SFI MVLEM Shearwall Element problem

[imurdereri]

Hi, i want to model Shearwalls with the SFI MVLEM element.
i downloaded the example Example 1. SFI_MVLEM.zip avaible on:
http://opensees.berkeley.edu/wiki/index ... r_RC_Walls
This example runs fine

I'm testing the same wall (RW-A15-P10-S78 (Tran and Wallace, 2012)) but changing only the cyclic analysis using the "sp" command instead of the proc used in the example (proc GeneratePeaks)

But i get this this error:

Singular SFI_MVLEM_K/nSingular SFI_MVLEM_K/nSingular SFI_MVLEM_K/nSingular SFI_MVLEM_K/nSingular SFI_MVLEM_K/nSingular SFI_MVLEM_K/nSingular SFI_MVLEM_K/nSingular SFI_MVLEM_K/nWARNING BandGenLinLapackSolver::solve() -LAPACK routine returned 22
WARNING AcceleratedNewton::solveCurrentStep() -the LinearSysOfEqn failed in solve()
StaticAnalysis::analyze() - the Algorithm failed at iteration: 0 with domain at load factor 0.1
OpenSees > analyze failed, returned: -3 error flag+

This is the code:

# ----------------------------------------------------------------
# Example 1: Simulation of wall cyclic behavior using SFI_MVLEM
# Specimen: RW-A15-P10-S78 (Tran and Wallace, 2012)
# Created by: Kristijan Kolozvari (kkolozvari@fullerton.edu)
# Date: 7/2015
# ----------------------------------------------------------------

# --------------------------------------------------------
# Start of model generation (Units: kip, in, sec, ksi)
# --------------------------------------------------------

# Set Up Directories
set modelName "SP4"; # Model Name
set dataDir SFI_MVLEM_$modelName; # Name of output folder
file mkdir $dataDir;

# Create ModelBuilder for 2D element (with two-dimensions and 2 DOF/node)
model BasicBuilder -ndm 2 -ndf 3

# --------------------------------------------
# Set geometry, nodes, boundary conditions
# --------------------------------------------

# Wall Geometry
set H 72; # Wall height
set t 6; # Wall thickness

# Create nodes
# node nodeId xCrd yCrd
node 1 0 0;
node 2 0 12;
node 3 0 24;
node 4 0 40;
node 5 0 56;
node 6 0 $H;

# Boundary conditions
fix 1 1 1 1; # Fixed condition at node 1

# Set Control Node and DOF
set IDctrlNode 6;
set IDctrlDOF 1;

# ------------------------------------------------------------------------
# Define uniaxial materials for 2D RC Panel Constitutive Model (FSAM)
# ------------------------------------------------------------------------

# STEEL ...........................................................
# uniaxialMaterial SteelMPF $mattag $fyp $fyn $E0 $bp $bn $R0 $a1 $a2
# steel X
set fyX 58.4103; # fy
set bx 0.01; # strain hardening

# steel Y web
set fyYw 58.4103; # fy
set byw 0.01; # strain hardening

# steel Y boundary
set fyYb 69.0; # fy
set byb 0.002; # strain hardening

# steel misc
set Esy 29000.0; # Young's modulus
set Esx $Esy; # Young's modulus
set R0 20.0; # initial value of curvature parameter
set A1 0.925; # curvature degradation parameter
set A2 0.15; # curvature degradation parameter

# Build steel materials
uniaxialMaterial SteelMPF 1 $fyX $fyX $Esx $bx $bx $R0 $A1 $A2; # steel X
uniaxialMaterial SteelMPF 2 $fyYw $fyYw $Esy $byw $byw $R0 $A1 $A2; # steel Y web
uniaxialMaterial SteelMPF 3 $fyYb $fyYb $Esy $byb $byb $R0 $A1 $A2; # steel Y boundary

# CONCRETE ........................................................
# uniaxialMaterial ConcreteCM $mattag $fpcc $epcc $Ec $rc $xcrn $ft $et $rt $xcrp <-GapClose $gap>

# unconfined
set fpc 8.09; # peak compressive stress
set ec0 -0.002371; # strain at peak compressive stress
set ft 0.335798; # peak tensile stress
set et 0.00008; # strain at peak tensile stress
set Ec 5403.2172; # Young's modulus
set xcrnu 1.022; # cracking strain - compression
set xcrp 10000; # cracking strain - tension
set ru 15; # shape parameter - compression
set rt 1.2; # shape parameter - tension

# confined
set fpcc 10.479723; # peak compressive stress
set ec0c -0.005873; # strain at peak compressive stress
set Ecc 5953.9187; # Young's modulus
set xcrnc 1.023; # cracking strain - compression
set rc 12.072964; # shape parameter - compression

