Horizontal reinforcing in cantilevered retaining wall stems

[CConrad]

ACI 318-14 Section 11.1.4 refers to sections 22.2 through 22.4 for the design of cantilevered retaining walls, and makes specific reference to section 11.6 for horizontal reinforcing requirements.

ACI 318-14 Table 11.6.1 says:

rho_t must be at least 0.0020 for cast-in-place walls using deformed bars on No. 5 or smaller, provided fy is less than or equal to 60000 psi.

It also says rho_t must be at least 0.0025 for cast-in-place walls using deformed bars larger than No. 5.

Fast forward to ACI 318-19, where cantilevered retaining walls are now referenced in Chapter 13 - Foundations.

Section 13.3.6.1 states:
The stem of a cantilever retaining wall shall be designed as a one-way slab in accordance with the applicable provisions of Chapter 7.

(Knowing which are the "applicable provisions" seems to be the key.)

Assuming that it is an "applicable provision", Section 7.6.4.1 states:
Reinforcement shall be provided to resist shrinkage and temperature stresses in accordance with 24.4.

Section 24.4.1 states:
Reinforcement to resist shrinkage and temperature stresses shall be provided in one-way slabs in the direction perpendicular to the flexural reinforcement in accordance with 24.4.3 or 24.4.4.

Section 24.4.3.1 states:
Deformed reinforcement to resist shrinkage and temperature stresses shall conform to Table 20.2.2.4(a) and shall be in accordance with 24.4.3.2 through 24.4.3.5.

Section 24.4.3.2 states:
The ratio of deformed shrinkage and temperature reinforcement area to gross concrete area shall be greater than or equal to 0.0018.

So are we seeing a change to the code requirements for transverse reinforcing, or is one of my two interpretations incorrect?

Thanks in advance for any insight.


Director of Technical Services
ENERCALC, Inc.
Web:

http://www.enercalc.com

 

[KootK]

I see it as a change. From a software perspective, I'd love to constrained to the code minimum be also be able to accept a recommendation based on my anticipated joint spacing.

 

[CConrad]

KootK, thanks for the second look!

Director of Technical Services
ENERCALC, Inc.
Web:

http://www.enercalc.com

 

[dik]

I would read that as a minor change in reinforcing for using rebar >#4, and I don't know why except... by using smaller more distributed bars cracking is better distributed. For exterior exposure, something more than minimum temperature and shrinkage reinforcing is prescribed.

Rather than think climate change and the corona virus as science, think of it as the wrath of God. Feel any better?

-Dik

 

[CConrad]

Dik,

Do you read this to say that if using No.6 horizontal bars in a cantilevered retaining wall stem, ACI 318-14 required a ratio of 0.0025, and ACI 318-19 requires a ratio of 0.0018?

Director of Technical Services
ENERCALC, Inc.
Web:

http://www.enercalc.com