pushover analysis

[behnamsa]

Hi everyone.
I have written this code for a simple frame with SAWS material but it doesn't work. I have tried different 'system', 'algorithm' , etc with different tolerances but it still doesn't work. Thanks..
#Units : KN , mm
wipe;
model BasicBuilder -ndm 2 -ndf 3;

node 1 0.0 0.0;
node 2 2438.4 0.0;
node 3 0.0 2438.4;
node 4 2438.4 2438.4;
fix 1 1 1 1;
fix 2 1 1 1;
mass 3 [expr 0.5*0.04412322] 0. 0.;
mass 4 [expr 0.5*0.04412322] 0. 0.;
geomTransf Linear 1;

uniaxialMaterial Elastic 1 1e12; # rigid
uniaxialMaterial SAWS 2 25.0 5.0 25.0 7.7 0.09 -0.025 0.75 0.005 0.70 1.10;

set A 90000.0;
element truss 1 1 3 $A 1;
element truss 2 3 4 $A 1;
element truss 3 2 4 $A 1;
element twoNodeLink 4 1 4 -mat 2 -dir 1;

pattern Plain 1 Linear {
load 3 1.0 0.0 0.0
}

recorder Node -file node4disp.out -time -node 4 -dof 1 disp;
recorder Node -file node1reac.out -time -node 1 -dof 1 reaction;
recorder Node -file node2reac.out -time -node 2 -dof 1 reaction;

rayleigh [expr 2*0.01*(2.0*3.14/0.5)] 0.0 0.0 0.0;
constraints Plain;
numberer RCM;
system UmfPack ;
test NormDispIncr 1.e-8 100;
algorithm ModifiedNewton;
integrator DisplacementControl 4 1 0.01;
analysis Static;
analyze 1000;
loadConst -time 0.0;

[mhscott]

You are using truss elements with 3 DOF/node in a 2D model, so the rotational stiffnesses are all zero.

https://portwooddigital.com/2021/09/19/ ... ing-nodes/

[behnamsa]

You are using truss elements with 3 DOF/node in a 2D model, so the rotational stiffnesses are all zero.

https://portwooddigital.com/2021/09/19/ ... ing-nodes/

@mhscott
Thank you so much, Dr. Scott, for your response.
I added the following lines to my code:
fix 3 0 0 1;
fix 4 0 0 1;
and now it works. The problem is that When I plot displacement vs force(which is reaction in node 2) it does not have unloading and pinching branches ,unlike the figures shown in this link:
https://opensees.berkeley.edu/wiki/inde ... S_Material

Could you please help me with this as well?
(In fact, I did a test based on ASTM E2126-19, and now that I have force-displacement data, I'd like to compare it with the results from OpenSees)

Thanks.