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yuanzhenwei wrote:
> Have you solve your problem？I am a beginner in opensees，I met the same
> problem with you. I need to model a single degree of freedom structure for
> doing IDA analysis,but now I haven't solve the problem , Whether can you
> give me the code ? We can communicate with each other through the mail ,
> my email is hit-yzw@outlook.com . thank you very much !

Hi,
Use something like this :
___________________________________________
# Model for SDOF system
model BasicBuilder -ndm 3 -ndf 6
#Nodes, restraints, material end element
node 1 0.0 0.0 0.0
node 2 0.0 0.0 0.0 -mass 4.446e+02 0.0 0.0 0.0 0.0 0.0
fix 1 1 1 1 1 1 1
fix 2 0 1 1 1 1 1
# uniaxialMaterial Hysteretic $matTag $s1p $e1p $s2p $e2p <$s3p $e3p> $s1n $e1n $s2n $e2n <$s3n $e3n> $pinchX $pinchY $damage1 $damage2 <$beta>
uniaxialMaterial Hysteretic 1 2.764e+03 2.516e-02 2.764e+03 1.583e-01 8.419e-03 4.700e-01 -2.764e+03 -2.516e-02 -2.764e+03 -1.583e-01 -8.419e-03 -4.700e-01 0.000e+00 0.000e+00 0.000e+00 0.000e+00 8.000e-01
# section Aggregator $secTag $matTag1 $dof1 $matTag2 $dof2 ....... <-section $sectionTag>
section Aggregator 1 1 P
# element zeroLengthSection $eleTag $iNode $jNode $secTag <-orient $x1 $x2 $x3 $yp1 $yp2 $yp3> <-doRayleigh $rFlag>
element zeroLengthSection 1 1 2 1
_____________________________________
best regards,

Dear all,
how can we know exactly what is the usage of this parameters in hyseretic material command :
$pinchx pinching factor for strain (or deformation) during reloading
$pinchy pinching factor for stress (or force) during reloading
$damage1 damage due to ductility: D1(mu-1)
$damage2 damage due to energy: D2(Eii/Eult)
$beta power used to determine the degraded unloading stiffness based on ductility, mu-beta (optional, default=0.0)
please send me a paper or text that can clear me with this subject.

Dear fmk,
Thank you for your help
best regards,
gahremani

Dear all
How can I create a nonlinear SDOF model for using in nonlinear response history analysis?
and which parameters should I have to create this model?
I'll be very grateful for any instruction or script that could help.
P.S : my model has viscous damping and it need to be applied in modeling too .

you can use it for both option's.

Dear fmk
I don't know how to thank you for your help.
that worked .
what was that extra 1 at the end of test command for?
I used your command like this and it worked. however it took more time than further analysis:
#-----------------------------------------------------------------------------------------------------
#all units are in meter-kg-Newton
constraints Plain
numberer RCM
system BandGeneral
test NormDispIncr 1.0e-12 1000 1
algorithm Newton
analysis Static
#new commands
set dU 0.0001; # Displacement increment
# Change the integration scheme to be displacement control
# node dof init
integrator DisplacementControl 441 1 $dU
# Finally perform the analysis
# ------------------------------
# Set some parameters
set maxU 0.3; # Max displacement
set currentDisp 0.0;
set ok 0

while {$ok == 0 && $currentDisp < $maxU} {

set ok [analyze 1]

# if the analysis fails try initial tangent iteration
if {$ok != 0} {
puts "regular newton failed .. lets try an initail stiffness for this step"
test NormDispIncr 1.0e-12 10000 1
algorithm ModifiedNewton -initial
set ok [analyze 1]
if {$ok == 0} {puts "that worked .. back to regular newton"}
test NormDispIncr 1.0e-12 1000 1
algorithm Newton
}
set currentDisp [nodeDisp 441 1]
}

if {$ok == 0} {
puts "Pushover analysis completed SUCCESSFULLY";
} else {
puts "Pushover analysis FAILED";
}
#--------------------------------------------------------------------------------------------
Thank you a lot again.

Dear fmk
I've tried your method but I could not see any differences between old and new model's response ,
Here is the scripts I used before and the scripts that I used according your instruction ,
please contact me If you find anything that can help me with this:
____________________________
Old script :
____________________________
#all units are in meter-kg-Newton
constraints Plain
numberer RCM
system BandGeneral
test NormUnbalance 1.0e-6 400
algorithm Newton
integrator DisplacementControl 441 1 0.001
analysis Static
analyze 1000
__________________________
New script :
__________________________
#all units are in meter-kg-Newton
constraints Plain
numberer RCM
system BandGeneral
test NormDispIncr 1.0e-12 100
algorithm Newton
analysis Static
#new commands
set dU 0.001; # Displacement increment
# Change the integration scheme to be displacement control
# node dof init
integrator DisplacementControl 441 1 $dU
# Finally perform the analysis
# ------------------------------
# Set some parameters
set maxU 1; # Max displacement
set currentDisp 0.0;
set ok 0

while {$ok == 0 && $currentDisp < $maxU} {

set ok [analyze 1]

# if the analysis fails try initial tangent iteration
if {$ok != 0} {
puts "regular newton failed .. lets try an initail stiffness for this step"
test NormDispIncr 1.0e-12 1000
algorithm ModifiedNewton -initial
set ok [analyze 1]
if {$ok == 0} {puts "that worked .. back to regular newton"}
test NormDispIncr 1.0e-12 100
algorithm Newton
}
set currentDisp [nodeDisp 441 1]
}

if {$ok == 0} {
puts "Pushover analysis completed SUCCESSFULLY";
} else {
puts "Pushover analysis FAILED";
}
________________________________
P.s:
thank you very much for your time and attention
Please contact me if you find anything that can help me with this
I can send you the entire model scripts if it is needed.

