Convergence Problem!

azari · Post by **azari** » Sun Jul 30, 2006 8:05 am

Hi
I'm a new user in Opensees. I'm working on MPA.The structural model is made by nonlinear beam column elements. when the model is analysed by nonlinear history analysis, I face a problem:the model shows nonlinear behavior, a warning message is appeared and the analysis would be stopped.the problem is a convergence problem and even after 1000 iteration it can not solve it. when I make the time steps smaller or change the algorithm the problem wouldn't be solved.please help me to overcome this problem.

silvia · Post by **silvia** » Mon Jul 31, 2006 9:12 am

please send me your files at:
opensees-support@berkeleyDOTedu (replace the DOT with a .)

QI · Post by QI » Tue Aug 08, 2006 6:04 am

hello,azari ,i am studying the MPA,can i make a contact with you .
maybe we can make communion on the MPA.here is my email,wenqiguang81412@126.com

azari · Post by **azari** » Thu Aug 10, 2006 5:03 am

silvia wrote:please send me your files at:
opensees-support@berkeleyDOTedu (replace the DOT with a .)

Dear Silvia,
Did you receive my E-mail?It would be great if you tell me if it is correct to use the DispBeamColumn element instead of nonlinearBeamColumn element?
Thank You

silvia · Post by **silvia** » Thu Aug 10, 2006 5:33 pm

sorry i haven't look at your files, i've been working on next week's workshops. please re-send me the files, and check up on me on thursday/friday next week.

azari · Post by **azari** » Fri Aug 18, 2006 11:08 pm

Dear Silvia,
have you seen my file?I have just this questionit is a serious problem:"I changed the elements to dispBeamColumn elements(instead of nonlinearBeamColumn elements)without any other changes,is it correct?
I'm REALLY waiting for your reply....
Hoda Azari

silvia · Post by **silvia** » Sat Aug 19, 2006 8:34 am

I ran your file (I removed some strange characters and put in the returns) and it ran successfully.
It took a little while, but it ran and it says it was successful!

the comments it gives to the screen are okey, as they tell you that it failed with one analysis command but worked with the next.

please look over the output once you run it and let me know.

azari · Post by **azari** » Sat Aug 19, 2006 11:06 pm

Hi,
I think you ran the new file with dispBeamColumn elements...yes it works but I dont know if it's correct to use dispBeamColumn instead of nonlinearBeamColumn...I've been working on it for 2 weeks, so I prefer to use dispBeamColumn if it's right...please answer me as soon as possible...
thank you indeed
Hoda

silvia · Post by **silvia** » Sun Aug 20, 2006 9:42 am

it is right, as it is the fundamental formulation.
however, you should discretize each structural element into many elements. and the disp-based element might have problems with softening systems.
you might want to compare the two element types, as they should give you similar results.

azari · Post by **azari** » Sun Aug 20, 2006 1:12 pm

yes,I compared the results fo some records and they were similar,but I didnt discritize the element and I just replaced dispBeamColumn elements,with no other changes and it worked and the results were the same,but I dont know if it's right!!!!!!!!!!may I use this type of elements with no discritization?

silvia · Post by **silvia** » Sun Aug 20, 2006 4:10 pm

was your response nonlinear?

azari · Post by **azari** » Sun Aug 20, 2006 11:31 pm

yes,the structure shows little nonlinear behavior and this little nonlinearity is clear in pushover curve

azari · Post by **azari** » Tue Aug 22, 2006 2:16 am

so what should I do?shall I use dispBeamColumn elements with no discritization?(with little nonlinear response)
I check roof displacement for both elements(nonlinearbc & dispbc) for some records and they were the same...I'm waiting for your reply...
Hoda Azari

silvia · Post by **silvia** » Tue Aug 22, 2006 7:44 am

i'd stay with the nonlinear beam-column element if it works with your case, as it certainly does not require discretization.
if you have problems with that element, then use the disp-based one.

azari · Post by **azari** » Tue Aug 22, 2006 11:07 am

with no discritization?cuz I'm working on my models and it would be so time consuming to change my models and discritize dispbc....I tried nonlinearbc but it doesnt work for some records...I dont know why it doesn't work?!!