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Design for Stability in Steel Columns

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How does the program satisfy AISC requirements for "Design for Stability"?

 

Back in the day, steel design used to be easy.  You could just use the Effective Length method and compare the applied stresses or factored loads to the allowable stresses or design loads and move on.

 

Then came "Design for Stability".

 

When you study the Steel Column module, it is very clear that it is not performing the complex Direct Analysis method.  So that leaves "Alternative Methods of Design" as outlined in AISC 360-10.  This opens the door to either the Effective Length method or the First-Order Analysis method from Appendix 7.

 

SEL is most oriented toward the Effective Length method, because it allows you to specify K factors.  The only downside to this method is that it does require the application of Notional Loads, which is not automated in SEL.  But that's just a requirement that AISC has imposed, so it must be done manually by the user.

 

AISC indicates that the First-Order Analysis method is also an option.  But this one also requires:

the application of Notional Loads,

having to check the provision that you mentioned, to be sure that the required compressive strength of any members whose flexural stiffness contributes to the lateral stability of the structure does not exceed 0.5Py, and

the Beta1 factor from Appendix 8.

 

So there is little benefit to going this route as opposed to the Effective Length method, unless the use of shorter lengths in design is worth the extra design effort.