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hello everybody,

In the drucker prager material of opensees there is a constant To used for softening parameter delta2 is the value of constant correct
that value should not be maximum tensile strength of the material where it becomes plastic
please explain be the softening parameters in drucker prager

i have been applying softening on following problem and i stress-strain curve is not changing it remains plastic

please help me

wipe

model BasicBuilder -ndm 3 -ndf 3

#--create the nodes
node 1 1.0 0.0 0.0
node 2 1.0 1.0 0.0
node 3 0.0 1.0 0.0
node 4 0.0 0.0 0.0
node 5 1.0 0.0 1.0
node 6 1.0 1.0 1.0
node 7 0.0 1.0 1.0
node 8 0.0 0.0 1.0

#--uniaxial test boundary conditions
fix 1 0 1 1
fix 2 0 0 1
fix 3 1 0 1
fix 4 1 1 1
fix 5 0 1 0
fix 6 0 0 0
fix 7 1 0 0
fix 8 1 1 0

#--define material parameters for the model
set E 30760;

set v 0.2;

set G [expr $E/(2*(1+$v))];

set K [expr $E/(3*(1-2*$v))];


#---yield stress
set sigY 8.36
#---failure surface and associativity
set rho 0.67
set rhoBar 0.67
#---isotropic hardening
set Kinf 0.0
set Ko 0.0
set delta1 0.0
#---kinematic hardening
set H 0
set theta 1
#---tension softening
set delta2 300
#---mass density
set mDen 2.5

#--material models
# type tag k G sigY rho rhoBar Kinf Ko delta1 delta2 H theta density
nDMaterial DruckerPrager 2 $K $G $sigY $rho $rhoBar $Kinf $Ko $delta1 $delta2 $H $theta $mDen

#--create the element
# type tag nodes matID bforce1 bforce2 bforce3
element stdBrick 1 1 2 3 4 5 6 7 8 2 0.0 0.0 0.0

puts "model Built..."

#-------------------------------------------------------
# create the recorders
#-------------------------------------------------------
set step 0.1

# record nodal displacements
recorder Node -file displacementst.out -time -node 5 -dof 1 2 3 disp

# record the element stress, strain, and state at one of the Gauss points
recorder Element -ele 1 -time -file stress1tec.out material 2 stress
recorder Element -ele 1 -time -file strain1tec.out material 2 strain
recorder Element -ele 1 -time -file state1tec.out material 2 state


puts "recorders set..."

#-------------------------------------------------------
# create the loading
#-------------------------------------------------------

#--pressure magnitude
set p 10.0
set pNode [expr $p/4]

#--loading object for hydrostatic pressure
pattern Plain 1 "Linear" {
load 1 $pNode 0.0 0.0
load 2 $pNode 0.0 0.0

load 5 $pNode 0.0 0.0
load 6 $pNode 0.0 0.0

}

#--loading object deviator stress
#pattern Plain 2 {Series -time {0 10 100} -values {0 1 5} -factor 1} {
# load 5 0.0 0.0 $pNode
# load 6 0.0 0.0 $pNode
# load 7 0.0 0.0 $pNode
# load 8 0.0 0.0 $pNode
#}

#-------------------------------------------------------
# create the analysis
#-------------------------------------------------------
numberer RCM
system SparseGeneral
constraints Transformation
test NormDispIncr 1e-5 10 1
algorithm Newton
analysis Static



set dU 0.00001; # Displacement increment

# Change the integration scheme to be displacement control
# node dof init Jd min max
integrator DisplacementControl 5 1 $dU 1 $dU $dU

recorder Node -node 5 -time -file node5s.out -dof 1 disp;

set maxU 0.0050000; # Max displacement
set numSteps [expr int($maxU/$dU)]

# Perform the analysis
set ok [analyze $numSteps]

if {$ok != 0} {

set currentDisp [nodeDisp 5 1]
print currentDisp
set ok 0
while {$ok == 0 && $currentDisp < $maxU} {

set ok [analyze 1]

# if the analysis fails try initial tangent iteration
if {$ok != 0} {
puts "regular newton failed .. lets try an initail stiffness for this step"
test NormDispIncr 1.0e-12 2000 1
algorithm ModifiedNewton -initial
set ok [analyze 1]
if {$ok == 0} {puts "that worked .. back to regular newton"}
test NormDispIncr 1.0e-8 100
algorithm Newton
}

set currentDisp [nodeDisp 5 1]
}
}

puts "";
if {$ok == 0} {
puts "Pushover analysis completed SUCCESSFULLY";
} else {
puts "Pushover analysis FAILED";
}

dear all

please someone can explain me softening parameter in drucker prager material
i have tried different values of delta 2 but there is no change in stress - strain curve i am posting my script please give me suggestions

After maximum tensile stress the stress strain curve remains constant and there is no tension softening
wipe

model BasicBuilder -ndm 3 -ndf 3

#--create the nodes
node 1 1.0 0.0 0.0
node 2 1.0 1.0 0.0
node 3 0.0 1.0 0.0
node 4 0.0 0.0 0.0
node 5 1.0 0.0 1.0
node 6 1.0 1.0 1.0
node 7 0.0 1.0 1.0
node 8 0.0 0.0 1.0

