[BC] Grass fires and tower loss in California

[towers at mre.com]

I don't believe the tower legs were the failure mode.  I've been through
field fires like this and it's the guying system which often fails.  This
fire is just like the ones we have.  Low burning and swift.  But if there
is enough underbrush/thatch, the fire will get hot enough to allow the guy
lines to stretch and break.  But not hot enough to cause that kind of pipe
to reach yield.  ESPECIALLY with the piers >7ft. AGL.  The flames never
much beyond that.

One of Bob's shots shows a failed Crosby clamp.  Which would make perfect
sense.  Guy line failure as the cause.  Not failed leg.

Additionally, if the fire got hot enough to cause a leg to fail, all the
framing around the tower would have also buckled AND the paint would have
been charred. The plaform steel is not very heavy steel and it survived
without much more than a blackened paint job.

MM

> Anyone want to see photos? go to
> http://gallery.me.com/bobgroome#100050
> These photos are owned by Electronics Research, Inc. So, look and review,
> but please don't re-publish with out ERI's approval.
> Looks like the hollow leg towers suffered the heat of the fire which
> caused the legs to suck in and the tower to fall. (Middle tower).  Strong
> case for solid leg towers, eh?
> Thanks and good viewing.
>
> --
> Bob Groome
> Personal Web Site is: www.bobgroome.com
> Work E-mail is: bgroome at eriinc.com
>
> --- On Thu, 7/16/09, PeterH <peterh5322 at rattlebrain.com> wrote:
>
> From: PeterH <peterh5322 at rattlebrain.com>
>
> On Jul 16, 2009, at 8:22 AM, borchert, mark wrote:
>
>> A grass fire in Sacramento, Calif., destroyed one radio tower July 15,
>> and damaged at least one other, according to Fox40 News, KXTL. 
>
> The towers were only 199 feet tall, not 600 feet.
>
> The ESE tower fell quickly, when the steel reached its yield strength.
>
> The C tower was felled as a safety precaution. It was already leaning 
> significantly, also as a consequence of yield.
>