stress, strain recorder for soil domain

[sreyadhar]

Hi! I'm working on site response analysis of soil and modeled the 2D soil domain of 40m depth and 4m wide with 4 noded quad elements (=40X4). Ground motion has been provided at the base soil nodes in horizontal direction. I want to record stress and strain of each element. But after analyzing my output results are not matching in stress and strain dimension. My command in the code to record output for element 1 is as follows,

recorder Element -file stress4.out -time -dT $motionDT -eleRange 1 1 material 1 stress
recorder Element -file strain4.out -time -dT $motionDT -eleRange 1 1 material 1 strain

in the stress output file I'm getting 5 columns and in strain output file 3 columns except the time column for both cases. I just want to know, which column represent what type of stress and strain??

thanks in advance

[fmk]

the num of cols should be the same .. the eleRange 1 1 may be confusing something in the code .. can you post the element and a material command for ele 1 ..

for now just use -ele 1 .. the strains and stresses should be just 11, 22 and 12 if plane stress.

[yegoroff]

Dear fmk,

could you please explain how this recorder works and what does it actually record? (11, 22, 12)?

I was struggling to find a good explanation on the wiki.

[fmk]

they will be outputting the stresses and strains for the material at element 1's 1'st gauss point.

[jdgome]

Dear fmk,

Actually I'm studying an opensees' example from soilQuake.net page, and I realized that the stress records .*out file for each gauss point of the quad only has 3 colums sx, sz, sxz (as you said above, the stress output for a planeStress problem) despite the element is defined as "PlaneStrain"?

I would thank sincerly your reply.

David Gomez.

wipe
#
#some user defined variables
#
set accMul 20 ;# acceleration multiplier
set massDen 2.0 ;# solid mass density
set fluidDen 1.0 ;# fluid mass density
set massProportionalDamping 0.0 ;
set stiffnessProportionalDamping 0.001 ;
set E 90000.0 ;#Young's modulus
set poisson 0.40 ;
set G [expr $E/(2*(1+$poisson))] ;
set B [expr $E/(3*(1-2*$poisson))] ;
set cohesion 30 ;
set peakShearStrain 0.1 ;
set press 0.0 ;# isotropic consolidation pressure on quad element(s)
set deltaT 0.010 ;# time step for analysis
set numSteps 2000 ;# Number of analysis steps
set gamma 0.600 ;# Newmark integration parameter
set period 1 ;# Period of applied sinusoidal load
set pi 3.1415926535 ;
set inclination 0 ;
set unitWeightX [expr ($massDen-$fluidDen)*9.81*sin($inclination/180.0*$pi)] ;# buoyant unit weight in X direction
set unitWeightY [expr -($massDen-$fluidDen)*9.81*cos($inclination/180.0*$pi)] ;# buoyant unit weight in Y direction
#############################################################

#############################################################

#create the ModelBuilder
model basic -ndm 2 -ndf 2

# define material and properties
nDMaterial PressureIndependMultiYield 2 2 $massDen $G $B $cohesion $peakShearStrain
nDMaterial FluidSolidPorous 1 2 2 2.2E+6

# define the nodes
node 1 0.0E0 0.0E0
node 2 1.0E0 0.0E0
node 3 1.0E0 1.0E0
node 4 0.0E0 1.0E0

# define the element thick material maTag press gravity
element quad 1 1 2 3 4 1.0 "PlaneStrain" 1 $press $unitWeightX $unitWeightY

updateMaterialStage -material 1 -stage 0
updateMaterialStage -material 2 -stage 0

# fix the base
fix 1 1 1
fix 2 1 1

#tie nodes 3 and 4
equalDOF 3 4 1 2

#############################################################
# GRAVITY APPLICATION (elastic behavior)
# create the SOE, ConstraintHandler, Integrator, Algorithm and Numberer
system ProfileSPD
test NormDispIncr 1.E-12 25 0
constraints Transformation
integrator LoadControl 1 1 1 1
algorithm Newton
numberer RCM

# create the Analysis
analysis Static
analyze 2

# switch the material to plastic
updateMaterialStage -material 1 -stage 1
updateMaterialStage -material 2 -stage 1
analyze 1

############################################################
# NOW APPLY LOADING SEQUENCE AND ANALYZE (plastic)

# rezero time
setTime 0.0
#loadConst -time 0.0E0
wipeAnalysis

# create a LoadPattern
pattern UniformExcitation 1 1 -accel "Sine 0 10 $period -factor $accMul"

# create the Analysis
constraints Transformation;
test NormDispIncr 1.E-12 25 0
algorithm Newton
numberer RCM
system ProfileSPD
rayleigh $massProportionalDamping 0.0 $stiffnessProportionalDamping 0.
integrator Newmark $gamma [expr pow($gamma+0.5, 2)/4]
analysis VariableTransient

recorder Node -file disp.out -time -node 1 2 3 4 -dof 1 2 -dT 0.01 disp
recorder Node -file acce.out -time -node 1 2 3 4 -dof 1 2 -dT 0.01 accel
recorder Element -ele 1 -time -file stress1.out -dT 0.01 material 1 stress
recorder Element -ele 1 -time -file strain1.out -dT 0.01 material 1 strain
recorder Element -ele 1 -time -file stress3.out -dT 0.01 material 3 stress
recorder Element -ele 1 -time -file strain3.out -dT 0.01 material 3 strain


#analyze
set startT [clock seconds]
analyze $numSteps $deltaT [expr $deltaT/100] $deltaT 10
set endT [clock seconds]
puts "Execution time: [expr $endT-$startT] seconds."