1989 ASD Shear Eq. F4-2 Questions
1989 ASD Shear Eq. F4-2 Questions
(OP)
I am having trouble using this spec to check for shear issues for a pile load test reaction frame.
In my version of the spec, the definition of Cv is self-referential, to wit:
Cv = (45,000 * kv)/(Fy * (h/tw)^2) when Cv is less than 0.8
= (190/(h/tw))*(kv/Fy)^0.5 when Cv is more than 0.8
Additionally, kv is undefined when there are no stiffeners, to wit:
kv = 4.00 + 5.34/((a/h)^2) when a/h is less than 1.0
= 5.34 + 4.00/((a/h)^2) when a/h is more than 1.0
a = clear distance between transverse stiffeners, in.
h = clear distance between flanges at the section under investigation, in.
My questions are,
1) What are the corrected limiting conditions for the equations for Cv?
2) What is the procedure to follow when 'a' is undefined (i.e., no stiffeners)?
Thanks in advance for your responses.
Jeff
In my version of the spec, the definition of Cv is self-referential, to wit:
Cv = (45,000 * kv)/(Fy * (h/tw)^2) when Cv is less than 0.8
= (190/(h/tw))*(kv/Fy)^0.5 when Cv is more than 0.8
Additionally, kv is undefined when there are no stiffeners, to wit:
kv = 4.00 + 5.34/((a/h)^2) when a/h is less than 1.0
= 5.34 + 4.00/((a/h)^2) when a/h is more than 1.0
a = clear distance between transverse stiffeners, in.
h = clear distance between flanges at the section under investigation, in.
My questions are,
1) What are the corrected limiting conditions for the equations for Cv?
2) What is the procedure to follow when 'a' is undefined (i.e., no stiffeners)?
Thanks in advance for your responses.
Jeff





RE: 1989 ASD Shear Eq. F4-2 Questions
RE: 1989 ASD Shear Eq. F4-2 Questions
Thanks. This is a big help. Now, what about the self-reference in the Cv definition?
Jeff
RE: 1989 ASD Shear Eq. F4-2 Questions
(authoritatively spoken but with lots of ???? after it..heh)
RE: 1989 ASD Shear Eq. F4-2 Questions
I could see using one or the other based on h/tw (this is in fact what happens in the 2005 version), but I can only imagine that the self-reference is a typo. I was hoping that someone had an errata sheet that would cover this instance.
Jeff
RE: 1989 ASD Shear Eq. F4-2 Questions
I think that's one of the most doofus ways that Cv could've possibly been expressed. The top one is for elastic buckling and the bottom one for inelastic. Putting them in that order makes it double-doofus.
Can you just use the 05 Spec.? Chapter G is very logical and easy to read and apply. kv is easier too and the difference is comical. The underlying theory is the same. See Salmon & Johnson for a great derivation of all that stuff.
RE: 1989 ASD Shear Eq. F4-2 Questions
This should help remembering how to figure out which Cv to use.
Cv is the ratio of shear buckling stress to shear yield stress, presumably about 0.6Fy, IIRC, or maybe Fy/sqrt(3)--can't remember which was used.
0.8 is the presumed proportional limit which in this case is used to separate inelastic and elastic buckling.
Sooooo, by calculating the first one (elastic buckling), you're assuming that the buckling stress is < 0.8 * the shear yield stress. If it comes out > 0.8, then your assumption was wrong and you have inelastic buckling-->now use the other one.
I still say that's an uber-doofus way to formulate it, but it is what it is (about to be extinct Thank God).
RE: 1989 ASD Shear Eq. F4-2 Questions
I especially like the highly technical term, "doofus".
RE: 1989 ASD Shear Eq. F4-2 Questions
RE: 1989 ASD Shear Eq. F4-2 Questions
RE: 1989 ASD Shear Eq. F4-2 Questions
Thanks for the insightful commentary. "Doofus" is very polite.
I have pretty much decided to adopt the 2005 spec for reasons of improved clarity over the 9th and compatibility with AASHTO (we are a highway bridge contractor, among other things).
Cheers,
Jeff