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Re: old wind speeds vs. new vs. weather station's

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Ken:
maybe neither - it depends. The wind speeds usually reported by the weather
service including the National Hurricane Center are for 1-minute sustained
winds meaning the average wind speed that is sustained over 60 seconds. The
3-second gust speed used in ASCE 7-98 is for a much shorter duration
obviously so the wind speeds are higher given the duration is so much
shorter.

The wind speeds used in building codes have been fastest mile or the time
is takes a mile of wind (5280 ft) to pass a point. This measurement is not
made by the weather stations and does not correlate directly to the other
averaging times. The use of the 3-sec gust at least can be compared to some
measurement made by the weather stations and more accurately reflects the
use of a wind speed averaging time that appears to cause damage to
buildings and other structures.

Hope this helps.
*************************************
Bill Coulbourne, P.E.
Principal Structural Engineer
URS Corp.
200 Orchard Ridge Drive
Suite 101
Gaithersburg, Md 20878
301-670-3344 (Office)
301-869-8728 (Fax)
703-850-2891 (Cell)
bill_coulbourne(--nospam--at)urscorp.com


                                                                                                           
                      "Ken Peoples"                                                                        
                      <kspeoples@lvta.         To:      "Seaint" <seaint(--nospam--at)seaint.org>                       
                      net>                     cc:                                                         
                                               Subject: old wind speeds vs. new vs. weather station's      
                      10/07/02 10:58                                                                       
                      AM                                                                                   
                      Please respond                                                                       
                      to seaint                                                                            
                                                                                                           
                                                                                                           




I understand that the current wind speeds are the 3-second gust speeds and
that is why our area here in PA has changed from 70 mph to 90 mph.  What I
am curious about is how either of these speeds relate to the speeds
reported by the weather folks when they are talking about 90 mph winds.
Would this weatherperson's 90 mph be compared to our old 70 mph or our new
90 mph or neither?  Just curious.
Ken

Kenneth S. Peoples, P. E.
Lehigh Valley Technical Associates
1584 Weaversville Road
Northampton, PA 18067-9039
Phone: (610) 262-6345
Fax: (610) 262-8188
e-mail: kpeoples(--nospam--at)lvta.net






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