I would just like to add some food for thought. I believe that UST deals
with many different types of customers, military, govt. agencies, and the
international market place as well. With this in mind I would think that it
would be more cost effective to have basically one set of specifications
used in the manufacturing of their towers. In many cases we may think these
specifications go beyond our amateur radio requirements. I would think that
if their specifications are acceptable to the above communities surly they
will be accepted for the most part by local building codes etc. I know from
experience that, that is not always the case. I Just want to through this
out there to keep in the back of your mind when trying to figure out the how
and why in their specifications.
73 Pete N4KW
----- Original Message -----
From: "David Gilbert" <xdavid@cis-broadband.com>
To: <towertalk@contesting.com>
Sent: Monday, May 24, 2010 6:38 PM
Subject: Re: [TowerTalk] re installing my hdxmdpl72 question on rebar
>
>
> Well, first off, I wasn't in any way suggesting that he should do
> anything different than UST recommended. In fact, I'm not sure how
> anyone would get zoning inspection approval if they didn't follow the
> drawing pretty much to the letter. I was trying to be facetious about
> the "on purpose to limit their liability" bit, but I guess I didn't put
> enough tongue into my cheek.
>
> I do find it odd, though, that two very similar towers (both
> freestanding heavy duty 70 footers) would have such different rebar
> specs. I have a friend who for several years designed concrete bridge
> structures here in Arizona, and he told me that within reasonable
> boundaries you get similar large scale tensile strengths with several
> smaller gauge rebar versus a few larger gauge rebar, but at a more
> localized level the several smaller rebar are better for holding
> everything togteher (which intuitively makes sense). It's pretty much
> up to the engineer whether he chooses to go with lots of small rebar
> versus a few large rebar, and my point was simply that I would have
> thought that a company like UST would have opted for the more user
> friendly approach.
>
> I suppose it is possible that a few sticks of #9 rebar might be stronger
> in shear than several sticks of #5 rebar, but I'm having a hard time
> picturing how that would apply to a tower foundation. Maybe California
> has some sort of general requirement that emphasizes shear strength.
>
> Lastly, I'm pretty sure that a rebar cage is stronger with formed
> corners than with tied corners, and some drawings insist on it. It
> seems to me that rather few people (or companies) are going to have
> equipment capable of forming #9 rebar, so I'm puzzled even more why UST
> would have gone with that.
>
> But to be clear, I was not trying to encourage anyone to roll their own
> regarding tower foundations, and a quick archive search will show that
> I've been pretty vocal on just the opposite. I apologize if I gave
> anyone the wrong impression.
>
> 73,
> Dave AB7E
>
>
>
> On 5/24/2010 11:54 AM, K7LXC@aol.com wrote:
>>
>> In a message dated 5/24/2010 10:29:23 A.M. Pacific Daylight Time,
>> towertalk-request@contesting.com writes:
>>
>>
>>> When I see specs like that it always makes me think that the
>>>
>> manufacturer does it on purpose to limit their liability,
>>
>> Ya think?!? They also do it to comply with various tower standards
>> and
>> building regulations.
>>
>>
>>
>>> knowing that almost nobody is going to actually going to follow the
>>>
>> print.
>>
>> Jeez, Dave - I know you've been on TT for some time and I can't
>> believe you made that statement. You're SUPPOSED to do what the
>> manufacturer
>> says. They have real live engineers that come up with those specs.
>> AMATEUR
>> back-of-the-envelope calculations ain't gonna cut it.
>>
>> Cheers,
>> Steve K7LXC
>> TOWER TECH -
>> Professional tower services for hams
>>
>>
>>
> _______________________________________________
>
>
>
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