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RE: Any Young Engineers Out There?

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Scott,

        I was not suggesting that ASD steel design is going to be simpler than LRFD design in the new code, but I like being able to use service loads for deflection checks and code strength checks. This may be a marginal benefit, but I still think it is helpful. It would then be nice to take the worst case reactions into the footings and do all the design with those loads rather than check the bearing stresses and then start a new set of  load combinations for the concrete design. If there were service checks developed for LRFD, as Bill P seems to suggest AASHTO has done, and if LRFD soil bearing checks were more readily available, than I would likely be a proponent of LRFD.

     For what its worth, I have used the LRFD 3rd edition for some items that I felt weren't covered really well in the ASD manual. Also, I have used the HSS Connections manual which is LRFD. It just seems to me that the more times you have to covert between service load cases and LRFD load cases the more chances there is to make an error.

    Also, I don't know that every school in the country is teaching LRFD. When I took my steel design class in 2000 at Penn State Harrisburg, ASD was taught.

Wesley C. Werner, EIT




-----Original Message-----
From: Scott Maxwell [mailto:smaxwell(--nospam--at)engin.umich.edu]
Sent: Tuesday, January 24, 2006 6:30 PM
To: seaint(--nospam--at)seaint.org
Subject: RE: Any Young Engineers Out There?


Wesley,

While I agree that as it stands right now (pre-2005 AISC spec), ASD is in general much simpler to use than LRFD.  But, it is more than just the load factors, I believe.  There are additional failure mechanisms and "checks" that are currently in LRFD that have not (until the 2005 AISC spec) made it into ASD.

When the 2005 AISC combined spec comes into full use, I am not so sure that there will be such a huge "benefit" to using ASD over LRFD.  The differences on the capactiy side will go away.  Yes, it will still be simpler in ASD as you only need to "nominally" do one load calculation for both strength and sevicibility.  But, I suspect that many may start to see that as a rather minor "benefit" and I expect that you will seem more of a transition to LRFD.  The old reason of sticking with ASD (i.e. your boss knows and uses ASD but you learned LRFD in school) may go away as ASD and LRFD will largely be identical with very minor differences.  Thus, new grads could conceivably be taught LRFD in school, do LRFD calcs on the job, and have their ASD boss (assuming that the boss ain't trying to get away with using "old" ASD) understand and be able to check the calcs.  The only unknown while be how schools "teach" it.  Technically, they will be teaching LRFD _AND_ ASD at the same time.

Regards,

Scott
Adrian, MI


On Tue, 24 Jan 2006, Wesley Werner wrote:

> Mike,
>
>     Since the 13th edition of the steel manual uses both a form of ASD
> and LRFD, I expect ASD will remain for longer than 15 years.
> Especially since serviceability checks are done with service loads.
> This makes steel design much simpler using ASD. I wish ACI was set up
> the way the new steel manual is.  Then I could use ASD for steel
> design, footing design, and soil bearing checks.
>
>
> Wesley C. Werner
>
>
> -----Original Message-----
> From: Mlcse(--nospam--at)aol.com [mailto:Mlcse(--nospam--at)aol.com]
> Sent: Tuesday, January 24, 2006 2:11 PM
> To: seaint(--nospam--at)seaint.org
> Subject: Re: Any Young Engineers Out There?
>
>
> Bill,
>
> I think it took about 30 years to change from working stress in
> concrete to strength design, so it will take just as long for LRFD in
> steel.. LRFD has been around for about 15 years or so in the design
> community, so probably another 15 years or so and everyone will be
> using just LRFD.
>
> Mike Cochran S.E. SECB
>
> In a message dated 1/24/2006 10:33:07 AM Pacific Standard Time,
> BPolhemus(--nospam--at)wje.com writes:
>
>       Here's the question that I want to see answered...and mark my words,
> it
>       will probably be asked before a year has gone by:
>
>       "How many engineers here--regardless of age--took one look at the new
>       Thirteenth Edition AISC Manual of Steel Construction, put it up
> on their
>       bookshelves and went right back to the Ninth Edition?"
>
>       (N.B. It's gonna take forty years traveling in the wilderness, like
>       Moses and the children of Israel, before the last vestiges of
> the ASD
>       Idolatry are snuffed out).
>
>

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