According to the Manual ETABS 2015 when Fast Nonlinear Analysis runs with not taken into account the plastic hinges are made. But I 'm doing runs and gives the FNA results . Now , these results are quite different from Direct Integration Time History Analysis. Anyone know about it. Thank you very much
In CSi programs the Wilsons' FNA method allows only for nonlinearity represented with link elements.
If you use ETABS Ultimate version there are nonlinear hinge link elements. Otherwise you need to present the hinge behaviour only with links.
Thanks Stoyan.
You have used FNA ?
What has been your experience in this regard
I have tried the FNA but only for simple tasks (it works well) with NNLIN Link elements. However we use SAP2000 rather than ETABS and I personally prefer the use of PMM Fiber elements for distributed plasticity so my weapon of choice is the direct integration procedure with Hilber Hughes Taylor technique.
Good After Noon Sir The results which we obtain from Fast Non Linear Analysis are just approximate results as compared to the Results Obtained from direct Integration method..Direct Integration method takes much time in analysis the results are much more accurate as Compared to FNA..which takes quite less time in Analysis...we Obtain the accuracy in the Results..we can go for many analysis combination..depending upon the type of the structure.
Hello, thank you!
I comment that. I have run Fast Nonlinear Analysis vs Direct Integration Time History and, if the nonlinearity is small, the result are identical. The difference is when plastic hinge goes beyond the point E.
I dont know
I have run FNA vs Direct Integration , and if the nonlinearity is small, the results are identical . The difference is when a plastic hinge goes beyond the point E.
I do not know if you have the same results
Dear Mr. Cristian Otto Bay,
In what type of a structure you obtained identical results? Have you published your results? I have seismically isolated building models and try to figure out the validity of the FNA results over NTHA without performing an NTHA.
Dear Seda Ôzdemir:
I obteined identical results in steel structure, E-Defense, with buckling restrained braces devices.
Validation was performed on SDOF Column following the step on ETABS help.
Dear Cristian Otto Bay,
Does the SAP2000 or ETAB consider the plastic hinge formation in beams and columns after using FNA technique ?
Dear Asad Naeem,
Only ETABS 2015 ultimate considerered hinge plastic after using FNA technique.
Etabs 2016 has an option of defining hinges as links. When performing FNA using plastic hinges you need to select the option of assigning your plastic hinges as link elements.
Good question.. Please share me the best answer might you trust...
Regards…
In SAP, material nonlinearity (for example, nonlinear hinges) are only considered in FNA if it is modeled as NLLink.
However, in ETABS Ultimate 17 you can select Analyze-Analysis of Model for Nonlinear hinges-Model hinges as separate links, and then you can run FNA with nonlinear hinges (no need to use NLLink).
It is worth mentioning that FNA doesn't consider P-delta/Large displacements effects. So, if you are trying to capture drifts near collapse of the structure I believe FNA won't give you reliable results.
Dear Professor Cristian Bay
We did it by the below paper:
Article Seismic Fragility Assessment of RC Frame Equipped by Visco-E...
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