Issues with Eigen analysis in a RC column

[iakv]

Hello,

I'm a graduate student and I'm new learning how to use OpenSees. I'm trying to model a large bridge for a project, but in order to get used to the program I decided to try to replicate the work done in a thesis by Bryant Nielson. For this case, I took the details and geometry of a small steel bridge of the thesis and tried to model it and run an eigen analysis. When I did, I got some errors depending the solver I was using. After reading the forum looking for some help I took the advise of Dr. McKenna and worked only an element of the bridge. I decided to do just one RC column but still is giving me the same error when I run an eigen analysis.

If I used a fullGenLapack solver I got:
FullGenEigenSolver::solve() - the eigenvalue 1 is numerically undetermined or infinite 1.797693e+308

If I used a genBandArpack solver I got:
ProfileSPDLinDirectSolver::solve() - aii < 0 (i,aii): (18,0)
ArpackSolver::Error with _saupd info= -9
Starting vector is zero
WARNING DirectIntegrationAnalysis::eigen() - EigenSOE failed in solve()

I checked the material, elements and constraints, but I don't see where I can be omitting something or making a mistake

I will appreciate any help or suggestions

Thank you!

[iakv]

This is the tlc script related to the RC column:


#SET UP#---------------------------------------------------------------
wipe; # clear memory of all past model definitions
model BasicBuilder -ndm 3 -ndf 6; # Define the model builder, ndm=#dimension, ndf=#dofs
source Units&Constants.tcl; # define basic and system units

# define NODAL COORDINATES-------------------------------------------------------------

# define some structure-geometry parameters
Global Axes are X, from left to right, Y, from center to up, Z, coming out of the screen.

#For Column
set Hcolumnpier [expr 4.6*$meter]; #Height of column

set Weight [expr 60*$KN/$meter]; #Weight
set massDens [expr ($Weight/$g)]; #mass
set Negligible 1e-9; # a very small number to avoid problems with zero

set X1 0.;
set Z1 0.;
set Y1 0.;
set Y2 [expr $Hcolumnpier];

# node $nodeTag (ndm $coords) <-mass (ndf $massValues)>

#Pier 1 Left side
node 1 $X1 $Y1 $Z1;
node 2 $X1 $Y2 $Z1;


#Constraints
#Columns Foundation Node#
fix 1 1 1 1 1 1 1;

# Define materials for bent beams and columns# ------------------------------------------
set IDconcCore 1; # material ID tag -- confined core concrete
set IDconcCover 2; # material ID tag -- unconfined cover concrete
set IDreinf 3; # material ID tag -- reinforcement

# nominal concrete compressive strength
set fc [expr -27.6*$MPa]; # CONCRETE Compressive Strength, ksi (+Tension, -Compression)
set Ec [expr 4700*sqrt(-$fc)]; # Concrete Elastic Modulus

# unconfined concrete
set fc1U $fc; # UNCONFINED concrete (todeschini parabolic model), maximum stress
set eps1U -0.002; # strain at maximum strength of unconfined concrete
set fc2U [expr 0.1*$fc]; # ultimate stress
set eps2U -0.006; # strain at ultimate stress

# confined concrete
set Kfc 1.031; # ratio of confined to unconfined concrete strength
set fc1C [expr $Kfc*$fc]; # CONFINED concrete (mander model), maximum stress
set eps1C [expr $Kfc*$eps1U]; # strain at maximum stress
set fc2C [expr 0.2*$fc1C]; # ultimate stress
set eps2C [expr 5*$eps1C]; # strain at ultimate stress

# CONCRETE tag f'c ec0 f'cu ecu
# Core concrete (confined)
uniaxialMaterial Concrete01 1 $fc1C $eps1C $fc2C $eps2C

# Cover concrete (unconfined)
uniaxialMaterial Concrete01 2 $fc1U $eps1U $fc2U $eps2U

#STEEL
set Fy [expr 414*$MPa]; # STEEL yield stress
set Es [expr 200*$GPa]; # modulus of steel
set Bs 0.018; # strain-hardening ratio

# Reinforcing steel tag fy E0 b
uniaxialMaterial Steel01 3 $Fy $Es $Bs

#DEFINE sections#-------------------------------------------------------------

# define section tags:
set ColSecTagFiber 222; # set tag for symmetric section
set SecTagTorsion 70;
set ColSecTag 22;

#Column properties and geometry#

set DSec [expr 0.915*$meter]; # Column Diameter
set coverSec [expr 50.8*$mm]; # Column cover to reinforcing steel NA.
set numBarsSec 12; # number of uniformly-distributed longitudinal-reinforcement bars
set barAreaSec [expr 645*$mm2]; # area of longitudinal-reinforcement bars

