Buckling-Restrained Braces ( BRB ) Modelling

[Mina Rizkalla]

When I model a retrofitted (RC) frame with BRB/s, I could get the global response hysteretic results (force vs displacement) for the whole time history/target displacements I enter, on the other hand, I could not get the whole hysteretic results for the truss element (BRB).
so how can I review the whole truss element (BRB) results ?

[z.gronti]

Dear Mina Rizkalla,

You may find the truss elements' results in the "Truss Forces and Deformations" tab of the "Element Actions Effects" in the post-processor.

[psi_14]

Hello,

I am having the same problem reported in this thread. I modelled a concrete structure with a truss (the truss is modelled like a truss element class) and when I run the pushover analysis it says "Axis Maximum Value must be >= Minimum" and no result is shown.

If I uncheck the target displacement box it runs the analysis. The problem is that I need to see the displacement and the capacity curve so I can see the elements that fail for the limit state SD.

How can I solve this?

Best regards

[seismosoft]

Please make sure that the direction of the forces and phases of pushover analysis is the same with the Control Direction in the target dispacement module. If this does not fix the problem, please send the model to support@seismosoft.com.

Seismosoft Support.

[psi_14]

I sent the model.

Everything is in the same direction, I don't know if it's a bug or something with my model.

[seismosoft]

We checked your model. The eigensolver does not give any solutions, it seems that there is one unconnected part in your model.
This is what is giving the problem.
Seismosoft Support

[Mina Rizkalla]

I have validated a BRB element.
When I add it into another model (whole building model, non ductile RC building), the structure deviates more (drift increases).
what considerations should be taken into account while modelling a whole building ?
or is that an acceptable/normal behavior ?

[seismosoft]

It all depends on the relative stiffness and strength of the BRB element and the rest of the frame, as well as the frequency content of the imposed earthquake loading. Although there can be exceptions, normally with the BRB there should be smaller drifts. Please check things with eigenvalue analysis (i.e. if the frame becomes stiffer) and/or pushover analysis. Make sure that the main direction of the BRB is in the main direction of the earthquake loading.
Seismosoft Support