>>> "Thor Matteson" <thor@yosemite.net> 01/28/2009 11:22 PM >>>
Shear flow is defined as VQ/I, whether steel or any material. The definition for Q is the area of the section you are considering connecting (called "A") times the distance from the NA of the *entire* section to the centroid of the section you are connecting (this distance is called "y-bar"). y-bar is a constant for a given configuration. Just plain "y" is the variable used to denote distance from the NA of the overall section. The maximum value that y can have is "c", and this is where we get S=I/c
So shear flow is NOT equal to VA/S, nor would it equal VA/Z.
(This is much easier to explain with diagrams--look in your mechanics of materials book, probably around chapter 7... )
Apologies if this has already been answered--I'm in digest mode, so a day behind everyone, PLUS the digests do funny things with equal signs and such and I really can't make sense out of anyone else's equations.
Thor Matteson, SE