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Concrete Foundatin walls Unbtraced length

Concrete Foundatin walls Unbtraced length

Concrete Foundatin walls Unbtraced length

(OP)
Is there any criteria for unbraced length of a concrete foundation wall. I know cmu walls have length to thickness ratios. does the same apply to poured concrete? Asked to look at a wall under construction that was backfilled too soon. Wall bowed inward 4" and cracked at three locations. Wall is 10' tall, 56' long and 10' high. No intermediate cross walls or pilasters.

RE: Concrete Foundatin walls Unbtraced length

Was it backfilled before the floor system was in place?

DaveAtkins

RE: Concrete Foundatin walls Unbtraced length

(OP)
Yes. That is what caused the failure. I am recommending the removal and replacement of the wall. Would like to know if pilasters are required.

RE: Concrete Foundatin walls Unbtraced length

10" isn't too slender for a 10' wall.

They just need to brace the wall for backfill, or you can design it as a cantilevered wall.

Pilasters not required.

When I am working on a problem, I never think about beauty but when I have finished, if the solution is not beautiful, I know it is wrong.

-R. Buckminster Fuller

RE: Concrete Foundatin walls Unbtraced length

For cantilever walls, either shear or bending becomes an issue well before any kind of buckling comes into play.

RE: Concrete Foundatin walls Unbtraced length

Or they could just install the floor diaphragm before backfilling the next time. Maybe now they've learned their lesson, and hopefully understand why engineers put notes like "do not backfill until floor structure including sheathing/decking is completely installed".

RE: Concrete Foundatin walls Unbtraced length

If this was designed as a basement or non - yielding wall then the steel is in the wrong face to be a cantilever or yielding wall. 10" is more than sufficient for either wall type for a 10 foot height.

Mike McCann, PE, SE (WA)


RE: Concrete Foundatin walls Unbtraced length

If the owner is willing to accept a cracked, bowed wall (but why would he?), the other option would be to install helical anchors. They would not take the bow out of the wall, but would prevent it from moving further.

DaveAtkins

RE: Concrete Foundatin walls Unbtraced length

Is this a basement wall for a future floor or a simple retaining wall? I agree with Mike.

RE: Concrete Foundatin walls Unbtraced length

(OP)
vertical steel is #5 bars at 72". one # 5 bar horizontal at top of wall. i know cmu walls require pilasters to break up their length. Did not think concrete walls did but thought I'd throw but the question. Thaks for the responses.

RE: Concrete Foundatin walls Unbtraced length

The steel sounds severly undersized for a wall of this size.

#5 @ 72" are much less than minimum steel. In fact I think about 3 times less than required. same for the horizontal steel.

RE: Concrete Foundatin walls Unbtraced length

The maximum spacing under ACI for the vertical steel is 18". This wall was either not designed by an engineer or designed by someone who did not know what they were doing. It needs to be torn down.

Mike McCann, PE, SE (WA)


RE: Concrete Foundatin walls Unbtraced length

It may have worked as unreinforced concrete if the floor system had been installed prior to backfilling.

DaveAtkins

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