Column Two Different Fiber Sections

[simonkey]

Hello,

I have a column discretized into about 10 elements. The bottom half uses one fiber section and the top half uses another fiber section.

When performing pushover analysis using displacement control, I get the following error:

WARNING - ForceBeamColumn3d::update - failed to get compatible element forces &
deformations for element: 85(dW: << 72.5314, dW0: 3133.55)
Domain::update - domain failed in update
DisplacementControl::update - model failed to update for new dU
WARNING NewtonRaphson::solveCurrentStep() -the Integrator failed in update()
StaticAnalysis::analyze() - the Algorithm failed at iteration: 11 with domain at
load factor 181.219
OpenSees > analyze failed, returned: -3 error flag

This error refers to the element in the bottom half JUST before the element in the top half with the other section. Therefore, I suspected the convergence issue might be related to the interface where I have two different fiber sections.

What can be done to fix this convergence issue?

Thanks!

[vesna]

Did you try increasing number of iterations and changing algorithm if analysis fails? In case you did not, here is the way to do it:

set ok 0
set currentDisp 0.0
while {$ok == 0 && $currentDisp < $maxU} {
set ok [analyze 1]
if {$ok != 0} {
test NormDispIncr 1.0e-6 1000 1
algorithm ModifiedNewton –initial
set ok [analiyze 1]
test NormDispIncr 1.0e-6 6 2
algorithm Newton
}
set currentDisp [nodeDisp $nodeTag $dof]
}

[simonkey]

Yea I've tried that code you posted already (btw there's a typo in "analyze" in case you're using it for your work). Additionally, I've tried to deliberately focus on the region of displacements that was giving me trouble and fine tune the dU in that region, but I was unable to get farther as well. As a result, I think it just indicates that, according to my material model, my structural elements were failing. But that's just my hypothesis....