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Re: Old Concrete Design

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 Only Rail or Hard Grade shall be used for column verticals.

     All other reinforcing may be intermediate grade steel.

What is the yield strength of rail, hard and intermediate steel?

According to the ACI 318-51, Billet Steel corresponded to ASTM A15, Rail Steel corresponded to ASTM A16 and Axle Steel corresponded to ASTM A160 and Deformations corresponded to ASTM A305.

The allowable stresses in tension were:

fs = 20000 psi for Rail Steel, Billet Steel and Axle Steel of intermediate and hard grades.

fs = 18000 psi for Billet Steel and Axle Steel of structural grades.
 

The allowable stresses in compression were:

40% of the minimum yield as specified by the ASTM, but not to exceed 30,000 psi

Minimum yields per CRSI's publication "Evaluation of Reinforcing Steel Sysytems in Old Reinforced Concrete Structures were:

structural grade         33,000 psi

intermediate grade    40,000 psi

hard grade                50,000 psi

square twisted          55,000 psi

why don't we use bent bars like in the olden days?

The cost of fabrication of trussed bars today is too expensive. They really haven't been used for many years. I believe the changeover came around the late 60's.
 

Jim Kestner, P.E.
Green Bay, Wi.