? Example 5.1 eigenvalues ?

[Marco Faggella 2]

Hi all

I am trying to find the eigenvalues of the example 5.1 structure, I've replaced all nonlinearBeamcolumn elts with linear elements

the structure is supposed to have 3X3= 9 DOF (rigid diaphragms)

but if i ask
[eigen 9]

it says:
"BandArpackSolver::Error with _saupd info = -9999
Could not build an Arnoldi factorization. IPARAM(5) returns the size of the current Arnoldi factorization. The user is advised to check that enough workspace and array storage has been allocated. "

It only works if I reduce to 4 the eigenvalue I ask
[eigen 4]

The same happen with other types of structures, regardless of the type of elements I use
In one case it seems tahat the eigen solver does not find all the torsional modes of a structure (3rd, 6th, 9th in one case)

Is there any special System command that works better with eigen analysis?

thanks

-----------------------------------------------------------------------------------
# OpenSees Example 5.1 + linear elts + eigen
# OpenSees Primer
#
# Units: kips, in, sec
model BasicBuilder -ndm 3 -ndf 6

set h 144.0; # Story height
set by 240.0; # Bay width in Y-direction
set bx 240.0; # Bay width in X-direction

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] $h
node 10 [expr -$bx/2] [expr $by/2] [expr 2*$h]
node 11 [expr $bx/2] [expr $by/2] [expr 2*$h]
node 12 [expr $bx/2] [expr -$by/2] [expr 2*$h]
node 13 [expr -$bx/2] [expr -$by/2] [expr 2*$h]
node 15 [expr -$bx/2] [expr $by/2] [expr 3*$h]
node 16 [expr $bx/2] [expr $by/2] [expr 3*$h]
node 17 [expr $bx/2] [expr -$by/2] [expr 3*$h]
node 18 [expr -$bx/2] [expr -$by/2] [expr 3*$h]

node 9 0 0 $h
node 14 0 0 [expr 2*$h]
node 19 0 0 [expr 3*$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

# Define rigid diaphragm multi-point constraints
# normalDir master slaves
rigidDiaphragm 3 9 5 6 7 8
rigidDiaphragm 3 14 10 11 12 13
rigidDiaphragm 3 19 15 16 17 18
# Constraints for rigid diaphragm master nodes
# tag DX DY DZ RX RY RZ
fix 9 0 0 1 1 1 0
fix 14 0 0 1 1 1 0
fix 19 0 0 1 1 1 0

geomTransf Linear 1 1 0 0

set A 369
set E 4030
set ni 0.5
set G [expr $E/(2*(1+$ni))]
set Iz 8640
set Iy 8640
set J 0

# $eleTag $iNode $jNode $A $E $G $J $Iy $Iz $transfTag
element elasticBeamColumn 1 1 5 $A $E $G $J $Iy $Iz 1
element elasticBeamColumn 2 2 6 $A $E $G $J $Iy $Iz 1
element elasticBeamColumn 3 3 7 $A $E $G $J $Iy $Iz 1
element elasticBeamColumn 4 4 8 $A $E $G $J $Iy $Iz 1
element elasticBeamColumn 5 5 10 $A $E $G $J $Iy $Iz 1
element elasticBeamColumn 6 6 11 $A $E $G $J $Iy $Iz 1
element elasticBeamColumn 7 7 12 $A $E $G $J $Iy $Iz 1
element elasticBeamColumn 8 8 13 $A $E $G $J $Iy $Iz 1
element elasticBeamColumn 9 10 15 $A $E $G $J $Iy $Iz 1
element elasticBeamColumn 10 11 16 $A $E $G $J $Iy $Iz 1
element elasticBeamColumn 11 12 17 $A $E $G $J $Iy $Iz 1
element elasticBeamColumn 12 13 18 $A $E $G $J $Iy $Iz 1

geomTransf Linear 2 1 1 0
# $eleTag $iNode $jNode $A $E $G $J $Iy $Iz $transfTag
element elasticBeamColumn 13 5 6 $A $E $G $J $Iy $Iz 2
element elasticBeamColumn 14 6 7 $A $E $G $J $Iy $Iz 2
element elasticBeamColumn 15 7 8 $A $E $G $J $Iy $Iz 2
element elasticBeamColumn 16 8 5 $A $E $G $J $Iy $Iz 2
element elasticBeamColumn 17 10 11 $A $E $G $J $Iy $Iz 2
element elasticBeamColumn 18 11 12 $A $E $G $J $Iy $Iz 2
element elasticBeamColumn 19 12 13 $A $E $G $J $Iy $Iz 2
element elasticBeamColumn 20 13 10 $A $E $G $J $Iy $Iz 2
element elasticBeamColumn 21 15 16 $A $E $G $J $Iy $Iz 2
element elasticBeamColumn 22 16 17 $A $E $G $J $Iy $Iz 2
element elasticBeamColumn 23 17 18 $A $E $G $J $Iy $Iz 2
element elasticBeamColumn 24 18 15 $A $E $G $J $Iy $Iz 2

set fc 4.0
set p [expr 0.1*$fc*$h*$h]
# Mass lumped at master nodes
set g 386.4; # Gravitational constant
set m [expr (4*$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
# tag MX MY MZ RX RY RZ
mass 9 $m $m 0 0 0 $i
mass 14 $m $m 0 0 0 $i
mass 19 $m $m 0 0 0 $i

#system SparseGeneral -piv
system BandGeneral
constraints Transformation
numberer RCM

# EIGENVALUE ANALYSIS
set lambda [eigen 9]
for {set i 0} {$i < 10} {incr i} {
puts [lindex $lambda $i]
}

[silvia]

it is a problem with the current eigenvalue solver.
you should add a tiny (10^-9) mass to another released dof, or two, to get the number of igenvalues of the system.

[Marco Faggella 2]

I've tried but it still doesn't work

if these are my masses
#mass 9 $m $m 0 0 0 $i
#mass 14 $m $m 0 0 0 $i
#mass 19 $m $m 0 0 0 $i

and I add a tiny mass, like:
set n 0.00000001
mass 9 $m $m $n 0 0 $i
mass 14 $m $m $n 0 0 $i
mass 19 $m $m $n 0 0 $i

I get the same error, wherever I put the little mass

?