tipped reinforcement 3

[DoubleStud]

I mostly do residential projects and I love looking at other company/people structural drawing. I see this one detail that I have never seen before on my friend's house. Have you seen or done this before? The reinforcement is tipped? Seems complicated especially at wall corners? This is the typical basement wall drawing and the floor framing is not shown. What do you think?

 

[Enable]

Is there a reversal of stresses from bottom to top during the construction period to warrant this? That's the only thing I can think of. But when we have that condition we usually use two matts.

Seems very strange to me. Also, unless the returns not shown occur at very close spacing it also seems like an unstable mess until lower beams are erected, ground floor framing is in, and earth is pressing against the wall.

Disclaimer: I woke up at 3am (after a family dinner party the night before) to drive my wife for work in a city 3.5 hours away and am still recovering. So good chance my eyes should not be trusted right now. This might make total sense.

 

[lexpatrie]

Boy that's some house. Drilled piers, structural steel "subfloor" and a 13'-6" retaining wall?

 

[driftLimiter]

this tipped bar thing is interesting. Are they trying simply to reduce steel and provide steel on the tension face for an element that is in contraflexure?

From engineering perspective, #4 @ 12 is too light. From construction perspective, tipped bars are difficult to install and inspect.

A single mat #5 @ 12" o.c centered seems like it performs just as well and is simple to build, and meets min. steel.

 

[hokie66]

Regardless of the amount or orientation of the vertical bars, how do they work? Where is the resisting element/footing at the bottom? What props it at the top?

 

[DoubleStud]

Hokie, it is missing detail of floor framing. There is no footing at the bottom, spaced piers due to expansive soil.

 

[hokie66]

But starting the bars on the outside seems to indicate expectation of moment restraint there. If it is pinned both bottom and top, I have no idea why the bars are shown to be 'tipped'.

 

[BAretired]

All in all, it is a daft detail.

 

[jerseyshore]

This screams architect to me. We've all seen bizarre details like this come from architects, especially since it says structural concrete floor by others. What engineer doesn't design the floor?

 

[DoubleStud]

No, the structural part is a different company. But you are right, it is weird that they did not specify the steel pan and reinforcement. This house was built 3 years ago and is estimated around $4.8 million.

 

[dik]

Never... it's a bad idea. There has to be some form of moment resistance at the bottom, too.

-----*****-----
So strange to see the singularity approaching while the entire planet is rapidly turning into a hellscape. -John Coates

-Dik

 

[HTURKAK]

If this is the detail, we are free to speculate and start guessing.

My guess is , the basement wall assume to have some fixity at the bottom and simply supported at floor framing level. The backfill followed the floor level construction .
Still the mystery for me total wall ht . min. 3'-6'' and max 13'-8''
This house estimated around $4.8 million with sinle layer reinf??




According to the grace of God which is given
unto me, as a wise masterbuilder, I have laid the foundation, and another buildeth thereon. . . .
I Corinthians 3:10

 

[Eng16080]

I never pass up the opportunity to look at structural details by others. It's always interesting.

As far as this detail goes, I can't make any sense of it. Perhaps I'm missing something obvious, but if there's a floor restraining the top of the wall laterally and it's also restrained at the bottom, then isn't the wall acting like a simply supported beam spanning vertically, with tension occurring to the inside (basement side)? If that's the case, I would want the vertical bars to be on that side. Even if the wall is instead spanning horizontally, I still don't see the logic in this. If there was a reversal of stress (as mentioned above), I could maybe see where they're coming from.

Even if there is a good reason for this from a structural design standpoint, though, asking the concrete contractor to slope bars like this is asking for problems.

Finally, I would bet that this doesn't meet code for the max. height of 13'-8". At midheight of the wall with #4 bars at 12" o.c. and a depth from compression face to bar center of only 5", this seems questionable. Again, perhaps I'm totally overlooking something here.

 

[JAE]

If the pier extends up and supports the bottom of the wall (top of the void forms) and the floor comes in and pushes back a bit higher, there could possibly be a little reverse moment behavior going on at the bottom, which also suggests the need for rebar on the outside face at that point.

But it seems that the moment could be resisted by
a) having a single vertical layer on the inside face and
b) some shorter bars on the outside face instead of this stupid tipping.

 

[JAE]

I was going to add the the detail doesn't clearly show how the wall is vertically supported - I presume the void forms are "in the way" of the visibility of the pier extending higher to support the wall but that's not what the detail directly shows.

 

[jerseyshore]

I could only imagine giving this detail to a few local masons and see how many different variations of the reinforcing we would see constructed.

 

[Lomarandil]

Someone has been overthinking the shear depth provisions of ACI 318 and couldn't bear to go to a 12" wall.

 

[jerseyshore]

And in a 10" thick wall do any engineers only use 1 layer of reinf? I can't remember ever seeing that for 10" and above thicknesses.

 

[Eng16080]

And in a 10" thick wall do any engineers only use 1 layer of reinf?

I often use one layer for a wall up to 10" thick, assuming it has sufficient strength. For thicker walls, like 12", I'll then switch to 2 layers.

 

[JAE]

jerseyshore - see ACI 318 under their "Wall" provisions you can have one layer on thicker walls assuming the wall resists lateral earth in constant bending to one direction.