ACI 318 Wall minimun Reinforcement

[hx200]

ACI require Cantilever retaining walls to be designed per Chapter 10. This has higher minimum vertical reinforcement requirements than section 14.3.3. What if I have a basement wall retaining soil. My understanding of the code is it goes to section 14.3.3 for minimun reinforcement.

But I think they have the same bending behavior and reinforcement requirements per Chapter 10 for ductility are the same important.

Do I understand the code wrong or their is some difference between Cantilever retaining walls and top restrained retaining walls that I have not think of. Thanks

 

[civilperson]

The moment diagram has maximum at bottom for cantilever. This moment must transfer to footing. In simple span model, the bottom could be pinned or fixed giving either side of wall the tension.

 

[hx200]

civilperson

In a simple span model, the max moment will be in the middle hight of the wall and it will be always bending toward the basement. We still don't want a brittle failure in the wall.

 

[civilperson]

My moment diagram for the simple span with pinned-pinned supports of wall has maximum below the middle since the loading is triangular with a resultant one third up the fill height. My terminology was wrong to include fixed ends in "Simple", should be only single span. If the sides of the wall are modeled as fixed or pinned, then maximum moments become less as per Roark's Formulas page 506-510.

 

[hx200]

Yes, We can design the wall for whatever moment based on the the actual conditions and resonable assumptions. But do we need to check for minimum reinforcement for bending per chapter 10, which ensure no brittle failure of the wall.

 

[civilperson]

Rather, use ACI 14.3 for minimums.

 

[hx200]

Civilperson, Thanks for your inputs.

I think what I am trying to say is both the cantilever and top restrain retaining wall has bending in the wall. The only difference will be tension on different face and the top restrained wall might have axial loading on it. I thin k the ductility concept (ACI chapter 10 min reinf. requirement) applies to the top restrained wall as well.

The ACI 14.3 for seems more appropriate for axial loaded walls.

 

[civilperson]

"Provisions of Chapter 14 shall apply for design of walls subjected to axial load, with or without flexure." 14.1.1

 

[hx200]

I had noticed 14.1.1. I just wanted to know why whould the code treat cantilevel walls and top restrained walls differently.