#--uniaxial test boundary conditions
fix 1 0 1 1
fix 2 0 0 1
fix 3 1 0 1
fix 4 1 1 1
fix 5 0 1 0
fix 6 0 0 0
fix 7 1 0 0
fix 8 1 1 0

#--define material parameters for the model
set E 30760;

set v 0.2;

set G [expr $E/(2*(1+$v))];

set K [expr $E/(3*(1-2*$v))];


#---yield stress
set sigY 8.36
#---failure surface and associativity
set rho 0.67
set rhoBar 0.67
#---isotropic hardening
set Kinf 0.0
set Ko 0.0
set delta1 0.0
#---kinematic hardening
set H 0.0
set theta 1.0
#---tension softening
set delta2 3000
#---mass density
set mDen 2.5

#--material models
# type tag k G sigY rho rhoBar Kinf Ko delta1 delta2 H theta density
nDMaterial DruckerPrager 2 $K $G $sigY $rho $rhoBar $Kinf $Ko $delta1 $delta2 $H $theta $mDen

#--create the element
# type tag nodes matID bforce1 bforce2 bforce3
element stdBrick 1 1 2 3 4 5 6 7 8 2 0.0 0.0 0.0

puts "model Built..."

#-------------------------------------------------------
# create the recorders
#-------------------------------------------------------
set step 0.1

# record nodal displacements
recorder Node -file displacementst.out -time -node 5 -dof 1 2 3 disp

# record the element stress, strain, and state at one of the Gauss points
recorder Element -ele 1 -time -file stress1tec.out material 2 stress
recorder Element -ele 1 -time -file strain1tec.out material 2 strain
recorder Element -ele 1 -time -file state1tec.out material 2 state


puts "recorders set..."

#-------------------------------------------------------
# create the loading
#-------------------------------------------------------

#--pressure magnitude
set p 10.0
set pNode [expr $p/4]

#--loading object for hydrostatic pressure
pattern Plain 1 "Linear" {
load 1 $pNode 0.0 0.0
load 2 $pNode 0.0 0.0

load 5 $pNode 0.0 0.0
load 6 $pNode 0.0 0.0

}

#--loading object deviator stress
#pattern Plain 2 {Series -time {0 10 100} -values {0 1 5} -factor 1} {
# load 5 0.0 0.0 $pNode
# load 6 0.0 0.0 $pNode
# load 7 0.0 0.0 $pNode
# load 8 0.0 0.0 $pNode
#}

#-------------------------------------------------------
# create the analysis
#-------------------------------------------------------
numberer RCM
system SparseGeneral
constraints Transformation
test NormDispIncr 1e-5 10 1
algorithm Newton
analysis Static



set dU 0.00001; # Displacement increment

# Change the integration scheme to be displacement control
# node dof init Jd min max
integrator DisplacementControl 5 1 $dU 1 $dU $dU

recorder Node -node 5 -time -file node5s.out -dof 1 disp;

set maxU 0.0050000; # Max displacement
set numSteps [expr int($maxU/$dU)]

# Perform the analysis
set ok [analyze $numSteps]

if {$ok != 0} {

set currentDisp [nodeDisp 5 1]
print currentDisp
set ok 0
while {$ok == 0 && $currentDisp < $maxU} {

set ok [analyze 1]

# if the analysis fails try initial tangent iteration
if {$ok != 0} {
puts "regular newton failed .. lets try an initail stiffness for this step"
test NormDispIncr 1.0e-12 2000 1
algorithm ModifiedNewton -initial
set ok [analyze 1]
if {$ok == 0} {puts "that worked .. back to regular newton"}
test NormDispIncr 1.0e-8 100
algorithm Newton
}

set currentDisp [nodeDisp 5 1]
}
}

puts "";
if {$ok == 0} {
puts "Pushover analysis completed SUCCESSFULLY";
} else {
puts "Pushover analysis FAILED";
}

hello everyone
can anyone please explain me the tension softening parameter in drucker prager material what should be it's value in case of masonry structure having tensile stress of 4.6N/mm2
i have got literature in which it is mention in terms of fracture energy can anybody help me in relating this with opensees parameters

dear fmk

as u said i model a 3d pier and i am getting only periods but no mode shapes i am posting my script can you please check

# Units: N, m, sec
# ----------------------------
# Start of model generation
# ----------------------------
# Create ModelBuilder with 3 dimensions and 3 DOF/node
model basic -ndm 3 -ndf 3
#--define material parameters for the model


set output out_t;

file mkdir $output;



set E 30750000000;

set v 0.2;

set G [expr $E/(2*(1+$v))];

set K [expr $E/(3*(1-2*$v))];

set density 2500;
#---yield stress
set sigY 458846.814;
#---failure surface and associativity
set rho 0.617
set rhoBar 0.617
#---isotropic hardening
set Kinf 0.0
set Ko 0.0
set delta1 0.0
#---kinematic hardening
set H 0.0
set theta 1.0
#---tension softening
set delta2 0.0



