Getting Tension while defining ENT material

[armkam]

Hi all,

I have modeled elastic 8 noded soil with a elastic beam (as a plate/shallow foundation) on top of it. The inteface in y direction (2nd dof) is modeled with elastic with no tension material (ENT), however when I record the node forces underlying the plate, still I have tension. Would you help me in this please?
I have no tension in my zerolength materials for instance when V=50KN and M=100KN.m was exerted on the middle node of the plate, I get the following forces in y-direction:

(Force in ENT spring connecting point 12 of soil to the plate node)= 200, (Reaction of point 12 of soil)= -200 (so far so good)

(Force in ENT spring connecting point 13 of soil to the plate node)= 0 , (Reaction of point 13of soil)= +150 (here is the problem, spring is not transferring tension to soil but we have tension force in soil)

(Force in ENT spring connecting point 14 of soil to the plate node)= 0 , (Reaction of point 14of soil)= 3.21133e-010



wipe
#################################
#Defining 2dof domain for soil modeling
#################################
model BasicBuilder -ndm 2 -ndf 2

#################################
#Soil Nodes
#################################
node 1 0 0
node 2 0.5 0
node 3 1.0 0
node 4 1.5 0
node 5 2.0 0
node 6 0.0 0.5
node 7 0.5 0.5
node 8 1.0 0.5
node 9 1.5 0.5
node 10 2.0 0.5
node 11 0.0 1.0
node 12 0.5 1.0
node 13 1.0 1.0
node 14 1.5 1.0
node 15 2.0 1.0


#################################
#Material Properties
#################################
# soil mass density (Mg/m^3)
set rho 1.7
# soil shear velocity
set Vs 250.0
# soil shear modulus
set Gmax [expr $rho*$Vs*$Vs]
# poisson's ratio of soil
set nu 0.2
# soil elastic modulus
set Es [expr 2*$Gmax*(1+$nu)]
# soil bulk modulus
set bulk [expr $Es/(3*(1-2*$nu))]

#################################
#Defining Soil Material and Elements
#################################
nDMaterial ElasticIsotropic 1 $Es $nu

set wgtX 0.0
set wgtY [expr -9.81*$rho]
element quad 1 1 2 7 6 1.0 "PlaneStrain" 1 0.0 0.0 $wgtX $wgtY
element quad 2 2 3 8 7 1.0 "PlaneStrain" 1 0.0 0.0 $wgtX $wgtY
element quad 3 3 4 9 8 1.0 "PlaneStrain" 1 0.0 0.0 $wgtX $wgtY
element quad 4 4 5 10 9 1.0 "PlaneStrain" 1 0.0 0.0 $wgtX $wgtY
element quad 5 6 7 12 11 1.0 "PlaneStrain" 1 0.0 0.0 $wgtX $wgtY
element quad 6 7 8 13 12 1.0 "PlaneStrain" 1 0.0 0.0 $wgtX $wgtY
element quad 7 8 9 14 13 1.0 "PlaneStrain" 1 0.0 0.0 $wgtX $wgtY
element quad 8 9 10 15 14 1.0 "PlaneStrain" 1 0.0 0.0 $wgtX $wgtY


#################################
#Defining 3dof domain for plate properties and boundar conditions
#################################
model BasicBuilder -ndm 2 -ndf 3


#################################
#Defining fixity of soil base
#################################
node 201 0 0
node 202 0.5 0
node 203 1.0 0
node 204 1.5 0
node 205 2.0 0

fix 201 0 0 1
fix 202 0 0 1
fix 203 0 0 1
fix 204 0 0 1
fix 205 0 0 1

equalDOF 1 201 1 2
equalDOF 2 202 1 2
equalDOF 3 203 1 2
equalDOF 4 204 1 2
equalDOF 5 205 1 2

node 301 0 0
node 302 0.5 0
node 303 1.0 0
node 304 1.5 0
node 305 2.0 0

fix 301 1 1 1
fix 302 1 1 1
fix 303 1 1 1
fix 304 1 1 1
fix 305 1 1 1

uniaxialMaterial Elastic 2 9e100
element zeroLength 301 301 201 -mat 2 2 -dir 1 2
element zeroLength 302 302 202 -mat 2 2 -dir 1 2
element zeroLength 303 303 203 -mat 2 2 -dir 1 2
element zeroLength 304 304 204 -mat 2 2 -dir 1 2
element zeroLength 305 305 205 -mat 2 2 -dir 1 2


#################################
#Defining plate properties and interface
#################################
node 1012 0.5 1.0
node 1013 1.0 1.0
node 1014 1.5 1.0

#uniaxialMaterial Steel01 $matTag $Fy $E0 $b
uniaxialMaterial Steel01 3 100 3900 .0000001
#uniaxialMaterial ElasticPP 3 3900 0.026
uniaxialMaterial ENT 4 $Es


node 10012 0.5 1.0
fix 10012 0 0 1
equalDOF 12 10012 1 2
element zeroLength 10012 10012 1012 -mat 3 4 -dir 1 2

node 10013 1.0 1.0
fix 10013 0 0 1
equalDOF 13 10013 1 2
element zeroLength 10013 10013 1013 -mat 3 4 -dir 1 2

node 10014 1.5 1.0
fix 10014 0 0 1
equalDOF 14 10014 1 2
element zeroLength 10014 10014 1014 -mat 3 4 -dir 1 2


section Elastic 1 200000000 0.5 0.0417
geomTransf Linear 1

element dispBeamColumn 106 1012 1013 3 1 1
element dispBeamColumn 107 1013 1014 3 1 1



print nodes.out -node
print ele.out -ele

#################################
#Vertical load on mid node of plate
#################################
pattern Plain 1 Constant {
set Wload [expr -50]
load 1013 0 $Wload 0
}


constraints Transformation
test NormDispIncr 1e-4 60 1
algorithm KrylovNewton
numberer RCM
system FullGeneral
integrator LoadControl 1
analysis Static
analyze 1

#################################
#Moment on mid node of plate
#################################
pattern Plain 2 Constant {
set Moment 50
load 1013 0 0 $Moment
}

#################################
#Recording displacements of beam nodes
#################################
recorder Node -file Disp1012.out -node 1012 -dof 1 2 3 disp
recorder Node -file Disp1013.out -node 1013 -dof 1 2 3 disp
recorder Node -file Disp1014.out -node 1014 -dof 1 2 3 disp
#################################
#Recording forces of underlying soil nodes
#################################
recorder Node -file force12.out -node 12 -dof 1 2 3 reaction
recorder Node -file force13.out -node 13 -dof 1 2 3 reaction
recorder Node -file force14.out -node 14 -dof 1 2 3 reaction
#################################
#Recording forces of beam nodes
#################################
recorder Node -file force1012.out -node 1012 -dof 1 2 3 reaction
recorder Node -file force1013.out -node 1013 -dof 1 2 3 reaction
recorder Node -file force1014.out -node 1014 -dof 1 2 3 reaction



constraints Transformation
test NormDispIncr 1e-4 60 1
algorithm KrylovNewton
numberer RCM
system FullGeneral
integrator LoadControl 1
#integrator DisplacementControl 1012 1 .001
analysis Static
analyze 1