Retaining Wall - Flexural Reinforcement from Stem Into Footing 21

[CWEngineer]

I am trying to get some clarification regarding the flexural reinforcement of the stem of a retaining wall into the footing.

Does the flexural reinforcement in the stem of a wall, need to be developed into the toe, such as show in Figure 1 of the attached document. Or is providing a standard hook (12db), sufficient, such as that show on Figure 2 of the attached document? If providing a standard hook is sufficient, can the hook be turned towards the heel?

Thanks in advance

 

[IDS]

If we want to arrive at the truth of how concrete works, it's worth acknowledging that all reinforced concrete - the pulley STM model included - relies fundamentally on concrete in tension.

Bar anchorage, shear, "phantom ties", the very fact that concrete is solid - all of this relies fundamentally on tensile forces. When we reinforce concrete we aren't eliminating tension, we are spreading and redistributing the tension out within the concrete so that it is manageable and hopefully the steel is the critical element. But we're still relying on it.

Good point, and I think it's something we all tend to forget.

In another context, I have been looking at research papers on tension stiffening effects, and it's quite interesting how virtually all of them (even the most recent ones) describe the strain effects of micro-cracking around the reinforcement, then go right back to talking about "bond slip" as thought the concrete somehow slips over the surface of the steel, in spite of the ribs.





Doug Jenkins
Interactive Design Services

http://newtonexcelbach.wordpress.com/

 

[Tomfh]

micro-cracking around the reinforcement, then go right back to talking about "bond slip"

One of the first things you learn in uni is that concrete is weak in tension, and that GOOD engineers never rely concrete in tension. So most engineers are quite good at deflecting our reliance on concrete tension without missing a beat.

 

[RFreund]

Another interesting hint at this discussion occurs in the ACI318-08 Commentary R12.10.6. When discussing a corbel they say that:
"An end hook in the vertical plane, with the minimum bend diameter bend, is not totally effective because an essentially plain concrete corner will exit near loads applied close to the corner. For wide brackets perpendicular to the plane of the figure (again the figure is a corbel) and loads not applied close to the corners, U-shaped bars in a horizontal plane provide effective end hooks."
Not sure how that eliminates the plain concrete corner though.

EIT

http://www.HowToEngineer.com

 

[KootK]

@RF: I believe that those statements are in reference to the end of the corbel farthest from the column.

I like to debate structural engineering theory -- a lot. If I challenge you on something, know that I'm doing so because I respect your opinion enough to either change it or adopt it.

 

[CELinOttawa]

Alright, admit it: Who else got crazy busy with the "get this done this year!" rush and forgot about this?