fracture critical steel

huangyhg

fracture critical steel
once a member is identified to be fracture critical does it require a different steel material, if so what material is require?
you don't indicate your industry, but here is a guess.
bridges:
"fracture critical" is a term used mostly in bridges, and although the definition is a bit fuzzy, i think the most common understanding is that a fracture critical member is a tension member which, if it failed, would cause collapse due to lack of redundancy.
the material used would be only one factor in designing this type   
from the bridge design code in canada (s6-06)
fracture-critical members — members or portions of members, including attachments, in a single
load path structure that are subject to tensile stress and the failure of which can lead to collapse of the
structure.
and
10.4.2 structural steel
structural steel shall conform to csa g40.21. the modulus of elasticity of structural steel, es , shall be taken
as 200 000 mpa and the shear modulus of elasticity of structural steel, gs, shall be taken as 77 000 mpa.
weathering steel members shall be of type a atmospheric corrosion-resistant steel as specified in
csa g40.21.
fracture critical is also used in buildings, and aerospace industry.
for bridges, you still use astm a 709, but you order it to the fracture-critical level of toughness.
hg