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RE: comm towers and staad pro

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Communication towers, and particularly guyed towers, require some fairly
specialized analysis, considering the EIA/TIA-222 loading standards and the
highly nonlinear guy behavior.  (If you like intellectual puzzles, try hand
calculating and resolving the attachment forces for a guy that is ice
covered and blown-out of its plane.  It's a lot of fun the first time.)
Though I have not researched their relevant capabilities recently, I have
never had much luck using general structural analysis or FEM software for
this type of work.  There are, however, specialized programs for doing
analysis and design of towers that automate some of the repetitive
geometry/material inputs and automatically generate EIA/TIA loads and code
checks.  If you're planning on doing a bunch of towers, I believe these
packages can save you many many hours.  The one that I have used and like
(particularly the very good support) is called TOWER from Power Line Systems
Inc at http://www.powline.com/  (The program's author, Dr. Alain Peyrot, was
my advisor at the University of Wisconsin, but that has not biased my choice
of programs - at least not on the conscious level:)  

Brian McDonald, SE
Menlo Park, CA

-----Original Message-----
From: arman s rivera [mailto:asrivera(--nospam--at)edsamail.com.ph]
Sent: Saturday, October 07, 2000 4:56 PM
To: seaint(--nospam--at)seaint.org
Subject: comm towers and staad pro


Peter,

presently, we are involved in the design and investigation of communication
towers for a leading telecom company here in the philippines.

so far, we have only worked with self supporting towers.  but later on, we
will also be working with guyed towers as well.

so far, in all the towers we have done, we have modeled the entire tower as
one 3-dimensional tower, complete with diagonal and horizontal bracings.
applied wind loads, antennae loads, and then have staad pro (the software
we're using) analyze it.  my concern is whether my analysis approach is
being inputted in staad pro correctly.  sometimes, our analysis is correct,
but then when we input the data into a program, there may be
misinterpretations as to what we want the program to do and what the program
is instructed to do by our input files.  and since i have had no formal
training on staad pro, i am not sure if my staad models are correct.

can you recommend some references in the design of communication towers?
(both self supporting and guyed towers)

we have looked into the program MS Tower by Microstran, does anyone have an
opinion on this product?

regards,
arman


>
>Regardless of the software your using, your questions relate more 
>to the analysis approach rather than the specifics of the program.
>
>Your approach is dependent on the level of suffication and what are 
>you determining. You can break the tower down to a number of 2D 
>plane frames i.e the 4 sides, diaphrams, crossarms. (oh..the days 
>of 2D analysis and non graphical input are coming back to haunt 
>me) or, define it as a space frame as you describe. 
>
>Since you have the power of the software there, space frame is the 
>approach I would take because now you can play the whole 
>torsional game on the tower checking what happens under 
>unbalanced conductor spans, broken conductor conditions etc.
>
>Of course, you now have to check different tower 
>configurations....deadend(terminal), in-line towers, deviation angle 
>towers etc.
>
>Then of course, are you designing self supporting lattice towers, 
>guyed lattice, etc.....??????
>
>If transmission lines is your main function, it may have been better 
>to purchase software such as PLS-CADD and associated 
>programs (i.e. Tower) which would do all the terrain modeling, sag - 
>tension etc. functions.
>
>ASCE has a number of manuals that can give you guidance.
>#52 - Guide for Design of Steel Transmission Towers
>#74 - Guidelines for Electrical Transmission Line Structural Loading
>just to name a few......
>
>I hope these comments help....
>
>Peter McCormack


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