Creating Mass-spring-Damper Model

[naba077]

HI,
I want to create a model with spring mass damper in parallel and series combination. I tried using zerolength element. But how can we put the element in parallel or series combination?
http://members.webs.com/MembersB/editAp ... =175499762

[vesna]

If you define to springs between same nodes they will be in parallel. Another way to do it is to have one element but to assign to it material that is consist of materials in series or in parallel. Check out: parallel and series materials: http://opensees.berkeley.edu/wiki/index ... al_Command.

[naba077]

Thank you Vesna But when I tried like this, it doesn't work in static and dynamic analysis. I don't know what is wrong with my model. Here is my model with simple static analysis.


wipe

#Define model
model basicBuilder -ndm 2 -ndf 3

#Define nodes
node 1 0 0
node 2 0 0
node 3 0 0
node 4 0 0
node 5 0 0

#some parameters
set pi 3.14

#Base system
set k 2.4e+5; #Spring
set c 8.16e+3; # Damper
set m 2.4e+2; #mass
#core system 1
set k1 8.64e+4; #Spring
set c1 2.59e+3;# Damper
set m1 5.18e+2; #mass
#core system 2
set k2 1.56e+5; #Spring
set c2 3.74e+3; # Damper
set m2 5.46e+2; #mass
#core system 3
set k3 1.2e+5; #Spring
set c3 2.16e+3; # Damper
set m3 6.0; #mass

set U 1.e10
set u [expr 1./$U]

# Boundary Conditions
fix 1 1 1 1
fix 2 0 1 1

#Define masses
mass 2 $m $u 0.
mass 3 $m1 $u 0.
mass 4 $m2 $u 0.
mass 5 $m3 $u 0.

# Materials Parameter & Element Connectivity
uniaxialMaterial Elastic 1 $k
uniaxialMaterial Viscous 2 $c 1.
uniaxialMaterial Parallel 3 1 2
element zeroLength 1 1 2 -mat 3 -dir 1
uniaxialMaterial Elastic 4 $k1
element zeroLength 2 3 2 -mat 4 -dir 1
uniaxialMaterial Viscous 5 $c1 1.
element zeroLength 3 1 3 -mat 5 -dir 1
uniaxialMaterial Elastic 6 $k2
element zeroLength 4 4 2 -mat 6 -dir 1
uniaxialMaterial Viscous 7 $c2 1.
element zeroLength 5 1 4 -mat 7 -dir 1
uniaxialMaterial Elastic 8 $k3
element zeroLength 6 5 2 -mat 8 -dir 1
uniaxialMaterial Viscous 9 $c3 1.
element zeroLength 7 1 5 -mat 9 -dir 1

#Define force

timeSeries Linear 1
pattern Plain 1 1 {
load 2 10000.0 0.0 0.0
}

# Analysis
system BandSPD
numberer RCM
constraints Plain
integrator LoadControl 1.0
algorithm Linear
analysis Static

analyze 1

# Output
puts "node 2 displacement: [nodeDisp 2]"
print node 2
print ele

[vesna]

I can not figure out what are you trying to do.

Few comments,:
1. viscous material can not be combined with other materials in parallel or series (check the notes of viscous material)
2. if you need viscous material to be in parallel with some other one then just define two zeroLenght elements between the same nodes
3. you need to define boundary conditions for nodes 3, 4, and 5 for all directions in which you do not define springs
4. if analyzing system that consist of nonlinear materials as viscous is, you may not be able to find a solution in one step of analysis.

[naba077]

Dear Vesna,
Thank you very much. I edited the program according to your comments number 3. & 4. and got the expected results.