single friction pendulum bearing element

[Opensees87]

I have been trying to model a single friction pendulum bearing element applied at the base of a simple frame ( inverted U) . Compared to fixed, I am getting larger displacements and much smaller member forces, which I think make sense. I have a doubt though. On this webpage for FPS:

http://opensees.berkeley.edu/wiki/index ... ng_Element

What is the member for which we need to define these:

-P $matTag tag associated with previously-defined UniaxialMaterial in axial direction
-T $matTag tag associated with previously-defined UniaxialMaterial in torsional direction

Is this for the material of the FPS? or the frame member? Wonder why it's required when it already asks to define a friction model (I used coulomb) for the FPS.

Here is the code:


wipe;
model BasicBuilder -ndm 2 -ndf 3;
file mkdir FPS36;

node 1 0 0
node 2 0 36
node 3 36 36
node 4 36 0
node 5 0 0
node 6 36 0

fix 5 1 1 1
fix 6 1 1 1

mass 2 5.0 0.0 0.0
mass 3 5.0 0.0 0.0
frictionModel Coulomb 1 0.163

uniaxialMaterial Elastic 11 29000
uniaxialMaterial Elastic 12 29000
geomTransf Corotational 1
element elasticBeamColumn 1 1 2 36 29000 108 1
element elasticBeamColumn 2 2 3 36 29000 108 1
element elasticBeamColumn 3 3 4 36 29000 108 1

element singleFPBearing 4 5 1 1 37.28 2.60 0.01 -P 11 -Mz 12 -orient 0 1 0 -1 0 0;
element singleFPBearing 5 6 4 1 37.28 2.60 0.01 -P 11 -Mz 12 -orient 0 1 0 -1 0 0;

recorder Node -file FPS36/2.txt -time -node 2 -dof 1 2 3 disp;
recorder Element -file FPS36/Fele12.out -time -ele 1 2 globalForce;

[vesna]

With friction model you only define friction coefficient for your sliding surfaces. With -P, you define uniaxial material in the axial direction of the bearing. Since in 2D, you do not need to worry about -T.

[Opensees87]

Thanks for the reply Vesna!