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Re: Rebar Strengths

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Frank,

I think that I would be very careful about analyzing a structure using USD 
that was designed under WSD.  Besides none of the splices will check out, WSD 
required checking to see that the stress in *neither* the steel nor the 
concrete exceeded the allowable.

   fc = 2*M/(b*k*j*d^2) <= 0.45f'c, and,

   fs = M/(As*j*d) <= .6fy

Also, the moment capacity due steel should be less than the moment capacity 
due to compression in the concrete in order to avoid sudden, explosive 
failure resulting from an over-reinforced section.

   Ms = Fs*As*j*d < Mc = Fc/[2*(b*k*j*d^2)]

where Fs and Fc are the allowable stresses in the steel and concrete, 
respectively.

A. Roger Turk, P.E.(Structural)
Tucson, Arizona

Frank Hartzell wrote:

. > For your interest, we are currently looking at a structure built in the
. > early 40's with reinforcing specified as "structural grade". This implies
. > that the yield stress is 33 ksi.  Using this yield, some members are very
. > highly overstressed.  We have called for reinforcing tests and the one
. > result so far available shows a yield of 53 ksi.  Go figure!

. > Frank Hartzell
. > fhartzell(--nospam--at)comcast.net

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