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Re: ACI 318-02 reinforcing steel questions

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--- "Michael L. Hemstad" <hemstad.ml(--nospam--at)tkda.com> wrote:
> Cliff,
> The requirement for slab reinforcing spacing applies
> everywhere.  By
> code, you can't have bars at 36 inches.  More to the
> point, why would
> you want to?

DESIGN-BUILD.

How much money will you save your
> client?  Enough to
> convince them not to extract 100 times that much
> through the services of
> the legal profession when it cracks?  

Many developers "flip" their projects as soon as their
finished. They don't care.

> Inadvertently narrow code language ("beams...")
> aside, I would stick
> with the 6 inch extension into the supports for
> slabs (after all, just a
> wide beam).  The point of that rule is that there is
> a stress riser at
> the discontinuity caused by a bar ending.  It's a
> likely place for a
> tension crack, which then propogates (since your
> bars are 36 inches
> apart) and becomes a shear problem.

GOOD POINT.

  The 6 inch
> embedment helps keep
> these cracks from starting, helps keep them tight
> when they do, and
> provides some help for the shear strength by way of
> dowel action (shear
> in the actual bar where it crosses a crack).

WHAT ABOUT WHEN WE HAVE A CONTINUOUS SPAN AND BOTTOM
OF SLAB AT THE END OF THE SPAN IS IN COMPRESSION?
THERE'S NO TENSION TO WORRY ABOUT. THERE ARE
CONTINUOUS TOP BARS OVER THE SUPPORT.


> embedment does all
> this for virtually no cost, since you've already
> paid for the bar to be
> designed, fabricated, shipped, placed, inspected,
> and entombed in
> concrete.  Pretty good bargain, all the way around.


"VIRTUALLY NO COST" IS NOT THE SAME AS "NO COST".


> And yeah, it does sound like you're splitting hairs,
> a little.  These
> rules might be the cheapest insurance you'll ever
> get.  They're safe,
> well-reasoned, and cheap.  And nobody's going to sue
> you for doing
> them--only for not.

CHEAP INSURANCE IS STILL COSTING THE OWNER MONEY. HIS
QUESTION WILL BE "DOESN'T FOLLOWING THE BUILDING CODE
GIVE ME ALL THE INSURANCE I NEED? I DON'T WANT ANY
EXTRA "CHEAP INSURANCE" - YOU'RE FIRED."

THANKS FOR YOU INPUT. I AGREE MOST OF WHAT YOU SAID. 

CLIFF SCHWINGER


	
		
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