a572 to a992

huangyhg

a572 to a992
can anyone tell me why the switch was made from a572 steel to a992 steel for typical structural steel?  i know that a572 is still available, but a992 is what we spec and i believe the most prevalent.
does it have anything to do with ductility problems associated with the northridge earthquake in california in 1994?
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yep, has to do with the ductility stuff.
there had been a special version of a 572 gr. 50 for a while ("astm a 572 grade 50 with special requirements
per aisc technical bulletin #3, dated march 1997"), giving an upper limit on the yield point.  as far as i know, the main reason for this is structural design along the "strong column weak beam" philosophy--it's hard to ensure that your column outlasts your beam if you can't control the overstrength in your beam.  my understanding was that the original intent was seismic applications.
here's an article about it:
a992 steel guarantees a maximum ratio of fy to fu of 0.85, to ensure that the material is ductile.  with a572, fy could theoretically go all the way up to fu, which wouldn't give you any elongation between yield and fracture.