GENERALLY: When the spalling (100# chunks?)is on top, or above the
surface, it is due to moisture / water in the concrete. In the case
shown in the first link, that appears to be the case exacerbated by poor
grounding. Inadequate and poor installation. Rerod cage too near the
surface and not connected to the tower, or not sufficiently connected.
Water can get into the concrete a number of ways
It's been my experience, Hams are unlikely to need guy anchor grounding
as typical practice is to break up the guys with insulators, or use non
conductive guys and the towers are connected to the rerod cages. Even a
ring of 3 ground rods should be considered the absolute minimum unless
you have a substantial UFER ground depending on soil conditions.
I don't have photos, but the last commercial tower I worked on used one
inch steel rope consisting of many fine strands. With these properly
tensioned, you could feel no vibration on calm or windy days. The did
oscillate though. Hit one with a wrench and the very clear tone was way
above middle C. That meant there was some substantial tension on those
cables.
Quite a few times I saw that tower take hits with the lightning jumping
of the guys to ground 50 feet or more
73, Roger (K8RI)
On 6/28/2017 Wednesday 9:29 PM, Gene Smar wrote:
TT:
There are lots of other examples and case studies of uber-lightning and
grounding installations linked from the main page of that site:
https://www.copper.org/ . Click the Applications tab, then, under
Electrical, click Power Quality. You also can find a series of articles on
the (copper) Statue of Liberty under Education. Fascinating site.
73 de
Gene Smar AD3F
-----Original Message-----
From: TowerTalk [mailto:towertalk-bounces@contesting.com] On Behalf Of Shawn
Donley
Sent: Wednesday, June 28, 2017 9:05 PM
To: towertalk@contesting.com
Subject: Re: [TowerTalk] Lightning
Here's one documented case of lightning damage to concrete. I had posted it
before but here's a repeat.
https://www.copper.org/applications/electrical/pq/casestudy/a6137/a6137.html
In this case a concrete guy anchor was damaged. But looking at the pictures,
this might have been caused by moisture entry due to surface cracking with
the lightning strike just finishing it off as the current pulse turned the
moisture into steam. Hard to say. I think the real question is if a
lightning strike can cause internal damage to a tower concrete foundation
that you can not easily detect.
N3AE
_______________________________________________
_______________________________________________
TowerTalk mailing list
TowerTalk@contesting.com
http://lists.contesting.com/mailman/listinfo/towertalk
_______________________________________________
_______________________________________________
TowerTalk mailing list
TowerTalk@contesting.com
http://lists.contesting.com/mailman/listinfo/towertalk
--
73
Roger (K8RI)
---
This email has been checked for viruses by Avast antivirus software.
https://www.avast.com/antivirus
_______________________________________________
_______________________________________________
TowerTalk mailing list
TowerTalk@contesting.com
http://lists.contesting.com/mailman/listinfo/towertalk
|