Warning for pile elements

[aminrahmani]

To whom it may concern

I am a M.Sc. student of geotechnical engineering in Sharif University of Technology (Tehran-Iran). My Thesis is on numerical modeling of Seismic behavior of a single pile in liquefiable soils with OpenSees. While performing dynamic analysis of the model, I got this warning for pile elements which are NonlinearBeamColumn:

WARNING-ForceBeamColumn3d::update-failed to get compatible element forces & deformations for element: (dW: <<1.#QNAN, dW0: 1.#QNAN)

Although increasing the strains of the pile material as follows, I got the same warning again.

uniaxialMaterial Concrete01 1001 -3.500000e+004 4.00e-003 -2.45e+004 17e-003
uniaxialMaterial Steel01 1002 1.860000e+006 2.00e+008 1.000000e-002

and element section is:

section Fiber 1 {
patch quad 1001 10 10 [expr -$BP/2] [expr -$BP/2] [expr $BP/2] [expr - $BP/2] [expr $BP/2] [expr $BP/2] [expr -$BP/2] [expr $BP/2]
layer circ 1002 4 3.1416e-4 0 0 0.2 0 360
}
BP is pile width (0.5 meter)

Besides, I encountered the term "1.#QNAN" in the warning, what does it mean?

I really appreciate your help.

[fmk]

you should be using dispBeamColumn element to model piles. you probably have too many forceBeamColumn elements.

[aminrahmani]

Hi,

I used system Umfpack command for static and dynamic analysis of the model which is defined in my previous question. I get the following warning:

UmfPackgenLineSOE::setSize-n 17600 nnz1.67438e+006 lVal 3.34877e+007
UMD2FA: LVALUE too small! Must be greater than 33680322
WARNING UmfpackGenLineSolver::solve(void)- - 4 returned in factorization, UMD2FA

The model consists 1500 EightNode_Brick_u_p elements and the soil Constitutive model is Dafalias-Manzri. Reducing number of elements into 550 elements, I don't get the warning anymore. I am confused; Please help me.

I used these commands for analysis:

set gamma 0.7
integrator Newmark $gamma [expr pow($gamma+0.5, 2)/4]
numberer Plain
constraints Penalty 1.0e12 1.0e12
test NormDispIncr 1.0e-2 30 0
algorithm Newton
system UmfPack
analysis Static

Thanks in advance

Amin