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WWII Allowable Structural and Reinforcin

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Frank,

The oldest ACI Code that I have is the 1956 code (which is about as thick as 
any code should be allowed <G>).

I believe that structural grade reinforcing had a yield of 33,000 psi, and 
intermediate grade had a yield of 40,000 psi.

Section 702(e) states, "1. Whenever at any section positive reinforcement is 
indicated by analysis, the amount provided shall be not less than 0.005b'd 
except in slabs of uniform thickness. ...

2. In structural slabs of uniform thickness the minimum amount of 
reinforcement in the direction of the span shall be:
   For structural, intermediate and hard grades and rail steel: 0.0025bd"

However, Chapter 12, Footings, Section 1204(e) states,

"In two-way reinforced footings, the total tensile reinforcement at any 
section shall provide a moment of resistance at least 85 percent of the 
moment computed in the manner prescribed in 1204(a) ..."

HTH

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

Frank Hartzell wrote:

. > I'm pretty long in the tooth but didn't study structural engineering until
. > just after the war. I am aware that the allowable structural steel stress
. > was increased for structures built during the war but am not sure about
. > reinforcing steel. I seem to remember that the allowable increase for
. > structural shapes was about 25%.

. > I'm currently looking at modifying a building built in 1945 and am finding
. > that the footing reinforcing steel is rather severely overstressed. The
. > drawings call for deformed structural grade reinforcing steel which I
. > believe would be 40 ksi yield with an allowable tensile stress of 18 ksi
. > according to the codes of the period. I'm also assuming that the 
. > structural steel is the old A7, 33 ksi yield.

. > The drawings call for 13-3/8 bars each way in a 7 ft square footing which
. > results in a steel ratio of only 0.0015, lower I think than even codes at
. > that time permitted. It also seems rather odd to use No 3 bars in a 
. > footing but perhaps wartime shortages resulted in all sorts of unusual
. > choices. It's also possible that the draftsman used 3/8 when he meant to 
. > use 5/8.

. > I intend to call for field investigation but, in the meantime, I was
. > wondering if any old timers (or better informed engineers of any age) 
. > could enlighten me on the wartime design criteria.

. > Thanks for any help.


. > Frank Hartzell
. > Jacobs Engineering

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