Detention Vault Walls

[msquared48]

Outside of the allowances of the ACI code, does anyone have any particular structural concerns with using only one layer of reinforcing in a 10" thick wall holding back earth and water for an underground R/C detention vault?

I normally use two layers, one at each face(2/3, 1/3 distribution), but the owner wants only one layer in the center, and, although other local structural engineers do that, it still bothers me.

Mike McCann
MMC Engineering

 

[JedClampett]

This isn't a deal breakerr, but if you have waterstop, it's nice to have reinforcing on both sides of it. It allows it to be tied off in two directions.

 

[TXStructural]

I don't think there is a problem, but I hope y'all design for full and empty conditions, and for variation in outside soil conditions. (You mention something about 1/3-2/3 distribution, which seems generic, so it would appear that you are using minimum reinforcement ratios.) I'm sure you are following ACI 350, and I don't have a copy of that handy. 318 doesn't address this situation.

One thing to ponder is that the deeper reinforcement is in a slab (or wall), the wider cracks at the surface will be. I would think that a single, centrally-located layer would be structurally inefficient, but at minimum steel, that might not matter, aside from doing a poor job of restraining crack width.

 

[hokie66]

What TX said.

 

[UcfSE]

Seems like with that much clear cover you could have some excessive crack widths.

 

[msquared48]

And what I thought...

I guess it's what the client can tolerate. Thanks for the opinions guys. Good to know I'm not off base here.

Mike McCann
MMC Engineering