Christopher Wright P.E. wrote
"By far the more interesting question is why AISC (among others) decided
the go with LRFD."
This has been discussed on this list server many times. We are in an
international market. Most steel design in the rest of the world is done based
on strength design. By supporting a strength design approach, AISC can utilize
international research data. Recent AISC publications like the HSS Manual, as
well as the next LRFD specification and manual, contain advances in design
methods that would not have been practical if international research data was
Another reason for structural engineers to support LRFD design is that all U. S.
seismic codes are strength design based, including 1997 UBC, 1997 NEHRP
Provisions, 1999 BOCA, ASCE 7-98, and 2000 IBC.
I understand that we are all comfortable with the green ASD Manual. Mine was
heavily used and has been reinforced several times with tape. However, it is
now 11 years old. I've taught both ASD design and LRFD design at California
universities. They two methods really aren't that different. The adjustment
from ASD design to LRFD design was a lot easier than the adjustment (in
progress) from the 1994 UBC to the 1997 UBC.
Rick Drake, SE
Fluor Daniel, Aliso Viejo, CA