AISC 9th edition vs. 13th edition 8

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?

 

[nutte]

I just want a stress design updated for 2009, a stress design that will produce mostly the same sizes.

That's the 13th edition black book.

 

[Teguci]

I use ASD design in the 13th edition. It addresses more situations than the green book. I have found that it is worth making the leap.

 

[Gumpmaster]

jsdpe25684,

I'd say you're breaking the law if the building permit authority that controls the jurisdiction of your project has adopted the 2006 IBC as it's building code (unless they have a specific provision to allow the 1989 AISC code). IBC 2006 section 2205.1 requires steel design to be in accordance with AISC 360 (no mention of the API spec is made).

If your jurisdiction has adopted the 2003 IBC, you're likely OK, because the 1989 specification is still one of the referenced standards.

We should all be designing with the building code adopted by the controlling jurisdiction, otherwise, we're technically breaking the law. I'm not saying that the older codes are unsafe, or wrong, just what the law says.

 

[JoshPlumSE]

JSDPE -

There's always been some debate whether the building codes (which are geared towards residential and commercial buildings) are truly appropriate for heavy industrial construction. I would put mining work in the same category (heavy industrial) as petrochemical and power plants.

Because of this reason, I would not necessarily say that your client is breaking the law by allowing ASD 89.

However, that argument is getting weaker and weaker with each code cycle. Member of some of the large industrial engineering companies (Fluor, Bechtel, et cetera) have put alot of effort in the code writing process over the last 10 to 20 years to make these building codes more appropriate for industrial.

At the very least, I will say that some jurisdictions will argue that they are breakinng the law and would not allow the old code.... Certainly the City or County of LA would not!!

 

[JAE]

Also, I am getting the feeling that those of us who prefer stress design are getting unfairly characterized as slow to learn.

I hope you all don't interpret my earlier posts as suggesting laziness or lack of brains. Nothing like that was intended.

My view, though, is that we engineers tend to follow this: we learn a means-of-design and use it, feel comfortable with it, and begin to trust it over time.

Right?

Nothing wrong with that at all.

But on the other hand, as new codes, specifications, etc. come out, I think it is essential that engineers stay on top of these requirements and methods and not allow themselves to sit back and remain comfortable with older methods when current, legally adopted codes mandate the newer methods. Mostly where the design is under a legally mandated code that requires certain methods and this would probably most apply to buildings.

In construction engineering and industrial settings perhaps this isn't as big of an issue.

 

[weab]

I guess this topic has run its course...EXCEPT...

nutte,

The 13th edition is NOT stress design as you suggest. That is the fallacy that is being perpetuated. "Stress" and "strength" are two words that AISC is attempting to use interchangeably. Just because the English language provides us these 2 words that sound similar and both begin with the letter "S", that doesn't mean that ASD89 = ASD05.

In the end, people should want to use this code because it is better, not because they are forced to, which in most instances is the case.

 

[DaveAtkins]

One more comment--AISC 360 is required by IBC, but IBC does not say it must be the latest version. That is why it is still acceptable to use the 1989 ASD.

DaveAtkins

 

[271828]

"The 13th edition is NOT stress design as you suggest."

If I'm using ASD89, I can work in terms of allowable moments instead of allowable bending stresses, right?

 

[JAE]

DaveAtkins, check out IBC Chapter 35. They specify which versions to use there.

 

[miecz]

JAE

You make a valid point. People do tend to stick with familier methods, even if better ones come along. I think the main reason some resist LRFD is that we're under such time pressure to get the job out. There's not enough money in the budget anymore to bury time spent learning new methods. Our project managers keep a very close watch on time charged to each project. (That's why my posts here are usually very short) Who wants to spend weekends and vacations learning a whole new design method?

 

[DaveAtkins]

I see. IBC 2006 no longer allows the use of the 1989 ASD.

IBC 2000 did allow that.

DaveAtkins

 

[271828]

IBC2000 and 2003 were before ASD2005, so ASD89 was the latest when they were released.

 

[nutte]

jsdpe25684, there is a difference, and it is overcome with a simple algebraic transformation. If engineers are complaining about this, then we have bigger problems to worry about.

 

[swearingen]

DaveAtkins,

It is my understanding that AISC 360 is a new number created for the 2005 spec. It does not apply to any former spec. The ones before this are only referred to by their date. I assume that subsequent revisions will be issued with a year designation - the first one is AISC 360-05, the next would be AISC 360-10, etc.


If you "heard" it on the internet, it's guilty until proven innocent. - DCS

http://www.eng-tips.com/supportus.cfm

 

[271828]

"Who wants to spend weekends and vacations learning a whole new design method?"

Nobody does, but shouldn't we expect to do some of this as highly-educated professionals? Not saying every night and every weekend, but some, right?

 

[HgTX]

Apparently not. That's why so many of the PE boards are mandating PDHs, because too many people think that learning new stuff isn't part of their jobs.

Hg

p.s. Yes, I know, as many PDH systems are implemented, teaching yourself new stuff wouldn't count. Separate topic.

Eng-Tips policies: faq731-376

 

[steellion]

Being out of college for just a few years now, I can tell you that at least at my university, it was taught about 80% LRFD and 20% ASD. We were familiar with both systems, but I think the focus was on LRFD because it is not as inherently intuitive, and if you can do LRFD, you can do 13th ASD as long as you know the ASD basics.

At work, I've used ASD almost exclusively. That is definitely the preference of the PE's that I work under because they have a better feel for it. ASD has become my preference as well. While it is true that for members controlled by strength, you can usually use slightly smaller members running an LRFD analysis, I find that you end up giving that savings right back when the beams are designed for serviceability anyway.

 

[TehMightyEngineer]

I'm in the exact same position as steellion and have also found that while being taught to use ASD and LRFD equally I find that I use ASD a lot more than LRFD as my work usually involves single or only a handful of members so the cost savings of LRFD don't justify the added time.

Anyway, I however find that I greatly prefer the 13th edition over the 9th edition probably because 90% of my work is done using a computer model so it's easy to get a stress ratio from that. I think about the only two things I liked about the 9th edition is the better quality paper used in the book and the fact that their tables go down to the small W sections (seriously why does the 13th ed. stop at W8 sections!?)

EIT with BS in Civil/Structural engineering.

 

[KootK]

I hear ya' with the paper quality complaint. The 13th eddition is practically printed on toilet paper. It is nice to have the connection stuff back in the main book though...

 

[271828]

Of course, if the 13th Ed. wasn't printed on bible paper, people would've complained that it was too thick! It weighs almost exactly 4.0 lb as it is.