what create initial stress??

[mahbobehmirzaie]

hello
I was create initial stress in a truss. I used “initstrain” in model. When run the model ,there is:
Unbalanced load. I have a question: this program is True???
wipe;
model BasicBuilder -ndm 2 -ndf 3
# Define Variables
set d 0.010
set L 1.0
set A [expr $d*$d]
set PT 10.
set E 200.0e6
puts "initStrain [expr $PT/($A*$E)]"
# Define Nodes
node 1 0.0 0.0
node 2 $L 0.0
# Define Boundary Conditions
fix 1 1 1 0
fix 2 1 1 0
# Define Materials
uniaxialMaterial Elastic 1 $E
uniaxialMaterial InitStrainMaterial 2 1 [expr $PT/($A*$E)]
# Define Element
element truss 1 1 2 $A 2
# Define Recorder
recorder Node -file LoadDispPT.txt -time -node 2 -dof 1 disp
constraints Plain
integrator LoadControl 20.0
numberer Plain
system BandGeneral
test NormDispIncr 1.0e-7 100
algorithm Newton
analysis Static
analyze 500
print ele
print node

[vesna]

You need to define a load pattern.