Caveat - not an expert here.
Steel wire is often stretched to increase its tensile strength at the expense
of elasticity. I do not know if EHS is normally prestressed. If it is, then you
would probably want to replace it. FWIW, 0.5' over 330' is like 0.15% which
seems to be in the range of the amount of stretch administered for prestressed
cables, depending on the cable design.
I think this is an example where no "real" engineering is done. Towers are
designed using tables to select materials that provide a large margin of error.
This isn’t aerospace design where a system is designed to simultaneously
minimize weight, optimize aerodynamics and maximize strength while fitting into
a particular performance envelope.
Al
AB2ZY
-----Original Message-----
From: TowerTalk <towertalk-bounces@contesting.com> On Behalf Of Keith Dutson
Sent: Wednesday, October 12, 2022 7:24 PM
To: towertalk@contesting.com; Lux, Jim <jim@luxfamily.com>
Subject: Re: [TowerTalk] stretched EHS
I would replace the wire. EHS is not stretchable, so no doubt it was damaged.
73, Keith NM5G
On Wednesday, October 12, 2022 at 06:04:49 PM CDT, Lux, Jim
<jim@luxfamily.com> wrote:
On 10/12/22 3:24 PM, Steve Maki wrote:
> I should have mentioned that the guy wire in question is ~330' long,
> and elongated by ~6". I know - it's amazing that it didn't break.
>
It's a fair ways from yield (fy) to failure (fu) for steel. I don't know the
alloy here, but looking over a table, it looks like fu is 10% higher than fy
for most of the "high strength" steels.
EHS 3/8" seems to be 15,400 lb breaking strength.
> -Steve K8LX
>
> On 10/12/2022 2:29 PM, Steve Maki wrote:
>> I have a question for the materials crew here. I'm writing up a job
>> report.
>>
>> Our crew went to a site where a huge tree had fallen on the two lower
>> guys of a 360' tower. We carefully (well as carefully as we could)
>> slacked off & disconnected one wire at a time, threw it over the
>> tree, and reconnected it. At that point the site was ready for the
>> tree crew to come.
>>
>> It was obvious that one of the wires (3/8" EHS) had stretched a few
>> inches. There were enough unused threads in the turnbuckle to enable
>> a good snug wire again.
>>
>> I'm recommending that the guy wire be replaced, but was wondering how
>> much strength in roundabout numbers is lost in this scenario?
>>
>> TIA
>>
>> -Steve K8LX
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