Analysis of partially composite steel beam 2

[Lion06]

Does anyone know where I can find a good example of how to find the moment capacity of a partially composite steel beam? S&J doesn't cover this and the only info I can find is for the old ASD.
If you don't know where to find an example, does anyone have a good procedure?

 

[271828]

What's wrong with Example 16.11.2?

 

[WillisV]

1. Sum Qn for studs from point of zero to max moment.
2. Check Qn vs. Maximum Concrete force (f'c*tc*beff*0.85) vs. AsFy of steel shape. Lowest one controls (which if partially composite means by definition Qn).
3. Locate PNA so that the sum of Fx is equal to zero about the PNA (so that the Qn force plus AsFy of the portion of beam above the PNA equals to AsFy below the PNA.
4. Sum moments of forces about PNA location located in 3 (so Qn times distance to PNA plus AsFy above PNA times distance to PNA plus AsFy below PNA times distance to PNA). Note that you can choose any arbitrary point to sum moment about, but the PNA is convenient.
5. Multiply 4 by phi or divide by OMEGA = design moment capacity.

 

[Lion06]

Didn't see that one, THANKS!!

I was really trying to figure out if the entire slab would be in compression as the PNA moves into the steel in the partial composite action so that I would be able to figure it out.

 

[miecz]

Structural Steel Design Volume 2 by Alan Williams has a good example. My 2001 Edition is based on the 3rd Edition LRFD, I believe.

 

[Lion06]

271828-

Just in case you happen to use this in class, there is an error in that example. On page 834 (of the 5th edition), about 1/3 of the way up the page, it says "Tmax - 121.6 = 334.5 kips > SumQn" when determining if the PNA is in the flange or the web. It should actually say "Tmax - 121.6 = 334.5 kips > SumQn + 121.6"

 

[271828]

Thank you very much.

I have them buy a book, but it's mainly so that they'll have it on hand and on their shelf in case they want to see a derivation. I also don't want them to be the guy in the office going around borrowing books!

I actually just wrapped up composite beams, which was their last topic in Steel I. I think they're totally saturated at this point!! It was all pretty smooth except for beam-columns/second-order effects. That topic is HARD to each, LOL.

 

[271828]

and to "teach"...