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Hello Developers,
Is it anyway to call acceleration when developing new material ? For example, I know we can use strain-rate to call velocity, I was wondering if there is a way to call acceleration or we should get the rate of strain-rate ?

Hello Everyone,
I modeled a 9story structure and I'd like to have specific damping ration for the first mode. I can calculate the critical damping (Cc=2mw), and we know damping ratio = (Damping-coefficient/Critical-Damping). Any idea how I can specify damping coefficient ? should I use Rayleigh command to specify the damping coefficient ? Thanks

Hello everyone,
I modeled that 3story SAC building and did the eigen analysis for the 3 modes. The first frequency is exactly matched with the references that I have, but the frequencies for mode 2 and 3 are different with my reference. the frequency of mode 2 is about 0.1 and the frequency of mode 3 is about 0.8 less than my reference. I checked all the mass, stiffness and everything seems correct to me. Any idea that what might cause this problem ? (As I go to higher modes frequencies my periods and frequencies will be more different from my reference).

Hello Engineers,

I want to get response spectrum for 2DOF while keeping the period of the second mode as a constant number. Let me clarify that with a example: I am changing the first period (T1: period of mode1 ) from zero to 4 second while the second period (T2: period of mode 2) is always 0.2.

My questions:

1. Is it possible to have T1 < T2 ? (period of mode 1 less than period of mode 2) for example: T1 = 0.05 and T2 = 0.2

Thanks

Thank you selimgunay

Any idea ?

Hello OpenSees Community,

I want to compare the result of MATLAB and OpenSees in a nonlinear analysis.
In order to have the same model in MATLB and OpenSees, I model my system in the way that periods for mode 1 and 2 of my system in OpenSees and MATLAB be identical.
When I do it in SDOF, the results are perfectly match but when I do it in 2DOF the results are different. Can anyone tell me why it happens ?
Is there any way I could model 2DOF with 2 springs and 2 masses in OpenSees.

Below is my code in OpenSees (No Damping)
...................................................................................................................................................................................
wipe all;
model BasicBuilder -ndm 2 -ndf 3;

set Output Output;
file mkdir $Output;

source Wsection.tcl;

set g 9.81; #m/sec2
set pi 3.1415;


# define nodal coordinates:
node 1 0. 0.
node 2 3. 0.
node 3 0. 3.
node 4 3. 3.
node 5 0. 6.
node 6 3. 6.

# Single point constraints -- Boundary Conditions
fix 1 1 1 1;
fix 2 1 1 1;

# Define ELEMENTS & SECTIONS -------------------------------------------------------------
set ColSecTag1 1;
set BeamSecTag1 11;

# define MATERIAL properties ----------------------------------------
set FyCol [expr 2.0*345000]
set Es [expr 285e5];
set nu 0.3;
set GsCol [expr $Es/2./[expr 1+$nu]];
set Hiso 0
set Hkin 1000
set ColmatIDhard 1
uniaxialMaterial Steel01 $ColmatIDhard $FyCol $Es 0.03


set FyBeam [expr 1.4*248000]
set GsBeam [expr $Es/2./[expr 1+$nu]];
set BeamMatIDhard 2
uniaxialMaterial Steel01 $BeamMatIDhard $FyBeam $Es 0.03

# ELEMENT properties
# Structural-Steel W-section properties
set inTOm 0.0254;

# 1 column sections: W14x500
set d [expr 19.6*$inTOm];
set bf [expr 17.0*$inTOm];
set tf [expr 3.5*$inTOm];
set tw [expr 2.19*$inTOm];
set nfdw 8;
set nftw 2;
set nfbf 16;
set nftf 4;
Wsection $ColSecTag1 $ColmatIDhard $d $bf $tf $tw $nfdw $nftw $nfbf $nftf

# 1 beam sections: W36x160
set d [expr 36.0*$inTOm];
set bf [expr 12.0*$inTOm];
set tf [expr 1.02*$inTOm];
set tw [expr 0.65*$inTOm];
set nfdw 8;
set nftw 2;
set nfbf 16;
set nftf 4;
Wsection $BeamSecTag1 $BeamMatIDhard $d $bf $tf $tw $nfdw $nftw $nfbf $nftf

