Combined Shear & Tension

[ToadJones]

I'm running through the design example II.B-4 off the CD that comes with AISC 360-05.
In the second step of the example they size the bolts.

Can someone explain this equation to me?

It appears that the bolt is designed purely for tension and not combined shear and tension.

 

[nutte]

The upper bolts are used for tension. The lower bolts, at the compression flange, are assumed to resist the shear. That way you avoid the necessity of checking the tension bolts with shear on them. Look at the top of page IIB-26.

 

[ToadJones]

ahh, I see.
Thanks Nutte