Assigning damping

[earthquakecivil]

Hi everyone
I modeled a 2DOF system with two zerolength elements and three nodes. Each element has a specific damping value. In order to assign rayleigh damping to each element, I used region command. I analyzed the system under earthquake excitation. But I encountered a problem. The rayleigh damping value is not assigned to first element (the element between node 1 and node 2). I change damping ratio value for first element (dampRatiob) from 0 to 0.8 but seismic responses are the same. What can I do for assigning rayleigh damping to element 1?

My script is :

wipe

model basic -ndm 1 -ndf 1

node 1 0.
node 2 0.
node 3 0.

fix 1 1

set PI [expr 2.0*asin(1.0)]
global PI

set periodb 2.0
set periods 0.5
set m1 1300000.0
set Finelbs [expr 800.0*1000.0]
set m2 113000.0
set q 500000.0
set k2 [expr ((4.0*pow($PI,2.0))*($m1+$m2))/(pow($periodb,2.0))]
set initStress $q
set wnb [expr 2.0 * $PI / $periodb]
set wns [expr 2.0 * $PI / $periods]
set ks [expr (pow($wns,2.0))*$m1]
set rhardening 0.0
mass 2 $m2
mass 3 $m1

uniaxialMaterial Steel01 1 $initStress 1000000000 [expr $k2/1000000000]

uniaxialMaterial Steel01 2 $Finelbs $ks $rhardening

element zeroLength 1 1 2 -mat 1 -dir 1 -doRayleigh 1

element zeroLength 2 2 3 -mat 2 -dir 1 -doRayleigh 1

set dampRatios 0.05
set dampRatiob 0.00001

set a0s [expr 2.0*$wns*$dampRatios]
set a0b [expr 2.0*$wnb*$dampRatiob]

region 2 -ele 2 -rayleigh $a0s 0. 0. 0.
region 1 -ele 1 -rayleigh $a0b 0. 0. 0.

set accel "Series -dt 0.02 -filePath EQ.txt -factor [expr 9.81]"

pattern UniformExcitation 3 1 -accel $accel

recorder Node -file node3.out -time -node 3 -dof 1 disp
recorder Node -file node2.out -time -node 2 -dof 1 disp

constraints Transformation
numberer RCM
system SparseGeneral
test NormDispIncr 1.0e-8 100
algorithm ModifiedNewton
integrator Newmark 0.5 0.25
analysis Transient
set TmaxAnalysis1 20.0
set dt1 0.02
analyze [expr int($TmaxAnalysis1/$dt1)] $dt1

[fmk]

that is mass prop damping you are assigning, i.e damping only at the nodes .. the 2 regions share node 2 .. and so only 1 of damping values will be used at node 2, when regions share nodes or elements we do not gaurantee which order the rayleigh factors are set.