ASD Green Book (9th edition) vs. LRFD / ASD Black book 1

[sshields]

Hey all!

I have a project manager at my office that insists that the green book is a better asd publication than the newer combined steel code.

My questions are:
1.) If we're required to use the most recent version of a particular code, wouldn't the black book govern?

2.) If we're not bound to use the black book, then do the ASD tables in the green book match those in the black book?

He is insisting that I need to purchase a green book, and I'd like to avoid the cost if possible.

Comments?

 

[nutte]

1) When are you required to use the most recent version? Typically you're required by the building code to use a certain one. If the building code says to use the 9th edition or the 3rd edition, then what's in the 13th edition isn't relevant.

2) They haven't radically changed the way steel is analyzed and designed, although there are a few minor changes between the two. The 13th edition does represent the latest research and developments in steel design. The 9th edition is based on information that is 20 years old, so I would not call it superior to the 13th edition.

 

[JAE]

nutte is right.

It is not up to your manager, it is up to the applicable code adopted by the jurisdiction in which your project occurs.

The IBC, for example, references the applicable AISC documents in Chapter 35.

 

[sshields]

My question isn't so much on which code to use (I agree its jurisdictional), my question is more on the asssertion of my supervisor that the ASD Green Book (9th) is NOT the same as the ASD published in the latest combined version (13th edition). (so lets assume that the 9th version of ASD is what my jursidiction requires)

Are they the same? Exactly the same? For the purpose of interchangability? The AISC website says the 13th edition contains the 9th edition of ASD and the 3rd edition of LRFD. But my super insists that they're not the same? I'm not going to tell him he's wrong by any means, but is he assuming that there are subtle but mostly negligable differences, or that there are major differences that justify using the green book's version of the 9th edition as opposed to the 13th editions version of the 9th? (I hope that makes sense).

 

[frv]

I think they are essentially the same, with only cosmetic changes and incorporation of new research.

The question is why on earth would your supervisor insist that you use that book. I know it's his responsibility to check your work, but you should be free to use what you want. It is very shortsighted to use the 9th edition to learn (I assume you are a new engineer) steel when it is very clear the entire industry is moving in toward LRFD. If you don't begin using LRFD, then you will have more of a headache wen you are required to do so (be that in 10 or 30 years).

 

[nutte]

In my above post, I state that their are some minor differences between the two.

 

[sshields]

Yep, I'm a new-ish engineer, I've been working in industry for two years now, half way through masters and 2yrs on the EIT, though my first job was at a general civil engineering firm in Las Vegas and I did more site civil then structural. I'm finally at a pretty large A/E firm in Michigan, (and loving it by the way).

My supervisor isn't that dissimiliar from other senior enigneers at my firm. The vast majority of them swear by the 'green book' and while I respect ASD and its place in industry, I just don't see why the 'black books' ''version'' of ASD is so taboo?! Thanks for the clarification. What it boils down to is at nearly $200 I'd love to avoid picking up a copy of a 20 year old publication that I essentially already have in my black book.

Thanks guys!

 

[sshields]

nutte,

In your expereince, and if you had the choice, do you think the changes are minor enough to justify a preference of black over green (or vice versa)?

 

[nutte]

The preference comes from familiarity. I would say a design done with either would be sufficient.

As far as picking up a copy, I would recommend getting one, because it is still so prevalent. Check eBay. Or you may get real lucky and get one at a used book store. I picked up a secomd copy this way for $5.

 

[civilperson]

Not the same, but similar. (Green ASD vs. Black ASD)

 

[whyun]

Or if you are nice to a guy who is very close to retirement, he may give it to you free of charge.

Code adopts ONLY the specifications (you can get pdfs of all specifications published to date from the AISC website). All other design tables in the Steel Manual are just reference material.

 

[frv]

whyun brings up a good point.

All the tables are simply tabulated values based on the specification.

If the specifications have changes, so too will the tables.

 

[DRC1]

Under the black book, LTB equations have become more cumbersome. Although a nice feature is that they incorperated a lot of information that was in different places, such as connections. If you are doing ASD, the green book in many ways is easier to find what you want as the black book is doing ASD & LRFD together.

