aisc 9th edition vs. 13th edition

huangyhg

aisc 9th edition vs. 13th edition
my company uses 9th edition, allowable "stress" design and not 13th edition allowable "strength" design.  our work in the petro-chemical, offshore, and general industry usually means that time is more important than saving 10% steel weight.  we must order steel often before sizes can be finalized and schedules are always critical.  stress design is crutial to our work.  i would like aisc, or another organization, to produce an updated stress design.
aisc is still pretending that everyone uses and loves strength design.  using their own publications and magazines such as "modern steel construction, i believe that they have monopolized the conversation.  when a question regarding 9th edition is posed, aisc ignores that and says to use 13th ed.
i'd like to know where the typical engineer stands on this matter.  what book does your company use?  did you move to 13th edition because you felt you have to because of codes?  
and please, don't try to argue that 13th is just as fast.  that argument is settled.
comments?
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we started using the 13th edition about a year and a half ago.  i only graduated in 2006 and i was actually taught steel design using the green book.  talk about being out of touch.  i definitely agree that it's easier to think in terms of stresses and not moments.  i also think it's easier to recognize, rather quickly, the efficiency of the section when dealing with allowable stresses as opposed to allowable moments.  if your allowable stress is 33ksi on an a992 beam, then it's efficient regardless of the section.  if the allowable moment is 300k-ft, that doesn't tell me very much.  is that 300k-ft with an s of 300in3, such that the allowable "stress" is only 12ksi or an s of 109 with an allowable "stress" of 33ksi?  
that being said, it is based on the latest research.  why should we not be designing with the latest information?
before the 2006 ibc came out i probably saw 90% of the projects that passed through my office were asd 9th.  now, it's probably down to 50%.... still surprisingly high considering that it's not even legally allowed anymore.  
the 13th edition is definitely not as fast as the 9th edition. however, i would say that (other than the new analysis requirements) it is probably the easiest to use strength based code that aisc has released.
no longer do we have to rely on lamda_c or lamda_o or some greek letters that i've never been able to read or pronounce.  we're back to use b/tf, h/tw, kl/r, et cetera.... that alone is a real breath of fresh air for me.     

seit and joshplum,
thanks for your input.  my understanding for strength design is that, besides being the latest, it usually results in lighter structures thereby making it more competitive with concrete.  savings could be up to 10% per beam and less than that on an overall project.
however, a quick stress design benefits my clients more.  additional steel weight is outweighed by getting oil wells online earlier.  at 100,000 barrels per day for an offshore platform at $50 per barrel (conservatively), our clients would be happy to save one week.
i think there is room for a dual system, stress design and strength design.
incidently, 9th ed is legal if clients agree.

i have worked in oil and gas companies for many years after i graduated and we have always used the green book never lrfd
i still don't understand the complaints between "stress" and "strength."  if it's easier to do stress, then do stress.  we're just talking about m/s and p/a here.
i was taught the 3rd ed. lrfd in school, but once i got into industry they quickly taught me the 9th ed. asd way.  9th ed. asd is much quicker for design (imho), but i find the 13th ed. does a better job of explaining the concepts.  
the allowable stress is still in the 13th ed. formulas, it just takes some algebra to take the strength and relate it to stress on the section modulus or area.  
it probably seems odd to rewrite these equations into stress, but i have a difficult time getting a "feel" for strength design.
joel berg
i've been a licensed practicing structural engineer for 19 years, and i use the 9th edition.
i agree 100% with being forced to use 13th.  i do not like the idea, at all, of taking all of my years of experience in stress, and now trying to redevelope a feel for structures based upon moments and strengths.  i believe that it reduces the public's safety in that the "feel" factor is removed.
good engineers are made as much by art as science.  i hear engineers backing the 13th addition from time to time, and almost every time, is by someone from aisc, or in academia, or who doesnt own the engineering business.
i understand both approaches (lrfd and asd).  i can use both.  having done so, asd is by far my preferred method.
and think about existing structures.  structures with low allowable stresses and shapes that havent been made in years.  you absolutely have to have a feel for the stresses to work with these structures.
i think there's a place for both methods and both should be supported.
right now we are using what ever code is required by the building code.  some of the jurisdictions i do work in still allow the 89 specification.  we are still in the process of verifying computer programs to make sure they apply the 05 spec correctly... and are finding problems which have yet to be resolved.
in college i was taught strength design, when i went to work i was taught allowable stress design.  when i went to grad school i had to learn strength design again.  back to work and back to asd.  then 3 years later aisc came out with the combined spec... now i have to learn a version of strength design again.
at this point it doesn't really bother me.  i find the 2005 spec does a better job of explaining issues that were left out of the 1989 spec.
most of the older people i work with basically don't want to learn the new spec and rely on me to make the necessary adjustments to their calcs.

i am a firm owner.
i have about 29 years in the business as a structural engineer.
i learned in school based on asd.
i learned lrfd on my own in the early 1990's.
i've used asd and lrfd both.
i don't see a significant difference in the resulting sizes unless live load is higher or lower than "typical".
lrfd, or strength design concepts in asd, are not that difficult to learn and use.
i have a feel for structural behavior whether it is with stress or strength - it really doesn't matter to me.
and finally - i've seen over the years many...many structural engineers resistant to change.  once i worked with an older engineer who was using aci concrete methods from the late 1950's in 1985.  never bothered to learn strength design in concrete.  i swore i'd never let myself get that archaic.
so many of us loose an edge in learning as engineers.  we get used to, and comfortable with, certain ways of designing and calculating and after a few years in the business find ourselves sometimes overwhelmed and perhaps even scared of all the new knowledge and technology that comes flying at us from new codes and standards.  i can certainly empathise with this.  but my view is that we engineers must always keep learning and growing in our field or we become dinosaurs.

jae,
i like what you have to say.  i fully agree about learning more and keeping up with the latest developments.  i wish that engineers would not be forced to get pdh's because they should want to advance themselves, but that's another matter.
i acknowledge that lrfd (and allowable strength design) is more realistic and accurate, though i find myself somewhat gratified that you find little difference in design.  maybe i'm wrong, but i think that the difference from stress to strength design in steel is not as dramatic as concrete design may have been.
i guess my gripe is that strength design offers little difference in steel cost, but makes our engineering costs less competitive so we have to use 9th edition just like all of our competitors in offshore work.  the 9th edition is very effective but has been abandoned.