Drucker-Prager yield surface in plane stress state

[WAELL]

Hello all;

I am tying to model concrete infill panel (infill panel for steel frame) using Quad element. My problem is how I can describe Drucker-Prager yield surface in plane stress state.

I found this link in one of your replies (timosidis-Posted: Thu Jul 15, 2004 1:13 pm Post subject: Reference for 3D-Template Elasto-Plastic Material)

http://sokocalo.engr.ucdavis.edu/~jerem ... mmands.pdf

and I found the following example in pages 9-10

------------------------------------------------------------------------------------
Drucker-Prager Model

# Elastic material
nDMaterial ElasticIsotropic3D 1 2.0e7 0.2 0.0

# Yield surface
set ys "-DP"

# Potential surface, must specify the dilation slope D as a input parameter
# D = 2 *sin(alpha) / (3^0.5) / (3-sin(alpha) ), alpha is the dilation angle
set ps "-DP 0.2"

# Scalar evolution law: linear hardening coef = 1.0
set ES1 "-Leq 1.0"

# Initial stress
set sts "0.01 0 0 0 0.01 0 0 0 0.01"

# EPState
# --alpha-- –k--
set EPS "-NOD 0 -NOS 2 0.2 0.0 -stressp $sts"

# where
# alpha = 2 *sin(phi) / (3^0.5) / (3-sin(phi) ), phi is the friction angle
# k = alpha*3*c/tan(phi), c is the cohesion

# Creating nDMaterial using Template Elastic-Plastic Model
# 2 is the material tag for the Template3Dep material
# 1 is the material tag of the previously defined elastic material

nDMaterial Template3Dep 2 1 -YS $ys -PS $ps -EPS $EPS -ELS1 $ES1
-------------------------------------------------------------------------------------

I followed this example in my simple model but I got NO ERRORS AND NO RESULTS?!!!!
Could you please help me solving this problem?!!!

Thank you in advance for your help

note:
if i changed the material properties (for concrete wall) into elastic isotropic material it works and i got results


This is my simple example


#---------------- infilled steel Frame under PushOver test -------------------
#- CONCRETE INFILL PANEL IS CONCIDERED AS ONE ELEMNT 5 BY 4 M -
#---------- FULL CONTACT BETWEEN FRAM AND WALL PANEL --------------
#-----------------------------------------------------------------------------------
# Units: M, N, kg, sec
#----------------------------------------------
# CREATE MODELBUILDER:
#----------------------------------------------
# Model of 2-D, 2 nodes/element, and 3 DOF/node
model basic -ndm 2 -ndf 3
#----------------------------------------------
# GEOMETRY PARAMETERS:
#---------------------------------------
set L 5.0; # Frame length
set H 4.0; # Frame height
set HH [expr $H/2]; # Frame half height
#----------------------------------------
# CREATE NODES:
#-------------------------------------
# node-tag X-coor Y-coord
node 1 0.0 0.0
node 2 $L 0.0
node 3 0.0 $HH
node 4 $L $HH
node 5 0.0 [expr $H+$HH]
node 6 $L [expr $H+$HH]
#------------------------------------
# BOUNDARY CONDISIONS [Constraints]:
#------------------------------------
# node-tag DX DY RZ
fix 1 1 1 0
fix 2 1 1 0
#-----------------------------------------------------------------------
# DEFINE COLUMNS AND BEAMS ELEMENTS:
#-----------------------------------------------------------------------
geomTransf Linear 1; # Geometry Transformation
# tag nd-i nd-j --A-- --E-- --Iz-- transf-Tag
element elasticBeamColumn 1 1 3 0.1 2e10 0.008 1
element elasticBeamColumn 2 2 4 0.1 2e10 0.008 1
element elasticBeamColumn 3 3 5 0.1 2e10 0.008 1
element elasticBeamColumn 4 4 6 0.1 2e10 0.008 1
# DEFINE BEAM ELEMENTS:
#----------------------------------------------------------------------
geomTransf Linear 2; # Geometry Transformation
# tag nd-i nd-j --A-- --E-- --Iz-- transf-Tag
element elasticBeamColumn 5 3 4 0.1 2e10 0.008 2
element elasticBeamColumn 6 5 6 0.1 2e10 0.008 2
#-----------------------------------------------------------------------
# DEFINE APPLIED LOADS:
#------------------------------------------------------
set Px 100000;
pattern Plain 1 Linear {
# node-tag FX FY MZ
load 5 $Px 0.0 0.0
}
#-----------------------------------------------------------
#------ CREAT CONCRETE WALL MODEL --------------
#-----------------------------------------------------------
# Model of 2-D, and 2 DOF/node
model basic -ndm 2 -ndf 2
#-------------------------------------

