The multiple editions of AISC's manual. 3

[StrEng007]

I've met an array of engineers that all have their favorite version of AISC's manual (most importantly the Specification). This post is not about the benefits of one versus another. Rather, I'm trying to understand how other engineers fulfill the obligation of using the latest standards adopted by code. By default, it seems like we should all have multiple editions of the manual/specification and know what changes exist in each. However, some people strictly utilize the 9th Edition ASD manual, others the 15th edition, and some in-between, etc.

From what I can tell, subsequent editions of the manual have been focused on creating the lightest and most efficient structures. There are more provisions provided today that will allow certain scenarios to be calculated with a "refined" factor of safety. If that's the case, why doesn't AISC provide exceptions that allow interpretations of older codes.

Can anyone share on how they manage the ongoing updates to each edition?

 

[skeletron]

Probably a bunch of routes to take depending on the situation:

1/ Use the newest edition or edition referenced by the AHJ for any brand-new construction.
2/ Use the existing edition for existing construction that you are checking. If there is something severely different or improved that has occurred between editions, I would use the "safest" answer but also be cognizant that what exists has existed.
3/ Use best engineering practices regardless of edition, but reference the AHJ's necessary edition on the drawings.

I think the role of the engineer is to make the construction/building safe. I always start with the current code since my standards/methods/tools are all designed for that case. If necessary, I would sharpen my pencil and look at understanding how it has worked.

TL;DR: I approach it from a safety + time management point of view.

 

[XR250]

Still using the Green Book over here.

 

[Aesur]

13th edition (Black book) here. I don't see a point in purchasing a new code every time one comes out, it gets expensive fast and only serves to make our lives more complicated. With todays technology and software most software uses the current codes and therefore if you know roughly what changed I would argue you are ok. As skeletron said, it's about building safety, and if you tell me that I have to use the newest code and can't use a few editions old one, then you are essentially telling me that the older buildings will all fall in a design event which is highly unlikely. It is also worth noting that some codes now allow for "alternate procedures" which I would interpret as allowing older codes as well.

 

[OldDawgNewTricks]

I have eight AISC steel manuals on my shelf but they are outnumbered by the ACI 318s on the next shelf down.

As OP alluded to, the Specification is the important part. That is the portion that is legally adopted by the building code. And it is available as a free download from AISC, so there's no excuse for not having it. The rest of the manual is just supporting information and design aids. So as long as you comply with the Specification, you can use the manual however you see fit. But do your due diligence to determine if there is any outdated information that would make your design not comply with the current code.

 

[dold]

I'm a red/burgundy book guy. Mostly because I hate the awful blue/teal color of the 15th edition . All the engineers in our office seem to use whatever book they purchased when in college, kinda. Surely some of the more tenured fellas/gals have upgraded since then, but there are still people using green books. Plenty use black books. Some use the dreadful teal book. The firm purchases copies of all new codes for the library of course, but everyone has their personal copy at their desk. Typically everyone browses around the "what's new in X edition" and makes notes/tabs in their personal copies for anything they deem "important". Granted, most people don't design "significant" structures by hand, as it were, but use software which stays up to date with the nitty gritty of the spec. That said, everyone always uses the latest editions of AISC 341 sesimic manual since it seems to evolve a little quicker as material specs change (e.g. expected strengths and new grades of HSS for braces, etc).

The biggest differences (other than the really in the weeds analysis stuff) are probably the materials (steel grades, and which spec is standard for such and such shape), and the shape database. Every version has a slightly different database of shapes - some versions add more shapes, some reduce the number. I know recently there has been an initiative by AISC and Bentley/RAM to survey structural firms across the country to get a feel for which shapes are most commonly used and which shapes are rarely used. I'm not sure of the inner workings (can't be that complicated though), but the program they have set up is to send Bentley/RAM your RAM Structural System models of any "significant" structures that the firm has completed. Then I'd assume Bentley extracts/outputs the material takeoffs and adds it to their database. My understanding is that they are trying to reduce the number of rolled sections if possible. Why? Not sure, other than to make life easier for the mills, and so they can save paper in their next edition of the spec....

