Are closed stirrups required for all beams? 1

[CLT123]

In reading through the Structural Integrity reinforcement requirements for cast-in-place beams (ACI 318-14 Section 9.7.7) I am led to the conclusion that all beams both perimeter and non-perimeter require closed stirrups based on the below logic:
- All beams are required to have some amount of integrity reinforcement.
- ACI 9.7.7.1(c) & 9.7.7.2(b) state longitudinal reinforcement shall be enclosed by stirrups per 25.7.1.6 (aka the requirement for closed stirrups)

Although in reviewing typical detailing practice it appears this is not always done. What am I missing here? The typical detailing practice for beams per this structure magazine article (

https://www.structuremag.org/?p=14709)

appears to only show closed stirrups required for perimeter beams.

Any help would be greatly appreciated. [URL unfurl="true"]https://res.cloudinary.com/engineering-com/image/upload/v1676161272/tips/ACI_9.7.7.1_and_9.7.7.2_u3b9vi.pdf[/url]

- J

 

[Illbay]

No.

"No one is completely useless. He can always serve as a bad example." --My Dad ca. 1975

 

[CLT123]

Thank you for the response. Can you explain what scenario using U stirrups without a cap tie would be acceptable? How do you get around the integrity reinforcement requirement?

- J

 

[KootK]

The trick here is to recognize that the two clauses shown below are OR rather than AND. If you provide one quarter positive reinforcement continuously, you don't need the closed stirrups.

In the sketch below, I've attempted to explain the logic for why the closed stirrups are necessary when the bottom bars are not made continuous. Basically, the beam needs to "hang" from the stirrups and top steel after a hypothetical concrete shear failure. Similar logic applies to a diagonal shear failure.

 

[CLT123]

Thanks! This makes sense. The “or” had evaded me.

- J