nonlinear time history analysis

[farazmizani]

Hello everyone,
I model a cantilever based on Performance Modeling Strategies for modern reinforced concrete bridge columns by michael P.Berry & Eberhard, and I use model's details from an article of PEER anyway, my question is , why my model has negligible displacement and base shear in nonlinear time history analysis but it works well for pushover analysis?
In the article it says that the column has 22.40 in. peak displacement but my peak displacement is 1.45e-02.
please someone help me about this matter.
here is my script:
################################################################################################################################################
model basic -ndm 2 -ndf 3 ; # Define the model builder, ndm=#dimension, ndf=#dof
source LibUnits.tcl
#=======================================Defining Initial Variables===========================================
set D [expr 4*$ft] ; #Column Diameter
set Ag [expr (3.14/4)*pow($D,2)] ; #Gross area
set H [expr 24*$ft] ; #Column Height
set Ws [expr 522*$kip] ; #Ws=2.32 MN = 2320 KN (522 kip) (superstructure weight)
set Ld [expr 1.41*$in] ; #Longitudinal R. Diameter
set Td [expr 0.625*$in] ; #Transverse R. Diameter
set Cover [expr ((2*$in)+($Td)+($Ld/2))] ; #Cover in opensees is from outer radius of section to center of longitudinal bar.
set N [expr 570*$kip] ; #Axial Load at column base kip
set Im [expr 3.62*10e6] ; #The rotational mass moment of inertia about the center-of-mass (kip*pow(in,20)/g)
set wc [expr 150*$pcf] ; #concrete unit weight
set eco 0.0026 ; #unconfined concrete compressive strain at maximum compressive stress
set ey 0.0026 ; #yield strain of Longitudinal and Transverse R.
set Esh [expr 800*$ksi] ; #Esh
set fyl [expr 75.2*$ksi] ; #yield strength of L. R.
set fyt [expr 54.8*$ksi] ; #yield strength of T. R.
set ful [expr 102.4*$ksi] ; #tensile strength of L. R.
set fut [expr 85.9*$ksi] ; #tensile strength of T. R.
set eult 0.122 ; #tensile strain L
set eut 0.125 ; #tensile strain T
set esh 0.011 ; #Strain corresponding to initial strain hardening
set s [expr 6*$in] ; #C/C longitudinal distance between hoops or spirals
set sc [expr $s-($Td*2)] ; #Clear longitudinal distance between hoops or spiral
set mass [expr ($Ws/$g)] ; #Nodal mass
set PCol $Ws
set Ec [expr 3320*$ksi]
#####################################################################################################
node 1 0 0 0 ; #Bottom node of model
node 2 0 $H 0 ; #Top node of model
node 3 0 0 0
##################
fix 2 0 0 0
fix 1 1 1 1
fix 3 1 1 1
##################
mass 2 $mass 1.0e-9 0.0
mass 1 0 0 0
mass 3 0 0 0
# MATERIAL parameters -------------------------------------------------------------------
set IDconcCore 1; # material ID tag -- confined core concrete
set IDconcCover 2; # material ID tag -- unconfined cover concrete
set IDreinf 3; # material ID tag -- reinforcement
# confined concrete
set fc [expr -5.7*$ksi]; # CONCRETE Compressive Strength
set Ats [expr ($Td*pow($Td,1)*3.14)/(2.0) ] ; #Double R. m^2
set dc [expr $D-(($Ld)+($Td*2)+($Cover*2))] ; #Unit in
set Psc [expr ($Ats*4.0)/($dc*$s)] ; #Volumetric ratio of transverse confinement steel to the concrete core
set Als [expr (($Ld*pow($Ld,1)*3.14)/(4.0))*(18.0)] ; #Total area of longitudinal R.
set Ac [expr (($D-(($Cover*2)+$Td))*($D-(($Cover*2)+$Td))*3.14)/(4.0)] ; #Area of concrete core measured from C/C of confinement steel
set Plc [expr ($Als/$Ac)] ; #Longitudinal steel ratio
set Ke [expr (1.0-(($sc/(2.0*$dc))/(1.0-$Plc)))] ; #Coefficient measuring the effectiveness of the confinement steel
set fpl [expr ($Psc*$fyt*$Ke*0.5)] ; #Effective lateral pressure on confined concrete provided by the confinement steel
set fc1 [expr 5.7*$ksi] ; #Concrete Compressive Strength
set fcc [expr (($fc1*(2.254*(sqrt(1.0+((7.94*$fpl)/($fc1))))-(2.0*($fpl/$fc1))-1.254))*$ksi)] ; #f'cc is the maximum compressive stress of concrete
