single-plate shear connections aisc table 10-9a

huangyhg

single-plate shear connections aisc table 10-9a
what is the difference between table 10-9a in the 13th edition and table 10 (x) in the 9th.  it seems the 13th has over 2 times the allowable load.
i am evaluating a single plate shear connection for a simply supported beam at a column.  (2) 3/4" dia a325 bolts with a 3/8" plate.  
it appears the 9th edition is applying a c coefficient for eccentric loads on fastener groups and the 13th is controlled by the bolt shear.  why has the methodology changed and is this new table applicable to my situation?

without digging out my 89 manual...
shear tabs have been heavily researched in the last 19 years.  the underlying design methods are different nowadays.
at a recent seminar we were told that the single plate shear connection tables were revised to reflect new research and study and that, yes, their capacities have been increased.
read the pages before the tables in the 13th edition manual.  they explain the design procedure for shear tabs.  then go read the same pages in the 9th edition manual, and you'll see a lot of differences.  it's all right in the text.
for one, there is no longer eccentricity on the bolts, given the connection falls within certain parameters.
the increase in shear tab capacity is most dramatic for short connections, like the 2-bolt connection in the original post.
excellent answer, imo.  pretty much says it all.