Pushover analysis

[medo]

Does anyone have tutorial for pushover analysis of RC frame in Robot and maybe comparison of the results with other structural analysis software like SAP2000?

[Tomasz.Fudala]

Please find attached the pdf file. Hope it helps. Please keep in mind that the document refers to an older version of the software.

[Marios]

Does it work also for RC structures Tomasz?

[medo]

Thank you Tomasz. I do have this tutorial, but I find it not very useful especially when defining nonlinear hinge models. There is no explanation if it takes into analysis axial forces or there has to be defined several diagrams for different axial forces.
Also, is there any option to define 'Acceptance criteria'? (Ok, found this under tab Parameters in Definition of nonlinear hinge model).
How to use Incremental method for Non-linear Analysis Option. By default it is not available?

[Tomasz.Fudala]

The typical effect in pushover analysis and non-liner hinges is capacity degradation. Such behaviour can be correctly considered only in case of “displacement control” methods –that is why only “Arc-length” method can be used in Push over analysis and not the Incremental method (which is “load control” method).

Nonlinear hinges can be used for RC bars when “Calculate limit rotation” and “Calculate limit moment” (or analogously displacement and force) is inactive in Parameters tab of non-linear hinge.

[Marios]

Thank you Tomasz and by the way you do a great job in the forum.

[medo]

The typical effect in pushover analysis and non-liner hinges is capacity degradation. Such behaviour can be correctly considered only in case of “displacement control” methods –that is why only “Arc-length” method can be used in Push over analysis and not the Incremental method (which is “load control” method).
This is clear and Ok, but why the Incremental method is displayed in the options but not available?


Nonlinear hinges can be used for RC bars when “Calculate limit rotation” and “Calculate limit moment” (or analogously displacement and force) is inactive in Parameters tab of non-linear hinge.
Can you please clarify these options? Why nonlinear hinges can only be used if this options are inactive?

Is it possible to define hinge property with interaction of axial force and moments like in SAP2000 (see the attached figures)?

[medo]

During Pushover analysis I get error 'Instability (of type 3) detected at node 30 in direction RY'. Node 30 does not exist in the model. Also, no convergence can be reached. Could you please try and figure out whats wrong?

[Tomasz.Fudala]

This is clear and Ok, but why the Incremental method is displayed in the options but not available?


Can you please clarify these options? Why nonlinear hinges can only be used if this options are inactive?

Is it possible to define hinge property with interaction of axial force and moments like in SAP2000 (see the attached figures)?

Non-linear hinges are considered an independent non-linear links for each degree of freedom in a given node. The interaction between different degrees of freedom is disregarded. For example, bending of a bar in one plane does not depend on bending in another plane and longitudinal forces.

[Tomasz.Fudala]

During Pushover analysis I get error 'Instability (of type 3) detected at node 30 in direction RY'. Node 30 does not exist in the model. Also, no convergence can be reached. Could you please try and figure out whats wrong?

I would send this type of inquiry to the Support Team.

[medo]

Non-linear hinges are considered an independent non-linear links for each degree of freedom in a given node. The interaction between different degrees of freedom is disregarded. For example, bending of a bar in one plane does not depend on bending in another plane and longitudinal forces.

But, if you consider column, then for sure the property of a hinge for column depends on the amount of axial force. As you now axial force may vary during analysis. As far as I know in other structural analysis software (i.e. SAP2000) you can define hinge with interaction.
In SAP2000 there are three types of hinge properties: default hinge properties, user-defined hinge properties and generated hinge properties. For example of default properties you have Default-M3, Default-P, Default-PMM, and Default-V2, as can be seen on figures in my previous post. Usually moment hinge properties (Default-M3) are assigned to beams and interacting hinge properties (Default-PMM) are assigned to columns.
In addition to moment-rotation relationships, a three dimensional interaction surface with axial force-bending moment interaction diagrams has to be defined for columns. Although SAP2000 could not update the moment-rotation relationships due to the variations in axial load levels during pushover analysis, the yield and ultimate moment values are updated by using the three dimensional interaction surface. Axial force-bending moment interaction diagrams about two major axes of each column section are utilized to determine the other three axial force-bending moment interaction diagrams required to define the three dimensional interaction surface.
With comparison of results obtained by ARSA and SAP2000 for RC frame quite big differences are obtained. I am trying to match the input data, but it seems that SAP2000 has more detailed input which obviously influences the results.

[Marios]

During pushover analysis is there any way to change the loading matrix from modal to uniform or triangular?

[pwkhang242253]

Hi, I am having the same issue. I am prompted with no convergence and type 3 instability warnings.

Have you guys found out the reason?

Appreciate it if someone could help...THANKS...

[supradhan08345878]

Could anyone help; how to calculate the user defined hinge properties of RC column for SAP2000 for pushover analysis