Modeling self-centering UPT wall in SeismoStruct – Different confined and unconfined concrete in same section

[Mouazzam]

Hi everyone,

I am modeling a self-centering unbonded post-tensioned (UPT) wall in SeismoStruct. I would like to assign two different concrete materials within the same cross-section: confined concrete for the inner core and unconfined concrete for the outer cover. This needs to be applied consistently to both the wall base (plastic hinge region) and the upper portions.

I noticed that the standard rcrws (Reinforced Concrete Rectangular Wall Section) only permits a single concrete material assignment. The program automatically calculates the confined region based on cover thickness and transverse reinforcement, but it applies the same base material properties throughout (applying internal confinement factors only to the core zone).

Important note: I have not added any transverse or longitudinal bars in my model — only PT bars are used.

Is there a recommended workaround or a specific section type that supports this kind of fiber discretization with separate confined and unconfined concrete materials?

[seismosoft]

Since the concrete material in the actual section is one, the only differentiation between the core concrete and the cover concrete can be done through the confinement factors for the two regions. You could assign different materials through the jacketed rcjrs section, however I am not sure if this can address your modelling needs.
Seismosoft Support