# CREATE NODES:
#-------------------------------------
# node-tag X-coor Y-coord
node 103 0.0 $HH
node 104 $L $HH
node 105 0.0 [expr $H+$HH]
node 106 $L [expr $H+$HH]
#------------------------------------------------------

# Mat-tag E v
nDMaterial ElasticIsotropic3D 4 2.0e7 0.2 0.0

#==============================================
set ys "-DP"
set ps "-DP 0.2"
set ES1 "-Leq 1.0"
set sts "0.01 0 0 0 0.01 0 0 0 0.01"

# -alpha- -k-

set EPS "-NOD 0 -Nos 2 0.2 0.0 -stressp $sts"
nDMaterial Template3Dep 16 4 -YS $ys -PS $ps -EPS $EPS -ELS1 $ES1
nDMaterial PlaneStress 5 16

#=============================================


# DEFINE CONCRETE INFILL ELEMENTS: (using Quadrilateral Elements)

#---------------------------------------------------------------------------
# Elem-tag Nd-i Nd-j Nd-k Nd-l thick Type mat-tag
element quad 7 103 104 106 105 1.0 "PlaneStress" 5

#----------------------------------------------------------------------------
# FORCE FOR EQUAL D.O.F.(1,2) FOR NODES 3,103 & 4,104 & 5,105 @ 6,106
#----------------------------------------------------------------------------

equalDOF 3 103 1 2
equalDOF 4 104 1 2
equalDOF 5 105 1 2
equalDOF 6 106 1 2
#--------------------------------------------------------------------

# MODIFICATION FOR PUSHOVER ANALYSSI
#--------------------------------------------------------------------
set dU 0.001; # Displacement increment
# change integ. schem to disp control; node dof init Jd min max
integrator DisplacementControl 5 1 $dU 1 $dU $dU
#--------------------------------------------------------------------

# RECORD RESULTS
#--------------------------------------------------------
recorder Node -file Node5.out -time -node 5 -dof 1 disp
recorder Element 7 -time -file elemnt13.out localForce
#--------------------------------------------------------

# ANALYSIS GENERATION:
#-----------------------------------------------------------------------------------
system BandGeneral
constraints Transformation
numberer RCM
test NormDispIncr 1.0e-12 10 0
algorithm Newton
analysis Static

#------------------------------------------------------------------------------------
# PERFORM THE ANALYSIS:
#------------------------------------------------------------------------------------
set maxU 1; # Max allowable displacement
set numSteps [expr int($maxU/$dU)]
analyze $numSteps; # Perform the displacement control
#-----------------------------------------------------------
# OUT PUT RESULTS:
#----------------------------------------------------------
print node 3 5; # Print out the state of nodes 3 and 4
print element; # Print out the state of ALL element
#----------------------------------------------------------

[dhshin]

Hello,
I recommend you that you check whether the opensees.exe is correct. In some cases an opensees.exe does not include ElasticIsotropicPlaneStrain2D or ElasticIsotropicPlaneStress2D models within nDMaterial Models, specifically within TclModelBuildernDMaterialCommand.cpp. If then, you have to modify the related source codes and compile them.

And one of the reasons that you could not get any results is, i think, the syntax " nDMaterial PlaneStress 5 16 " is not completed. In order to use correct syntaxes, please refer to OpenSees manual.

Thank you and Merry Christmas !!

[Boris]

the template material models are for 3D, you can use 3D brick to model 2D plane stress or plane strain model by appropriately fixing and releasing boundary conditions, the only overhead is then in doing constititive integration twice for integration points that have same X-Y corrdinates (assuming that Z direction is out of plane...).

so use brick with 8 nodes (better yet, 20 or 27 nodes) to get this model...

Boris