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Interpreting steel strength from old plans
8

Interpreting steel strength from old plans

Interpreting steel strength from old plans

(OP)
I'm trying to do a load rating for a bridge in South Carolina (built in the 60's). The plans say that both the structural steel and the rebar has "fs = 20,000 psi". Obviously, those are working stresses.
It further states that the structural steel is A-36, but doesn't give any mention of ASTM or similar for the rebar. So my question is... what should I say is fy for the reinforcement? Also 36 ksi since both have fs = 20000 psi? 36 seems weird to me for rebar. I would have expected 40, 50, or 60 ksi. 40 then?

Any help is greatly appreciated!
-Joel Darr

RE: Interpreting steel strength from old plans

2
Rebar grades 40, 60, and 75 were not accepted as standards until the late 1960s. Very possible that grade 36 rebar was used before the late 1960s.

www.SlideRuleEra.net idea

RE: Interpreting steel strength from old plans

2
Appendix A of ACI-318-89 for allowable stress design shows 20,000 psi for either Grade 40 or Grade 50, if that helps.
A reference book from the 1940's shows allowable stress at either 18,000 or 20,000 psi, but doesn't show the corresponding yields.
The 1968 Structural Engineering Handbook shows A615 at Grade 40 and Grade 60, A616 at Grade 50 and some higher value. It states 24,000 psi for Grade 60 and above, 20,000 psi for anything lower, but doesn't list anything below Grade 40. It references ACI-318-63.

RE: Interpreting steel strength from old plans

(OP)
SlideRuleEra and JStephen - y'all rock. Thanks for the advice.

RE: Interpreting steel strength from old plans

3
The AASHTO Condition Evaluation manual that is used for load ratings has tables if you are not sure what grades to use. I’m a bridge guy in the Northeast. Anything in the 1960’s is likely 40 ksi rebar and A36 or A441 steel.

I’ve had samples tested and only run into 30-33 ksi rebar if the bridge is from 1900-1930’s.

Find that table in the AASHTO Manual. If you are load rating bridges you should have that manual.

RE: Interpreting steel strength from old plans

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