NYC Code Basic Wind Speed 98 mph vs ASCE 7-10 (121 X 0.6 = 73 mph)

[PT999]

Section 1609.3 Basic Wind Speed - Is this velocity for ASCE 7-05 or ASCE 7-10
The referenced standards in the back of the code list both!

It appears to be ASCE 7-05 because Section 1609.1.1 - Determination of wind loads references ASCE 7 (no edition stated) references Chapter 6.

Looking at ASCE 7-10, it tells you Chapter 6 for Wind Loads was used in previous editions, now its Chapter 26-31.

So I think I have answered my question. ASCE 7-05

But then when you look at the wind maps in ASCE 7-10 for New York City area you are in 120-130 mph for Category III Exposure C, ATC website says 121 mph Ultimate for my location, but when converting to Allowable (0.6 x 121) wind velocity is just 73 mph.

So which Velocity is correct for New York City. Am I missing something? Of course I will use 98 mph, but I not understanding this difference. Is it just less wind force in the ASCE 2010 edition vs 2005 edition.

It seems to me anecdotally that its wind forces are increasing.

 

[JStephen]

I'm thinking the 0.6 factor would be for wind pressure/force, and the wind speed would be a 0.78 factor = square root of 0.6?

 

[klaus.]

The design concept has changes for wind....
Now the wind is a design value including safety factor already

The wind load itself is about the same


best regards
Klaus

 

[sponton]

Jstephen is right, 0.6 is applicable to pressure not wind speeds, you multiply them by (0.6)^.5 to turn them into the old ASD mph values.

 

[MacGruber22]

I will second JStephen's comment.

"It is imperative Cunth doesn't get his hands on those codes."

 

[EngineeringEric]

Sponton is correct. since force equals K*0.00256*V^2 you need to multiple speeds by 0.6^0.5 = 0.775 ---> 121*0.775 = 93.72 mph.

 

[bookowski]

Read the first paragraph of Chapter 16, Scope - it says that any reference to ASCE7 refers to '05' and only where it specifically references ASCE7-10 do you use 10. Wind is '05 still (seismic is 10)

 

[PT999]

OK- thanks everybody,
I see my mistake, and read the first paragraph.