Need a book? Engineering books recommendations...

Return to index: [Subject] [Thread] [Date] [Author]

RE: S-O-G C.J. with STRIP FOOTING

[Subject Prev][Subject Next][Thread Prev][Thread Next]
> Hi, All:

Greetings, Jerome.  Hope all is well in the islands.

> Our office engineers have designed the slab-on-grade to be
> part of the strip footing of several one-storey structures on
> one of our projects.

Very common detail.

> The slab is 125mm thk and the strip footing is 600mm wide x
> 850 mm deep. The outside adjacent ground is 250mm below the
> top of the strip footing. The slab is reinforced with WWF and
> dowels were provided to attach it to the strip footing.
>
> A thinning thickened slab with slope of 1:4 extends from the
> inner face of the strip footing up to the slab soffit 400mm long.

Sounds quite reasonable, to me.

> Questions:
>
> 1. Will providing a constuction joint at the interface of the
> slab and the strip footing negate the design assumption of
> continuity between the two elements? The CJ will be a
> straight vertical joint, wetted and epoxied before the next
> pouring will be done.

I should think that will be fine, so long as you look at the reinforcement
across the interface.

> 2. If answer to Question No. 1 is yes, then on the
> construction side, is it possible to prepare (compact) the
> subgrade (with its lean concrete and vapor barrier), dig to
> the shape of the strip footing and thickened edge of the
> slab, prepare the reinforcements and then cast the concrete?

This is commonly done in the states, and I think that the dimensions you
mention would allow this (though the 850 mm depth might give me cause for
concern re spalling of the wall of the excavation to the outside of the
building).

> 3. With No. 2, will this also mean preparing all the adjacent
> utilities?

Not sure what you mean by this.

> To be honest, I would like to separate the slab and the strip
> footing. From practice, I would clear and grub the site, dig,
> prepare the strip and reinforcements, cast the concrete,
> compact the area between the building strip footings, prepare
> the beddings, reinforcements, cast the concrete and proceed
> from there. This simplifies the analysis a lot and easy to
> implement at the field.

Personally, I think you're worrying too much about the "simplified
analysis." This is not a particularly difficult situation to analyze,
technically.

> I have never done No. 2 question procedure but this appears
> to be a common practice in Military projects but for a much
> thinner thickened edge slab.

As I mentioned, that would be my only concern as well.