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# Test Example for ISOLATOR2SPRING material
# Written: K. Ryan
# Date: November 22, 2005
#
# Description: A Single DOF isolator supporting a rigid mass. Generates lateral force deformation through
# application of a pseudo-static cyclic (sinusoidal) lateral force. Force deformation behavior varies
# as a function of the axial load P and normalized values of P/Pcr and P/Po
#
# Units: cm, dimensionless
set g 982.0
set PI [expr 2.0 * asin(1.0)]
# Define the model builder
model BasicBuilder -ndm 2 -ndf 3
# Assumed parameters which define system
# Period associated with second stiffness k2o
set Tb 2.5
# Normalized axial load parameter P/Pcr. Vary to produce data for Figure 4a
set PPcr 0.001
# Normalized axial load paramter P/Po. Vary to produce data for Figure 4b
set PPo 0.25
# Unit mass
set M 1.0
# Bearing shape factor
set S 20.0
# Yield displacement
set uy 1.0
# Strength coefficient (determines yield strength)
set mu 0.1
set tol 1.0e-10
# Parameters computed from the assumed ones
set wb [expr (2.0*$PI/$Tb)]
set k2o [expr $wb*$wb*$M]
set Fyo [expr $mu*$M*$g + $k2o*$uy]
set k1 [expr $Fyo/$uy]
set kvo [expr 6.0*$S*$S*$k2o]
set Pcr [expr $M*$g/$PPcr]
set Pe [expr 50.0*$Pcr]
set Ps [expr 1.0/50.0*$Pcr]
set hb [expr $Ps/$k2o]
set Po [expr $M*$g/$PPo]
# Define nodes
node 1 0.0 0.0
node 2 0.0 0.0
# Define single point constraints (Constrain the isolator against rotation)
fix 1 1 1 1
fix 2 0 0 1
# Create Iso2spring section
section Iso2spring 1 $tol $k1 $Fyo $k2o $kvo $hb $Pe $Po
# id ndI ndJ mattag
element zeroLengthSection 1 1 2 1
# Apply gravity load on isolated mass
set P [expr $M*$g]
pattern Plain 1 "Linear" {
load 2 0.0 -[expr $P] 0.0
}
system BandSPD
constraints Plain
numberer Plain
test EnergyIncr 1.0e-15 100
algorithm Newton
integrator LoadControl 0.1 1 0.1 0.1
analysis Static
initialize
analyze 10
loadConst -time 0.0
# Estimated postyield stiffness degradation
set k2oest [expr $k2o*(1.0-$PPcr*$PPcr)]
# Estimated yield strength degradation
set Fyoest [expr $Fyo*(1.0-exp(-$PPo))]
# Define amplitude of cyclic force to induce approx. 20 cm deformation
set Fu [expr $Fyoest + $k2oest*20.0]
# Apply sinusoidal lateral load
set SinePath "Trig 0.0 1.5 1.0"
pattern Plain 2 $SinePath {
load 2 $Fu 0.0 0.0
}
wipeAnalysis
recorder Node -file Node2.out -node 2 -dof 1 disp
recorder Element 1 -file Elem1.out force
system BandGeneral
constraints Plain
numberer Plain
test EnergyIncr 1.0e-15 100
algorithm Newton
integrator LoadControl 0.01 1 0.001 0.1
analysis Static
analyze 1500
print ele 1
print node 2