MODELING QUESTION

[yairbcn]

I obtain results but they dont make any sense at all, I dont know what i am doing wrong. Could somebody help me? I dont know why the time doesnt start in 0.0 either.




# SET UP --------------------------------------------------------------------------------------

wipe;
model basic -ndm 2 -ndf 3;
file mkdir Data;

# DEFINE GEOMETRY-------------------------------------------------------------------------------


node 1 0 0;
node 2 0 0;

# BOUNDARY CONDITIONS---------------------------------------------------------------------------

fix 1 1 1 1;
fix 2 0 1 1;

# MATERIAL PROPERTIES---------------------------------------------------------------------------

set K 29000000
set alpha 1000000
set Fy 65000
set lambda 2000
set dp 0.05
set dpc 0.1

uniaxialMaterial Bilin 1 $K $alpha [ expr $alpha * (-1) ] $Fy [ expr $Fy * (-1) ] $lambda $lambda $lambda $lambda 1 1 1 1 $dp [ expr (-1) * $dp ] $dpc [ expr (-1) * $dpc ] 0.001 -0.001 $dpc [ expr (-1) * $dpc ] 1 1


# DEFINE ELEMENTS---------------------------------------------------------------------------

set transfTag 1;
geomTransf Linear $transfTag;

element zeroLength 1 1 2 -mat 1 -dir 1


# DEFINE RECORDERS------------------------------------------------------------------------------------

recorder Node -file Data/RBase1.out -time -node 1 -dof 1 reaction;
recorder Node -file Data/Disp13.out -time -node 2 -dof 1 disp;



#--------------------------------------------------------------------------------------------------------



loadConst -time 0.0;
constraints Plain;
numberer Plain;
system BandGeneral;
test NormDispIncr 1.0e-8 6;
algorithm Newton;
integrator LoadControl 0.1;
analysis Static;


#PUSHOVER------------------------------------------------------------------------------------

pattern Plain 2 Linear {

load 2 1. 0. 0.
}

integrator DisplacementControl 2 1 0.01;
analyze 1000;




puts "Done!"

[vesna]

Your model looks ok, and results follow the material in the way you defined it. Your step of displacement of 0.01 looks like to big for your case. You should decrease it 10 to 100 times.

In the output file, the first time you see is never 0.0. It is a value that corresponds to the first displacement increment.

When defining a material for a zeroLength element make sure to specify it in terms of force-displacement.

If you do not like your results try changing your uniaxial material model until your results look good.

[yairbcn]

Thank you for the advice.

I am modeling a zero element with a bilin material and I want to obtain a hystereteic cycle applying a reversed cycle.
I am using the reverse cycle from example 4 varying some parameters.

When I use an elastic material I obtain a straight line with a slope in the 1st and 3rd quadrant, as it should be. But when I apply it in the bilin material I get something which has no sense. Maybe the parameters are not correct.

Thats what I put. I am working in inches and pounds.


set K 29000000
set alpha 1000000
set Fy 65000
set lambda 2000
set dp 0.5
set dpc 2

uniaxialMaterial Bilin 1 $K $alpha [ expr $alpha * (-1) ] $Fy [ expr $Fy * (-1) ] $lambda $lambda $lambda $lambda 1 1 1 1 $dp [ expr (-1) * $dp ] $dpc [ expr (-1) * $dpc ] 0.001 -0.001 $dpc [ expr (-1) * $dpc ] 10 10

For example the two last values 10 and 10, at the begining I had put 1 and 1 but the model didnt worked, so I chaned for a value upper than 2 and it worked.

Do you think the parameters make sense?

[vesna]

I never used bilin material. I suggest you to contact Dr. Dimitrios G. Lignos. He developed the material and will give you the best advices on how to set up different parameters.

[yairbcn]

Thank you for the advice. I'll send him an email!