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Hello,

I am modeling a reinforced concrete beam-column joint and need to create an unbonded zone in a part of the beam, but I don't know how to establish it. If you have any advice, I would be grateful.

What do you mean by "unbonded zone" ?

Concrete is not in contact with the reinforcing steel.

STKO Team wrote: ↑

Fri Jan 23, 2026 8:59 am

What do you mean by "unbonded zone" ?

Concrete is not in contact with the reinforcing steel.

It's about preventing the steel reinforcement and concrete from coming into contact in the middle area of the beam, but I don't know what to do.

In a beam model with fiber sections, the perfect bond between steel and concrete is assumed (plane sections remain plain).

If you want to use beam model then you should do something like this:
https://opensees.berkeley.edu/workshop/ ... ration.pdf

STKO Team wrote: ↑

Tue Jan 27, 2026 9:02 am

In a beam model with fiber sections, the perfect bond between steel and concrete is assumed (plane sections remain plain).

If you want to use beam model then you should do something like this:
https://opensees.berkeley.edu/workshop/ ... ration.pdf

I don't quite understand what you mean. What I mean is that steel bars in the circled area of the diagram are equipped with sleeve-like items to prevent contact with the concrete. Currently, I want to implement this idea in STKO, but I don't know how to proceed.

Hi, You might do the followings:
1] Model the concrete part using solid (ASDConcrete3D)
2] bonded rebars as embedded dispBeamColumn element with slip (ASDEmbeddedRebarWithSlip) interface between concrete and rebar,
3] the unbonded steel rebars as displBeamColumn element but without any embedment or interface between concrete