Elastic-Perfectly Plastic Material and parallel Material

[dynaforce]

Hi everyone.

I want to construct hysteretic model. and then I wiil input to zerolength element.

I used Elastic-Perfectly Plastic Material and parallel Material for multilinear model.

I want to model softening section. When I input negative figure for gredient(tangent), An error is occured.

Error is :

WARNING BandGenLinLapackSolver::solve() -LAPACK routine returned 1
WARNING NewtonRaphson::solveCurrentStep() -the LinearSysOfEqn failed in solve()
StaticAnalysis::analyze() - the Algorithm failed at iteration: 5 with domain at load factor -197.27
OpenSees > analyze failed, returned: -3 error flag

Please help me. why is this error occured?

thank you.

[fmk]

the error occurred because the matrix is singular, the lapack factorization of A into LU has determined that U(1,1) = 0, i suggest you are hitting the point where ElasticPP materials all have 0 tangent, suggest you put in an Elastic material with small tangent stiff and plot your stress-strain to see what is going on.

[dynaforce]

Thank for your comment

I have another question.

When I use Elastic material, can i fix certain section (ex, start point , end point) ?

[fmk]

can you rephrase the question as i have not a clue what you are asking