Steel Grade Used in 1987 Metal Building

[H57]

I am checking a building frame used in a metal building constructed in 1987. Can anyone provide any guidance as to the type of steel commonly used in metal buildings at this time? (A36, A572 Gr. 50, A992?) This is in regards to the main building frames that are using tapered sections.

 

[MikeE55]

Almost certain to be Grade 50 for a metal building tapered frame in this time period.

 

[connectegr]

I would think A36. Most wide flange beams, column, angles, and plate were A36 unless specified to be Gr.50. But, Gr.50 or dual cert was more expensive. I don't know why it would be needed for single story metal building. Sometimes we saw columns A572-50 and all other material A36.

Grade 50 material became more prevalent for wide flange shapes with A992, because they quit making A36.

http://www.FerrellEngineering.com

 

[JoshPlumSE]

My guess is that it is dual cert. Meaning that the engineer specified A36, but that for the wide flange beams it was cheaper to provide the dual cert 50 ksi material.

I'm not sure at what point dual cert became more economical. Can anyone shed some light on this?

All I know is that when the Northridge earthquake hit (1997) that's one of the things everyone started realizing.... All the structures that they thought were built with A36 were actually built with a higher strength (but less ductile) steel.

 

[MiketheEngineer]

Its a toss-up as you have probably surmised by now. Can you get a small piece and test it??

 

[H57]

When I go through the review of one of the frames the stresses come out right where they need to be for A36 without much additional capacity.

If the responses indicated that it was clearly grade 50 steel then I would adjust my report accordingly, but I'm really just verifying the original design capacity.

Based on previous metal building experience there usually isn't a lot of extra capacity in the building, so I'll proceed using the A36 and state the assumption in the report.

 

[weab]

Almost certainly, I'd say A36. I agree with connectegr. All that was used then was A36 unless you particularly needed more strength which is unlikely in a one story building. A992 and dual certs didn't take over until mid-late 1990's. Given no info, you must assume A36.

I'd guess that it was made from A36 with a yield around 42-45 ksi in reality. If you need additional strength, take a coupon and test. I'm certain that you have about 20% extra or more.

 

[BAretired]

According to both the 1981 and 1989 editions of CISC Handbook of Steel Construction, the Canadian standard was G40.21-M300 for rolled shapes and G40.21-M350 for HSS. These had a minimum yield strength of 300MPa (43,500psi) and 350MPa (50,700psi) respectively.

For steel plates in that time period, as I recall, it was not uncommon to find unidentified material which was routinely taken to be A36.

BA

 

[JoshPlumSE]

I did a bit of research on this and JSDPE is right. Dual Cert didn't make an appearance until the early 90's. And, probably didn't take over until completely for a few years.

 

[Ron]

Most PEMB manufacturers use A570 plate, A1011 plate, or A572 for their tapered main frames, all with yields of 50ksi or higher. Secondary structural members are usually A36.

A1011 was not a standard in 1987, so it would have been A570 or A572 for the tapered main frames.