ACI 318

[haynewp]

According to ACI 318 section 14.1.2, cantilever retaining wall vertical reinforcement designs are according to chapter 10 which has 200/fy as the minimum vertical reinf. ratio allowed. However, I have 2 books (one is "Design of Reinforced Concrete" by Jack Mccormac) which use section 14 (0.0012) as the minimum ratio of vertical steel for a cantilever retaining wall and one book "Basics of Retaining Wall Deisgn" by Hugh Brooks that uses the (200/fy) ratio. Does anyone know which one is correct to use for cantilever retaining wall minimum vert. and why?

 

[haynewp]

Sorry, ACI 318 1995 edition is my reference.

 

[JAE]

haynewp,
My interpretation is that Section 14.1.2 specifically designates cantilever walls as falling under the Chapter 10 provisions except for horizontal steel which it indicates is in accordance with 14.3.3.

This makes sense as the minimum vertical reinforcing given in chapter 14 are generally empirical in nature and similar to the minimum column reinforcing given in Chapter 10 (i.e. 1% to 8%).

A cantilever is acting mainly in bending, more like a beam than a column, so the 200/fy would be more applicable. If you still have doubts, you could simply use the larger of the two minimums but I would stick to the flexure minimum. Don't forget that you can use less steel than the 200/fy if you supply at least 1.33 times the area of reinforcing requried for flexure (ACI 10.5.3).

 

[haynewp]

Thanks JAE!

 

[ishvaaag]

In spanish EHE code, and for walls and fyk=400 MPa minimum geometrical reinforcement ratio for

vertical reinforcement is 1.2/1000 of brute section
(minimum for the face in tension)

horizontal reinforcement is 4.0/1000 of brute section
(to be distributed between both faces of the wall)
(may be reduced to its 2/3 for lengths less than 7.5 m)

of course the mechanical minimum reinforcement ratio requirement must also be met, if for flexure, that for flexure.

You need then meet the more exacting of the geometrical or mechanical requirements.