Hysteretic model!

[hrodrigues]

hi!
i'm trying to perform a pushover anl on a column with Hysteretic model avaliable.

CODE:
# pilar Experimental
# Uniaxial
# Units: kN, m, sec
#
wipe; # clear opensees model
model basic -ndm 2 -ndf 3; # 2 dimensions, 3 dof per node
set numNode 3;
#
# nodal coordinates:
#
# tag X Y
node 1 0.0 0.0
node 2 0.0 0.675
node 3 0. 1.350
#
# bondary conditions:
#
# tag DX DY RZ
fix 1 1 1 1
#

set e1p 120;
set e2p 170;
set e3p 180
set e1n -$e1p
set e2n -$e2p
set e3n -$e3p
set s1p 0.0007
set s2p 0.04
set s3p 0.1
set s1n -$s1p
set s2n -$s2p
set s3n -$s3p
set pinchx 1
set pinchy 1
set damage1 0
set damage2 0
set beta 0

uniaxialMaterial Hysteretic 2 $s1p $s2p $s3p $e1p $e2p $e3p $s1n $s2n $s3n $e1n $e2n $e3n $pinchx $pinchy $damage1 $damage2 $beta
section Uniaxial 1 2 My

set ColTransfType Linear;
geomTransf $ColTransfType 1 ;
# element connectivity:
set numIntgrPts 5; # number of integration points for force-based element
element nonlinearBeamColumn 1 1 2 $numIntgrPts 1 1; # self-explanatory when using variables
element nonlinearBeamColumn 2 2 3 $numIntgrPts 1 1; # self-explanatory when using variables
#
# Define gravity loads
#
set N 160.0; # nodal load - column weigth
#
set mss [expr $N/9.81];
mass 3 $mss $mss 0
mass 2 1E-50 1E-50 1E-50

pattern Plain 1 "Linear" {
# Create nodal loads at nodes 2,3,4,5,7,8,9 & 10
# nd FX FY MZ
load 3 0.0 [expr -$N] 0.0
}
#
# Create analysis
#
system BandGeneral; # how to store and solve the system of equations in the analysis - a sparse solver with partial pivoting
constraints Transformation; # how it handles boundary conditions - Transformation method
numberer RCM;
set Tol 1.0e-8; # renumber dof's to minimize band-width - the reverse Cuthill-McKee algorithm
test NormDispIncr $Tol 35 0; # determine if convergence has been achieved at the end of an iteration step - stops after 35 steps without convergence
set algorithmType Newton
algorithm $algorithmType; # use Newton's solution algorithm: updates tangent stiffness at every iteration
integrator LoadControl 0.1 1 0.1 0.1; # determine the next time step for an analysis, # apply gravity in 10 steps
analysis Static; # define type of analysis - static
initialize

remove recorders; # so the eigenvector output is not repeated
analyze 9; # perform gravity analysis and performs 9 steps
#
puts "Gravity Done"

i'm getting some warnigs in the analysis can some one tell me why?

[silvia]

yes, please look at the format for the hysteretic material.
it is stresss strain, stress strain, you have stress stress stress...

[hrodrigues]

Silvia
Thanks for your help.

I’ve change the line to:
uniaxialMaterial Hysteretic 2 $s1p $e1p $s2p $e2p $s3p $e3p $s1n $e1n $s2n $e2n $s3n $e3n $pinchx $pinchy $damage1 $damage2 $beta

and the error keep the same warning
ForceBeamColumn2d:update – failed to get compatible element forces & deformations for element: 1<dW: << 0.000256>
Any reason for these error ??

[silvia]

you have a singular stiffness matrix.
you do not have enough constraints in the elements. you need to assign some sort of axial stiffness.

[hrodrigues]

done!
it's working!
TKX

[achengtw]

Hi,

I think this is a good example for a beginner of OPENSEES. I tried to keep everything the same but these three lines:

uniaxialMaterial Hysteretic 2 $s1p $e1p $s2p $e2p $s3p $e3p $s1n $e1n $s2n $e2n $s3n $e3n $pinchx $pinchy $damage1 $damage2 $beta
uniaxialMaterial Elastic 3 1e10
section Aggregator 1 2 My 3 P

to add axial stiffness but it still showed the same warning message. Could hrodrigues or silvia help me to figure it out?

[silvia]

check your model and the constraints,
do you have any eigenvalues? [eigen]