No change in time period with addition of viscous damper

[Prafullamalla]

I used the single bay frame with viscous damper from the example. When I checked the time period with and without viscous damper it is same in tcl version. In python version the time period changes when using viscous damper. Change the uniaxialmaterial with # for viscous damper
wipe all; # clear memory of past model definitions
model BasicBuilder -ndm 2 -ndf 3; # Define the model builder, ndm = #dimension, ndf = #dofs

set L 5000.0
set h 3000.0
node 1 0 0
node 2 $L 0
node 3 0 $h
node 4 $L $h
node 5 $L $h
fix 1 1 1 1
fix 2 1 1 1


set W 1000.0
set g 9810.0
set m [expr $W/$g]
puts "mass = $m "

set Tn 0.7; # sec (Natural Period)
set pi [expr acos(-1.0)];


set K [expr pow(2*$pi/$Tn,2)*$m]; # KN/mm
set E 200.0
set Ic [expr $K*pow($h,3)/(24*$E)];
set Ib [expr 1e12*$Ic]
set A 1e12
puts "STIFFNESS = $K "
set Tstiff [expr 2*$pi*pow($m/$K,0.5)]
puts "Tstiff = $Tstiff "

mass 3 [expr 0.5*$m] 0 0
mass 4 [expr 0.5*$m] 0 0
geomTransf Linear 1
element elasticBeamColumn 1 1 3 $A $E $Ic 1
element elasticBeamColumn 2 2 4 $A $E $Ic 1
element elasticBeamColumn 3 3 4 $A $E $Ib 1
# Damper properties
set Kd 25.
set Cd 20.7452
set ad 0.35
#uniaxialMaterial ViscousDamper 1 $Kd $Cd $ad
uniaxialMaterial Elastic 1 $K
uniaxialMaterial Elastic 2 [expr 9999*$K]
#element twoNodeLink 4 1 3 -mat 1 2 2 -dir 1 2 3

element elasticBeamColumn 4 1 5 $A $E $Ib 1
element zeroLength 5 5 4 -mat 1 2 2 -dir 1 2 3


# set damping based on first eigen mode
set freq [expr [eigen 1]**0.5]
set period [expr 2*$pi/$freq]
puts ("freq",$freq)
puts ("period",$period)
set damp 0.02;
rayleigh [expr 2*$damp*$freq] 0. 0. 0.