One approach I've used in the past for triangular gussets is to treat strips of the gusset as columns and calculate allowable compressive strength of each strip. Then sum total allowable load or moment of the gusset. Don't know how that compares to the referenced document.
Does this hold true for a gusset welded accross the top to the bottom flange of a steel beam. I have a K brace condition where two braces come into the gusset (compression and tension. Is the free edge of the gusset between the brace points considered slender? How is the free edge stiffened without having to increase the plate thickness?
I assume that you are talking about a chevron (inverted V) not a K brace.
I have used 2 approaches for stiffening the free edge:
Add a stiffening angle on the lower edge of the gusset
or
Use a single vertical stiffeners from the top flange of the beam down to the bottom of the gusset to cut the length of the free edge in half.
Steve, look on page 14 of the PDF file. The first two images in Figure 2.7 show the edge stiffener. You add this stiffener, which reduces your free edge buckling length. For these cases, the length to check for would be from the end of the stiffener to the corner of the gusset. If your plate still doesn't check out, you might be looking at a thicker plate.
Note that the edge stiffener can't continue across your hinge line, if you're detailing for seismic.
The AISC seismic design manual has some information on this as well.
