Is most rebar compression steel in aged concrete structures yielded?

[ishvaaag]

It is already 9 years ago that I did the worksheet of the attached printout. With creep of concrete upon loading and age, compression members having high compressive stress ratios will have all its steel nominally yielded or close to it.

Is this something enough acknowledged in the codes and practices? Because if not upon some violent shakeout, like an earthquake, plastic hinges being present almost anywhere of maximum moment, the deformations to which strain hardening appears and braking action to the rotation of the hinges makes presence will be at the high strains of strain hardening, and so, at concomitant unmanageable non-structural damage and life loss.

 

[Teguci]

ACI commentary for minimum column reinforcement notes the need for minimum steel due to long term creep of the concrete.

 

[ishvaaag]

I think the reason why this almost yielded effect has not the relevance it could is because upn sudden sway one of the sides of the columns starts to accumulate strains towards the elongation side, soon entering the elastic realm. The other accumulates shortening. Our first side so starts going down in the hysteresis cycle whilst the other side is going horizonally to the left at Fy. So a standing state of almost yielded rebar is not as detrimental to lateral stiffness as it looks at first sight, for most than anything change from where the hysteresis cycles start.

 

[dik]

it doesn't matter if it has yielded, generally.

Dik