Direct Analysis Method AISC Example
Direct Analysis Method AISC Example
(OP)
I am in the process of verifying the use of the Direct Analysis Method (per AISC Appendix 7)within a software package using the AISC 14th ed. examples posted on their website. (http ://www.ais c.org/Work Area/showc ontent.asp x?id=29596)
The example problem given for the DAM (Example C.1A) is a fairly simple problem, but I cannot seem to arrive at the same answer working it with the software package, or by going through DAM step by step manually (still utilizing the same software for pdelta).
It is late in the day and I may be missing something extremely simple, but the first order analysis results given in the problem do not seem correct to me. Can anyone currently using DAM verify that the referenced example is worked correctly.
I once told my grandfather that I thought the aim was off on his rifle. He shot once then informed me that it was not the aim that was off, but the "aimer"... that is more than likely the case here too, but I thought I would check in before wasting more time.
Thanks in advance
The example problem given for the DAM (Example C.1A) is a fairly simple problem, but I cannot seem to arrive at the same answer working it with the software package, or by going through DAM step by step manually (still utilizing the same software for pdelta).
It is late in the day and I may be missing something extremely simple, but the first order analysis results given in the problem do not seem correct to me. Can anyone currently using DAM verify that the referenced example is worked correctly.
I once told my grandfather that I thought the aim was off on his rifle. He shot once then informed me that it was not the aim that was off, but the "aimer"... that is more than likely the case here too, but I thought I would check in before wasting more time.
Thanks in advance






RE: Direct Analysis Method AISC Example
Some programs include shear deformation in addition to flexural deformation. Sometimes this creates results that are different from traditional hand calcs that only include the flexural.
RE: Direct Analysis Method AISC Example
RE: Direct Analysis Method AISC Example
SteelPe, any tips on effective use of DAM in STAAD? I feel fairly confidant in the correct application of notional loads, the stffness reduction, and according to the ref. manual both large and small pdelta are accopunted for in analysis.
RE: Direct Analysis Method AISC Example
Did you reduce the stiffness of the members?
RE: Direct Analysis Method AISC Example
Acording to STAAD's technical information, both the stiffness reduction and the intermediate nodes (p small delta) are taken care of within the program if DAM is specified. I have verified this by running DAM manually. I think the differing results is with the first-order moments (which probably points to an error in my input..) I will ahve to comb through carefully when I get a free second.
SteelPE, I do not see an examples within Appendix 7 (V13 or V14), only in the AISC online design examples. Which example problem were you referring to in your earlier post?
RE: Direct Analysis Method AISC Example
Maybe I don't know what I am talking about.
RE: Direct Analysis Method AISC Example
May not be a bad idea to run these problems just to check that you are selecting all the appropriate "flags" within the program to run the DAM.
RE: Direct Analysis Method AISC Example
RE: Direct Analysis Method AISC Example
RE: Direct Analysis Method AISC Example
I'll work through the examples in the commentary during lunch. The example that I am unlimately wanting to compare to is a portal frame example in the AISC Design Example publication available free online. Would someone familiar with DAM mind verifying the results?? It is a fairly simple frame. I have checked my work and have not found any glaring errors and I'm beginning to think I am going crazy.
Thanks for all the help so far.
RE: Direct Analysis Method AISC Example
RE: Direct Analysis Method AISC Example
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RE: Direct Analysis Method AISC Example
Thanks for the help.
RE: Direct Analysis Method AISC Example
I get a base shear (for the LRFD loads) in the column of 5.7 and 6.2 kips. Then I get a moment at the tops of the column of 113.4 k-ft and 124.9 k-ft.
If your numbers match mine then I would feel pretty confident that the AISC example is wrong.
RE: Direct Analysis Method AISC Example
My results for the full DAM yield 109 k' and 128 k' at top of columns (although I ran the frame in ASD and I re-factored the results by a "weighted load factor" of 1.5 to arrive at LRFD)
I feel pretty good about results now, but you would think that if AISC is going to publish benchmark examples for the purpose of verifying the use of given methodology and computer output they would have gone through them with a fine-toothed comb...
RE: Direct Analysis Method AISC Example
"We have looked into it and have confirmed that the 1st order analysis in the design examples is incorrect." per Heath Mitchell.
I'm a big fan of AISC and think the Design Examples are very useful, but they drop bombs occasionally.
RE: Direct Analysis Method AISC Example