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RE: grade of reinforcing steel in the 20's

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This is a follow-up on Paul's reply (with some historical 
background).

In a PCA article a few years ago, Gustav Erlemann summarized 
"Reinforcing Bar Specifications--1911 through 1968."  He wrote "The 
first Standard Specification for Billet Steel Concrete Reinforcement 
Bars was adopted by ASTM in 1911, revised in 1914, designated A 15.  
The A 15 specification had three classes of bars: plain, deformed, 
and cold-twisted.  The plain and deformed bars were specified in 
three grades: structural, intermediate, and hard.  Cold-twisted bars 
conformed to structural grade only."  He then provides the values 
Paul noted for yield and ultimate (for each grade).

I spoke with him a few minutes ago to clarify an apparent 
contradiction.  Cold-twisted bars conformed to structural grade 
(which would imply Fy = 33 ksi), but had a yield stress of 55 ksi.  

His clarification is as follows:
Square bars were cold twisted to improve bond and raise the yield 
strength (due to cold working).  If the bars were tested prior to 
twisting they had to conform to structural grade.  If they were 
tested after twisting the yield had to be at least 55 ksi.  In either 
case, the yield strength of 55 ksi would be achieved.  Due to cold 
working, the ultimate strength would be higher than the "55 to 70 
ksi" value for the untwisted bar, but the values were not reported.  
He also noted that the values obtained from present-day testing of 
these old bars is always very close to the specified values (for 
instance, usually 33 to 34 ksi for structural grade undeformed bars).

**************
> From:          "Paul Meyer" <PMeyer(--nospam--at)HASimons.com>
> Date:          Wed, 22 Sep 1999 12:08:55 -0700
>
> From the 1923 Carnegie Steel Company "Pocket Companion for 
> Engineers, Architects and Builders."
> 
> fs= unit tensile stress of steel (allowable)
> rod reinforcement 16,000 psi
> wire reinforcement 20,000 psi. 
> 
> Strength of materials:
> Concrete bars:  plain structural grade 55-70 ksi ultimate, 33 yield
> 		plain intermediate grade 70-85 ksi ultimate, 40 yield
> 		plain hard grade 80 ksi ultimate 50 yield
> same strengths for deformed bars.
> cold twisted bars have no listing for ultimate, but 55 ksi yield.
> > 
> > 
> > Does anyone know what the grade of reinforcing steel was in 
> > the 1920's.

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Michael Valley                                   E-mail: mtv(--nospam--at)skilling.com
Skilling Ward Magnusson Barkshire Inc.                  Tel:(206)292-1200
1301 Fifth Ave, #3200,  Seattle  WA 98101-2699          Fax:        -1201