From: Charles Greenlaw <cgreenlaw(--nospam--at)speedlink.com>
Date: Wed, 26 Apr 2000 16:22:28 -0700
I use ASD because my steel design work is a minor, incidental, accessory
part of my work. ASD is simple enough to pull out of my head when needed,
and does not suffer from a low position on a re-learning curve. On the same
basis of expediency and sufficiency, I take the standard deduction on my
income taxes. But I don't resent those who prefer the available "long form"
Having said that, I have to demur from the particular reasons Rick Drake
gave for embracing 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
This is like saying British and Japanese automotive engineers cannot
use research developed elsewhere in the automotive world because at home
they drive on a different side of the road. ASD always was based on testing
to failure; the results were rendered into ASD idioms afterwards for user
convenience. Nothing prevents int'l research from being "translated"
similarly. I have designed structures in Baltic Birch plywood, whose
Scandinavian structural design parameters are inside-out from the way APA
does it for Douglas Fir plywood. No problem, really. APA hopefully will
carry on as before, under no stigma to go foreign.
>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.
This is no more than a circular argument. Here, the egg is chasing
the chicken. The code basis is as arbitrary as is the steel design choice.
Either could just as well be the other way around.
>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.
Just because a headache is easier to abide than an upset stomach
does not make it a delight, or even a good thing. Many engineers were taught
the concept of benefit-to-cost ratio, but code-designing engineers seem to
have ignored it. Those who design new codes for the rest of us to stumble
over, only to succeed in coping as the next wholesale revision makes the
achievement useless, are like architects of earlier generations who, for the
sake of change, made handrails too big to grasp, and made stair treads and
risers vary diversely in the same stairway. Code stopped that. There needs
to be a code on codewriting, to save us from equivalent hazards.
Charles O. Greenlaw, SE Sacramento CA