Error in Rectangular Fiber Section of STKO

[ankurjain1992]

Respected Sir,

I was defining a fiber model using the Mander model as defined in STKO.
I found that the Ineffective area calculated in STKO having some error. The area calculated using the value of w' as center to center distance of bars. But actually, the distance should be the clear distance between bars as define in the Mander et. al. 1988.

I have attached the screenshot of the paper also. Kindly check once and correct me if I am wrong.

Thank you in advance.

[diego.talledo]

Dear user,
you are right, indeed the original model by Mander et al. considers the clear distance between longitudinal bar in order to define the ineffective confined concrete. Furthermore the same is true in the other plane taking into account the distance between the stirrups.
On the other hand, other standards (like for instance EC 1998-3 or Italian National Standard) refer to the center-center distance for computing the ineffective confined concrete.
For this reason STKO uses the center-center distance for all the models since it computes that quantity (independently from the selected model for confinement) when the geometry of the section is changed.

Keep in mind that the assumption of using the center-center distance is on the safe side since STKO considers a bigger parabola of ineffective concrete.

[ankurjain1992]

Ok sir.