problem on yield strain

[homashanehsaz]

I have a problem in my file that I can not find. this happens near yield strain point.
help me please. I am really in troubles.


# units: N, m
# Remove existing model
wipe
# Create ModelBuilder (with two-dimensions and 2 DOF/node)
model BasicBuilder -ndm 2 -ndf 3
# Create nodes
# ------------
# Create nodes & add to Domain - command: node nodeId xCrd yCrd
node 1 0. 0.
node 2 1. 0.
# Set the boundary conditions - command: fix nodeID xResrnt? yRestrnt?
fix 1 0 1 1
fix 2 1 1 1
# Define materials for truss elements
# -----------------------------------
# Create Elastic material prototype - command: uniaxialMaterial Elastic matID E


uniaxialMaterial ElasticPP 1 200000. 0.0012

# Define elements
# Create truss elements - command: element truss trussID node1 node2 A matID
element corotTruss 1 1 2 1 1


# Define loads
# ------------


pattern Plain 2 Linear {
# Create the nodal load - command: load nodeID xForce yForce
load 1 1.0 0. 0.
}


# Create a recorder to monitor nodal displacements

# create a Recorder object for the nodal displacements at node 1
recorder Node -file disp1.out -time -node 1 -dof 1 disp
recorder Node -file reac2.out -time -node 2 -dof 1 reaction


# create a Recorder for element forces, one for global system and the other for local system
recorder Element -file eleGlobal.out -time -ele 1 localforces
recorder Element -file eleLocal.out -time -ele 1 basicForces

# Create the constraint handler, a Plain handler is used as homo constraints

constraints Plain

# Create the DOF numberer, the reverse Cuthill-McKee algorithm
numberer Plain
# dasture azmune hamgerayee safhe 85,
test EnergyIncr 1.0e-6 150
# Create the system of equation# systeme hale moadelat ra miguyad
system BandGeneral

# Create the solution algorithm, a Linear algorithm is created
algorithm ModifiedNewton


set j 0.0002
for {set i 1} {$i<=40} {incr i 1} {
set j [expr -1*$j]
integrator DisplacementControl 1 1 $j
# # create the analysis object
analysis Static
set ok [ analyze 1500]

puts $i
}
#

puts "node 1 displacement: [nodeDisp 1]"
print node 1
print element

[MLO]

I think some thing is not reasonable
the material properties was defined as following:
uniaxialMaterial ElasticPP 1 200000. 0.0012

strain=0.0012
length of the element=100 cm
so yield deformation=0.0012*100=0.12 cm

but you expected from this element following analysis:

integrator DisplacementControl 1 1 0.0002
analyze 1500

delta=0.0002*1500=0.3 m=30cm !!!!

30 cm >>0.12 cm isn't it?

you expect an element by ductility =30/0.12=250 !!!

it isn't reasonable

[homashanehsaz]

what about this one?
it seems reasonable but still with problem about yield point:

# units: N, m
wipe
# Create ModelBuilder (with two-dimensions and 2 DOF/node)
model BasicBuilder -ndm 2 -ndf 3
node 1 0. 0.
node 2 1. 0.

fix 1 0 1 1
fix 2 1 1 1
# Define materials for truss elements
uniaxialMaterial ElasticPP 1 200000. 0.001

element corotTruss 1 1 2 1 1
# Define loads
# create a Linear TimeSeries with a tag of 1
# Create a Plain load pattern associated with the TimeSeries,
# command: pattern Plain $patternTag $timeSeriesTag { load commands }

pattern Plain 2 Linear {
# Create the nodal load - command: load nodeID xForce yForce
load 1 1.0 0. 0.
}

# create a Recorder object for the nodal displacements at node 1
recorder Node -file disp1.out -time -node 1 -dof 1 disp
recorder Node -file reac2.out -time -node 2 -dof 1 reaction

# create a Recorder for element forces, one for global system and the other for local system
recorder Element -file eleGlobal.out -time -ele 1 localforces
recorder Element -file eleLocal.out -time -ele 1 basicForces

# Create the constraint handler, a Plain handler is used as homo constraints
constraints Plain

# Create the DOF numberer, the reverse Cuthill-McKee algorithm
numberer Plain

test EnergyIncr 1.0e-6 150
# Create the system of equation# systeme hale moadelat ra miguyad
system BandGeneral

# Create the solution algorithm, a Linear algorithm is created
algorithm ModifiedNewton

set j 0.0001
for {set i 1} {$i<=40} {incr i 1} {
set j [expr -1*$j]
integrator DisplacementControl 1 1 $j
# # create the analysis object
analysis Static
set ok [ analyze 20]

puts $i
}

puts "node 1 displacement: [nodeDisp 1]"
print node 1
print element

[MLO]

you are right homashanehsaz ;
excuse me,I did not pay attention to the negative sign, i'll check it again and I will let you know if I find the problem.