Constitutive law for confined concrete

[elena.miceli]

Dear STKO team,

is it possible to know how the software computes the ultimate strain and strength in compression of the confined concrete?

My doubt derives from the fact that the paper from Mander et al. (1988) seems not give those information, so I was wondering if the software computes them in line with other codes or papers.

Thanks and best regards

[kesavapraba]

Hi, STKO indeed refers the relevant papers and guidlines for calculating the confined concrete strength (also the stress-strain curve).

For the mander's model[1], you can get the confined strength and the corresponding strain following the equations as seen in the attached figure. Ultimate strain (eps_cu), in the model, is related to the fracture the steel rebars (lateral ties/spiral hoops).

[1] Mander, John B., Michael JN Priestley, and Robert Park. "Theoretical stress-strain model for confined concrete." Journal of structural engineering 114, no. 8 (1988): 1804-1826.

[STKO Team]

If you refer to the confinement model in the RectangularFiberSection, you can look into the Python file in:
C:\Program File\STKO\external_solvers\opensees\physical_properties\sections\RectangularFiberSection.py

At line 1562 you will find the Mander Model