Axial loading of pile

[kavya1811]

Please, can anyone help me? I am doing the simulation of axial loading of pile (no liquefaction effect included here) - the pile soil interaction has been done using equal DOF and the load transfer using T-z and Q-z material model.
Here I am giving the tcl of simple model.
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model BasicBuilder -ndm 2 -ndf 2
node 1 10.000 0.000
node 2 5.000 0.000
node 3 10.000 5.000
node 5 5.000 5.000
node 6 5.000 5.000
node 7 0.000 0.000
node 8 10.000 10.000
node 10 5.000 10.000
node 11 0.000 5.000
node 12 5.000 10.000
node 14 0.000 10.000

puts "read soil nodes"

nDMaterial ElasticIsotropic 1 20900 0.3

puts "read soil properties"

element quad 3 2 6 11 7 1 PlaneStrain2D 1 0 20 0 0
element quad 4 6 12 14 11 1 PlaneStrain2D 1 0 20 0 0
element quad 5 1 3 6 2 1 PlaneStrain2D 1 0 20 0 0
element quad 6 3 8 12 6 1 PlaneStrain2D 1 0 20 0 0

puts "read soil elements"

fix 1 1 1
fix 2 1 1
fix 3 1 1
fix 7 1 1
fix 8 1 1
fix 11 1 1
fix 14 1 1

puts "read soil boundaries"

uniaxialMaterial TzSimple1 2 2 40 0.028 0.0

element zeroLength 2 12 10 -mat 2 -dir 2

puts "read tz material and element"

uniaxialMaterial QzSimple1 3 2 9.8125 0.028 0.0 0.0

element zeroLength 1 6 5 -mat 3 -dir 2

puts "read qz material and element"

fix 5 1 0
fix 10 1 0

puts "read tz, qz boundaries"

model BasicBuilder -ndm 2 -ndf 3
geomTransf Linear 1
node 4 5.000 5.000
node 9 5.000 10.000
node 13 5.000 11.000 -mass 0.0 -10 0.0

puts "read pile nodes"

element elasticBeamColumn 7 13 9 0.1963 27900000 0.0123 1
element elasticBeamColumn 8 9 4 0.1963 27900000 0.0123 1

puts "read pile elements"

fix 4 1 0 1
fix 9 1 0 1

puts "read pile boundaries"

equalDOF 5 4 1 2
equalDOF 10 9 1 2

puts "nodes tied"

system ProfileSPD
test NormDispIncr 1.e-12 25 0
constraints Transformation
integrator LoadControl 1 1 1 1
algorithm Newton
numberer RCM

puts "initial gravity application"

analysis Static

puts "read initial analysis"

analyze 1

puts "analyzing..."

pattern Plain 1 Linear {
load 13 0.0 -800 0.0
}

puts "read loading pattern"

recorder Node -file dis.out -time -nodeRange 1 14 -dof 1 2 disp
#recorder Node -file Rnode.out -time -nodeRange 1 14 -dof 1 2 reaction

puts "noticed recorder successfully"

constraints Transformation
numberer RCM
system ProfileSPD
test NormDispIncr 1.0e-6 25
algorithm Newton
integrator LoadControl 1 1 1 1

puts "read loading analysis"

analysis Static

analyze 2

puts "analyzing..."

puts "done"

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I am getting the error message as...
WARNING: CTestNormDispIncr::test() - failed to converge after 25 iterations
NewtnRaphson::solveCurrentStep() - the ConvergenceTest object failed in test ()
StaticAnalysis::analyze() - the Algorithm failed at iteration: 0 with domain at load factor 2
Opensees> analyze failed, returned: -3 error flag

Please kindly help me...why I am getting this error...where I have done the mistakes???

Thanks in advance!

[JoseLeo]

you might be applying a pile axial load that is way too big for your total skin-friction and end-bearing resistances.

try smaller axial loads.

"integrator LoadControl 1" and "analyze 2" means double the applied load.

try "integrator LoadControl 0.1" and "analyze 10" to apply the load in 10 steps to see at which load magnitude level it fails to converge and determine your ultimate load capacity.

[kavya1811]

Thanks JosLeo, but I tried that too...before It wasnt converging...!

[JoseLeo]

reset after the gravity analysis:

loadConst -time 0

[kavya1811]

mm...just now before, tried as you said...
again error...