set ecc [expr 0.0026*(1.0+5.0*(($fcc/$fc1)-1.0))] ; #ecc is the strain at the maximum compressive stress
set Ft [expr (0.625*(sqrt($fc1)))*$ksi] ; #Maximun tensile strength
set ecuu [expr 5.0*$ecc]
# unconfined concrete
set fc1U $fc; # UNCONFINED concrete (todeschini parabolic model), maximum stress
set eps1U -0.003; # strain at maximum strength of unconfined concrete
set fc2U [expr 0.2*$fc1U]; # ultimate stress
set eps2U -0.01;
#steel
set Fy [expr 75.2*$ksi];
set Fu [expr 102.4*$ksi];
set Es [expr 29000.*$ksi];
#####################################################################################
uniaxialMaterial Concrete04 $IDconcCore -$fcc -$ecc -$ecuu $Ec
uniaxialMaterial Concrete04 $IDconcCover $fc $eps1U $eps2U $Ec
uniaxialMaterial ReinforcingSteel $IDreinf $Fy $Fu $Es $Esh $esh $eult
#===============================================================Bond-Slip=================================================================
set db $Ld ; #db is rebar diameter
set alphaBS 0.4 ; #alphaBS is a parameter used in the local bond-slip relation and can be taken as 0.4 in accordance with CEB-FIP Model Code 90
set Pow [expr (1.0/$alphaBS)]
set Sy [expr (((((($db*$Fy*1000.0)/(4000.0*(sqrt($fc*-1000.0))))*((2.0*$alphaBS)+1.0))*pow($Pow,1))*0.1)+0.013)]
set Su [expr $Sy*35]
set b 0.4
set R 0.4
set Fu [expr 102.4*$ksi]
set bondslipMat 5
uniaxialMaterial Bond_SP01 $bondslipMat $Fy $Sy $Fu $Su $b $R
# section GEOMETRY -------------------------------------------------------------
set numBarsSec 18; # number of uniformly-distributed longitudinal-reinforcement bars
set barAreaSec [expr 1.25*$in]; # area of longitudinal-reinforcement bars
set SecTag 1; # set tag for symmetric section
set ri 0.0; # inner radius of the section, only for hollow sections
set ro [expr $D/2]; # overall (outer) radius of the section
set nfCoreR 9; # number of radial divisions in the core (number of "rings")
set nfCoreT 18; # number of theta divisions in the core (number of "wedges")
set nfCoverR 1; # number of radial divisions in the cover
set nfCoverT 18; # number of theta divisions in the cover
set endAng [expr (360-(360/$numBarsSec))]
# Define the fiber section
section fiberSec $SecTag {
set rc [expr $ro-$Cover]; # Core radius
patch circ $IDconcCore $nfCoreT $nfCoreR 0 0 $ri $rc 0 360; # Define the core patch
patch circ $IDconcCover $nfCoverT $nfCoverR 0 0 $rc $ro 0 360; # Define the cover patch
set theta [expr 360.0/$numBarsSec]; # Determine angle increment between bars
layer circ $IDreinf $numBarsSec $barAreaSec 0 0 $rc 20 360; # Define the reinforcing layer
}
#Section of Bond-Slip
set SecTagBS 3
section fiberSec $SecTagBS {
patch circ $IDconcCore $nfCoreT $nfCoreR 0 0 $ri $rc 0 360 ; # Define the core patch
patch circ $IDconcCover $nfCoverT $nfCoverR 0 0 $rc $ro 0 360 ; # Define the cover patch
layer circ $bondslipMat $numBarsSec $barAreaSec 0 0 $rc 20 360 ; # Define the reinforcing layer
}
#Aggregator
set shearsec 4
set secAgg 6
set G [expr (($Ec)/2.4)]
set GA [expr $G*$Ag]
uniaxialMaterial Elastic $shearsec $GA
section Aggregator $secAgg $shearsec Vy -section $SecTag
#################################################################################################################
set ColTransfTag 1; # associate a tag to column transformation
geomTransf Linear $ColTransfTag ;
set EleTag 2
set eleTag 1
set iNode 2
set jNode 1
set ibNode 1
set jbNode 3
set Ni 5
set numIntgrPts 5
element nonlinearBeamColumn $eleTag $iNode $jNode $numIntgrPts $secAgg $ColTransfTag
#ZeroElement of Bond-Slip
element zeroLengthSection $EleTag $ibNode $jbNode $SecTagBS
#Define GRAVITY
timeSeries Constant 1
pattern Plain 1 1 {
load 2 0 -$PCol 0
}
################################################################################################################################################
file mkdir OutputDynamic
recorder Node -file OutputDynamic/Disp.txt -time -node 2 -dof 1 disp; # displacements of top node
recorder Node -file OutputDynamic/VBase.txt -time -node 1 -dof 1 reaction; # support reaction
