AISC Design Guide 1 - LRG Moment BP Question

[jba970]

Going through the 'Large Moment, Triangular Pressure Distribution Approach (B.5.2)' base plate design method in AISC Design Guide 1 (ASD).

I'm running into an issue with fpa(m) being negative. fpa(m) = fpa*((A - critical section)/A) where the critical section = (N - 0.95d)/2. The critical section being larger than A is causing this negative value.

Has anyone ever run into this? If so, what did you do to work around it? Blodgett method?

Please help. Thanks in advance!

 

[PMR06]

Your compressive stress block is entirely outside the critical section, whereas the stress block in Example B.5.2 extends further down the baseplate.

I'd draw the condition you have (somewhat to scale) and work out the statics summing moment from the critical section. You should get something like Mapl = (fpa*A)/2 * (m - A/3)