error in analysis of bidirectional section

[go]

Silvia,
I can not find the reason why my model does not work. could you please help me to find it? the script is as follows:

[code]wipe; # clear memory of all past model definitions
model BasicBuilder -ndm 3 -ndf 6; # Define the model builder, ndm=#dimension, ndf=#dofs
set dataDir Data; # set up name of data directory -- remove
file mkdir $dataDir; # create data directory
source LibUnits.tcl; # define units

node 1 0.0 0.0 0.0
node 2 0.0 3000.0 0.0
node 3 0.0 0.0 0.0


# BOUNDARY CONDITIONS
fix 3 1 1 1 1 1 1;

mass 2 10.0 0.001 10.0 0.001 0.001 0.001

set J $Ubig;
section Elastic 1 20000 160000 2133333333 2133333333 8333.33 $J


set IDColTransf 1; # all columns
set ColTransfType Linear ; # options, Linear PDelta Corotational
geomTransf $ColTransfType $IDColTransf 0 0 1 ; # only columns can have PDelta effects (gravity effects)

set np 5; # number of Gauss integration points for nonlinear curvature distribution

# columns
element nonlinearBeamColumn 1 1 2 $np 1 $IDColTransf; # First floor columns

section Bidirectional 2 100 2000 0 33.33

element zeroLengthSection 2 3 1 2

pattern Plain 1 Linear {
load 1 4000 0. 4000. 0. 0. 0.
}

recorder Node -file $dataDir/D1.out -time -node 1 -dof 1 3 disp; # displacements of mass nodes

# Gravity-analysis parameters -- load-controlled static analysis
set Tol 1.0e-8; # convergence tolerance for test

constraints Plain ; # how it handles boundary conditions
numberer Plain; # renumber dof's to minimize band-width (optimization), if you want to
system BandGeneral ; # how to store and solve the system of equations in the analysis (large model: try UmfPack)
test EnergyIncr $Tol 50 ; # determine if convergence has been achieved at the end of an iteration step
algorithm Newton; # use Newton's solution algorithm: updates tangent stiffness at every iteration
#set NstepGravity 10; # apply gravity in 10 steps
#set DGravity [expr 1./$NstepGravity]; # first load increment;
integrator LoadControl 0.1 ; # determine the next time step for an analysis
analysis Static; # define type of analysis: time-dependent
analyze 10;

puts "model built"[/code]

[silvia]

have you constrained all dofs between elements? otherwise, i'd guess you'd have a singular stiffness matrix.