Wind Loads on Tall Parapets 2

[spaseur]

I have a building that is 326' to the roof. The owner wants to put the cooling towers on the roof and hide them by extending the parapet up 30'. When I calculate the wind loads on the parapet using MWF pressures, the total base shear is 2700 kips with 631 (23%) being applied at the roof due to the height of the parapet. There is some discussion in the office that these parapet pressures are not realistic. Some do not think that you can get the vortex to be big enough that it would encompass the entire back side of the parapet. Some do not believe that what ever test was done would apply to a 30' tall parapet. What are your thoughts?

 

[rowingengineer]

Seems like a very difficult item too prove with the current code, I would suggest a CFD model before progressing with any assumptions.

 

[spaseur]

CFD? Wind tunnel study?

 

[dik]

computational fluid dynamics... a mathematical 'wind tunnel'

Rather than think climate change and the corona virus as science, think of it as the wrath of God. Feel any better?

-Dik

 

[rowingengineer]

https://www.simscale.com/blog/2017/05/wind-loads-buildings/

 

[KootK]

The vortex argument does resonate with me. You might explore the procedures for billboards and free standing walls for comparison.

 

[DaveAtkins]

I was amazed several years ago when the parapet wind loads increased so drastically in ASCE 7. I hadn't heard about a rash of parapets flying off buildings

DaveAtkins

 

[dik]

rowingengineer: is that ever a neat site... thanks

Rather than think climate change and the corona virus as science, think of it as the wrath of God. Feel any better?

-Dik

 

[brut3]

Check out the latest edition of Structure magazine. Beginning on page 12 of the magazine they address some of the parapet loading questions and when parapet wind loads are appropriate compared to a freestanding wall analysis.

https://www.structuremag.org/?page_id=17505

 

[dik]

Not trying to hyjack this thread... Good publication, thanks... did you take a look at the info on SOG construction... I thought it was informative, but one item 'raised the hackles' a bit.

I've not been involved with any huge concrete pours, but the contractor has to mobilise in a fashion to achieve sawcutting in a correct manner, since IMHO, this is critical to SOG construction. He also has to mitigate additional shrinkage stresses due to the dimension of the pour. Without added information, I'm not sure how he can make that statement. Ron may have some thoughts on this that would be welcome. My project notes stipulate things in accordance with standards, 'AND AS INCLUDED IN THE PROJECT NOTES'.



Rather than think climate change and the corona virus as science, think of it as the wrath of God. Feel any better?

-Dik