#...................

set IDColTransf 1;
set IDBeamTransf 2;
geomTransf Linear $IDColTransf ;
geomTransf Linear $IDBeamTransf

# Define Beam-Column Elements
set np 5;

element nonlinearBeamColumn 1 1 3 $np $ColSecTag1 $IDColTransf;
element nonlinearBeamColumn 2 2 4 $np $ColSecTag1 $IDColTransf;
element nonlinearBeamColumn 3 3 4 $np $BeamSecTag1 $IDBeamTransf;
element nonlinearBeamColumn 4 3 5 $np $ColSecTag1 $IDColTransf;
element nonlinearBeamColumn 5 4 6 $np $ColSecTag1 $IDColTransf;
element nonlinearBeamColumn 6 5 6 $np $BeamSecTag1 $IDBeamTransf;

mass 3 80. 0. 0.;
mass 4 80. 0. 0.;
mass 5 50. 0. 0.;
mass 6 50. 0. 0.;


#pattern Plain 1 Linear {
# load 3 0. [expr -1.0*50.*$g] 0.
# load 4 0. [expr -1.0*50.*$g] 0.
# load 5 0. [expr -1.0*50.*$g] 0.
# load 6 0. [expr -1.0*50.*$g] 0.
#};

# Define RECORDERS -------------------------------------------------------------
recorder Node -file $Output/Disp1.out -time -node 4 -dof 1 disp;
recorder Node -file $Output/Disp2.out -time -node 4 -dof 2 disp;
recorder Node -file $Output/Disp3.out -time -node 4 -dof 3 disp;

set lambda1 [eigen 1];
set lambda2 [eigen 2];

set omega {}
set f {}
set T {}
set pi 3.141593

foreach lam $lambda2 {
lappend omega [expr sqrt($lam)]
lappend f [expr sqrt($lam)/(2*$pi)]
lappend T [expr (2*$pi)/sqrt($lam)]
}

puts "periods are $T"
puts "omega are $omega"



set dt 0.005;

set accelSeries "Series -dt $dt -filePath Erzincan_NS_005_g.txt -factor [expr 9.81]";
pattern UniformExcitation 500 1 -accel $accelSeries;
set dt 0.005;
set tmax 21.3;


# create the analysis
wipeAnalysis;
constraints Transformation;
numberer RCM;
system UmfPack;
test EnergyIncr 1.0e-10 100;
algorithm KrylovNewton;
integrator Newmark 0.5 0.25 ;
analysis Transient;
analyze [expr int($tmax/$dt)] $dt;

puts "Done!"

.........................................................................................................................................................................................
Thanks

Thank you so much

Thank you Selimgunay for the response,
That would be great if you could post a example.
Zero-length Element for 2DOF ? Can you tell me which uniaxial material I should use ?

Thanks

Hello all,
What is the best way to model 2DOF ? I only need to get the lambda 1 and lambda 2 ?
Can I do that with 2 Two node link element and Uniaxial Material Elastic ?

Thanks

Hello OpenSees Community,
I added new material and could compile and run it successfully and get reasonable results for a SDOF model.
When I put my material in series with uniaxialMaterial Elastic, it will be ignored. Can anyone tell me why that is and What I should do??

Here is my code :

....................................................................................................................................................................................................
wipe all; # clear memory of past model definitions
model BasicBuilder -ndm 2 -ndf 3; # Define the model builder, ndm = #dimension, ndf = #dofs

# create data directory
set Output Output;
file mkdir $Output;

# define nodal coordinates:
node 1 0. 0. 0.;
node 2 0. 0. 0.;

# Single point constraints -- Boundary Conditions
fix 1 1 1 1;
fix 2 0 1 1;

# mass
set g 9.81; #m/sec2
set pi 3.14;
set m 1000.;

# assign mass
mass 2 $m 0. 0.;

#Material
uniaxialMaterial Elastic 1 7840.

