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Hi,

I am writing an analysis for a 9DoF system with a constant modal damping ratio of 0.05 so that I can compare my results with SAP linear analysis. How can I do that?

Thanks,
Sugandha Singh

Thank you very much. That worked out with a loop for analysis.

Hi,

I have written a code to obtain response spectra for a 9DoF system. However, I am having a problem with the recorder command. I can't extract the information from the recorder file to another file at every loop because the recorder file does not get updated until the analysis is finished and we close the OpenSees interface. I have tried various things in order to extract absolute maximum displacement from recorder file at every loop but nothing worked. Here is a list of commands I have already tried:
1. Include -closeOnWrite tag in the recorder command.
2. Used logFile command to append the recorder file.

Can someone please help me with this?

Thanks,
Sugandha

Hi,

I am using ElasticMultiLinear model to define a model which is elastic and has a gap of 1mm. when i check results and find stiffness, I don't get correct stiffness(k=31585000). Following is my code, please let me know how can I change this. Thank you.

#Analysis of SDoF system subjected to El Centro EQ of 10/15/79
#Material Model:- Elastic with 1mm gap
wipe;
#user defined variables
set mass 2000;
set g 9.81;
#build model
model BasicBuilder -ndm 2 -ndf 3
node 1 0 0;
node 2 0 0;
fix 1 1 1 1;
fix 2 0 1 1;
mass 2 $mass 0 0;
#define material
uniaxialMaterial ElasticMultiLinear 1 -strain -1 -0.002 -0.001 0 0.001 0.002 0.003 1 -stress -31585000 -63170 -31585 0 0 31585 63170 31553415
#element connectivity
element zeroLength 1 1 2 -mat 1 -dir 1;
#define recorders
recorder Node -file GapSDoF/NodeDisp.out -time -node 2 -dof 1 disp
recorder Node -file GapSDoF/NodeVel.out -time -node 2 -dof 1 vel
recorder Node -file GapSDoF/NodeAccel.out -time -node 2 -dof 1 accel
recorder Element -file GapSDoF/EleForce.out -time -ele 1 force
#recorder plot GapSDoF/NodeDisp.out "Nodal Displacement" 10 10 1000 400 -columns 1 2
#recorder plot GapSDoF/NodeAccel.out "Nodal Acceleration" 10 10 1000 400 -columns 1 2
#define load
timeSeries Path 1 -dt 0.02 -filePath ElCentro.ACC;
pattern UniformExcitation 1 1 -accel 1;
#define analysis commands
constraints Plain;
numberer Plain;
system FullGeneral;
test NormDispIncr 1.0e-8 100;
algorithm Newton;
integrator Newmark 0.5 0.25;
analysis Transient;
set T 50.02;
set dt 0.001;
analyze 50020 $dt;

Sugandha

Hi,

I am trying to get force for a zerolength element using the following command:-

recorder Element -file Data/Force.out –time -ele 1 force;

but my output file is empty. Can you please help me with that?

Thanks,
Sugandha

Thank you very much sir. I used multilinear model which lets my model built but still my analysis is giving error which may be due to the method I have defined the load. It is blast load at the node defined at different times for which I have used path time series and assigned reference load value 1.0 (as suggested in another post at forum). I have posted my code below, please let me know where I am going wrong.

#Nonlinear Analysis of Single Degree of Freedom System
#user defined parameters
set c 0.2;
set m 0.1;
set T 0.8;
set h 0.1;
set n [expr int($T/$h)]
#create model
file mkdir Data;
model BasicBuilder -ndm 2 -ndf 3;
node 1 0 0;
node 2 0 0;
mass 2 $m 0 0;
fix 1 1 1 1;
fix 2 0 1 1;
#define material- Multilinear for spring and viscous for damping
uniaxialMaterial MultiLinear 1 0 0 0.6 4.544 1.2 7.552 1.5 8 2.4 8;
uniaxialMaterial Viscous 2 $c 1;
#uniaxialMaterial Parallel 3 1 2 - I did not use this as suggested as OpenSeesWiki mentions viscous material cannot be used in parallel or series
#define elements- zerolength to represent spring
element zeroLength 1 1 2 -mat 1 -dir 1
element zeroLength 2 1 2 -mat 2 -dir 1
#define recorders
recorder Node -file Response.out -time -node 2 -dof 1 disp vel accel incrDisp
recorder Element -file ForceDisp.out -time -ele 1 force stiffness
puts "Model Built!"
#define load pattern
timeSeries Path 1 -dt $h -values {0 1 4 9 9 6 0 0}
#pattern UniformExcitation 1 1 -accel 1
pattern Plain 1 1 {
load 2 1 1 0
}
#set analysis
constraints Transformation
numberer Plain
system SparseGeneral -piv
test EnergyIncr 1.0e-8 10 0;
algorithm Newton -initial;
integrator Newmark 0.5 0.25;
analysis Transient;
analyze $n $h

WARNING SuperLU::solve(void)- Error 1 returned in factorization dgstrf()
WARNING NewtonRaphson::solveCurrentStep() -the LinearSysofEqn failed in solve()
DirectIntegrationAnalysis::analyze() - the Algorithm failed at time 0.1
OpenSees > analyze failed, returned: -3 error flag
-3

Thanks,
Sugandha

Hi,

I am trying to do code almost same model but with non linear stiffness. I am having trouble as to which material type should I use for defining stiffness?

Thanks,
Sugandha

Hi,

I am trying to perform impedance analysis for SSI using OpenSees. I can use ShallowFoundationGen command to create material for discrete springs but how do I model damping characteristics of soil? Is it inclusive in ShallowFoundation command?

Thanks,
Sugandha