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Re: Square Reinforcing Bars

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I have always seen 1/4" bars, deformed in San Francisco. About 15 cases. Smooth
has always shown up as a round bar or wire.

John MacLean wrote:

> I'm reviewing an old paper machine frame. The existing design drawings show
> 1 1/4" square reinforcing bars for top steel in some of the beams. The steel
> strength is listed as fs = 20,000 psi.
>
> Does anyone know anything about square reinforcing bars. Were they always
> plain bars or were they deformed? Our old ACI code (1963) says to use 1/2
> the allowable bond stress for deformed bars when designing for plain bars.
> That seems generous. I notice that the later codes ruled out using plain
> bars altogether or required hooked ends. Any thoughts on what I should allow
> for development length or bond stress for these bars?
>
> The drawings list an allowable "fs" = 20,000 psi. What sort of yield
> strength would that be equivalent to?
>
> I've also heard of twisted square bars. Was that common for the larger bar
> sizes? Did it have any effect on development length or allowable bond
> stress?
>
> One interesting thing I've found in an old copy of the CRSI Handbook (1962)
> was a comparison of "old" and "new" bars. The "old" bars larger in area than
> a #8 bar were all square. The equivalent of a #11 bar was a 1 1/4 inch
> square bar. That appears to be why a "new" #11 bar is 1.410" in diameter
> rather than 1.375". The 1.410" diameter gives a cross sectional area
> equivalent to a 1 1/4 inch square bar.
>
> Any assistance would be appreciated.
>
> John MacLean
> Vancouver, B.C.
>
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