Cp Calculation for Beam analysis

[EntryLevelEIT]

If Lb falls inbetween Lp and Lr the Cb value is required to find the bending moment. Suppose the applied load to the beam is unsymmetric. I have a simple span with an off center point load.
Is the Cb = 12.5M/(2.5M+3Ma+4Mb+3Mc)Rm equation still valid or should I just rely on the AISC available moment charts.

Thanks guys!

 

[steellion]

Yes, the equation is still valid. Or, you can always conservatively take Cb=1.0.

 

[EntryLevelEIT]

My Cb value is causing the Mn between Lp<Lb<Lr to be greater than FyZx. How can this be?

 

[slickdeals]

You can never use Mn > Mp (FyZx). The upper bound is Mp

 

[frv]

Slick is right. In fact, every beam limit state has as its upper limit Mn= xxx <= Mp.

What Cb allows you to do is shift the entire LTB moment curve "up", but never beyond the plastic moment capacity.