Stress-Strain Fiber Outputs

[Alshaebi]

Hello everyone, please help. I'm using 2D model for precast segmental bridge column with uniaxial concrete02 and material-No tension for the zero-length section between the two segments of the column. I want to get and show the damage to the concrete like cracks, spalling, and crushing by using a stress-strain fiber recorder.

1-why the model is showing "tension" in the concrete fibers however it is a rocking object and only PT strand should be in tension ?

2-why does the tensile stress output reach the max tensile strength of the concrete? even if I use a high tensile value for the concrete. also, I tried to reduce the drift ratio to a low value, the tensile stress still reaches the highest tensile value of concrete (concrete failed )

I have used a very simple model to make sure with a small displacement (less than 10 mm) however I got the same issue (the concrete failed), please check it below:

# The nodes
model BasicBuilder -ndm 2 -dnf 3
node 1 0 0
node 2 0 1500

fix 1 1 1 1
#the Materials
uniaxialMaterial Concrete02 1 -49.5 -0.005 -9.2 -0.01 0.1 3.834 1917
uniaxialMaterial Steel02 4 480 200000 0.01 18 0.925 0.15 0 1 0 1 0
# section
section Fiber 1 {
patch quad 1 16 2 -225.5 -225.5 225.5 -225.5 225.5 -166.5 -225.5 -166.5
patch quad 1 2 12 166.5 -166.5 225.5 -166.5 225.5 166.5 166.5 166.5
patch quad 1 16 2 -225.5 166.5 225.5 166.5 225.5 225.5 -225.5 225.5
patch quad 1 2 12 -225.5 -166.5 -166.5 -166.5 -166.5 166.5 -225.5 166.5
patch quad 1 16 1 -225.5 -253.5 225.5 -253.5 225.5 -225.5 -225.5 -225.5
patch quad 1 1 18 225.5 -253.5 253.5 -253.5 253.5 253.5 225.5 253.5
patch quad 1 16 1 -225.5 225.5 225.5 225.5 225.5 253.5 -225.5 253.5
patch quad 1 1 18 -253.5 -253.5 -225.5 -253.5 -225.5 253.5 -253.5 253.5
patch quad 1 10 1 -138.5 -166.5 138.5 -166.5 138.5 -138.5 -138.5 -138.5
patch quad 1 1 12 138.5 -166.5 166.5 -166.5 166.5 166.5 138.5 166.5
patch quad 1 10 1 -138.5 138.5 138.5 138.5 138.5 166.5 -138.5 166.5
patch quad 1 1 12 -166.5 -166.5 -138.5 -166.5 -138.5 166.5 -166.5 166.5
#reinforcement
layer straight 4 8 78.54 -220.5 -220.5 220.5 -220.5
layer straight 4 8 78.54 -220.5 -171.5 220.5 -171.5
layer straight 4 4 78.54 220.5 -110.25 220.5 110.25
layer straight 4 4 78.54 171.5 -110.25 171.5 110.25
layer straight 4 8 78.54 -220.5 220.5 220.5 220.5
layer straight 4 8 78.54 -220.5 171.5 220.5 171.5
layer straight 4 4 78.54 -220.5 -110.25 -220.5 110.25
layer straight 4 4 78.54 -171.5 -110.25 -171.5 110.25
}

geomTransf PDelta 1
geomTransf Linear 2
# element dispBeamColumn $eleTag $iNode $jNode $numIntgrPts $secTag $transfTag <-mass $massDens> <-cMass> <-integration $intType>
element dispBeamColumn 1 1 2 3 1 2
#0utput
pattern Plain 1 Linear {
load 2 0 0 0
}
constraints Penalty 1.0e16 1.0e16
numberer Plain
system BandGeneral
test NormDispIncr 1.0e-6 200
algorithm Newton
integrator LoadControl 1
analysis Static
analyze 1
loadConst -time 0
recorder Node -file SimpleModelNode4.out -time -node 2 -dof 1 disp
#recorder Element -file ele1sec1StressStrain.out –time -ele 1 section 1 fiber $y $z <$matID> stressStrain
recorder Element -file StressStrainE1.out -time -ele 1 section 2 fiber 0 220 stressStrain
pattern Plain 2 Linear {
load 2 1 0 0
}
constraints Penalty 1.0e16 1.0e16
numberer Plain
system BandGeneral
test NormDispIncr 1.0e-6 200
algorithm Newton
integrator DisplacementControl 2 1 0.002
analysis Static
analyze 1000
integrator DisplacementControl 2 1 -0.004
analysis Static
analyze 1000
integrator DisplacementControl 2 1 0.004
analysis Static
analyze 1000
integrator DisplacementControl 2 1 -0.004
analysis Static
analyze 1000
integrator DisplacementControl 2 1 0.005
analysis Static
analyze 1000
integrator DisplacementControl 2 1 -0.006
analysis Static
analyze 1000
integrator DisplacementControl 2 1 0.006
analysis Static
analyze 1000
integrator DisplacementControl 2 1 -0.006
analysis Static
analyze 1000
integrator DisplacementControl 2 1 0.008
analysis Static
analyze 1000
integrator DisplacementControl 2 1 -0.01
analysis Static
analyze 1000
integrator DisplacementControl 2 1 0.01
analysis Static
analyze 1000
integrator DisplacementControl 2 1 -0.01
analysis Static
analyze 1000
integrator DisplacementControl 2 1 0.015
analysis Static
analyze 1000
integrator DisplacementControl 2 1 -0.02
analysis Static
analyze 1000
integrator DisplacementControl 2 1 0.02
analysis Static
analyze 1000
integrator DisplacementControl 2 1 -0.02
analysis Static
analyze 1000
integrator DisplacementControl 2 1 0.025
analysis Static
analyze 1000
integrator DisplacementControl 2 1 -0.03
analysis Static
analyze 1000
integrator DisplacementControl 2 1 0.03
analysis Static
analyze 1000
integrator DisplacementControl 2 1 -0.03
analysis Static
analyze 1000
integrator DisplacementControl 2 1 0.035
analysis Static
analyze 1000
integrator DisplacementControl 2 1 -0.04
analysis Static
analyze 1000
integrator DisplacementControl 2 1 0.04
analysis Static
analyze 1000
integrator DisplacementControl 2 1 -0.04
analysis Static
analyze 1000
integrator DisplacementControl 2 1 0.05
analysis Static
analyze 1000
integrator DisplacementControl 2 1 -0.06
analysis Static
analyze 1000
integrator DisplacementControl 2 1 0.06
analysis Static
analyze 1000
integrator DisplacementControl 2 1 -0.06
analysis Static
analyze 1000

wipe

[selimgunay]

Hello, In a displacement-based beam-column element, curvature is linear along the length of the element, therefore use of a single displacement element is not sufficient to properly model the inelastic response in your column. You should either use multiple displacement based elements, or use a force-based element.

[Alshaebi]

Thank you selimgunay for your response, I have tried to use each "element nonlinearBeamColumn, element forceBeamColumn, and element dispBeamColumn" to simulate the column but the issue still stands.

Alshaebi