×
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

Grade of Steel

Grade of Steel

Grade of Steel

(OP)
I am evaluating an existing steel structure for current loads. I modeled the structure only to realize that the whole structure is failing, while in reality the structure is doing just fine. There is not explicit note on the drawings saying it is Fy=50 ksi structural steel and hence, I modeled it with 36ksi steel. Are there any tests out there that I can tell the owner to perform to confirm the grade of steel? Please let me know your thoughts on this subject.  

RE: Grade of Steel

Pick an ASTM standard, such as A572 and test to that standard.  It will require removing a coupon specimen from the structure, but that can be done without compromising the structure.

RE: Grade of Steel

And don't forget that real loads versus code loads are often quite different.  Code loads are based on at least a 50 year building life cycle.  In other words - the building MAY only see those loads once in fifty years..

RE: Grade of Steel

A lot of the 36 ksi materials will have 50 ksi yield strengths, so I don't know that you could tell for sure with cutting samples out.

RE: Grade of Steel

In addition to the higher strength that is likely there, and the probability of the lack of the building seeing the design loads (as noted by Mike), there are also other built-in "conservatisms" that we neglect - there is some end restraint at simple connections.  Even if it's only 5% at each end, that going to help the midspan moment.  Non-composite beams will often behave in a composite manner for non-ultimate loads due to deck welding and friction.  Even if it does see the full design service LL, there is still a F.S. of roughly 1.67.  Our stick models use length of beam as center to center of column when it's actually face to face of column (for beams not going to column web) - this can cut down on the length of the beam by a foot, typically.
I'm sure there are more that others will point out, but you get the picture.

RE: Grade of Steel

It would be unwise to assume that the steel is any better than A36.  A better evaluation, in my mind, would be to tell the owner that the structure is adequate to sustain gravity, wind and seismic loads of x, y and z psf respectively based on your calculations.  

Why should you assume responsibility for certifying material properties which you cannot confirm?  Unless, of course you enjoy the exhilaration of retaining lawyers, preparing statements of defense, giving evidence at examinations for discovery, appearing at court and finally, convincing the judge who hasn't the faintest idea of what you are talking about that you really were justified in assuming the steel had a yield of 50 ksi or more.

BA

RE: Grade of Steel

It might help to know how the useage has changed, and a better description of the structure.  We know it is steel, but that doesn't tell us much.

RE: Grade of Steel

Rolling mills often identify the shapes on the web as they are rolled, you might start there...

RE: Grade of Steel

And could it even be A7?
I might start by considering what was available and most widely used during the era of the date on the drawings.
It would seem that something out of the ordinary would have been so noted.   

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