# Build concrete materials
uniaxialMaterial ConcreteCM 4 -$fpc $ec0 $Ec $ru $xcrnu $ft $et $rt $xcrp -GapClose 0; # unconfined concrete
uniaxialMaterial ConcreteCM 5 -$fpcc $ec0c $Ecc $rc $xcrnc $ft $et $rt $xcrp -GapClose 0; # confined concrete

# ---------------------------------------
# Define 2D RC Panel Material (FSAM)
# ---------------------------------------

# Reinforcing ratios
set rouXw 0.0074; # X web
set rouXb 0.0082; # X boundary
set rouYw 0.0074; # Y web
set rouYb 0.0587; # Y boundary

# Shear resisting mechanism parameters
set nu 0.2; # friction coefficient
set alfadow 0.012; # dowel action stiffness parameter

# nDMaterial FSAM $mattag $rho $sX $sY $conc $rouX $rouY $nu $alfadow
nDMaterial FSAM 6 0.0 1 2 4 $rouXw $rouYw $nu $alfadow; # Web (unconfined concrete)
nDMaterial FSAM 7 0.0 1 3 5 $rouXb $rouYb $nu $alfadow; # Boundary (confined concrete only)

# ------------------------------
# Define SFI_MVLEM elements
# ------------------------------

# element SFI_MVLEM eleTag iNode jNode m c -thick fiberThick -width fiberWidth -mat matTags
element SFI_MVLEM 1 1 2 5 0.4 -thick $t $t $t $t $t -width 9 10 10 10 9 -mat 7 6 6 6 7
element SFI_MVLEM 2 2 3 5 0.4 -thick $t $t $t $t $t -width 9 10 10 10 9 -mat 7 6 6 6 7
element SFI_MVLEM 3 3 4 5 0.4 -thick $t $t $t $t $t -width 9 10 10 10 9 -mat 7 6 6 6 7
element SFI_MVLEM 4 4 5 5 0.4 -thick $t $t $t $t $t -width 9 10 10 10 9 -mat 7 6 6 6 7
element SFI_MVLEM 5 5 6 5 0.4 -thick $t $t $t $t $t -width 9 10 10 10 9 -mat 7 6 6 6 7

# ------------------------------
# End of model generation
# ------------------------------

# Initialize
#initialize

# ------------------------------
# Recorder generation
# ------------------------------

# Nodal recorders
recorder Node -file $dataDir/MVLEM_DTop.txt -time -node 6 -dof 1 disp
recorder Node -file $dataDir/MVLEM_RBase.txt -time -node 1 -dof 1 reaction

# ---------------------
# Define Axial Load
# ---------------------

set N [expr 149.0]; # kips

# >>>> MODIFICATION FOR CYCLIC ANALYSIS

# Gravity

# Patrón de carga
pattern Plain 1 Linear {
load 6 0 [expr -$N] 0
}

constraints Transformation
numberer RCM
system BandGeneral
test NormDispIncr 1.0e-5 100;
algorithm Newton
integrator LoadControl 0.1;
analysis Static
analyze 10;
puts ">>>> GRAVITY OK <<<<"
loadConst -time 0.0;


# Lateral Load
timeSeries Path 1 -dt 0.1 -filePath TESTS/TW-TEST-D-648-INCH.txt;
pattern Plain 2 1 {
sp 6 1 1
}

# OPCIONES DE ANALISIS PARA CARGA CICLICA
constraints Transformation
numberer RCM;
system BandGeneral;
test NormDispIncr 1.0e-5 1000;
algorithm KrylovNewton;
integrator LoadControl 0.1;
analysis Static ;
analyze 648

.............................................................................
So the only difference here is the command sp, since i have the test data.
I looked into the SVN:
http://opensees.berkeley.edu/WebSVN/fil ... _MVLEM.cpp
and this error occurs when you have a singular stiffness matrix ¿why?

Thanks you so much for your help!

[imurdereri]

Hi,

i tried changing the constraint to "Penalty Method"

constraints Penalty $alphaS $alphaM

$alphaS penalty αS factor on single point constraints
$alphaM penalty αM factor on multi-point constraints

Now i dont get the error mencioned above, but why i cant use the transformation constraint?
Since i'm using the "sp command" i must use this type of constraint?

I use "constraints Penalty 1e20 1e20", wich are the same alpha values used by Xinzheng Lu for the ShellMITC4 element (can also model shear walls).

How can i obtain a theorical value for alpha's?

Thanks in advance