Base Plate Design per AISC ASD 9th Ed 1

[TomBarsh]

The AISC ASD 9th Ed provides two procedures for determining required thickness 'tp' of column base plates; in general both of these must be checked to determine the governing condition. The two methods are described in Figures 1 and 2 on page 3-106 of the ASD.

For the second method (page 3-106 and 3-107) it is stated (page 3-107) "Designing for fp = Fp, the required plate thickness may be calculated as follows" and the expression results:

t = L * sqrt(3 * fp / Fb)

From this statement I am led to believe that the calculated bearing stress 'fp' should be replaced by the allowable bearing stress 'Fp' in this expression. But in Step 6 of the handy "Steps in the design of a base plate" on page 3-108 AISC continues to use fp, not Fp. Can anyone confirm whether fp or Fp should be used in this case?

(I understand that there are other methods of determining base plate thickness, as in Steel Design Guide #1 from AISC, but I am really only interested in the method presented in the ASD manual).

Regards and Thank you.

 

[DaveAtkins]

You do not have the update to pages 3-106 through 3-110. I have the revisions to these pages; they came from AISC. With the revised method, one follows the steps on page 3-108. There are not two different thicknesses to calculate. You just calculate m, n, and lambda*n', and use the largest value in the plate thickness formula.

DaveAtkins

 

[mickeymouse]

Thank you Dave Atkins,

I didn't ask the question, but your answer sure helped me. I was fighting a quadratic equation to arrive at "L" late last night, and I kept questioning the formulas, and by experience I knew something didn't seem right. I will request the revision from AISC in the morning. I prefer the first method (if I have my druthers), but space limitation of my client was reducing "m & n". Thanks again for you help. I don't know if you'll see this, but you deserve a star!