air moving thru the bldg....what to use?..maybe the 0.55 already mentioned.
In the occupied condition and depending on what is stored there, one could definitely see air blockage which could result in say the 0.55 already mentioned.

WIND @ 45
Again depending on the dimensions of the bldg, one could have a combination of all of the above.

I guess where all this is heading is that the OP should investigate the differnt wind direction vectors and based on the dimensions of the bldg determine in his own engineering judgement what wind condition might apply and may only exist on a portion of the bldg...given the multiple possible wind loading cases I would usually go consrvative and move on....