Wind Tunnel ?

[SKJ25POL]

When a full scale wind tunnel is needed or required?
I've been asked in what structures or cases/situations a Full Scale wind Tunnel is performe.

I appreciate if you can assist me with a correct respond since I never have delt with this issue.

Thank you

 

[cvg]

not sure what a "full scale" wind tunnel test is. the tests I have witnessed were buildings at a greatly reduced scale. I know the Wind Engineering and Fluid Dynamics Lab at Colorado State University has several wind tunnels used for scale model testing. you might give them a call to discuss

Contact CPP

http://www.cppwind.com/who-we-are/company-history

 

[JStephen]

See 6.6.1 and 6.5.2 in ASCE 7-05.

A couple of years ago, I took a 2-day class on ASCE 7-10 taught by Jon Raggett, who does wind tunnel testing. Informative class, good speaker, and recommended if you have a chance to take it. It's an ASCE class.

 

[racookpe1978]

The ONLY time a "full scale" wind tunnel test is justified is when the benefits of the test are greater than the total costs of the test.

OK. Fine a nice general statement true under all circumstances, and equally useless in the real world.

But think about it. Even a 100% four-story high wind tunnel test of a "tower" or a mast or a building is going to have approximations and assumptions that will NOT be right in the real world. Even a 1/4 scale wind tunnel test of a building with all of the streets and the adjacent buildings (also to scale) on a perfect rotating base to mimic every wind direction will not ever exactly match the real hurricane that blows by.

Decide how accurate your assumptions are going to be, decide how vclose your approximations to mimic your guesses about the future actual conditions will be. Then go scale an appropriate test.

By the way. A wind tunnel that does allow full-scale testing is going to be very, every expensive compared to a tunnel that can work with a 1/4 or 1/8 model of your mast or street pole or TV antenna. And, those "full scale" wind tunnels know they can charge anything they want because they are booked up years in advance. Would you a "perfect answer" 5 years from now? Or a good enough cheaper answer in two months?

 

[KootK]

We discussed this with you recently OP: Link.

You mean "full blown" rather than "full-scale (1:1)", right? Full scale wind tunnel testing in Civil Engineering is almost unheard of. Nobody's building full scale replicas of city blocks and river valleys.

The greatest trick that bond stress ever pulled was convincing the world it didn't exist.

 

[SKJ25POL]

Dear KootK (Structural),
I have seen (video clips - not in person) sometimes they built a large (like full size) of one story building (I have seen wood building in research lab) and blow wind.

What I meant by full scale, I meant full size of structure.
Please correct me if wind tunnel is not done on full size models of structures.
I have no knowledge in wind tunnel tests but as engineer they have asked me and I am trying to research and gain some info.

Any articles that discuss this in basic language will be helpfull and I will appreciate it.

Sincerely,

 

[jayrod12]

Wind tunnel tests are typically performed on higher rise and/or irregular shaped buildings due to cost. Those type of structures are expensive to build, more so if you have to use the "typically" conservative values in the code. So the cost of scale testing is worth it to them to ensure they're exploring every avenue to reduce the structural member sizing.

The full scale tests of the small wood buildings (and some small masonry bunkers) are more for checking performance of connections or lateral systems and not the same as wind tunnel testing.

Again I was speaking in general, obviously there may be specific cases that are contrary to the above.

 

[canwesteng]

I've seen videos of full scale testing of wood buildings (midrise height) against earthquake loading. Full scale loading can only be justified for establishing code requirements in my opinion, and is also impossible for most structures.

 

[KootK]

My bad SKJ25POL. I guess you really did mean full scale. I stand by my original assessment however: it's almost unheard of in the world of civil engineering structures. As others have said, it would need to make economic sense which narrows the field to stuff like:

1) Research, where the results will be used over and over.
2) Specialty products used on buildings, where you'll make a zillion of them and it pays to shave the loads down.
3) Structures where the stakes are incredibly high. NASA does some full scale wind tunnel testing.

In plane language: anything small enough to fit in a wind tunnel full scale isn't likely to be significant enough to warrant the expense of doing so on a one-off building project. There are some other reasons for doing wind tunnel testing besides shaving down wind loads. We discussed those a fair bit in the the other thread that I linked to above.

The greatest trick that bond stress ever pulled was convincing the world it didn't exist.

 

[SKJ25POL]

Thank you very much gentlemen especially jayrod12 (Structural) and KootK (Structural).

Also, KootK (Structural) uou mentioned other reasons for wind tunnel testing.
Please refresh my memory, I love to know what are other reasons of doing wind tunnel testing on structures?

I apprecaite it.

 

[KootK]

You're most welcome SKJ. You'll find the other reasons in that thread that I linked to above.

We could probably give you much more targeted advice if you gave us some additional context. What kind of work is your client considering having wind tunnel tested?

The greatest trick that bond stress ever pulled was convincing the world it didn't exist.

 

[SKJ25POL]

KootK (Structural),

This is not for a client. I am trying to learn this field. I am very interested in this subject.
There are not much straight forward and simple language information for a newbie like me or I don't know where to find them.

Again thank you very much for sharing.
Sincerely,
SKJ

 

[KootK]

I see. I would recommend calling RWDI: Link. One of their people will likely be happy to walk your through the kind of work that they typically do and what the motivations for it are. There's also this book that I've been meaning to buy authored by the "I" in RWDI: Link. In case you're wondering, I do not work for RWDI. They just always seem to be the wind guys on my projects.

The greatest trick that bond stress ever pulled was convincing the world it didn't exist.

 

[tbuelna]

It depends on what type of test is being conducted. Testing an entire building structure at full scale in a wind tunnel at wind speeds of 50mph+ is not practical. But testing the entire building at subscale would be possible. It would also be possible to test a small section of the building structure at full scale in a wind tunnel.

The largest wind tunnel test facility in the US is the 40 ft. NASA tunnel. But it requires huge amounts of power to operate and is extremely expensive.