×
INTELLIGENT WORK FORUMS
FOR ENGINEERING PROFESSIONALS

Log In

Come Join Us!

Are you an
Engineering professional?
Join Eng-Tips Forums!
  • Talk With Other Members
  • Be Notified Of Responses
    To Your Posts
  • Keyword Search
  • One-Click Access To Your
    Favorite Forums
  • Automated Signatures
    On Your Posts
  • Best Of All, It's Free!
  • Students Click Here

*Eng-Tips's functionality depends on members receiving e-mail. By joining you are opting in to receive e-mail.

Posting Guidelines

Promoting, selling, recruiting, coursework and thesis posting is forbidden.

Students Click Here

Jobs

Old Reinforcing Material
4

Old Reinforcing Material

Old Reinforcing Material

(OP)
I have some old drawings that I am analyzing the existing 2- way flat slab for an occupancy load increase. The drawings are over 40 years old and list the following:

Vertical Reinforcing in Columns (intermediate grade)..fs=16,000psi
Welded Wire Mesh....fs=24,000 psi
All other Steel (intermediate grade)...fs=20,000 psi
All concrete to have a compressive strength of f'c=3,000 psi

I think the reinforcing is being given as the allowable design stresses using a factor of 0.4. In other words, the "all other steel" actually has fy=20/0.4=50 ksi reinforcing steel material, and the column steel is 16/0.4=40ksi material.

Is this correct for 40 year ago ACI practice?
 

RE: Old Reinforcing Material

If it helps- In App. A of the 1989 ACI-318, they give allowable tensile stress as 20,000 for Grade 40 OR Grade 50.  Columns were required to be designed per the strength design method, with allowable stress as 40% of the result using that method.  The commentary states that this was a change from the 1963 and previous codes.

RE: Old Reinforcing Material

I don't think you can assume anything better than grade 40 rebar without doind some testing

RE: Old Reinforcing Material

Here is another paper (the first page anyway).  Notice at the bottom right hand corner of the page, the allowable stresses are called out as 16 ksi for compression bars (what your column bars are called out as), and 20 ksi for tension bars (presumably your "other" bars).  Both of these are for 40 ksi steel.

RE: Old Reinforcing Material

I am not sure why they listed fs on the drawings rather than fy, but in the late 60's "intermediate grade" meant 40 ksi, and was gradually being replaced by 60 ksi as the most prevalent grade for everything but ligatures.  So I don't think there was any 50 ksi reinforcing steel available, and your bars are most likely 40 ksi, but depending on the date and location, it is possible that 60 ksi was substituted.

For WSD, the 1983 Code restricted reinforcement in spiral columns to .4fy, and tied columns to .85 x .4fy.

Red Flag This Post

Please let us know here why this post is inappropriate. Reasons such as off-topic, duplicates, flames, illegal, vulgar, or students posting their homework.

Red Flag Submitted

Thank you for helping keep Eng-Tips Forums free from inappropriate posts.
The Eng-Tips staff will check this out and take appropriate action.

Reply To This Thread

Posting in the Eng-Tips forums is a member-only feature.

Click Here to join Eng-Tips and talk with other members!


Resources