NCEES SE Practice Exam mistakes? 1

[STR04]

I found this post so and it didn't answer my question so I probably need some clarification on this one.

http://www.eng-tips.com/viewthread.cfm?qid=383898.

This is in regard to problem #120. I was curious as to why the author did not apply AISC eq (4-1) to solve for an equivalent (KL)y_eq. This would govern the design and it would follow a similar example from "AISC Design Examples 2014" ex. E.4B

TIA.

 

[Antnyt23]

I believe in the solution they are using the KyL/ry to govern.... if you look at table 4-22 they use the value for 93.8 (y governing) in lieu of 61.1(x governing).

To your concern about KLy_eq vs KLy....see page 4-4 it states "to determine the available strength in axial compression, the table should be entered as the larger of KLy and KLy_eq

KLy = 15'(1.0) = 15'
KLy_eq = 15'(2.0)/(3.07) = 9.77'

Therefore KLy would be the governing value you enter table 4-22 with.

Looked at this quickly so hopefully this is correct and what you were looking for.

 

[Antnyt23]

I looked at AISC Design examples..... see assumption in example E.4A "Assume the column is continuously supported in the transverse direction (the y-y axis of the column)." So they are pretty much saying KLy will not govern so that is why it isn't compared in your example E.4B and they only use the KLy_eq which would govern due to this assumption.

 

[STR04]

Yep...that's it. Thank you!

 

[TehMightyEngineer]

Only 2 more weeks. Good luck!

Professional and Structural Engineer (ME, NH)
American Concrete Industries

http://www.americanconcrete.com

 

[Antnyt23]

Good luck!

 

[STR04]

Thanks! Got another one from the NCEES example problem...panic!!! For problem #107, why does the author not include stresses from the the dead load moment (9.6 k-ft) into the interaction? TIA!!!