ASTM A36 - Weathering Steel?

[snteng]

Does anybody know if a 36 ksi weathering steel has ever been produced?

We routinely load rate existing logging bridges that have no drawings or material specifications available. Our experience in new designs is that all weathering steel bridge girders in the last 25 years are invariably 50 ksi yield.

Would it be true that if weathering steel is observed in the field the yield strength would be 50 ksi as opposed to knocking down to 36 ksi for unidentified steel

 

[KootK]

The very first paragraph of this article would seem to imply that your assumption is correct: Link. I'm sure that you'll want to find something a little more bullet proof before proceeding however.

I like to debate structural engineering theory -- a lot. If I challenge you on something, know that I'm doing so because I respect your opinion enough to either change it or adopt it.

 

[SlideRuleEra]

US Steel COR-TEN weathering steel was developed in the 1930's, but not used for structural shapes until the early 1960's. I'm pretty sure that most structural shapes have been 50 ksi since being introduced. Some very thick shapes may have been as low as 42 ksi. Properties per ASTM A242 or ASTM A588.

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[Ron]

To my knowledge, A36 is not and has not been a "weathering steel". As SRE notes, A242 and A588 specifically mention corrosion resistance. A36 has no reference to corrosion resistance.

 

[JStephen]

In the older AWWA tank specifications, one of the user options was to specify if copper-bearing steel was to be used. I gather this was steel produced to normal specifications, A36/A7 or whatever, that had low copper content. And, the specifications don't say, but I understand this was done for increased corrosion resistance. (For tank applications, this would have always been coated, not used bare.)

The point being that all "weathering steel" might be 50 ksi, but trying to deduce if old bare rusty steel is actually "weathering steel" or not could have some potential pitfalls. Especially in dry parts of the country, you'll see old mining equipment that's been out there for a 100 years and looks just fine.

 

[dhengr]

Snteng:
Look up the ASTM A242 and A588 stds./specs. from that era, as suggested by SRE & Ron, they were the predominant weathering steel specs. used and materials supplied, both plate and rolled sections. There were varying Fy’s & Fu’s as a function of thickness, with Fy’s from 50-42ksi. I don’t think I’ve ever heard of any 36ksi weathering steel. I’ve also used steel with added copper as suggested by Jstephen, it had slightly improved corrosion properties over the steels without copper. But, it was intended to be painted, and supposedly held paint a little better, but if not painted did not weather like the real weathering steels. Are most of the framing systems and details the same on these bridges, or only a few variations, so that once you’ve looked at a few of them you have some confidence in the general design. Then, you are primarily checking span lengths vs. section properties, and otherwise looking for defects and significant abnormal deterioration. If you had any 36ksi steel in those main bridge members I’d think you would see some permanent set in the girders if they had been intended to be 46 or 50ksi. Although almost all A36 steel tested significantly better than 36ksi, and in fact some higher strength steels which didn’t meet their intended spec. would be sold as A36 when there were no other problems with doing this. You might want to take some samples, both for tensile tests and for chemistry, so you can pin down the actual material spec. for your file, and then save the remaining samples and pieces. Over the years, I’ve seen some samples of steel plates, showing color and surface texture over time.

 

[snteng]

Thanks for all the feed back.
I think I will tell them to take some samples and have them tested.