Somewhat sidenote:
A firm I used to work for had a somewhat kinda sorta similar program in place: we'd go through our completed "significant" projects and run the material takeoffs from our RAM models (tonnage, essentially), and compare that with the actual final tonnage of ALL primary and miscellaneous structural steel on the project that which the fabricators would provide us with. This would include every single piece of miscellaneous steel and loose pieces, etc. - deck edge angles, kickers, gusset plates, baseplates, backing bars for full pen welds (crazy, right?), yadda yadda. This only works with the bigger detailers/fabricators because they model the crap out of the entire building using SDS2 or Tekla or whatever. We'd use this to give the clients a somewhat "calibrated" expected tonnage based on square footage and "fanciness" of the project. Pretty neat. IIRC the final tonnage was anywhere between 20-35% higher than the RAM material takeoffs. I think we had about 10 or so large projects in the database when I left.

But...AISC 360 is probably the only code that might be considered (by the user...) kosher to "use" older versions of since it's really more of a reference of sorts, if that makes sense? I.e., nobody is using old versions of ASCE 7 or ACI 318 or IBC, etc. Those evolve much faster and to a greater extent, as I'm sure everyone is aware. NDS might be another code that some people still use slightly out of date versions of (Not so much SDPWS though).

 

[DrZoidberWoop]

In the last 3 AISC editions (Black => Red => Blue), there have been a lot of changes to bolted connections, especially shear plates. 13th Edition is a pain in the ass for slip critical bolting because of strength vs servicability. 14th Edition drastically reduces the strength of shear plates because they require a check on the torsional strength of single-plate connections. The proponents of this were asked about it at an NASCC conference and they said it most likely wouldn't govern. They were dead wrong, and it's a constant annoyance on 14th Edition jobs.

15th Edition is definitely the best out of the 3, as far as connection design goes.

I once had to check the work of a senior engineer. He referenced his textbook from 1962. It was bogus.

 

[WinelandV]

[Small rant warning]The 15th edition is nice, but I still do NOT like how Chapter K was gutted. From my perspective, it was OK for Ch. K to give such detailed guidance on HSS-HSS connections because it was dealing with behavior/failures that most engineers don't mess around with. So now you get "See Chapter J for checks" which is not terribly helpful. It's really "go to the updated Part 9 for checks", and while I appreciate the updated equations per yield line theory, now none of the 15th edition checks match what was done in the 14th edition (and before).

More on topic...

I have a 13th b/c of steel class in colleges. Enough co-workers had the 14th edition that I didn't bother to buy one (1 nice thing about 14th and bolting is the increased capacity in bolt shear based on "short connection length"). My current employer bought everyone a 15th edition, so I also have one of those.

When checking an existing structure, I'll start with the current edition. If it tells me that I'm already failing before doing anything to it, then I try to go back to the spec that it was designed under. Though, I usually find it passed more due to the code loading at the time it was designed instead of the analysis/capacity differences.

 

[271828]

[Small rant warning]The 15th edition is nice, but I still do NOT like how Chapter K was gutted. From my perspective, it was OK for Ch. K to give such detailed guidance on HSS-HSS connections because it was dealing with behavior/failures that most engineers don't mess around with. So now you get "See Chapter J for checks" which is not terribly helpful. It's really "go to the updated Part 9 for checks", and while I appreciate the updated equations per yield line theory, now none of the 15th edition checks match what was done in the 14th edition (and before).

I agree completely. I've done a lot of work with HSS over the last few years and struggled mightily with the 15th ed. It took me a while, but I figured out why.

There are two basic approaches to laying out such provisions:

Option 1: Detailed cook-book approach that the engineer can follow whether he or she understands what's going on or not. All inclusive, so the engineer doesn't need to know where else to look.

Option 2: lay out the big picture and rely on the engineer's knowledge of the applicable limit states and where to go look for Paul Harvey's "Rest of the Story" (Part 9 in this case).

The 15th ed. Chapter K is in No Man's Land in between these two options.

It doesn't help that Design Guide 24 doesn't coordinate with the 15th edition. You end up having to piece together how to do these checks with the 15th ed. Chapter K, 15th ed. Part 9, and filling in some blanks with the old Design Guide 24.

 

[WinelandV]

Apparently there is an update to DG 24 coming [SOON (TM)]. In the meantime, I found these tables from the Steel Tube Institute to be very helpful.

 

[Settingsun]

an update to DG 24 coming [SOON (TM)]

That's a clear trademark violation of Standards Australia.

On the other hand, 24 years of changes to our steel code amount to adding block shear and correcting typos, so there's definitely a silver lining.