recorder Drift -file OutputDynamic/Drift.txt -time -iNode 1 -jNode 2 -dof 1 -perpDirn 2 ; # drift
################################################################################################################################################
# Gravity-analysis parameters -- load-controlled static analysis
set Tol 1.0e-6; # convergence tolerance for test
constraints Plain ; # how it handles boundary conditions
numberer Plain ; # renumber dof's to minimize band-width (optimization), if you want to
system BandGeneral ; # how to store and solve the system of equations in the analysis
test NormDispIncr $Tol 6 ; # determine if convergence has been achieved at the end of an iteration step
algorithm Newton; # use Newton's solution algorithm: updates tangent stiffness at every iteration
set NstepGravity 10; # apply gravity in 100 steps
set DGravity [expr 1./$NstepGravity]; # first load increment;
integrator LoadControl $DGravity; # determine the next time step for an analysis
analysis Static; # define type of analysis static or transient
analyze $NstepGravity; # apply gravity
loadConst -time 0.0
wipeAnalysis
puts "Maintain Constant Gravity Loads and Reset Time to Zero"
puts "MODEL BUILT"
# DYNAMIC EQ ANALYSIS --------------------------------------------------------
# Uniform Earthquake ground motion (uniform acceleration input at all support nodes)
set GMdirection 1; # ground-motion direction
set GMfile "kobe.txt" ; # ground-motion filenames
set GMfact 1; # ground-motion scaling factor
# set up ground-motion-analysis parameters
set sec 42
set DtAnalysis [expr 0.01]; # time-step Dt for lateral analysis
set TmaxAnalysis $sec; # maximum duration of ground-motion analysis -- should be 50*$sec
# Uniform EXCITATION: acceleration input
set IDloadTag 2; # load tag
set dt 0.01; # time step for input ground motion
set GMfatt 1; # data in input file is in g Unifts -- ACCELERATION TH
set AccelSeries "Series -dt $dt -filePath $GMfile -factor $GMfatt"; # time series information
pattern UniformExcitation $IDloadTag $GMdirection -accel $AccelSeries ; # create Unifform excitation #DAMPING-----------------------------------------------------------------------------------------------------------------
# apply Rayleigh DAMPING from $xDamp
# D=$alphaM*M + $betaKcurr*Kcurrent + $betaKcomm*KlastCommit + $beatKinit*$Kinitial
set xDamp 0.05; # 5% damping ratio
set nEigenI 1
set nEigenJ 1
set lambdaN [eigen [expr $nEigenJ]]
set lambdaI [lindex $lambdaN [expr $nEigenI-1]]
set lambdaJ [lindex $lambdaN [expr $nEigenJ-1]]
set omegaI [expr pow($lambdaI,0.5)]
set omegaJ [expr pow($lambdaJ,0.5)]
set alphaM [expr $xDamp*(2*$omegaI*$omegaJ)/($omegaI+$omegaJ)];
set betaKcurr 0.;
set betaKcomm [expr 2.*$xDamp/($omegaI+$omegaJ)];
set betaKinit 0.;
rayleigh $alphaM $betaKcurr $betaKinit $betaKcomm;
#
#
###################################
# DYNAMIC ANALYSIS PARAMETERS #
###################################
constraints Transformation ;
numberer Plain
system SparseGeneral -piv
set Tol 1.e-6; # Convergence Test: tolerance
set maxNumIter 10; # Convergence Test: maximum number of iterations that will be performed before "failure to converge" is returned
set printFlag 0; # Convergence Test: flag used to print information on convergence (optional) # 1: print information on each step;
#set TestType EnergyIncr; # Convergence-test type
set TestType NormDispIncr; # Convergence-test type
test $TestType $Tol $maxNumIter ;
set algorithmType KrylovNewton
algorithm $algorithmType;
set NewmarkGamma 0.5; # Newmark-integrator gamma parameter (also HHT)
set NewmarkBeta 0.25; # Newmark-integrator beta parameter
integrator Newmark $NewmarkGamma $NewmarkBeta
analysis Transient
set Nsteps [expr int($TmaxAnalysis/$DtAnalysis)];
analyze $Nsteps $DtAnalysis
#
#
#
#
puts "Ground Motion Done. End Time: [getTime]"
############################################################################################