#FIBER SECTION for column#

set ri 0.0; # inner radius of the section, only for hollow sections
set ro [expr $DSec/2]; # overall (outer) radius of the section
set nfCoreR 8; # number of radial divisions in the core (number of "rings")
set nfCoreT 12; # number of theta divisions in the core (number of "wedges")
set nfCoverR 2; # number of radial divisions in the cover
set nfCoverT 12; # number of theta divisions in the cover
section fiberSec $ColSecTagFiber {; # Define the fiber section
set rc [expr $ro-$coverSec]; # Core radius
patch circ $IDconcCore $nfCoreT $nfCoreR 0 0 $ri $rc 0 360; # Define the core patch
patch circ $IDconcCover $nfCoverT $nfCoverR 0 0 $rc $ro 0 360; # Define the cover patch
set theta [expr 360.0/$numBarsSec]; # Determine angle increment between bars
layer circ $IDreinf $numBarsSec $barAreaSec 0 0 $rc $theta 360; # Define the reinforcing layer
}; # end of fibersection definition


# ASSIGN torsional Stiffness for 3D Model

uniaxialMaterial Elastic $SecTagTorsion $Ubig; # define elastic torsional stiffness
section Aggregator $ColSecTag $SecTagTorsion T -section $ColSecTagFiber; # combine section properties for column


#define ELEMENTS---------------------------------------------------

# define geometric transformation: performs a linear geometric transformation of beam stiffness and resisting force from the basic system to the global-coordinate system
set ColTransfTag 2; # associate a tag to column transformation
set ColTransfType Linear; # options, Linear PDelta Corotational
geomTransf $ColTransfType $ColTransfTag 0 0 -1; # only columns can have PDelta effects (gravity effects)

#define Beam-Column Elements
set numIntgrPts 5; # number of integration points for force-based element

#Column#
element dispBeamColumn 1 1 2 $numIntgrPts $ColSecTag $ColTransfTag <-mass $massDens $Negligible $Negligible>;

# perform eigen analysis#-----------------------------

set numModes 2;
set lambda [eigen -fullGenLapack $numModes];
# calculate frequencies and periods of the structure
set omega {}
set f {}
set T {}
set pi 3.141593

foreach lam $lambda {
lappend omega [expr sqrt($lam)]
lappend f [expr sqrt($lam)/(2*$pi)]
lappend T [expr (2*$pi)/sqrt($lam)]
}
puts "periods are $T"

[Jatkinson]

In the wiki, optional inputs are bracketed like so: <-mass num num num>

In your tcl file, you shouldn't include those <> brackets if you want to use that input flag.

Just change your element to:

element dispBeamColumn 1 1 2 $numIntgrPts $ColSecTag $ColTransfTag -mass $massDens $Negligible $Negligible;

[iakv]

Thank you for your observation Jatkinson!

[iakv]

Dear users,

I could moved from modeling one element to put the members together and try to run an eigen analysis for the whole bridge.

In doing this, I'm having some issues with the zerolength element that I'm using as a representation of the fixed bearings on top of my beam bent that will connect with the deck. I defined two materials, steel01 and hysteretic, to be used in parallel but my model stopped and showed me a small windows which said that Opensees.exe stopped working due to a problem, when I started pasting the code of my zerolength element in Opensees.exe That's why I think I might have a problem which the zerolentgh element.

These are the commands for defining the material that I'm using with the zerolength elements:

# Define materials for bearing# -----------
set BearingSteelTag 4;
set BearingHysteTag 5;

#STEEL
set Fy1 [expr 430*$KN];
set Es1 [expr 200*$GPa];
set Bs1 0.06;

#uniaxialMaterial Steel01 $matTag $Fy $E0 $b
uniaxialMaterial Steel01 4 $Fy1 $Es1 $Bs1

#Hysteretic
set F1p [expr 232.5*$KN];
set e1p [expr 0.4*$mm];
set F2p [expr 0.093*$KN];
set e2p [expr 20*$mm];
set F1n [expr -232.5*$KN];
set e1n [expr -0.4*$mm];
set F2n [expr -0.093*$KN];
set e2n [expr -20*$mm];
set pinchX 1.00
set pinchY 0.00
set damage1 0.00
set damage2 0.00
set beta 0.00

# Hysteretic material
#uniaxialMaterial Hysteretic $matTag $s1p $e1p $s2p $e2p <$s3p $e3p> $s1n $e1n $s2n $e2n <$s3n $e3n> $pinchX $pinchY $damage1 $damage2 <$beta>
uniaxialMaterial Hysteretic 5 $F1p $e1p $F2p $e2p $F1n $e1n $F2n $e2n $pinchX $pinchY $damage1 $damage2 $beta

I will appreciate any suggestion or advise

Thank you!

[iakv]

Dear users,

I got a solution for the situation. I just put .0 after the numbers. Ex: 20.0*$mm and it worked without closing the program.