questions about OS

zhenxinli1999 · Post by **zhenxinli1999** » Wed Nov 28, 2007 10:17 am

When I use the Example7 of Examples manual to do the pushover analysis, and only change the controlled dispalcement to 0.2*LBuilding-86.4 inch, the convergence failed at displacement 58.428.
The monitoring displacement-base force curve is not consistent with the concrete02 stress-strain curve. Why is the poseyielding curve up? Is this right?
When I use the concrete02 material to do the pushover of continuous girder bridge, the postyielding curve falls too quick ,I think it is not normal. Is this curve right?

Another question is the nodal result for displacement, velocity and acceleration is relative to ground or absolute.

recorder EnvelopeNode -file $dataDir/Nenvy.out -time -node 6 -dof 1 2 3 disp
recorder EnvelopeElement -file $dataDir/FEnvy175.out -ele 175 localForce
When I use these commands, no file is got. Is there something wrong?

silvia · Post by **silvia** » Wed Nov 28, 2007 11:45 am

what is the resultant hinge length?
the post-yield curve for the force-displacement is affected by the steel model. -- are you having a compression failure or a tension failure?

do the nodes and elements specified exist?
you should put in -time in the element recorder too.

the results for the pushover are relative, I believe.

zhenxinli1999 · Post by **zhenxinli1999** » Wed Nov 28, 2007 10:28 pm

Nonlinear Beam Column Element is used for Example07 and continuous girder bridge.

When the pushover is analyzed the following warnings appear.
WARNING: CTestEngernyIncr::test<> -the failed to converge after: 6 iterations
NewtnRaphson::solveCurrentStep<> -the convergenceTest object failed in test<>
StaticAnalysis::analyze<> - the Algotithm failed at iteration: 135 with domain at load factor 1.5262
analyze failed, returned: -3 error flag
.......
NewtonLineSearch::solveCurrentStep<> -the convergenceTest object failed in test<>
StaticAnalysis::analyze<> - the Algorithm failed at iteration: 0 with domain at load factor 1.52492
analyze failed, returned: -3 error flag
PROBLEM Pushover analysis: CtrlNode 141, dof 1, Disp=58.428 inch
the above warnings mean the result before load factor 1.52492 is believable ?

You mean the up postyielding curve affected by steel model(I use steelo2 material)is probably right?

I am sure the nodes and elements specified exist because I have use the Node Recorder and Element Recorder to get the results.

The nodal results and element results for earthquake dynamic analysis are relative or absolute?

Thank you for attention and reply!

silvia · Post by **silvia** » Thu Nov 29, 2007 7:41 am

the uniform excitation analysis results are relative.

there is a problem with your analysis, it seems. some section has reached its strain limits, likely. check the local response.

zhenxinli1999 · Post by **zhenxinli1999** » Thu Nov 29, 2007 7:38 pm

The above analysis is for the Example07 of OS examples manual. I only change the controlled dispalcement to 0.2*LBuilding.
If the above warnings appear the results are unbelievable?
When some section has reached its strain limits how the OpenSees deal with this case? continue to analyze until more sections reach strain limits, the structure stiffness becomes singular? I think results is still believable, right?
From which waring can I see the strain limits problems?
I still get no file about the Node Recorder and Element Recorder.
Are The Multiple-support excitation analysis results absolute?

silvia · Post by **silvia** » Fri Nov 30, 2007 8:43 am

this is a big with opensees that we haven't been able to figure out. when you have very very high demands on a section/fiber, you have problems converging.
remember, even though you only have 20% drift for the entire building, likely you are at 100% drift on some story, which is way too unreasonable. Hence, not a well-designed building or demand.

in MS excitation, yes, the results are absolute since you are imposing displacements at the support.

about the recorders, try changing them to regular recorders, not envelope, and see what you get.
Likely, you are not getting anything because the program failed to converge. see if you get something if you stop the analysis earlier..

zhenxinli1999 · Post by **zhenxinli1999** » Sat Dec 01, 2007 1:32 am

In MS excitaion, when I only use accelerations to impose, the results are believable? For this case how to get the displacements? Integrate? How to deal with the floating? Is it better to impose both accelerations and displacements?

About the recorders, results for node recorder and element recorder are right.

When the program failed to converge the results are still got, and the front result datas for controlled displacement 0.2*LBuilding is the same with displacements 0.1*LBuilding, the post-yield curves for the force-displacement of both cases is up. So I think the results before the converge failing are believable, is that right?

silvia · Post by **silvia** » Sat Dec 01, 2007 6:53 am

with MS you can only input displacements. that is the way it was formulated.
typically, you should have displacement records as well as acceleration records, otherwise, integrate.

about the recorders, then opensees is not giving you output because of the failure to converge, so it does not get the max/min -- you can just do this in postprocessing.

yes, i think 0.2 is too high.

zhenxinli1999 · Post by **zhenxinli1999** » Sat Dec 01, 2007 5:25 pm

Thank you for reply!

About EnvelopeNode recorder and EnvelopeElement recorder, when I use the Example07 to analyze, and no warnings appear OS is still not giving output.

silvia · Post by **silvia** » Sun Dec 02, 2007 7:03 am

then you need to check the format of the command.

zhenxinli1999 · Post by **zhenxinli1999** » Sun Dec 02, 2007 8:15 am

recorder EnvelopeNode -file $dataDir/Nenvy.out -time -node 6 -dof 1 2 3 disp
recorder EnvelopeElement -file $dataDir/FEnvy175.out -time -ele 175 localForce
Is there something wrong?
I can get the output for Node recorder and Element recorder.

silvia · Post by **silvia** » Sun Dec 02, 2007 10:03 am

and if remove the word envelope you get good results?

try removing the -time from the commands. i have realized that you don't want that there.

zhenxinli1999 · Post by **zhenxinli1999** » Mon Dec 03, 2007 4:51 pm

Yes.

I still get no outputs for Example07 of OS Example Manual.

silvia · Post by **silvia** » Tue Dec 04, 2007 10:57 am

???
you get no output for the examples as i had them?

zhenxinli1999 · Post by **zhenxinli1999** » Wed Dec 05, 2007 5:17 pm

Yes. J just use Example07 to do pushover analysis with no changes. I get good results, but have problems with Envelope Recorder.
I want to know why.
Thank you