#--material models
# type tag k G sigY rho rhoBar Kinf Ko delta1 delta2 H theta density
nDMaterial DruckerPrager 1 $K $G $sigY $rho $rhoBar $Kinf $Ko $delta1 $delta2 $H $theta $density
# Define geometry
;




node 1 0.00000 0.00000 0.0000
node 2 6.900 0.00000 0.0000
node 3 6.900 12.760 0.000000
node 4 0 12.760 0.000000
node 5 0 0 2.420
node 6 6.900 0 2.420
node 7 6.900 12.760 2.420
node 8 0 12.760 2.420
node 9 6.900 18.660 0.000000
node 10 0 18.660 0.000000
node 11 6.900 18.660 6.420
node 12 0 18.660 6.420


# ele Node mat
element stdBrick 1 1 2 3 4 5 6 7 8 1

element stdBrick 2 4 3 9 10 8 7 11 12 1




recorder display ShakingBeam 0 0 300 300 -wipe
prp -100 100 120.5
vup 0 1 0
display 1 0 1


# boundary conditions
fix 1 1 1 1 0 0 0
fix 2 1 1 1 0 0 0
fix 5 1 1 1 0 0 0
fix 6 1 1 1 0 0 0

# Create the analysis object
# create the analysis

#-------------------------------------------------------

system BandGeneral



# Create the constraint handler, the transformation method

constraints Transformation



# Create the DOF numberer, the reverse Cuthill-McKee algorithm

numberer RCM

for { set k 1 } { $k <= 12 } { incr k } {
recorder Node -file [format "modes/mode%i.out" $k] -nodeRange 1 12 -dof 1 2 3 "eigen $k"
}
set lambda [eigen 12];

# calculate frequencies and periods of the structure

# calculate frequencies and periods of the structure
#---------------------------------------------------
set omega {}
set f {}
set T {}
set pi 3.141593



foreach lam $lambda {
lappend omega [expr sqrt($lam)]
lappend f [expr sqrt($lam)/(2*$pi)]
lappend T [expr (2*$pi)/sqrt($lam)]
}

puts "periods are $T"

set period "modes/Periods.txt"
set Periods [open $period "w"]
foreach t $T {
puts $Periods " $t"
}

what if i want to have mode shapes of a solid bridge pier i have to model it as 2D with lumped masses and then find its mode shapes? or there is any other way in opensees through which i can get mode shapes of solid 3D bridge pier

perfect thankyou very much

hey everybody,
here i have modelled a cantilever beam using 3d elements as per opensees example 8 but still it says it is failing kindly check my code and let me know my mistake please
# ----------------------------
# Start of model generation
# ----------------------------
# Create ModelBuilder with 3 dimensions and 6 DOF/node
model basic -ndm 3 -ndf 3
# create the material
nDMaterial ElasticIsotropic 1 100 0.25 1.27
# Define geometry
# ---------------
# define some parameters
set eleArgs "1"
set element stdBrick
#set element BbarBrick
set nx 6
set ny 2
set nz 2
set nn [expr ($nz+1)*($nx+1)*($ny+1) ]

# mesh generation
block3D $nx $ny $nz 1 1 $element $eleArgs {
1 0 0 0
2 10 0 0
3 10 0 2
4 0 0 2
5 0 2 0
6 10 2 0
7 10 2 2
8 0 2 2
}
recorder Node -file Node.out -time -node 7 -dof 2 disp
recorder plot Node.out CenterNodeDisp 625 10 625 450 -columns 1 2
recorder display ShakingBeam 0 0 300 300 -wipe
prp -100 100 120.5
vup 0 1 0
display 1 0 1
# --------------------------
set load -0.1
# Constant point load
pattern Plain 1 Linear {
load $nn 0.0 $load 0.0
}
# boundary conditions
fixX 0.0 1 1 1
# --------------------------------------------------------------------
# Start of static analysis (creation of the analysis & analysis itself)
# --------------------------------------------------------------------
# Load control with variable load steps
# init Jd min max
integrator LoadControl 1.0 1 1.0 10.0
# Convergence test
# tolerance maxIter displayCode
test NormUnbalance 1.0e-10 20 1
# Solution algorithm
algorithm Newton
# DOF numberer
numberer RCM
# Cosntraint handler
constraints Plain
# System of equations solver
system ProfileSPD
# Analysis for gravity load
analysis Static
# Perform the analysis
analyze 5
# --------------------------
# End of static analysis
# --------------------------
# ----------------------------

hey kgkoktsi

so finally is your problem solved,i am also trying to work on similar type of model, if possible can you please post the script of your program it will be very helpful since i am new to open sees

did u find any answer? if yes please give me i m trying same

Hey can i use Open Sees for modelling a Solid Continuum in my case a Masonry pier for non-linear dynamic analysis,if yes can any one please post some programmed examples it will be really helpful to me