Time history analysis error

[Zeeshanbhat]

Thank you so much for your suggestions. I tried to run this analysis, but I am not getting any eigenvalues. Could you please tell me where I am doing wrong?

Regards,
Zeeshan

[marafini.f]

Dear Zeeshanbhat,

I didn't get that what you want is to visualize the eigenvalues and their derived quantities. The eigen command which is implemented in STKO only allows you to see eigenvectors in the post processor. More will be available soon, as discussed by Dr. Petracca in this webinar https://www.youtube.com/watch?v=vUXKVm5_rn0.

For now, there are two ways to plot what you want, and for both you need to use customCommand tcl scripts.

You can find one at this link viewtopic.php?t=75#p126
and one at this other link viewtopic.php?f=40&t=1513#p1731

The first is quite straightforward, I will paste the code here:

Code: Select all

# set the required number of eigenvalues here
set num_eigen 3

# run the eigen command and store the resulting eigenvalues
# in the "lambdas" list
set lambdas [eigen $num_eigen]

# manually call record if there is no other analysis after the eigen command.
# unfortunately in opensees the eigen command does not call automatically a record...
puts "record eigen"
record

# process all eigenvalues and obtain periods
# print them to screen and to a file
set out_file [open "eigenvalues.txt" w]
set format_string "%16s%16s%16s%16s"; # used to format the header of the table
set format_double "%16g%16g%16g%16g"; # used to format floating point values of the table
set pi [expr acos(-1.0)]
puts [format $format_string "lambda" "omega" "frequency" "period"]
puts $out_file [format $format_string "lambda" "omega" "frequency" "period"]
for {set i 0} {$i < $num_eigen} {incr i} {
	set lambda [lindex $lambdas $i]
	set omega [expr {sqrt($lambda)}]
	set frequency [expr $omega / 2.0 / $pi]
	set period [expr 1.0 / $frequency]
	puts [format $format_double $lambda $omega $frequency $period]
	puts $out_file [format $format_double $lambda $omega $frequency $period]
}
close $out_file

You will not need to use the eigen command if you use one of these two scripts, nor add a record at the end, as you can notice it is already part of the script.
You will obtain a result like this

6.png (5.72 KiB) Viewed 4164 times

Let us know if you need anything else.

Francesca

[Zeeshanbhat]

Dear Francesa,

Thank you. I applied the custom command. Now I am getting the eigenvalues, but the value of the Time period of first mode is quite high as shown in the attached figure. Could you please give some suggestions regarding this?. The pushover curve obtained in the x-direction is exactly the same as of the original model(without masses) obtained from the example demonstrated in one of the webinars. I think there is some problem in model only because it takes so many iterations in gravity load analysis.

Regards,
Zeeshan

[marafini.f]

Dear Zeeshan,

I think you got lost in all the suggestions I gave you.

Specifically you missed this one.

When an eigen command is called before any analysis command, STKO calls default settings in order to run it. These default settings include a generic Transient analysis (as shown in the warning you posted) and the Transformation method as a constraints handler. Such handler is not suitable for models with master-slave pairs and duplicate constraints (over-constrained system), which is exactly the condition imposed by the RC beam-column joint automatism.
Therefore, if you wish to call the eigen command before loading your structure, you need to create a dummy analysis command selecting the right type of analysis and constraint handler, with 0 duration and/or 0 number of increments.

If your eigen analysis is the first, even when called from a customized script, is going to run with STKO internal default settings, Transient (hence the error in the command line) and Transformation Method (hence the loose constraints and high value of period). Add the dummy analysis before, as shown in the previous model I uploaded, and you will get good results.

As for the iterations, you are including material nonlinearities in your model, so it is more than normal that some iteration are needed to reach convergence at each load step.

Enjoy your modeling.

Francesca

[Zeeshanbhat]

Dear Francesa,

I applied the dummy analysis also before custom eigen analysis, but I am still getting the same result.

regards,
Zeeshan

[marafini.f]

Dear Zeeshan,

You invoked the wipe command at the end of the dummy analysis, so its settings will not apply to the eigen one.

try to compare your model with this one:

BUILDING_WITH_OFFSET_AND_JOINTS_edits_2.zip

(439.59 KiB) Downloaded 230 times

It's the same one I uplaoded in this post viewtopic.php?f=33&t=1823#p2886, I just substituted the eigen command with the custom script to extract eigenvalues and derived quantities.

Francesca

[Zeeshanbhat]

Thank you very much.

[Zeeshanbhat]

I tried to do Time history analysis, I am getting an error as shown below;

Capture.JPG (40.67 KiB) Viewed 4139 times

[marafini.f]

Dear Zeeshan,
from a superficial look, the NTH you set up does not seem to have any errors. Non convergence problems can arise simply because the structure is failing under the conditions you defined.
I would suggest you try to run analyses on models you have control over, and have an idea of the expected behavior.
Francesca

[marafini.f]

Dear Zeeshan,
from a superficial look, the NTH you set up does not seem to have any errors. Non convergence problems can arise simply because the structure is failing under the conditions you defined.
I would suggest you try to run analyses on models you have control over, and have an idea of the expected behavior.
Francesca