Thank You.
Faraz Mizani

[fmk]

do you have the kobe.txt file

[farazmizani]

yes I have it, and I tried other ground motions but the results were negligible Again.

[selimgunay]

If the accelerations in the input file is in g's, you need to covert to in/s2.

[farazmizani]

Thank you selimgunay and fmk for your guide , I have 21.9117in. peak displacement now.

[XIONGNENG]

Hello:
I've had a similar problem lately about the rotational moment of inertia of the mass .I find you've defined it: set Im [expr 3.62*10e6],but Your quality definition doesn't exist: mass 2 $mass 1.0e-9 0.0 ,How to add this rotation moment of inertia of the mass to the model, Can I define it like that:mass 2 $mass 1.0e-9 $Im

[selimgunay]

Yes you can do it like that

[BIal]

This is not related to your question (I think), but I was just taking a look at your code and I noticed that you have both node 1 and 3 fully restrained if I am not mistaken. Your Zero Length Section element seems to be fully restrained, but only the shear deformations should be restrained. Am I right?

[selimgunay]

Please note that it is not a zerolength element, it is a zerolengthsection

[parasismique]

Dear Farazmizani,

First of all, thank you for your question. With this type of problem we can learn a lot of things.
I am modelling RC column using the fiber section. I am using nonlinear BeamColumn element with zero length section element (Bond-slip).
and I based myself on your program for establishing mine. I trying to perform a linear static pushover simulation. The materials are defined as follows: concrete01 for unconfined concrete, concrete02 for confined concrete and ReinforcingSteel whose characteristics are given as follows:
# confined concrete

set fc1C -34.474; # [MPa] CONFINED concrete (mander model), maximum stress
set eps1C -0.004; # strain at maximum stress
set fc2C -21.0; # [MPa] ultimate(crushing) stress
set eps2C -0.014; # strain at ultimate stress
set lambda 0.1; # ratio between unloading slope at $eps2 and initial slope $Ec
# tensile-strength properties
set ftU [expr -0.14*$fc1C]; # tensile strength +tension
set Ets [expr $ftU/0.002]; # tension softening stiffness

# unconfined concrete

set fc1U $fc; # UNCONFINED concrete (todeschini parabolic model), maximum stress
set eps1U -0.002; # strain at maximum strength of unconfined concrete
set fc2U 0.0; # ultimate stress
set eps2U -0.008; # strain at ultimate stress

# Steel propreties

set Fy 526.0; # [MPa] STEEL yield stress
set Fu 717.0; # [MPa] STEEL ultime stress
set Es 200000.; # [MPa] modulus of steel
set Esh 5600.0; # [MPa] modulus ultimate steel
set esh 0.011; #Strain corresponding to initial strain hardening
set eult 0.122; #tensile strain L


#===========UniaxialMaterial of concrete and steel==============

####uniaxialMaterial Concrete01 $matTag $fpc $epsc0 $fpcu $epsU
uniaxialMaterial Concrete01 $IDconcCover $fc1U $eps1U $fc2U $eps2U; # build cover concrete (unconfined)

####uniaxialMaterial Concrete02 $matTag $fpc $epsc0 $fpcu $epscu $lambda $ft $Ets
uniaxialMaterial Concrete02 $IDconcCore $fc1C $eps1C $fc2C $eps2C $lambda $ftU $Ets ; # build core concrete (confined)

####uniaxialMaterial ReinforcingSteel $matTag $fy $fu $Es $Esh $esh $eult
uniaxialMaterial ReinforcingSteel $IDreinf $Fy $Fu $Es $Esh $esh $eult; # Steel

I define the lateral load as portion of the weight as following:
load 2 $Hload 0.0 0.0;
and redefine integrator for pushover analysis:
integrator Displacement Control 2 1 $Dincr
When I run the code in OpenSees.exe. I got error messages 'material failed in setTrial strain: Large trial compression strain' !
I hope someone can help as I really need this simulation to work for my dissertation.

[hesamgholamigmail]

Hello
I have 40 records with different time-steps [0.02 sec, 0.005 sec,0.004 sec], what is the best identical time-step for all records to perform the transient analysis?

[selimgunay]

If you want an identical analysis time step for all motions, you can use the smallest, which is 0.004 sec. But if there is no specific reason for running all with the same analysis step, you can run each with the corresponding ground motion step. What is the period of your structure?

[hesamgholamigmail]

If you want an identical analysis time step for all motions, you can use the smallest, which is 0.004 sec. But if there is no specific reason for running all with the same analysis step, you can run each with the corresponding ground motion step. What is the period of your structure?

salutes to dear selimgunay
an identical analysis time step considered 0.004s (smallest).ok
the period of a bridge is 0.63 sec.
nevertheless, do I necessitate to (test unconditionally stability)?