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Re: Greetings!

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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






Date sent:      	Thu, 5 Oct 2000 23:49:07 -0600
From:           	"arman s rivera" <asrivera(--nospam--at)edsamail.com.ph>
To:             	seaint(--nospam--at)seaint.org
Subject:        	Greetings!
Send reply to:  	seaint(--nospam--at)seaint.org
Organization:   	http://www.seaint.org

Dear fellow engineers!

Greetings!

I am Arman Rivera, a practicing structural engineer in the Philippines.  Our firm recently purchased the software Staad Pro 2000 and from the limited hands-on I have had on it, this software is remarkable.  However, as I've been reading the manual that came with the software, I have many 
questions regarding it.  Is anybody familiar with Staad Pro 2000 that won't mind answering questions from a novice user?

I've been using Staad Pro 2000 to design communication towers.  My first question is, should the tower be classified as SPACE or TRUSS?  What I've done is to treat it is a space and then assign the moment releases at the end of the diagonals and verticals only (not the main posts), so that these 
members would carry only axial forces.  Is this correct?

My next question is on the support conditions.  I have modeled the mat foundation using finite elements in Staad Pro 2000.  I have defined the joint supports as ELASTIC MAT by specifying the modulus of subgrade reactions (kv).  Given the allowable soil bearing capacity, how is the modulus of 
subgrade reaction computed?

I have many more questions regarding this software, any help you could give me would be greatly appreciated.

Thank you very much.


Regards,
Arman S. Rivera

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