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RE: Direct Analysis Method

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One point of caution on this subject: 
There are a lot of ways to do a 2nd order analysis, and even the some of the
well respected methods may need "adjustment" in some cases. Usually when you
have lateral load applied between floor levels, or when you have a
cantilevered column.

Therefore, it is a good idea to validate your program using the "Benchmark"
problems that AISC gives in the commentary to their Appendix 7.  These
problems tend to put too much emphasis and importance on the P-little delta
effect (which is where even some of the "rigorous" methods have difficulty).
But, that ends up being a good thing.... Because, if you can prove that your
program can handle these problems, then you can have that much more
confidence that the program will handle the more common situations. 

Simply put, those benchmark problems give you guys (the real practicing
engineers) a relatively easy test method to determine if your analysis
software is up to snuff.  

Below is a link to a different white paper on the subject (this one written
by me). The link also includes the slides from a short presentation I gave
at the 2007 North American Steel Construction Conference (NASCC).... Just as
importantly, the download also includes the actual RISA files used to run
those AISC benchmark tests (graphs of which are shown in the paper and

I hope that this information ends up being useful!  


Josh Plummer, SE
RISA Technologies
(949) 951-5815 (voice)
(949) 951-5848 (fax)

3                                Message:0003                            3
From: Matthew Newton <matthew.newton(--nospam--at)>
To: <seaint(--nospam--at)>
Subject: Direct Analysis Method

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CSC recently published an article about the direct analysis.


The 2005 AISC Specification for Structural Steel Buildings brings
significant changes to the way stability analysis and design is required to
be carried out. For the first time, the specification has something to say
about the analysis you and your design software is performing. Do you know
how your favorite software package has implemented the new requirements?
Does it simply meet the minimum code requirements using old methods intended
more for hand calculations or does your software offer you the most
accurate, reliable and flexible tools available?





Matthew Newton

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