Flat Slider Bearing Element : Friction Damper

[SINHA]

Hello,
I'm trying to model Friction damper with Flat Slider Bearing element. For Stick-Slip model of friction damper 'Kinit' should be ideally infinite. But for much higher value ( 1.0e15) it's showing numerical instability.

Can anyone help me with the 'Kinit' value for Flat Slider Bearing element when to be used as friciton damper?

Thank you.

[selimgunay]

You can reduce it until you get an unacceptable change in the period. So start with 1e15, record the period and continue reducing the initial stiffness until the difference between the new period and the original is unacceptable (acceptable difference can be as low as 0.05 sec). Then you can see if you have any numerical issues with the revised initial stiffness.

[Gunner]

selimgunay wrote:
> You can reduce it until you get an unacceptable change in the period. So
> start with 1e15, record the period and continue reducing the initial
> stiffness until the difference between the new period and the original is
> unacceptable (acceptable difference can be as low as 0.05 sec). Then you
> can see if you have any numerical issues with the revised initial
> stiffness.

Glad... Thank you selim.

[SINHA]

According to the OpenSees documentation 'Kinit' is the slope between Friction Coefficient (i.e., Mu) and displacement of the slider (i.e., dy/dz). Is it actual K (stiffness) of the slider or the different parameter of slider? what is actually 'Kinit' and how this parameter works? can anyone help it's bit confusing.

Thank You..