Friction damper

[ONE]

Hello everyone.
I have a question about friction damper. I have simulated a friction damper in Opensees by combining a Zerolength unit with a Steel01 material model, but there is a problem with the time curve of the force, so I hope I can get some help from you.

Thank you very much!
wei liu


Here are the commands:

wipe
puts "System"
model basic -ndm 3 -ndf 6
puts "restraint"
node 1 0.0 0.0 0.0
node 2 1.0 0.0 0.0

puts "element"
fix 1 1 1 1 1 1 1;
fix 2 0 1 1 1 1 1;

uniaxialMaterial Steel01 80 2.4e4 2e6 0.1;
uniaxialMaterial Viscous 50 31830 1.0;
uniaxialMaterial Elastic 10 2e6;
uniaxialMaterial Steel01 91 5e4 1e15 0.0

element zeroLength 1 1 2 -mat 91 -dir 1
element Truss 2 1 2 1 80;
element Truss 3 1 2 1 50;

mass 2 50000 0 0 0 0 0

recorder Node -file node1.out -time -node 2 -dof 1 disp
recorder Node -file node2.out -time -node 2 -dof 1 vel
recorder Node -file node3.out -time -node 2 -dof 1 accel
recorder Node -file nodef.out -time -node 2 -dof 1 reaction