Change of convergence tolerance

[buddhasarah]

Hello, I'm trying to perform nonlinear time history analysis of a building.
The building is slightly complex and it fails to converge when a certain brittle member yields. So my solution is to increase the tolerance at the instant when the brittle member yields, but I only know how to define the tolerance initially.
Can anybody tell me how I can change the tolerance for just a certain time steps at a certain instant and change the tolerance back after that?

Thank you very much in advance!

[vesna]

Most of the time tolerance is not the only parameter that is to be changed for the analysis to work. I would suggest you to use Silvia's code for changing algorithm, test, number of iteration...

set Nsteps [expr int($TmaxAnalysis/$DtAnalysis)];
set ok [analyze $Nsteps $DtAnalysis]; # actually perform analysis; returns ok=0 if analysis was successful

if {$ok != 0} { ; # if analysis was not successful.
# change some analysis parameters to achieve convergence
# performance is slower inside this loop
# Time-controlled analysis
set ok 0;
set controlTime [getTime];
while {$controlTime < $TmaxAnalysis && $ok == 0} {
set ok [analyze 1 $DtAnalysis]
set controlTime [getTime]
set ok [analyze 1 $DtAnalysis]
if {$ok != 0} {
puts "Trying Newton with Initial Tangent .."
test NormDispIncr $Tol 1000 0
algorithm Newton -initial
set ok [analyze 1 $DtAnalysis]
test $TestType $Tol $maxNumIter 0
algorithm $algorithmType
}
if {$ok != 0} {
puts "Trying Broyden .."
algorithm Broyden 8
set ok [analyze 1 $DtAnalysis]
algorithm $algorithmType
}
if {$ok != 0} {
puts "Trying NewtonWithLineSearch .."
algorithm NewtonLineSearch .8
set ok [analyze 1 $DtAnalysis]
algorithm $algorithmType
}
}
}; # end if ok !0

I copied this from:
Ex2b.Canti2D.InelasticSection.EQ.tcl at
http://opensees.berkeley.edu/wiki/index ... ic_Section

[buddhasarah]

Thank you for your help vesna!

Changing algorithm indeed deals with convergence problem sometimes but there are some analysis in which no matter how I change the algorithm it doesn't work, so I have no choice but to change the tolerence for a little bit.
Can you tell me how I can change only the tolerence? I tried to modified the code you posted but it doesn't work, I don't know Tcl language well (ㅜㅜ)
Thank you in advance!

[vesna]

Here is another example with the tolerance only:

set tFinal 15.0;
set Tol1 1.0e-6
set Tol2 1.0e-2
constraints Transformation
numberer RCM
system BandGeneral
test NormDispIncr $Tol1 6 2
algorithm Newton
integrator Newmark 0.5 0.25
analysis Transient
set ok 0
set currentTime 0.0
while {$ok == 0 && $currentTime < $tFinal} {
set ok [analyze 1 0.01]
if {$ok != 0} {
test NormDispIncr $Tol2 6 2
set ok [analyze 1 0.01]
test NormDispIncr $Tol1 6 2
} set currentTime [getTime]
}

[mohsenkh]

Dear Vesna

I used VariableTransient comment for analysis. The analysis sometimes is failed. I would change convergence tolerance. Do I use the following comments?

“
Here is another example with the tolerance only:

set tFinal 15.0;
set Tol1 1.0e-6
set Tol2 1.0e-2
.
.
.
set ok 0
set currentTime 0.0
while {$ok == 0 && $currentTime < $tFinal} {
set ok [analyze 1 0.01]
if {$ok != 0} {
test NormDispIncr $Tol2 6 2
set ok [analyze 1 0.01]
test NormDispIncr $Tol1 6 2
} set currentTime [getTime]
}
“

Thanks.

[silvia]

personally, if i was having convergence problems, i'd check my model!