FWIW I *do* recall a gent, on this list, a few years back, that said
that lightning had, in fact,
caused his concrete *guy anchor* to fail, resulting in the loss of the
tower, at some point
some years prior. This was in one of these similar threads.
That's not to say that it's safe to assume anything about the anchor
prior to the strike.
I'm merely pointing out that, in the "real world", there appears to be
at least one case
of this happening.
I locate underground water leaks here in Florida, and lots of them are
caused by lightning,
and I've seen *plenty* of spalling associated with those same strikes.
And, yes, lightning
does do just whatever it wants to do. Enough of it can make it into a
home and down a
buried 3/4" copper pipe to leak anywhere in the home it wants to. I feel
like "most" of
the strikes I deal with come down the electrical mains, and yet do not
necessarily cause
the leak at some point near the electrical service entrance. Whatever
the mode may be,
however it "gets in", it feels no obligation to cause the leak very near
to the outer perimeter
of the home, as one might expect...if you "expect" lightning to behave
predictably.
73 and HNY
Randy
KZ4RV
On 12/30/2012 9:45 PM, Jim Lux wrote:
On 12/30/12 3:06 PM, Hans Hammarquist wrote:
Anecdote or not. If you push enough current though any conductor it
will "explode". (This is actually use in one type of detonators.)
Oddly, I have personal experience with exploding wires (not EBW
detonators, but in other applications)...
THere's nowhere near enough *energy dissipated* in a lightning strike
through a Ufer ground to do this. The actual stroke is about 100
kJ/meter & the dissipation in the stroke in air is substantially
higher than in a grounding system. To put 100kJ in context, TNT is
about 4 MJ/kg. about 110kJ/ounce. So, put an ounce of TNT in a
properly designed hole in some concrete, and you can split it or spall
it.
I
don't know how much current required to crack concrete and if a
direct lightning strike can be enough, but I don't think we have to
worry so much about that as such a "super" strike will cause more
harm in other places around the tower hit.
Yes..
I have my present house designed to take a "super" strike. I am using
3/4" copper pipes in all four corners of the house. According to the
engineer, helping with this design, my house is ready for one of
these "super" strikes, observed on occasions. I believe it is a
lightning with a peak current of 300 kA, maybe it was even more.
Anyhow, after three confirmed, direct hits in the house, I feel
relatively sure I did something right.
yes..
The key thing on destruction is the I^2*t (called the action)..
Because that's related to the energy deposited
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