How do you Convert a 5-second wind speed to a 3-second wind speed

[CNCLLC]

I am working on determining the cause of a collapse where wind may have been a contributing factor. The climatologically date is given in 5 second gust speeds. Is there a way to mathematically convert this to a 3 second gust speed in order to compare to the ASCE-7, design loads? Thanks in advance.

 

[JStephen]

Look in the commentary to ASCE 7-05. There's a graph there showing measured wind speeds relative to the time period involved. I'm not sure you can really tell the difference between a 3-second and 5-second gust, as it is a log scale.

I seem to recall from past experience that use of different wind codes would give you substantially different wind velocities but similar wind pressures. The design pressures from the applicable code might be of more interest than the velocity.

 

[jnadeau]

See the Durst curve in ASCE 7-05 Section C6.5.4.2. The 3-second average wind speed is approx 3% greater than the 5-second wind speed (for non-hurricane winds).

 

[CNCLLC]

Thanks to all