reinforcement property 1940s

[bob96]

What material property for concrete reinforcement steel would have been used in the central U.S. in the mid-1940s?

I know the ACI36 states 20,000 psi but am wondering if there may be a possibility that 40,000 psi was used in the mid 1940s (World War II era).

Thanks

 

[crossframe]

The synopsis is that is appears to be unlikely that Grade 40 reinforcing steel was used in the 1940's, but it is possible.


I'm more familiar with AASHTO than ASTM, but this may help.

AASHTO's Manual for Condition Evaluation of Bridges lists the following yield stresses in Article 6.6.2.3:

Structural or unknown grade prior to 1954: 33,000 psi
Grade 40 billet, intermediate of unknown grade (after 1954): 40,000 psi
Grade 50 rail or hard: 50,000 psi
Grade 60: 60,000 psi


The following is a excerpt I have in my references from Ray Hackett of Caltrans. I have made minor edits, but these are largely Mr. Hackett's words (any typos are mine):

"The early AASHO (now AASHTO) materials specifications The early AASHO materials specifications did not contain a cross reference to ASTM specifications. Caltrans seems to have always referred to the ASTM specifications for reinforcing steel. Although the older AASHO specifications may have been worded differently from ASTM, it is reasonable to assume that they are based on the same material and that the yield strengths given in AASHO would be the same as that found in corresponding years of ASTM. To assume otherwise would mean that AASHO was calling for material different from that used by the rest of the construction industry.

The 1931 edition of the AASHO specifications listed AASHO M-31 which has been adopted in 1924 and which should correspond to the then current ASTM A-15. It gave two grades of reinforcement, structural (yield = 33,000 psi) and intermediate (yield = 40,000 psi).

In 1942, AASHO revised the M-31 specification to include a hard grade (yield = 50,000 psi) in addition to the other two grade found in the 1931 specification. M-42 was added in 1942 which appears to compare with ASTM A-16 (yield = 50,000 psi) which is rail steel for reinforcement. In 1952, the AASHO specifications were revised to directly correspond to the ASTM specifications. No change in yield was found until 1961 when the AASHO M-42 specification (which corresponds to ASTM A-16) for rail steel was broken down into a regular grade (yield = 50,000 psi) and a special grade (yield = 60,000 psi).

In 1964, AASHO added a specification, M-174, for large size bars (#14 and #18) which corresponds to ASTM A-408 which had the same grades and yields as for bars under AASHO M-31 or ASTM A-15, structural (yield = 33,000 psi), intermediate (yield = 40,000 psi) and hard (yield = 50,000 psi).

The Caltrans June 1925, July 1927, January 1929 and January 1930 Standard Specifications all referred to ASTM A-15 without listing any grade. For this period, we could assume the structural grade with a yield of 33,000 psi. The January 1935 Standard Specifications called for bars conforming to Intermediate Grade of ASTM A-15 which would be the 40,000 psi yield material.

The July 1940 and April 1945 Standard Specifications resorted back to the Structural Grade of ASTM A-15 which is the 33,000 psi yield material.

It is unclear when the switch was made from 33,000 psi to 40,000 psi, and when it was switched back to 33,000 psi. Unless there is some positive indication on the plans for structures constructed between 1930 and 1940, we should probably assume that structural grade had been used and base analyses on 33,000 psi yield. If a positive indication can be found during this period for the higher grade material, then the structure can be analyzed for 40,000 yield.

The January 1949 Standard Specifications allowed either structural or intermediate grade A-15 material or A-16 material. With these options, structural grade should be assumed using a yield of 33,000 psi.

The August 1954 Standard Specifications called for either intermediate or hard billet steel conforming to ASTM A-15 or the rail steel of A-16. A yield of 40,000 psi may now be used."