ACI 318 15.4. I'm at a loss in interpreting this.

[manstrom]

For a two way flat slab on columns...

I am banging my head against the wall trying to understand the requirements here. I've been looking at this for hours and I'm going nuts. This is new to the ACI 318-14 as far as I can tell. In the past, shear reinforcing was not required at columns as long as your punching shear worked. This says you always need transverse reinforcing at edge or corner columns no matter what.

15.4.1 Beam-column and slab-column joints that are restrained in accordance with 15.2.4 or 15.2.5, respectively, and are not part of a seismic-force-resisting system need not satisfy the provisions for transverse reinforcement of 15.4.2.
15.4.2 The area of all legs of transverse reinforcement in each principal direction of beam-column and slab-column joints shall be at least the greater of (a) and (b):
(a) 0.75 sqrt (f′c) * b * s / fyt
(b) 50 * b * s / fyt
where b is the dimension of the column section perpendicular to the direction under consideration.
15.4.2.1 At beam-column and slab-column joints, an area of transverse reinforcement calculated in accordance with 15.4.2 shall be distributed within the column height not less than the deepest beam or slab element framing into the column.
15.4.2.2 For beam-column joints, the spacing of the trans- verse reinforcement s shall not exceed one-half the depth of the shallowest beam.]

It's asking for transverse reinforcing. Is this transverse to the slab? (i.e. beam stirrup)

Or to the column? (i.e. column tie)

I assume beam stirrups.

The area required is very low. 0.13 si. That's one #4. Can I just do one? Can I do a single S shaped tie?

Are there specific detailing requirements for anchorage or spacing?

If someone can link me to a detail showing this, I would appreciate it. This should be easy, but I have never seen a detail with stirrups in a two way slab.

When I am working on a problem, I never think about beauty but when I have finished, if the solution is not beautiful, I know it is wrong.

-R. Buckminster Fuller

 

[HTURKAK]

- This reinf. is for the joint..


I am not sure how did you calculate 0.13 si . If #4 bars are used as column tie, the same size can be used for the joint .and the spacing could be checked with 15.4.2(a) and 15.4.2( b) . You can just do one located at mid height of the joint.

I will suggest you to look ( The Reinforced Concrete Design Handbook A Companion to ACI 318-14 ).