i can not figure out why,help please

huangyhg

i can not figure out why,help please.
i just got an aisc 13th edition manual. comparing table iii framed beam connection in aisc 9th (p4-26) and table 10-2 bolted dbl angle connection in 13th edition (p10-46). it gives such a big different result for the same connection. i can not figure out why. is there anybody can help me?
for example, for a 5.5" long angle, fy=50 ksi beam, 3/16 weld size, weld a (70 ksi):
9th edition's capacity is 37.1 kip, min. web thickness =0.28,
13th edition's capacity is 50.2 kip, min. web thickness =0.28,

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i don't have either edition, but it sounds like working strength design vs. limit states design.
ba
no, no, no.  i was trying to get in before something like this popped up.
the specification in the 9th edition manual doesn't take into account the increased strength of fillet welds when loaded on an angle relative to the weld axis.  the 13th edition specification does.  this increase first showed up in the 2nd edition lrfd specification, some 16 (!) years ago.  this illustrates my argument that we shouldn't fear the 13th edition and stubbornly hang on to the 9th because it's "easier," when we're really talking about familiarity.
nutte has it exactly right...
if you "heard" it on the internet, it's guilty until proven innocent. - dcs
thank you nutte. i am glad there are a lot of knowledgeable engineers here.
is any book or website list all update items for edition 13?  some other engineers in my office still use edition # 9. i would like to show them the difference.
actually i find web available strength in edition 13 is lower than edition 9th.  for example,  for w14x26 beam with 4 rows lev=1 ?" leh=1 ?, sta hole, coped at top flange only bolt connection, beam web available strength per inch thickness in 13th edition is 175 kip/in (aisc 13th edition p 10-21). the strength for 0.255 web thickness is 175x0.255=44.6 kip. while the strength is 50 kips if i use 9th edition to calculate the same connection. 10% less! that did surprise me. i wish i can see some book listed all difference and their reasons.