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--- Mensaje Original ---
De: Bob [BOB(--nospam--at)csiberkeley.com]
Tema: RE: Modeling Cable Behavior in SAP2000
Para: "'josemvv(--nospam--at)LatinMail.com'"[josemvv(--nospam--at)LatinMail.com]

>Dear José Velásquez,
>

>
SAP2000 has extensive capabilities for modeling cable structures, including
>
large deflections. It has been used on many bridge structures throughout the
>
world.
>

>
For most suspension and cable-stayed bridges, the tension-stiffening
>
behavior of the cables is the most significant effect. This can be modeled
>
using Frame elements and the P-delta analysis feature. You may directly
>
specify the tension in the cables if you know it, or you may have the
>
program compute the tension iteratively. The latter method is generally
>
recommended. You need to provide a small bending stiffness for the cable
>
elements to prevent the problems you were having with zero stiffness for the
>
rotations, but it is simple enough to find a realistic value for any
>
physical cable, and it will not significantly affect your results. We do not
>
recommend using end releases for cable elements.
>

>
The restriction here is that the tension-stiffening effect, once calculated,
>
is then assumed to be constant for all subsequent static and dynamic
>
analyses. This is almost always adequate for suspension bridges, and very
>
often for cable-stayed bridges as well. Modal analysis, response-spectrum
>
analysis, vehicle moving-load analysis, and linear/nonlinear time-history
>
analysis all include the tension-stiffening effect. The advantage of this
>
approach is its great computational economy.
>

>
In addition, SAP2000 Nonlinear (version 7.0 and later) includes nonlinear
>
static analysis capability that can be used to model the full geometric
>
nonlinearity of cables, including tension-stiffening, large displacements
>
and rotations, and slackening. Again, you use the Frame element with a small
>
but realistic value of bending stiffness. Geometric nonlinearity is included
>
in all element types in SAP2000 nonlinear static analysis.
>

>
I hope this helps.
>

>
You may forward this message to the SEAINT list server if you feel that
>
others might benefit from this answer.
>

>
Sincerely,
>

>
Bob Morris
>
Computers and Structures, Inc.
>
510-845-2177 Voice
>
510-845-4096 Fax
>
bob(--nospam--at)csiberkeley.com
>

>

>
-----Original Message-----
>
From: José Velásquez [mailto:josemvv(--nospam--at)LatinMail.com]
>
Sent: Tuesday, September 05, 2000 3:46 PM
>
To: seaint(--nospam--at)seaint.org
>
Subject: Modeling Cable Behavior in SAP2000
>

>

>
Hello my friends,
>

>
My name is Joseph and I am from Peru. I need to know how to model the
>
behavior of cables in the SAP2000 (including non-linear behavior) because I
>
am modeling a cable-stayed bridge but I think SAP2000 is not capable to
>
compute only axial forces (tensions). How about a suspensin bridge ? Even
>
when I model a cable as little frame elements conected in a parabola curve
>
with moment releases at the ends, the program can't make the analysis
>
because it tells me that it didn't find some stifnees coefficients at the
>
degrees of freedom of rotation. If anybody is able to help me, I will be
>
very thankful.
>

>
Truly
>
José Velásquez
>

>

>

>
_________________________________________________________
>
http://www.latinmail.com.  Gratuito, latino y en español.
>

>

>
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_________________________________________________________
http://www.latinmail.com.  Gratuito, latino y en español.


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