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RE: Greetings!

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Arman,

I've been using STAAD for over 10 years with much success.  It is my primary
tool used for structural analysis and design and I've developed much
confidence in it over the years.  I'd be glad to answer any questions you
have.  E-mail me directly and we can discuss.

With regard to your question concerning communications towers - I believe
your methodology is correct.  The diagonals should be modeled as 2 force
members and the columns or posts as flexure/bending members.  Couple of
things though, be aware of joint instabilities and make sure all of these
"kinks" are worked out before you finalize your design.

If you are using the latest build of STAAD - it has a compression only
spring for elastic mat.  Be certain that you verify that STAAD is assigning
the proper stiffness to each spring.  The spring support generation
algorithm is based upon the "convex hull" supposition.  If the surface your
modeling does not meet the convex hull criteria, ie, there are no internal
angles in the polygon exceeding 180 degrees, you will not get the proper
distribution of loading across the mat.

Please email with other questions.

John Whitty, P.E.

-----Original Message-----
From: arman s rivera [mailto:asrivera(--nospam--at)edsamail.com.ph]
Sent: Friday, October 06, 2000 1:49 AM
To: seaint(--nospam--at)seaint.org
Subject: Greetings!


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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