Dear all
I am performing nonlinear static analysis on three steel structure with 3 ,6 and 12 stories that their plastic behavior modeled with concentrated plastic hinges just as done in the example represented for a 2 story steel frame in wiki opensees site.
for each structure at specified displacements convergence error happens and analysis cannot continue further and analysis fails.
for example for 3,6 and 12 structures the final displacements is 19 ,65 and 28 cm. I except the 12 story structure to have a higher displacement but converging error happening in 28 cm displacement and I don't know really what causes this error and How can I Overcome this problem.
I performed push over on the same structure using Sap2000 and the structure can have a displacement up to 90 cm without any error in analysis.
I've already checked the entire example represented for this process and I can't find any differences between creation of my models and the model given in the example and I don't know the cause of problem occured in my model.

I will be very grateful for your instructions and kind helps
best regards
gahremani

Thank you so much.

my model is constructed of elastic elements with localized plastisity at both end using zerolength elements."
I am running opensses on my steel structure to perform a pushover analysis but the analysis fails and none of my recorders works correctly and I have no output after running the model.
when I use Transformation constraints this warning appears :
________________________________________________________
Modified Ibarra-Medina-Krawinkler Model with Bilinear Hysteretic Response
WARNING: CTestNormDispIncr::test() - failed to converge
after: 3000 iterations
ModifiedNewton::solveCurrentStep() -the ConvergenceTest object failed in test()
StaticAnalysis::analyze() - the Algorithm failed at iteration: 87 with domain at load factor -0.0379817
OpenSees > analyze failed, returned: -3 error flag
________________________________________________________
and when I use the Plain constraint the below massage appears :
________________________________________________________
Modified Ibarra-Medina-Krawinkler Model with Bilinear Hysteretic Response
WARNING PlainHandler::handle() - constraint at dof 0 already specified for constrained node in MP_Constraint at node 221
WARNING PlainHandler::handle() - constraint at dof 1 already specified for constrained node in MP_Constraint at node 221
WARNING PlainHandler::handle() - constraint at dof 0 already specified for constrained node in MP_Constraint at node 231
WARNING PlainHandler::handle() - constraint at dof 1 already specified for constrained node in MP_Constraint at node 231
WARNING PlainHandler::handle() - constraint at dof 0 already specified for constrained node in MP_Constraint at node 241
WARNING PlainHandler::handle() - constraint at dof 1 already specified for constrained node in MP_Constraint at node 241
WARNING PlainHandler::handle() - constraint at dof 0 already specified for constrained node in MP_Constraint at node 321
WARNING PlainHandler::handle() - constraint at dof 1 already specified for constrained node in MP_Constraint at node 321
WARNING PlainHandler::handle() - constraint at dof 0 already specified for constrained node in MP_Constraint at node 331
WARNING PlainHandler::handle() - constraint at dof 1 already specified for constrained node in MP_Constraint at node 331
WARNING PlainHandler::handle() - constraint at dof 0 already specified for constrained node in MP_Constraint at node 341
WARNING PlainHandler::handle() - constraint at dof 1 already specified for constrained node in MP_Constraint at node 341
WARNING PlainHandler::handle() - constraint at dof 0 already specified for constrained node in MP_Constraint at node 421
WARNING PlainHandler::handle() - constraint at dof 1 already specified for constrained node in MP_Constraint at node 421
WARNING PlainHandler::handle() - constraint at dof 0 already specified for constrained node in MP_Constraint at node 431
WARNING PlainHandler::handle() - constraint at dof 1 already specified for constrained node in MP_Constraint at node 431
WARNING PlainHandler::handle() - constraint at dof 0 already specified for constrained node in MP_Constraint at node 441
WARNING PlainHandler::handle() - constraint at dof 1 already specified for constrained node in MP_Constraint at node 441
________________________________________________________

the analysis features of my model is :

"constraints Transformation
numberer PLain
system BandGeneral
test NormDispIncr 1.e-6 3000
algorithm ModifiedNewton
integrator DisplacementControl 441 1 0.001
analysis Static
analyze 500"
______________________
I'm looking forward to your kind helps and instructions.
best gratitudes .

I appreciate your help.
could you give me the name of referred paper "Lignos and Krawinkler (2011)" ?

thanks a lot.

In defining bilin material there are four parameters known as cyclic deterioration parameters (Lamda_S,Lamda_C,Lamda_A,Lamda_K) that I don't know the correct values that must be assigned to them.
I studied the corresponding references , but there is only one Lamda parameter that is around 1 according to given equation and in another on of references there is four cyclic deterioration parameter named as Omega_S,Omega_C,Omega_A and Omega_K that have values more than 25.
nominally these are different parameters but I think I should use these parameter's values instead of the so called Lamda's in Bilin material parameters.
I am looking forward for your instruction.
thanks for your attention and kind help.

thank you.
so we cannot download it anymore?

in this command is the number of points arbitary or we need to define a specific number of points to form the envelop?
and if we need to define the negative part of the envelop we must enter that points ditinctly or defining the positive part of the envelop is enough ?
I am very grateful for your attention and kind help.