Dear Koukellis

It is not viable to capture hysteretic behavior of elements properly in SAP2000. However, you can obtain the envelope curve under monotonic loading using detailed finite-element models. subsequently, you define an axial MultiLinear Plastic Link and use the envelope as a backbone curve in SAP2000 with Pivot [1] or Kinematic hysteresis model. This is a reliable and time efficient approach.

Best Regards

[1] Dowell, RK, Seible, F, Wilson, EL. Pivot hysteresis model for reinforced concrete members. ACI Struct J 1998;

P.S. By the way, if it is not possible to conduct a detailed FE analysis, there is also another way which I adopted somewhere else. My researches mainly focuses on RC structures and I don't have exact information on steel structures but this example can give you the whole idea. For instance, to determine the backbone curve of an RC beam under flexural action approximately, you can determine the yield moment and corresponding rotation easily.

based on these results you are able to define the backbone curve using Generalized Force-Deformation Relation for structural components given in ASCE 41.

ASCE 41 permits to define the backbone curve in accordance with these generalized load-deformation envelopes. Actually these relations are idealized backbone curves obtained from experimental data. More information can be found in ASCE 41-13.

Dear Mohammad,

Thank you for taking the time to reply to my question. Although I mostly focus on braced steel frames, your answer is quite useful for me and I will have a look on the papers.

In the following article (see attached PDF), Sap2000 and Abaqus are used for modelling of Steel Structures with Buckling-Restrained Braces.

In the sap2000 modeo, buckling resistant brace modeling was done using the definition of the plastic joints. The plastic joints of the buckling resistant braces have been defined at the two ends of the brace like the plastic joints of columns. In the buckling resistant brace, the joints can be formed at the two ends like the columns because buckling is not given to the brace, and it will not be like the common braces that the plastic joints are defined at the center of the element.

Karimi, M. R. B., Yaghin, M. A. L., Nezhad, R. M., Sadeghi, V., & Aghabalaie, M. (2015). Seismic Behavior of Steel Structure with Buckling-Restrained Braces. World Academy of Science, Engineering and Technology, International Journal of Civil, Environmental, Structural, Construction and Architectural Engineering, 9(4), 488-496.

You can read this paper titled "Seismic Performance of Buckling-restrained Braced Frames with Varying Beam-column Connections"

Thank you Behrouz Ahmadi-Nedushan and Said Elias for the papers. They are very useful for my research.

Hello everyone,

I was recently trying to model a BRB using SAP2000 by defining axial plastic hinges at either ends of the brace. But the problem that I am facing while doing pushover analysis is that the brace is buckling in compression and hence achieving much lower axial strength than what it is having in tension. I have referred to the paper : Karimi, M. R. B., Yaghin, M. A. L., Nezhad, R. M., Sadeghi, V., & Aghabalaie, M. (2015). Seismic Behavior of Steel Structure with Buckling-Restrained Braces. World Academy of Science, Engineering and Technology, International Journal of Civil, Environmental, Structural, Construction and Architectural Engineering, 9(4), 488-496. But could not solve the issue.

Can anyone help?

can you tell me the properties you obtained for the buckling restrained bracing system

Mohammad Mahdi Javidan

Michail Koukellis

For the frame modeling you can fallow as in SAP2000 defaults element and material.

For the BRB section and element, you need to add the brace element with a built up one and the cross-section area as BRB is. To prevent from the buckling, there are many methods. The one which I am suggesting is to assign hinge with axial properties at the center of the brace element. The axial hinge properties need to check with the modified option, the properties you may see it would be less compression capacity, and it means the buckling one. This backbone has to modify according to the designed one of BRBs (beta ...). Article Fragility assessment of buckling-restrained braced frames un...

Hello, everyone

You can model the BRB in SAP2000 by calculating the equivalent area of BRB. Nonlinear properties of BRB are entirely concentrated in plastic hinge. So the backbone curve of BRB element can be obtained from ASCE 41, or from experimental results The plastic hinge should be assigned at middle.

Thank you