 

[DaveAtkins]

I used the 9th Edition (the green book) for many years, but finally transitioned over to the 14th Edition about 9 years ago. The biggest adjustments for me were:
* You no longer check allowable stress versus actual stress; you calculate an ultimate capacity and divide it by omega and compare it to demand
* P-big delta and P-little delta are handled explicitly; you no longer reduce the allowable stress to account for buckling, etc.

Interestingly, when I want to do a quick check of something, I find myself reverting to checking stress, not capacity.

DaveAtkins

 

[JedClampett]

When AISC tried to replace the Green Book with LRFD, the was much renting of garments and gnashing of teeth. And I was one of the main renters and gnashers. But it's worn me down. I use the 15th Edition and haven't cracked the ninth edition in a long time.
IMHO, when AISC imposed LRFD on the industry (around 1979), they made some strategic mistakes:
[ul]
[li]They removed the detailing information and some other useful tables from from the manual. This pissed off a lot of people.[/li]
[li]They didn't sell the change to LRFD.[/li]
[/ul]
A lot of engineers were very comfortable with the ASD formulae, presentation and just used to doing it. LRFD was a foreign language. So AISC in their wisdom said: "We're changing everything you're used to. Buy our new more expensive manual without as much stuff in it. Or go to the steel manual down the street."
I do very little design from the specification. I use the Tables in chapters 3 through 6, which are pretty handy and are in both ASD and LRFD. It's the most current code and the legal code. Still using the 9th edition puts you at risk. Very little risk, but imagine sitting on the witness stand answering the lawyer,"...why aren't you using the current, legal code?"

 

[JoshPlumSE]

I have always used the latest version of the manual for the most part. But, I keep the older versions around because I like to refer back to sections that may have changed and understand why.

My Green Book (9th)is the most worn of all of them because it wasn't replaced until the black book (13th edition). I used my Silver Book (LRFD 2nd edition) a lot as well because it had a lot of connection information (in the 2nd volume) that wasn't in some of the newer versions.

 

[StrEng007]

14th Edition drastically reduces the strength of shear plates because they require a check on the torsional strength of single-plate connections.

I haven't done a side by side comparison of this to the 13th edition. Do you mind referencing where in Connections, Section 10, you are referring to?

15th Edition is definitely the best out of the 3, as far as connection design goes.

Anyone else agree? I've tried to replicate the capacity shown in some connection tables from the 13th and 14th editions. Even when following the design examples provided by AISC, there are values they provide in their design tables and I'm not sure how they arrived at those capacities.

I don't have a copy of the 15th edition manual. Is it worth buying just for the connection design tables? I've also noticed the new combined forces tables lists everything in terms of Moments, and you no longer have to take (8/9)(1/bx 10^-3) just to determine available moment (I prefer table 6-1 over the unbraced length tables).

 

[DrZoidberWoop]

14th edition. Page 10-106. Equations 10-7a & b. Probably 25% of the shear tabs I do on any given 14th Ed. job are governed by this limit state, especially at roof levels without a restraining deck slab. It can be argued that decking perpendicular to the beam could be considered to bring on constrained-axis torsional buckling and allow use of the second component in the equation, but it's a grey area and open to interpretation.

The proponents of this check didn't realize what they had done until the designers were banging their heads on their desks in frustration. Thankfully, this check is gone in the 15th edition.

 

[sbisteel]

Honestly I think the 15th edition really dropped the ball for HSS connection design, otherwise it's fairly similar to the 14th edition. I've also been surprised at a few changes that were harder to notice. For instance, they removed beam cope capacity values from the double angle connection tables, and also changed the equation for cope bending strength.

 

[WillisV]

@Dr. Z - Manual is a guide - not binding - nothing requiring you to implement those shear tab torsional equations if you don't want to as it is not in the Spec.

 

[DrZoidberWoop]

That's simply not true. There are always binding contract documents that require adherence to the standardized methods.....

 

[StrEng007]

Do you live in a jurisdiction where the specific design requirements for extended plate configurations were being flagged by the plan reviewers? Seeing that the design check is gone, what would have happened if you HAD already omitted this design check while performing designs per the 14th Edition. Obviously it wouldn't have been a failure in your structure... If that was still the limiting case, it would have been determined to be a requirement and wouldn't have been removed from the 15th edition.

It would be nice if AISC provided a reference to allow us to track changes on this specific level. Stuff like this leaves me wondering how engineers can stick to one code and not be concerned about constant changes.