AISC Design Guide No. 1 û Column Base Plates

[jheidt2543]

I’m almost done writing my own Excel spread sheet for off-set base plates with vertical and moment loads (something Enercalc doesn’t have yet) and I’m looking for a little help deciphering the equation for Mpl in Example 15. I’m having “brain freeze”, where do they get the 0.67 in the numerator of the second term?

 

[271828]

Which version of DG1 are you using?

 

[jheidt2543]

I'm using the Rev. 3/1/03

 

[kslee1000]

The distance from the reaction to the critical section = 0.67x3.2" (for triangle stress block).

 

[jheidt2543]

Kslee1000:

I still don't see it. The distance A = 5.1", the critical section is at 3.22". 5.1-3.22 = 1.88" is the leg of the similar triangle. The reaction should be at 2/3 x 1.88 = 1.25" I don't see how they get a lever arm of .67".

The stress is by similar triangles: (1.88/5.1)x 2.1 = .774 ksi.(their .78 ksi).

 

[kslee1000]

The critical location is under the column flange. The stress block between the flange and the free edge therefore is trapezoidal, that has been broke into 0.78 uniform, and 2.1-1.78= 1.32 (1.3 used) max for the triangle block. Thus, the lever arms are 0.5x3.22 & 0.67x3.22 (3.2 used) respectively. Make sense?

 

[jheidt2543]

Kslee1000:

Thank you, you cured my Myopia! Sometimes the simple is not so simple when we try to make it more difficult than it is. Thanks, for the quick response too.

 

[Lion06]

I'd be careful, that DG is currently unavailable for a reason.

 

[jheidt2543]

StructuralEIT:

Yes, I found that out, they are rewriting it; but I believe the rewrite has more to do with the anchor bolts and ACI Appendix D than the plate itself. The method is very similar to that in Salmon & Johnson. Thanks for the cautionary reminder.