Hello everyone,
I am testing the behaviour of an FPS (single friction pendulum system) and i want to see what happens in case of an uplift. When i don't have an uplift my model works perfectly and i obtein the results that i expect. However when i increase the scale factor of my seismic excitation in order to provoke the uplift the program stops and i have a message of failure ( my element cannot find the shear force). Has anyone tested the uplift of the FPS and if yes how can i do it.
Thanks
Ion
FPS- uplift
Moderators: silvia, selimgunay, Moderators
Re: FPS- uplift
yes it has been tested. and of course the element will provide no shear resistance when the element is in uplift. there is only a shear force present when element is in compression and mag of shear force is dependent on mag of axial load.
when you get past your modeling issue for the uplift, when it drops again there is contact which can set up high frequency stuff that needs to be damped out numerically.
when you get past your modeling issue for the uplift, when it drops again there is contact which can set up high frequency stuff that needs to be damped out numerically.
Re: FPS- uplift
Hello again ,
Thank you Dr McKenna for your reply, of course there is no shear force during the uplift i understand that. Moreover i read the manual of the Opensees which concerns the FPS and it also writes about numerical damping. I used a numerical damping like this but still i face the same problem. If you have any suggestion i would be grateful.
set kv [expr 300000*$MN/$m]
set mv [expr 1*$mass]
set zetaVertical 0.05
set cv [expr 2.0*$zetaVertical*sqrt($kv*$mv)]
uniaxialMaterial Elastic 1 $kv $cv
uniaxialMaterial Elastic 2 0.0
set mu 0.08
# frictionModel Coulomb tag mu
frictionModel Coulomb 1 $mu
#parameters for friction pendulum system
set R [expr 1*$m] ; #Radius for period 2 sec T = 2$pi$racine(R/g)
set dyield [expr 0.0001*$m] ; #yield displacement
set Kinit [expr $mass*$g*$mu/$dyield]; # K initial
element singleFPBearing 5 1 2 1 $R $Kinit -P 1 -Mz 2 -orient 0 1 0 -1 0 0
Best
Ion
Thank you Dr McKenna for your reply, of course there is no shear force during the uplift i understand that. Moreover i read the manual of the Opensees which concerns the FPS and it also writes about numerical damping. I used a numerical damping like this but still i face the same problem. If you have any suggestion i would be grateful.
set kv [expr 300000*$MN/$m]
set mv [expr 1*$mass]
set zetaVertical 0.05
set cv [expr 2.0*$zetaVertical*sqrt($kv*$mv)]
uniaxialMaterial Elastic 1 $kv $cv
uniaxialMaterial Elastic 2 0.0
set mu 0.08
# frictionModel Coulomb tag mu
frictionModel Coulomb 1 $mu
#parameters for friction pendulum system
set R [expr 1*$m] ; #Radius for period 2 sec T = 2$pi$racine(R/g)
set dyield [expr 0.0001*$m] ; #yield displacement
set Kinit [expr $mass*$g*$mu/$dyield]; # K initial
element singleFPBearing 5 1 2 1 $R $Kinit -P 1 -Mz 2 -orient 0 1 0 -1 0 0
Best
Ion