# ASD vs LRFD in AISC



## DC_PE_TBD (Oct 15, 2011)

Hey all-

I'm gearing up for the October SE Vertical exam and have a quick question regarding ASD vs LRFD. I don't have the 13th edition of the AISC manual that combines LRFD and ASD and have done nearly all of my steel design (not program based) by ASD. All information I had read to date says "examinees will have the option to work problems in ASD or LRFD".

I'm working through a few sample problems and some specify which IBC combination to use, one of which is a steel design problem specifying and LRFD combo. Are you restricted to LRFD in this case? If so, I need to get my hands on a revised steel manual.

Thanks and good luck to all preparing for the exam.


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## civilized_naah (Oct 16, 2011)

I am pretty sure you will have the option for ASD and LRFD. However, one of the purposes for the 13th edition was to realign ASD with LRFD and make it "Allowable Strength Design" as opposed to "Allowable Stress Design" in ASD9. As a result, there were some 'significant' changes to ASD. One thing comes to mind - the equations (and therefore the tables) for design of compression members changed drastically. In the combined 13th edition, both ASD and LRFD draw on the SAME value of the nominal strength in compression (P_n). So, you need to take care. I would suggest getting your hands on AISC13


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## kevo_55 (Oct 16, 2011)

civilized_naah said:


> I would suggest getting your hands on AISC13


+1 on that.

For any steel type problem, you can use either ASD or LRFD. You can download the specifications for the 13th edition for free from AISC but you won't have any of the tables.

For the SE exam, you really need all of the NCEES references.


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## CRNewsom (Oct 17, 2011)

kevo_55 said:


> civilized_naah said:
> 
> 
> > I would suggest getting your hands on AISC13
> ...


Other than the dimensional tables at the front, what other tables would one be lacking?


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## kevo_55 (Oct 18, 2011)

^^ There are design aids for bending, axial, and shear design of selected standard shapes as well as tables for connections.


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## CRNewsom (Oct 18, 2011)

kevo_55 said:


> ^^ There are design aids for bending, axial, and shear design of selected standard shapes as well as tables for connections.


Good show! I usually use my printed 3-ring binder since I don't feel bad about making margin notes, highlighting, etc. but I will make sure to use the black book for my studies.


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## McEngr (Oct 18, 2011)

I especially like the beam tables and the Zx and Ix tables because they have Lp, Lr, and capacities already built in.

Table 4-22 could be created with a spreadsheet pretty easily, but it's so convenient for column design that I would be lost without it... especially for beam columns. Concentric column tables are helpful too. If there is a composite beam question, good luck trying to just use the _Specification_.


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