Problem in Cyclic-Pushover for ElastoPlastic Material

[Sudan]

Dear fmk,

I encounter a problem in the cyclic pushover analysis for zerolength element.
Model runs well for elastic material but when I change the material to Elasto plastic material, it shows warning.
I have also run the same model for other inelastic material like Steel01, SelfCentering, it runs well for them too.
Even for those two inelastic material when i use post yield stiffness equal to 0 it shows warning.

Is it not working because of zero stiffness value?
Also it is working for the very small value of post yield stifness i.e. for steel01 material [uniaxialMaterial Steel01 5 $Fy $Ki 0.0000001;] model runs well.

The error shown is:
OpenSees > source StaticCycle.tcl
Model Built
WARNING BandGenLinLapackSolver::solve() -LAPACK routine returned 1
WARNING NewtonRaphson::solveCurrentStep() -the LinearSysOfEqn failed in solve()
StaticAnalysis::analyze() - the Algorithm failed at iteration: 0 with domain at load factor 459
OpenSees > analyze failed, returned: -3 error flag
Trying Newton with Initial Tangent ..
WARNING BandGenLinLapackSolver::solve() -LAPACK routine returned 1
DisplacementControl::newStep(void) - failed in solver
StaticAnalysis::analyze() - the Integrator failed at iteration: 0 with domain at load factor 450
OpenSees > analyze failed, returned: -2 error flag
Trying Newton with Initial Tangent ..
WARNING BandGenLinLapackSolver::solve() -LAPACK routine returned 1
DisplacementControl::newStep(void) - failed in solver
StaticAnalysis::analyze() - the Integrator failed at iteration: 0 with domain at load factor 450
OpenSees > analyze failed, returned: -2 error flag
Trying Broyden ..
WARNING BandGenLinLapackSolver::solve() -LAPACK routine returned 1
DisplacementControl::newStep(void) - failed in solver
StaticAnalysis::analyze() - the Integrator failed at iteration: 0 with domain at load factor 450
OpenSees > analyze failed, returned: -2 error flag
Trying NewtonWithLineSearch ..
WARNING BandGenLinLapackSolver::solve() -LAPACK routine returned 1
DisplacementControl::newStep(void) - failed in solver
StaticAnalysis::analyze() - the Integrator failed at iteration: 0 with domain at load factor 450
OpenSees > analyze failed, returned: -2 error flag
PROBLEM Cyclic analysis: CtrlNode 002, dof 1, Disp=0.0510 mm
-1

[fmk]

do you not understand what a 0 stiffness post yield does to the matrix equation! .. look at the error from the solver if you do not .. there are alternatives you can try .. -initial on the soln algorithm