Survival and Operational Wind Speeds vs 10 min. Average

You calculate both separately for two design conditions. I don't know your code but I think that the Operational wind is a service load and all normal deflection and stress limits apply. I think that Survival wind is an ultimate condition, the structure can have permanent damage but must not fall down; stresses can go to yield and suffer permanent set, but not fail totally.

Thanks.

For me the point is to make a correct converting.

Look, each time I open some foreign standard I see values for fastest mile, but I don't understand if that values are for service load (Operational) or ultimate (Survival).

Same for that table for converting wind speed.

Usually what kind of values are mentioned in tables and wind region maps? Service or ultimate?

They are not anything. You do your service load calculations with the 160kph wind forces and the survival load case with the 200kph wind forces.

It doesn't matter between survival and operational speeds. In each case, convert the km/h to mph, look up the number in the "fastest mile" column, scan over to the number in the "10 min. average" column, and then convert back to km/h.

160→100→83→133 (approx.)

200→125→101→162 (approx.)

Thanks.

But in our (post Soviet Union) standard for 10 min. average there is no survival and operational types (or ultimate and service loads). So I have to use only one of these values.

We calculate like this:

Wind load is being calculated as a sum of 2 parts.

1. Central component: Wm=Wo*K*C,

2. Pulsation component.

Wo here is given in 10 min. average.

K is a coefficient which shows how the wind pressure is being changed depending on height.

C is the aerodynamic coefficient.

Safety coefficient for wind load is 1.4

We calculate wind load, multiply it by safety coefficient, apply the result to the structure and chose profiles.

But when we consider deflections we do not apply safety coefficient.

Do you think that difference between operational and survival wind load is same what is described with mentioned safety coefficient?

What about safety in your standards? When do you apply a safety coefficient?

I don't know your local code and terminology enough to go further. Once upon a time, I did a Coast Guard wind load calculation for a helipad on a large fishing boat, but I've never done this for land-based codes.

Let's forget about my code.

You have a code and you calculate for 2 loading types - survival and operational.

But in your tables and wind region maps I see only one value given in fastest mile.

So which one is usually given in your tables and wind region maps? Survival or operational?

Let me rise this question once again as I steel didn't get it.

I'd like to look from another point.

I want to understand what is service load and ultimate condition deeper.

How do you take loadings for these conditions if in the beginning you know only the basic wind load for 50 years probability?

Can you advice any book or standard to me?

Or maybe someone can tell more?

Seems like I understood. :)

As a survival wind speed is taken max possible wind speed during 50 years.

And operational wind = 0.7x (survival wind speed).

Under survival wind speed structure can go to yield but not fall down.

Under survival wind structure can have permanent damage but must not fall down; stresses can go to yield and suffer permanent set, but not fail totally.

Under operational wind tower must work without damages, tilt and twist limits must be kept.

The only think that I am complained about is that I understood this not from any code, but finding some pieces of information from different documents or forums, and from here.

Can anyone help to ground statements above with any code?

Even though it is quite clear that you haven't understood the advice thus far, please do not be discouraged. Your knowledge is way ahead of the dopey bureaucraps trying to hamstring your noble efforts. Therefore be daring; question their technical incompetence and lack of legal authority wherever you can! (Ooh, did I really say that? Maybe not, but I did mean it, at least under the table.) You will have to decide on the difference (if any) between practical and philosophical guidance. A little Zen might help....

--Eugen I

Which advice did you mean?

I think I understood how the basic wind is chosen in USA codes. Do you think I understand it wrong?

Thanks for your advice also about bureaucraps. But now it is not about it. I just want to understand how it is done in your standards, for my knowledge.

For my case I did following:

I took code of my country as a base and did calculations in accordance with requirements of my code for mentioned area (towers will be erected in my country so my code is more important). During my calculations I didn't use value for wind from the client. I took exact wind values for certain areas.

Also I have asked one of supplier companies which works with USA code to do their own design using values of wind mentioned by the client.

Then I have compared both designs and got that calculations are giving very close result in material aspect.