#Damper
set C [expr 0.5*$m];
uniaxialMaterial Inerter 2 $C
uniaxialMaterial Elastic 3 78400.
uniaxialMaterial Series 4 3 2

#Element
element zeroLength 1 1 2 -mat 1 -dir 1

#Damper
element zeroLength 2 1 2 -mat 4 -dir 1

puts "Model Built"

# Define RECORDERS -------------------------------------------------------------
recorder Node -file $Output/Disp.out -time -node 2 -dof 1 disp;
recorder Node -file $Output/Acc.out -time -node 2 -dof 1 accel;


# set damping based on first eigen mode
#set freq [expr [eigen 1]**0.5]
set freq [expr [eigen -fullGenLapack 1]**0.5]
set period [expr 2*$pi/$freq]
puts $period

set dt 0.005;

set accelSeries "Series -dt $dt -filePath Erzincan_NS_005_g.txt -factor [expr 9.81]"; # define acceleration vector from file (dt=0.01 is associated with the input file gm)
pattern UniformExcitation 500 1 -accel $accelSeries; # define where and how (pattern tag, dof) acceleration is applied

set dt 0.005;
set tmax 21.3;


# create the analysis
wipeAnalysis; # clear previously-define analysis parameters
constraints Transformation; # how it handles boundary conditions
numberer RCM; # renumber dof's to minimize band-width (optimization), if you want to
system UmfPack; # how to store and solve the system of equations in the analysis (large model: try UmfPack)
test EnergyIncr 1.0e-10 100; # test Eneregy incerment
algorithm KrylovNewton; # use Kyrlow-Newton algorithm
integrator Newmark 0.5 0.25 ; # determine the next time step for an analysis
analysis Transient; # define type of analysis: time-dependent
analyze [expr int($tmax/$dt)] $dt; # apply 10*4096 steps for 0.001-sec time steps in analysis


puts "Done!"

....................................................................................................................................................................................................
Thanks.

I got it. Thank you so much.

Thanks selimgunay,
It worked indeed.
Can you tell me what that is ?

Hello Opensees community,
when I do SDOF analysis with Zerolength element I get this error:
NCV must be greater than NEV and less than or equal to N.

...................................................................................................................
below is my code. Can anyone tell where I made a mistake(s).

...................................................................................................................

wipe all;
model BasicBuilder -ndm 2 -ndf 3;


# define nodal coordinates:
node 1 0. 0. 0.;
node 2 0. 0. 0.;

# Single point constraints -- Boundary Conditions
fix 1 1 1 1;
fix 2 0 1 1;

# mass
set g 9.81; #m/sec2
set m 1000.;

# assign mass
mass 2 $m 0. 0.;

# Define Elastic Material
uniaxialMaterial Elastic 1 7840.

# Define Elements
element zeroLength 1 1 2 -mat 1 -dir 1

puts "Model Built"

#timeSeries Path $tag -dt $dt -filePath $filePath <-factor $cFactor>
timeSeries Path 1 -dt 0.01 -filePath TAKY.th -factor [expr 0.30*$g];

# Define RECORDERS -------------------------------------------------------------
recorder Node -file $Output/Disp.out -time -node 2 -dof 1 disp;

#first eigen
set freq [expr [eigen 1]**0.5]
set period [expr 2*$pi/$freq]
puts $period

#pattern UniformExcitation $patternTag $dir -accel $tsTag <-vel0 $ver0>
pattern UniformExcitation 1 1 -accel 1;


# create the analysis
wipeAnalysis;
constraints Transformation;
numberer RCM;
system UmfPack;
test EnergyIncr 1.0e-10 100;
algorithm KrylovNewton;
integrator Newmark 0.5 0.25 ;
analysis Transient;
analyze [expr 10*4096] 0.001;

puts "Done!"

...................................................................................................................
Thanks.

Hello Opensees community,

Can anyone tell me what the difference(s) between trial and commit is ?
For example, Can I say trial strainRate is the strainRate for time t and the commit StrainRate is the the strainReate for the time t+dt ?

Thanks