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Steel Reinforcement Elongation Limit

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ASTM requires 11 to 12 percent (min.) for Grade 40 steel, and 7 to 9 percent 
for Grade 60 steel.

Since this is much beyond the cracking strain of concrete, the concrete will 
crack and go along for the ride.  (Take a piece of paper and cut one edge in 
parallel strips and glue a rubber band across the strips.  Pull the rubber 
band and see if the glue comes loose.)

At these strains, deflected shape becomes a part in determining the capacity 
of the structure with the structure behaving like a cable supported structure 
more than a flexural member.

We (at least *I* do) want our structures to look like a sway-backed mule 
before it collapses.  I do not want strains limited so that collapse comes 
suddenly and without warning.!

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

Jim Korff wrote:

>>The steel reinforcement "yield point" is at an elongation of .002  (0.2%)

Does ACI Code give a maximum permitted elongation for internal reinforcement
??

(For DIN it is 0.5% and for the Euro Standard it is 1.0% )

Are there any papers or research on this subject -maximum elongation to
avoid steel/concrete bond failure ??<<

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