MyFloridaCode.com

Based on what you have described I believe the minimum code required
wind speed is 130mph at an importance factor of 1.15. The importance
factor appears as a multiplier in the wind pressure equation and does
not change the wind speed so the design wind speed in this case would
still be 130mph not 150mph.

Rather than arbitrarily tinkering with the wind speed. It is more
appropriate to decide on a mean recurrence interval and then design to
whatever wind speed that gives you. So for example you would need to
decide on the life expectancy of the structure and design to a 50, 100,
500 or 1000 year mean recurrence interval (MRI). In your case, the FBC
130mph (1.0 importance factor) wind speed is based on an approximate
50-year mean recurrence interval. The 1.15 importance factor gets you up
to a 100+ year mean recurrence interval which is similar to the MRI for
flood load design. The EHPA recommendation to add 40mph at an importance
factor of 1.0 is based on a 1000+ year mean recurrence interval.

Ultimately, once you exceed the code minimum, the design criteria is
based on the expectations of the client (community) and the engineer. It
might also be advisable to communicate with the insurance underwriter to
see the effect of the various design criteria.

Christopher Banbury, PE
President
 
Ark Engineering, Inc.
PO Box 10129, Brooksville, FL 34603
22 North Broad ST, Brooksville, FL 34601
Phone: (352) 754-2424
Fax: (352) 754-2412
www.arkengineering.net
 


> -----Original Message-----
> From: codetalk-bounces at myfloridacode.com [mailto:codetalk-
> bounces at myfloridacode.com] On Behalf Of Bryan Holland
> Sent: Tuesday, December 02, 2008 1:15 PM
> To: codetalk at myfloridacode.com
> Subject: [Florida Code Talk] EHPA Wind Speed Design
> 
> Hello All,
> 
> 
> 
> We have a project under development for an educational / community
> center that will be used for an emergency shelter.  I am trying to
> determine the wind speed to design the structure to.  When comparing
> other EOC and buildings of the like, I feel an importance factor of
1.15
> would be the classification of to use.  With a starting wind speed of
> 130 mph, this would mandate a design of 150 mph.
> 
> 
> 
> However, the EHPA criteria guidelines provided in section 423.25.4
> indicate wind speed plus 40 mph (1.00 importance factor).  This would
> mandate a design of 170 mph.
> 
> 
> 
> A third reference, FEMA 361 suggests using a wind speed of 200 mph.
> 
> 
> 
> Economically speaking, we would like our building to meet the minimum
> design criteria for a community shelter, but at the same time not be
so
> overdesigned to become cost prohibitive and unattractive.
> 
> 
> 
> Based on this background, what opinions do you have on the matter?
> 
> 
> 
> 150 mph?
> 
> 170 mph?
> 
> 200 mph?
> 
> 
> 
> 
> 
> Thanks for all your input!
> 
> 
> 
> 
> 
> 
> 
> Different Jobs, Different Tools, Same Mission - Saving Lives!
> 
> 
> 
> Bryan P. Holland
> 
> 
> 
> Bryan P. Holland, ECO.
> 
> City of North Port
> 
> 4970 City Hall Blvd.
> 
> North Port, FL 34286
> 
> (941) 429-7053
> 
> bholland at cityofnorthport.com
> 
> www.iaeifl.org <http://www.iaeifl.org/>
> 
> 
> 
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