Hello everybody!
I'm dealing with a problem concerning timehistory analysis.
I have used the SSPbrick element, the ElasticIsotropic3D nDMaterial, and the analysis parameters as follows:
constraints Transformation
test NormDispIncr 1e-3 15 1
algorithm Newton
numberer RCM
system ProfileSPD
integrator Newmark $gamma $beta
rayleigh $a0 $a1 0.0 0.0
analysis Transient
analyze $nSteps $dT
In order to check my model, I recorded the acceleration, the velocity and the displacement of a point belonging to the top of the structure. But the results are far from being realistic since neither the acceleration nor the displacement have the form I was expected to.
Is there any problem with the model parameters I've chosen?
If anybody knows, please let me know..!
Thanks.
P.S.I have checked the eigen analysis and is totally correct.
Here is my script with a sample of nodes, elements and fixities used:
# SET UP ----------------------------------------------------------------------------
#units: kN,m,ton
wipe; # clear memory of all past model definitions
model BasicBuilder -ndm 3 -ndf 3; # Define the model builder, ndm=#dimension, ndf=#dofs
set dataDir Data; # set up name for data directory
file mkdir $dataDir/; # create data directory
set GMdir "../GMfiles"; # ground-motion file directory
set motionDT 0.01; # time step in ground motion record
set pi 3.141592653589793
#-----------------------------------------------------------------------------------------
# 1. CREATE STRUCTURAL 3D NODES
#-----------------------------------------------------------------------------------------
# nodal coordinates:
node 1 6.149986303 22.92 2.999999998
node 2 6.15 22.92 3.3419867
node 3 5.137482879 22.92 3.341986699
node 4 7.162489728 22.92 3.341986699
node 5 8.174993152 22.92 3.3419867
node 6 9.187496576 22.92 3.341986699
node 7 4.124979455 22.92 3.341986699
node 8 3.11247603 22.92 3.341986699
node 9 6.14995575 22.92 4.133894602
node 10 5.137493931 22.92 4.133952976
puts "Nodes Defined"
fix 43 1 1 1
fix 45 1 1 1
fix 47 1 1 1
fix 49 1 1 1
fix 61 1 1 1
fix 63 1 1 1
puts "Fixities Defined"
nDMaterial ElasticIsotropic3D 1 1800000 0.25 2.243
nDMaterial ElasticIsotropic3D 2 1800000 0.25 2.535
puts "Material Defined"
element SSPbrick 1 287 483 484 6176 313 312 6188 6189 1 0 0 -22
element SSPbrick 2 175 5927 5757 1 177 176 3 2 1 0 0 -22
element SSPbrick 3 5904 175 1 5735 178 177 2 4 1 0 0 -22
element SSPbrick 4 5902 5904 5735 5733 179 178 4 5 1 0 0 -22
element SSPbrick 5 5900 5902 5733 5731 180 179 5 6 1 0 0 -22
element SSPbrick 6 5543 5900 5731 5400 5544 180 6 5401 1 0 0 -22
element SSPbrick 7 5927 5925 5755 5757 176 181 7 3 1 0 0 -22
element SSPbrick 8 5925 5923 5753 5755 181 182 8 7 1 0 0 -22
element SSPbrick 9 5923 5561 5418 5753 182 5562 5419 8 1 0 0 -22
element SSPbrick 10 177 176 3 2 184 183 10 9 1 0 0 -22
puts "Elements Defined"
#-------------------------------------------------------------------------------------------
# 8. DEFINE TIME SERIES
#-------------------------------------------------------------------------------------------
#---ANALYSIS PARAMETERS
# Newmark parameters
set gamma 0.5
set beta 0.25
# reset time and analysis
setTime 0.0
wipeAnalysis
#-----------------------------------------------------------------------------------------
# 5. RECORDERS
#-----------------------------------------------------------------------------------------
## record nodal displacments, velocities, and accelerations at each time step
recorder Node -file Data/L.top.displ.out -time -node 362 -dof 1 2 3 disp
recorder Node -file Data/L.top.accel.out -time -node 362 -dof 1 2 3 accel
recorder Node -file Data/L.top.vel.out -time -node 362 -dof 1 2 3 vel
recorder Node -file Data/L.bottom.displ.out -time -node 373 -dof 1 2 3 disp
recorder Node -file Data/L.bottom.accel.out -time -node 373 -dof 1 2 3 accel
recorder Node -file Data/L.bottom.vel.out -time -node 373 -dof 1 2 3 vel
recorder Node -file Data/thol.top.displ.out -time -node 1266 -dof 1 2 3 disp
recorder Node -file Data/thol.top.accel.out -time -node 1266 -dof 1 2 3 accel
recorder Node -file Data/thol.top.vel.out -time -node 1266 -dof 1 2 3 vel
# record stress and strain at each gauss point in the soil elements
recorder Element -file Data/Gstress.out -time -ele 154 stress
recorder Element -file Data/Gstrain.out -time -ele 154 strain
puts "Finished creating recorders..."
#-----------------------------------------------------------------------------------------
# 9. DEFINE ANALYSIS PARAMETERS
#-----------------------------------------------------------------------------------------
#---GROUND MOTION PARAMETERS
# time step in ground motion record
set motionDT 0.01
# number of steps in ground motion record
set motionSteps 4000
#---RAYLEIGH DAMPING PARAMETERS
# damping ratio
set damp 0.05
# lower frequency
set omega1 [expr 2*$pi*7.04]
# upper frequency
set omega2 [expr 2*$pi*11.09]
# damping coefficients
set a0 [expr 2*$damp*$omega1*$omega2/($omega1 + $omega2)]
set a1 [expr 2*$damp/($omega1 + $omega2)]
puts "damping coefficients: a_0 = $a0; a_1 = $a1"
#-------------------------------------------------------------------------------------------
# 9. DYNAMIC ANALYSIS
#-------------------------------------------------------------------------------------------
# create load pattern: apply acceleration to all fixed nodes with UniformExcitation
# define constant factor for applied acceleration
model basic -ndm 3 -ndf 3; # 3 spacial dimensions,3 DOF's per node
set cFactor 1
# define acceleration time history file
set accelerationFile 277_H1.col.asci.acc.txt
# timeseries object for applied force history
# command: pattern UniformExcitation $patternID $GMdir -accel $timeSeriesID
set mSeries "Path -dt 0.01 -filePath $accelerationFile -factor $cFactor"
# loading object
pattern UniformExcitation 10 1 -accel $mSeries
puts "Dynamic loading created..."
set nSteps 4000
set dT $motionDT
puts "number of steps in analysis: $nSteps"
puts "analysis time step: $dT"
# analysis objects
constraints Transformation
test NormDispIncr 1e-3 15 1
algorithm Newton
numberer RCM
system ProfileSPD
integrator Newmark $gamma $beta
rayleigh $a0 $a1 0.0 0.0
analysis Transient
analyze $nSteps $dT
puts "Finished with dynamic analysis..."
wipe
time history analysis
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