Foundation rebar layout for non orthogonal structure 3

[Tstruct]

I have a structure with one side retaining walls non orthogonal (see attachment). Should I place reinforcement in foundation in global orthogonal direction or perpendicular to the angled retaining wall? Any reference from ACI if possible would be very helpful. Neglect the markings on the drawing. Thanks

 

[milkshakelake]

I don't see a clear answer, so you can go either way.

For me personally, I think it's hard to shop detail non-orthogonal rebar (I do some shop drawings), and hard for the EOR and the inspector to check it. I just add something like (4)#6 T&B (meaning 2 top, 2 bottom) along all the edges and do everything else orthogonally, using the projected rebar with trigonometry.

Edit: The closest I can get to a reference is from CRSI Design Guide for Economical Reinforced Concrete Structures. It doesn't go over it directly, but gives a clue.

 

[JoelTXCive]

I see your slab is 9" thick. Could you go to a ~14" thick region along the diagonal wall? Then, you could add bottom bars that are perpendicular to the diagonal wall run in that region, and keep your typical orthogonal reinforcement setup.

 

[Tstruct]

@JoelTXCive My slab (foundation) is 18" thick as mentioned on the drawing, and I was thinking the same as you said. Thanks.

@milkshakelake Thank you for your response.

 

[SlideRuleEra]

Tstruct - Suggest taking milkshakelake's advice, orthogonal rebar. The problem you are working on comes up often with some of the rebar in skewed (angled) bridge decks. Rebar intersections can be either orthogonal, or not. It's done both ways depending on the skew angle. Here is the orthogonal concept:

Investigations indicate orthogonal placement is somewhat better. See:

"Effect of Reinforcement Pattern on the Behavior of Skew Slab"

 

[HTURKAK]

Apparently non orthogonal retaining wall has 45 degr.

My opinion , ( based on past experience)

- Provide mat reinf T&B in global orthogonal direction,

- Find the retaining wall moment global direction components Mxx=Myy= 0.707 Md and check with the reinf. provided ,

- If necessary , add reinf . perpendicular to the angled retaining wall

IMO , JoelTXCive 's comment is valuable







I cannot give you the formula for success, but I can give you the formula for failure..It is: Try to please everybody.

 

[Tomfh]

Go orthogonal.

 

[Tstruct]

@HTURKAK Thank you for your valuable response.
But incase of both perpendicular and angled reinforcement will make it hard or impossible for concrete to reach the bottom. Any solution?

 

[HTURKAK]

If required , you will need additional reinf. at bottom and anyway you shall provide starter bars L shaped for wall reinf., just extend the bottom arm to justify the moment developing .. I do not expect any but in case of congestion i would question the thk. of the raft.











I cannot give you the formula for success, but I can give you the formula for failure..It is: Try to please everybody.

 

[Matt PE]

I agree with @milkshakelake and @SlideRuleEra.

Perpendicular to the wall is easier to detail, construct, and inspect.

I would also add that perpendicular to the wall is more efficient in that the axis of your steel is aligned with the direction of bending, so that you can count on the full area of the steel.

Depending on spacing, we have used a couple short bars where you make the turn, tied off to the "main steel" (See sketch.) Just make sure your widest spacing at the open end of the triangle meets your maximum spacing requirements.

https://files.engineering.com/getfi...-380a-4c44-804b-71de51836acc&file=Sketch1.pdf

If the spacing of the bars is wide, you may be able to just drop full length bar in at the angle point and not get too congested.

 

[Greenalleycat]

I've done non-orthogonal retaining walls before and I have always maintained the reinforcement to be 90 degrees to the wall
This means you get some clashes at the intersection where the angle change occurs, but so be it
I much prefer the overall structural simplicity and confidence from having reinforcement running in the way that makes sense to me