 

[nutte]

The only difference between ASD and LRFD in the 13th manual is do you multiply by phi or divide by omega. The LTB equations have gotten more cumbersome, not because of LRFD, but because they represent the "state of the art" method for determining the capacity. The green ASD might be easier, but it is outdated and not current, and it does not represent the latest information on the topic.

That said, it would be interesting to see a comparison between the green ASD and the current ASD to see how different the results are between the two procedures. Perhaps the difference is negligible.

 

[whyun]

ASD was originally intended to be "phased out" completely and be replaced with the LRFD method. Pure LRFD specs went through several cycles of revisions (up to the one included with the Third Edition). ASD was re-introduced and integrated with the LRFD in the 13th Edition due to its "popularity" and/or resistance from the engineering community to move forward with the pure LRFD. For the most part, the AISC's intent of re-introducing ASD was to "align" the design solutions using either methods, not due to significant state-of-the-art changes in the ASD methods.

The difference in general design solutions from ASD(9th) vs ASD(13th) will be similar to ASD(9th) vs LRFD(2nd or 3rd). ASD(13th) vs LRFD(13th) should generate same solutions.

 

[cap4000]

This Steel Construction Manual is the thirteenth major update of the AISC Steel Construction Manual, which was first published in 1927. With this revision, the previously separate Allowable Stress Design and Load and Resistance Factor Design methods have been combined. Thus, this Manual replaces both the 9th Edition ASD Manual and the 3rd Edition LRFD Manual. Much of the HSS Connections Manual has also been incorporated and updated in this Manual.

The following major improvements have been made in this revision:

The number of design examples has been expanded and included in a companion CD.
All tabular information has been updated to comply with the 2005 Specification for Structural Buildings and the standards and other documents referenced therein.
Shape information has been updated to ASTM A6-05, including the new W36 shape series.
Design methods have been delineated by making use of a dual-color format, with numbers indicated in blue type representing LRFD design values, and numbers indicated in green shading representing ASD design values. Tabulated values presented in black type are independent of design method.
Information on HSS connections has been integrated throughout this Manual.
W8 members have been reintegrated into design tables with cautionary statements regarding accessibility and dimensional constraints for connections made to them.
Shapes with special design considerations, such as slenderness in compression or noncompactness in flexure, have been indicated throughout the member selection tables with footnotes.
Workable flat dimensions of HSS members have been tabulated.
Design properties for pipe are now tabulated using the same wall thickness reduction factor used for HSS.
An overview of provisions and a simplified method have been included for second-order analysis and stability requirements.
New information has been added on corrosion protection and compatibility of dissimilar metals.
Charts have been added for shear strength of plate girders.
Lower-bound strengths for eccentrically loaded single angles have been tabulated.
Tables have been added for the critical buckling stress of compression members.
Tables for members subjected to combined axial load and bending have been expanded and improved.
A table has been provided for calculating the strength of concentrically loaded weld groups.
A direct calculation method has been added for calculating the buckling strength of double-coped members.
Prying action provisions have been modified so that the tensile strength is used in the calculation rather than the yield strength.
Beam bearing constants have been expanded to include all crippling and yielding cases.
Revised design procedures for single-plate shear connections have been adopted, including a new design procedure for extended single-plate shear connections.
An updated design procedure for moment end-plate connections has been adopted based upon yield-line analysis.
The uniform force method weld ductility factor has changed from 1.4 to 1.25.
Guidance on washer selection for anchor rods has been expanded.
The design of bracket plates has been modified so that the plastic section modulus is used rather than the elastic section modulus.
The AISC Design Guide Series and other supporting references have been further integrated through indexing and references to this material, where appropriate.

 

[swearingen]

There is one very big difference in bringing the 9th edition "up to date": linear interpolation between Euler buckling and the plastic limit in bending.

Compare the bending moment charts in your green and black books. See the big step-down in the green book charts? That isn't there in the black book. You just got a bump up in capacity for fairly short, heavily loaded beams.



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

 

[Whiffle]

Your supervisor's concern is common. My supervisor checks my LRFD work with his "Green Dragon" because he's familiar with it.
The ASD in the 13th Edition is "Allowable Strength Design" and the ASD in the 9th Edition is "Allowable Stress Design". So they are not exactly the same, but similar, as civilperson so eloquently put it.
ASD in the 13th is still based on strength, not stress, so it doesn't make sense to me why they still have 2 methods. My guess is to keep the old-timers happy.