Historical Structural Steel Grades - ASTM A7 Riveted Steel vs Structural Steel

[Everynameistaken]

Hello,

I am working on an assessment of an old structure and elevated water tank, it looks like it was designed in the late 1920's and built in 1930's (before 1931). The fabrication of the structure appear to have been by Horton Steel in Ontario Canada.

I am looking to try and determine the historical steel strengths for the materials used in this structure as we start to develop some initial structural checks and determine what/if and the extent of any further material testing is required. There is no reference to steel strength in the drawings that I can see.

When I look at several sources for reference historical information I get some slightly different materials strengths.

In Canada CSA S6 (bridge code) has some typical values, referenced conservative numbers, and then there are quite a few American references AISC ASCE 41 etc.

When I review and compare these references I get:

CSA S6
Fy = 210 MPa (30 ksi)

From AISC Ch 15
ASTM A7/A9 Struct Steel Fy>30 ksi, Fu= 55/65
Rivet Steel Fy>25 ksi, Fu= 46/56

From ASCE 41
ASTM A7/A9 Struct Steel Fy>30 ksi, Fu= 55
Rivet Steel Fy>30 ksi, Fu= 50

My key question is:

How is the different types of steel per ASTM A7/A9 defined? What is the difference between structural steel and riveted steel? If there are any rivets in the structure at all is it considered riveted steel? If we have very large structural steel member that have a few braces and end connections that use rivets is that structural steel or riveted steel?

I know the Fy different between 25 ksi and 30 ksi is seems small, but its 17% which is significant!

Thanks,

 

[Lomarandil]

Rivet steel refers to the material of the rivets themselves.

A7 was the bridge specification, and A9 was the building specification. My understanding is that the two materials were very similar.

It's possible (but unlikely in the 1920s) that unspecified structural steel did not meet the requirements of A7/A9. It's a good starting point, but as you noted, be aware that should your structure have specific requirements for ductility, for fracture resistance, for metallurgy and weldability, etc., you may require additional testing.

 

[dik]

A caution with old rivetted steel... it may have lots of sulphur and may not be weldable.

-----*****-----
So strange to see the singularity approaching while the entire planet is rapidly turning into a hellscape. -John Coates

-Dik

 

[Lomarandil]

Yes, other alloys were silicon heavy and differently difficult to weld.