Algorithm Failed at Iteration

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duttaANURAG
Posts: 37
Joined: Fri Mar 23, 2018 2:56 am
Location: NERIST

Algorithm Failed at Iteration

Post by duttaANURAG » Thu Apr 19, 2018 1:43 am

Good Afternoon,

I am working on Wall-Backfill-Foundation Soil interaction.

Recently, I started working on on of my problem in OpenSees. However, the analysis failed and it showed an error message as follow -

WARNING SuperLU::solve(void)- Error 4598 returned in factorization dgstrf()
WARNING AcceleratedNewton::solveCurrentStep() -the LinearSysOfEqn failed in solve()
StaticAnalysis::analyze() - the Algorithm failed at iteration: 3 with domain at load factor 0.04
OpenSees > analyze failed, returned: -3 error flag

My analysis commands are as follows -

Before Initial State Analysis -

constraints Transformation
test NormDispIncr 1e-5 15 1
algorithm Newton
numberer RCM
system SparseGeneral
integrator LoadControl 0.01
analysis Static
analyze 4

and after Initial State Analysis turned off, my analysis commands are as follows -
constraints Transformation
test NormDispIncr 1e-4 60 1
algorithm KrylovNewton
numberer RCM
system SparseGeneral
integrator LoadControl 0.01
analysis Static
analyze 4

Please help me as I am not being able to understand what is the actual problem? Should I change my algorithm and proceed?

Your kind help will be appreciated a lot.

Thank You.

fmk
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Re: Algorithm Failed at Iteration

Post by fmk » Thu Apr 26, 2018 5:28 am

if the solver fails it means the tangent matrix is singular, i.e. a 0 encountered on diagonal during factorization, i.e. your model is unstable. .. as it does get through the first few steps you could try swicthcing to a ModifiedNewton with initial stiffness iterations

duttaANURAG
Posts: 37
Joined: Fri Mar 23, 2018 2:56 am
Location: NERIST

Re: Algorithm Failed at Iteration

Post by duttaANURAG » Tue May 01, 2018 8:26 pm

Thank You Sir

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