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Ieff for composite steel beam
2

Ieff for composite steel beam

Ieff for composite steel beam

(OP)
Can someone point me to a reference on how to calculate Ieff for a partially composite steel beam?  I can't find anything in S&J or online except for a reference to BS 5950-3).

RE: Ieff for composite steel beam

2
Ieff = 0.75Iequiv
Iequiv = Provided as equation C-I3-3 on p16.1-309 of 13th edition (incorrectly noted as Ieff).   

RE: Ieff for composite steel beam

(OP)
Thank!!!  That is quite a little gem that was tucked away in the commentary.

RE: Ieff for composite steel beam

WillisV, I am not sure that's correct.  What source did you use to decide that Iequiv is the quantity computed using Eq. C-I3-3?

For what it's worth, my mentor back in grad school is one of the big-name AISC guys and has been teaching steel for 40 years and he uses Eq. C-I3-3 in deflection calcs.  Of course, that's the way I've been doing it for years too, but it's just because I followed his lead.

Also, to further muddy the water, Segui uses Ieff=0.75Itr in one of his example problems (Page 580 of the 4th Ed.).
 

RE: Ieff for composite steel beam

(OP)
271828-

That note about Iequiv is in the errata (I did look for that myself).

I noticed RAM also uses Ieff=Iequiv, not 0.75Iequiv.  Also, my S&J text talks about using 0.33 to 0.5Ec when determining Itr to account for concrete creep and shrinkage.

RE: Ieff for composite steel beam

OK, perhaps that's correct.

I think Segui's method is clearly not correct because it totally leaves out the effect of more or fewer studs.  Even ILB in Table 3-20 varies depending on Sum(Qn).

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