Section analysis

[X]

Hi,
I want to calculate the forces corresponding to a given axial deformation and curvatures in a rc section.
How could I do?

Thanks

[silvia]

look at the section-analysis example in the examples manual and modify it, i have it for a specified axial force.

[cvjchuang]

[quote="silvia"]look at the section-analysis example in the examples manual and modify it, i have it for a specified axial force.[/quote]
would you please send me it ?
thank you very much.

[X]

I think you are referring to example 9. I looked at it but I believe it doesn't solve my problem. In that example the axial force is assigned and only a curvature about one axis is considered.

I'm a new user so I don't know OpenSees in depth.

Please, can you show me how I can do?



Thanks.

[silvia]

spend some time trying to figure it all out, please.

[X]

Are you sure that OpenSees can do it?

[silvia]

not sure what you are trying to do.

[X]

I try to explain better the problem:
I know the axial deformation and the two curvatures.
Can I calculate the axial force and the moments that produce, in a rc section, these components of deformation?

[silvia]

yes, impose them using the sp command in the load pattern and do a load-controlled analysis.

[X]

I did what you told me, but OpenSees exit.
Can you check my data file?
I built a rectangular section using a file similar to "Ex9c.build.RCSection.RectUnconfinedSymm3D.tcl".
Then I created the following analysis file:

# *********************************************************
# *********************************************************
# set maximum axial deformation:
set Eg [expr -0.00175668514256*$m];
# set maximum Curvature:
set Kux [expr 0.01219942361702/$m]
set Kuy [expr 0.00251650356025/$m]

# Define two nodes at (0,0)
node 1001 0.0 0.0 0.0
node 1002 0.0 0.0 0.0

# Fix all degrees of freedom except axial and bending
fix 1001 1 1 1 1 1 1
fix 1002 0 1 1 1 0 0

# Define element
# tag ndI ndJ secTag
element zeroLengthSection 2001 1001 1002 $SecTag3D

# Create recorder
recorder Node -file data/NMxMy.out -time -node 1001 -dof 1 5 6 reaction; # output axial force (col 1) moment x (col 2) & moment y (col 3)

# Define load
pattern Plain 3001 "Linear" {
# Impose deformations
sp 1002 1 $Eg;
sp 1002 5 $Kux;
sp 1002 6 $Kuy;
}

# Define analysis parameters
integrator LoadControl 0 1 0 0
system SparseGeneral -piv; # Overkill, but may need the pivoting!
test EnergyIncr 1.0e-6 10
numberer Plain
constraints Plain
algorithm Newton
analysis Static

# Do one analysis for fixed deformations
analyze 1
# *********************************************************
# *********************************************************

Where is the error?
Thanks.

[silvia]

put some "puts " along the file to see what command bumps you out.

[X]

Using PrintScreen command I captured the OpenSees window just before it exit.
There are three warnings(equal) and a fatal:

WARNING PlainHandler::handle() – non-homogeneos constraint for node 1002 homo assumed
WARNING PlainHandler::handle() – non-homogeneos constraint for node 1002 homo assumed
WARNING PlainHandler::handle() – non-homogeneos constraint for node 1002 homo assumed
FATAL SparseGenColLinSOE::getX - vectX == 0

Where is the problem?

[zvidrih]

You should use another constraints handler, such as Lagrange... anything but Plain...
See the manual on constraints for reference...

[X]

Thank you very much for your suggestion. Now the program doesn't exit, but the reactions are zero.
Did you solve a similar problem?

[fmk]

record the element forces and see if they are also zero.