Young's Modulus for A992 Steel 2

[CorporalToe]

Why is E for A992 Steel 29000 ksi when AISC says the Fy = 50 ksi, and typically es = 0.002?

 

[JStephen]

I'm not sure I understand the question, but see if this helps answer it:

https://www.instron.com/en-us/resources/glossary/offset-yield-strength

 

[3DDave]

Also interesting:

https://www.aisc.org/globalassets/a...rties-database-for-design-and-reliability.pdf

ABSTRACT
This report summarizes the mechanical properties of ASTM A992 steel as detennined by
tests of 207 flat-strap tensile test specimens at the University of Minnesota and the
University of Western Ontario carried out in accordance with ASTM A370. 3mples
were obtained from 38 heats of steel from eight different shapes provided by three
producers. The objectives of the study were to quantify statistical parameters for the
mechanical properties of A992 steel and to investigate the necessity of updating the
resistance factor for steel in the AlSC LRFD Specification (AlSC, 1999).

 

[rb1957]

because E .NE. fy ... ??

now, if you mean that the yield strain = 50/29000 = 0.0017 (and not 0.002) ... well, let's call that round off.

"Hoffen wir mal, dass alles gut geht !"
General Paulus, Nov 1942, outside Stalingrad after the launch of Operation Uranus.

 

[271828]

Because the yield strain is not 0.00200000000.

 

[rb1957]

do you know what "round off" means ?

the value in the book is 0.002, not "0.00200000...". 0.002 is an acceptable round off of 0.0017.

"Hoffen wir mal, dass alles gut geht !"
General Paulus, Nov 1942, outside Stalingrad after the launch of Operation Uranus.

 

[271828]

Yes.

I assumed from the first post that the confusion is 50 ksi / 0.00200 does not equal 29000 ksi.

 

[3DDave]

0.002 is an arbitrary 0.2% elongation and the Fy is after the knee in the strain curve where that elongation is reached.

 

[met33]

Those numbers seem fine to me. Maybe some diagrams and example calculations will help.

There are different ways to determine yield strength and elastic modulus (see various ASTM standards).

Yield strength is commonly determined as the stress at which a 0.2% strain offset line intersects the stress-strain curve. I believe this is how it has been done by some for A992 (e.g., see the article mentioned above by 3DDave:
Bartlett et al. (2003), Updating standard shape material properties database for design and reliability. Engineering Journal, 40(1), 2-14.)

Young's modulus, E, can be calculated as the slope of the stress-strain curve in the linear region.

Below is a schematic diagram showing how to determine 0.2% offset yield strength and Young's Modulus, E:

And here is an annotated (by me) A992 stress-strain curve and corresponding example calculations (the stress-strain curves below are for A992 after various thermal treatments, I used the room temperature curve):

Figs. 9 and 21 above are from Lee, J., Engelhardt, M. D., & Taleff, E. M. (2012). Mechanical properties of ASTM A992 steel after fire. Engineering Journal, 49(1), 33-44. I added the red and blue annotations & calculations to Fig. 9.

 

[lexpatrie]

I could have sworn Dexter was the P.I. on that one.

3DDave's referenced article is here:
Bartlett, F. Michael; Dexter, Robert J.; Graeser, Mark D.; Jelinek, Jason J.; Schmidt, Bradley J.; Galambos, Theodore V. (2003). "Updating Standard Shape Material Properties Database for Design and Reliability," Engineering Journal, American Institute of Steel Construction, Vol. 40, pp. 2-14. (currently a free download as of 7/2/24, should one want a slightly shorter version of the research paper)

Met33's referenced article is here:
Lee, Jinwoo; Engelhardt, Michael D.; Taleff, Eric M. (2012). "Mechanical Properties of ASTM A992 Steel After Fire," Engineering Journal, American Institute of Steel Construction, Vol. 49, pp. 33-44. (currently a free download as of 7/2/24)

On the fire exposure side of things, Jinwoo references Tide which is a pretty cogent article:

Tide, Raymond H.R. (1998). "Integrity of Structural Steel After Exposure to Fire," Engineering Journal, American Institute of Steel Construction, Vol. 35, pp. 26-38. currently a free download as of 7/2/24)

Nobody asked, but I figured the links would be useful to at least one person sometime in the next forty years.

As a side note, that 0.2% offset is more typically associated with Aluminum and various alloys of Aluminum as they lack a distinct yield point. Steel has a distinct yield point, upper and lower, and I have no idea what the OP means when they mention es = 0.002. es isn't ey, anyway, much ado about a rather daffy question.

We are going to be "stuck" with E = 29,000 ksi for a good while. Unless something really odd happens technologically on the material science side of things. I would happily argue once we don't have "steel" with an E = 29,000 ksi, we aren't dealing with steel anymore.

 

[rb1957]

but the OP posted "Why is E for A992 Steel 29000 ksi when AISC says the Fy = 50 ksi, and typically es = 0.002?"

Yes, E for steel is anything from 29000 to 30000 ksi ... no question.

Fty for steel is all over the place depending on the "flavour" (the alloying) and the temper and manufacturing quality. You guys use 50ksi (we in aero would use 90 to 125 ksi, with many caveats).

strain for yield is .2%, by standard definition.

I don't understand what can be confusing, I think we need to OP to clarify. Was is just 50/29000 = 0.0017 .NE. 0.002 ??

time to put a lid on this teacup ...


"Hoffen wir mal, dass alles gut geht !"
General Paulus, Nov 1942, outside Stalingrad after the launch of Operation Uranus.

 

[CorporalToe]

Yes it was just 50/29000 = 0.0017 and not 0.002