eigen values in 3D

[Paolo]

Hi all users!
I have a problem with eigen values analysis in a simple 3D example.
Also in 2D examples I can't find all eigen values thai I expected,
I think because the last are less important (is this right?).
But in 3D I can only obtain the first eigen value.
My example is:

# OpenSees TELAIO 1p an.dinamica
# Units: Kg, cm, s
# ----------------------------
# Start of model generation
model BasicBuilder -ndm 3 -ndf 6
set h 300.0
set by 700.0
set bx 500.0
node 1 [expr -$bx/2] [expr $by/2] 0
node 2 [expr $bx/2] [expr $by/2] 0
node 3 [expr $bx/2] [expr -$by/2] 0
node 4 [expr -$bx/2] [expr -$by/2] 0
node 5 [expr -$bx/2] [expr $by/2] $h
node 6 [expr $bx/2] [expr $by/2] $h
node 7 [expr $bx/2] [expr -$by/2] $h
node 8 [expr -$bx/2] [expr -$by/2] $h
node 9 0 0 $h
fix 1 1 1 1 1 1 1
fix 2 1 1 1 1 1 1
fix 3 1 1 1 1 1 1
fix 4 1 1 1 1 1 1
rigidDiaphragm 3 9 5 6 7 8
# I diaframmi sono vincolati a muoversi nel loro piano
fix 9 0 0 1 1 1 0
# Core concrete (confined)
uniaxialMaterial Concrete01 1 -345.7 -0.0024 –345.7 -0.0206
# Cover concrete (unconfined)
uniaxialMaterial Concrete01 2 -290.5 -0.002 –290.5 -0.004
set fy 4400.0
set E 2100000.0
uniaxialMaterial Steel01 3 $fy $E 0.01
set colWidth 30
set colDepth 30
set cover 3.0
set As 2.01
set y1 [expr $colDepth/2.0]
set z1 [expr $colWidth/2.0]
section Fiber 2 {
patch rect 1 10 10 [expr $cover-$y1] [expr $cover-$z1] [expr $y1-$cover] [expr $z1-$cover]
patch rect 2 10 2 [expr -$y1] [expr $z1-$cover] $y1 $z1
patch rect 2 10 2 [expr -$y1] [expr -$z1] $y1 [expr $cover-$z1]
patch rect 2 2 10 [expr -$y1] [expr $cover-$z1] [expr $cover-$y1] [expr $z1-$cover]
patch rect 2 2 10 [expr $y1-$cover] [expr $cover-$z1] $y1 [expr $z1-$cover]
layer straight 3 2 $As [expr $y1-$cover] [expr $z1-$cover] [expr $y1-$cover] [expr $cover-$z1]
layer straight 3 2 $As [expr $cover-$y1] [expr $z1-$cover] [expr $cover-$y1] [expr $cover-$z1]
}
# Column torsional stiffness
set G 126087
set J [expr 0.141*30*30*30*30]
set GJ [expr $G* $J]
uniaxialMaterial Elastic 10 $GJ
section Aggregator 1 10 T -section 2
geomTransf Linear 1 1 0 0
# Number of column integration points (sections)
set np 4
element nonlinearBeamColumn 1 1 5 $np 1 1
element nonlinearBeamColumn 2 2 6 $np 1 1
element nonlinearBeamColumn 3 3 7 $np 1 1
element nonlinearBeamColumn 4 4 8 $np 1 1
# Define beam elements
geomTransf Linear 2 0 0 1
geomTransf Linear 3 0 0 1
set np 3
# tag ndI ndJ nPts secID transf
element nonlinearBeamColumn 5 5 6 $np 1 3
element nonlinearBeamColumn 6 6 7 $np 1 2
element nonlinearBeamColumn 7 7 8 $np 1 3
element nonlinearBeamColumn 8 8 5 $np 1 2
# Define gravity loads
# Gravity load applied at each corner node
# 10% of column capacity
set P [expr 0.1*(345.7*$colWidth*$colWidth+15*4*$As)]
# 31125.06
# Mass lumped at master nodes
set g 981
set m [expr (4*$P)/$g]
# Rotary inertia of floor about master node
set i [expr $m*($bx*$bx+$by*$by)/12.0]
# Set mass at the master nodes
mass 9 $m $m 0 0 0 $i
# End of model generation
# -----------------------
# Start of analysis generation
# Create the convergence test
# tol maxIter printFlag
test EnergyIncr 1.0e-8 20 3
algorithm Newton
# Create the system of equation storage and solver
system SparseGeneral -piv
# Create the constraint handler
constraints Transformation
integrator Newmark 0.5 0.25
numberer RCM
analysis Transient
# End of analysis generation
# --------------------------
puts "eigen values at start of transient: [eigen 3]"

Is there anybody who knows the reason?

Thank you for the attention.
Best regards.

[silvia]

the problem has to do with the poor eigensolver.
you can only solve for n-1 eigenvalues. here you have 2 masses defined, so you can only solve for 1 eigenvalue.
you should assign to the other mass dof's really tiny mass values like 1e-9, and then it should work.
please let me know if this does not fix it.