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RE: Tornadic Gust Wind Speeds vs Seismic

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65% of all tornadoes are F0 or F1 which can be resisted by properly designed construction using current wind velocities and pressures.  Some F2's might also be OK, but you are into your safety factor.  But if your local weatherman says it is a F3 or greater, it is time to head for the shelter (tornado humor - F numbers are assigned after the event). 

That is the concept of school designs that include an Enhanced Tornado Protection Area (ETPA).  The school is designed for the code minimum, but an internal classroom or 2 is "hardened" to resist higher loads and wind borne missile impact.

Harold Sprague
Krawinkler, Luth & Assoc.
4412 W. Eisenhower Blvd.
Loveland, CO 80537
Voice: 970 667-2426
Fax: 970 667-2493
Email: hsprague(--nospam--at)

-----Original Message-----
From:	Al Grathwol [SMTP:AGrathwol(--nospam--at)]
Sent:	Friday, May 08, 1998 11:39 AM
To:	'seaoc(--nospam--at)'
Subject:	RE: Tornadic Gust Wind Speeds vs Seismic

I would think it very impractical to "design" for tornado forces.  Many couldn't afford to buy their homes !  How could you design in an economic manner for a 250+ mph wind force?