Explicit Newmark integrator

[Gholamreza]

Hello all,

integrator Newmark $gamma $beta

is there any command for using Explicit Newmark integrator ? I know opensees has this integrator but I don't find it in the website or manual.
I know if beta=0, Newmark integrator become Explicit Central Difference but I don't know about Explicit Newmark integrator.

Thanks for your help

[Gholamreza]

I guess the command is as follows:
integrator NewmarkExplicit $gamma

When I use this command, I 'll get the following error:
........................................................................................................................................................................
WARNING: numeric analysis returns 1 -- Umfpackgenlinsolver::solve
WARNING NewtonLineSearch::solveCurrentStep() -the LinearSysOfEqn failed in solve()
DirectIntegrationAnalysis::analyze() - the Algorithm failed at time 0.01
OpenSees > analyze failed, returned: -3 error flag
........................................................................................................................................................................
I also get this error when I use central difference. Is it because those methods are not always stable ? What can I do about it ? reducing the time steps didn't help.

[selimgunay]

Explicit Newmark is conditionally stable. It is unstable for a model with massless degrees of freedom as there are zero period modes. You can try assigning little masses to such DOF