[TowerTalk] How Important is a Straight Tower?
Fri, 15 Sep 2000 18:48:27 EDT
In a message dated Fri, 15 Sep 2000 12:38:06 PM Eastern Daylight Time, Steve Maki <firstname.lastname@example.org> writes:
Pete Smith <email@example.com> wrote:
>For the last several years, my Rohn 25G tower has been perfectly happy with
>what I'd estimate is a 2-3" bend toward one top guy (up through the middle
>guy seems pretty straight to me). I haven't changed anything because it
>would have involved replacing a big grip on that side, but in the process
>of worrying the issue it occurs to me to ask just how important
>super-straightness really is.
>After all, a guyed tower is dynamically balanced -- it is flexible enough
>that it adjusts any differences in guy length so that the tension on all 3
>guys at a level remains the same, or nearly so. That said, as long as the
>bend isn't really severe, does it matter? Is the strength of the structure
>Any of you engineers want to take that one?
OK, let's all get the code out and have a reading from the ANSI/TIA/EIA-222-F. Let's turn to section 6.1.2 and read along in case I miss-type something.
18.104.22.168 Plumb -- The horizontal distance between the vertical centerlines at any elevation shall not exceed .25 percent of the vertical distance between the two elevations.
Now we will turn to our ROHN Maintenance & Inpection Manual. You know the one you got with your NEW ROHN tower. This section is a bit dated and on page 88-224R1-2:
22.214.171.124 plumb - For guyed structures, the maximum deviation from the true vertical shall be one part in 400, (3 in. per 100 ft). For self-supporting structures, the maximum deviation from true vertical shall be one part in 250, (4.8 in. per 100 ft).
126.96.36.199 Linearity - For guyed structures, the maximum deviation from a straight line between two points shall not exceed one part in 1000, (1.2 per 100 ft.)
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