It is overconservative in my opinion. I think the majority of the moment will be reacted by the two bolts at +/-7", if the plate is stiff.

Cheers

Greg Locock


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Quote (JD P.E.
.... I attached my napkin sketch. Is this a reasonable, conservative, approach to approximate?)

It is not reasonable and overkilling. If we assume the bracket is rigid enough, the faying surface will transfer the compression stress and a NA will develop around 11 in. from the right first bolt row. In this case, the tension developing at the first bolt row should be in the range of T= 576000/14= 41000 lbs.

Obviously the front row of bolts is critical. I would look at the problem with this question in mind: "If the front row of bolts failed, what would happen?" The 2nd row of bolts would fail and then the whole body would rotate about either the rear row of bolts or the back edge. The rear row of bolts is the worse case. So I would look at the whole free body diagram as if the pivot point was at the rear row of bolts. I would calculate the moment that the applied force creates about that pivot point. Then the front row of bolts have to create an equal and opposite moment about that same point (the rear row of bolts) to keep the free body from rotating. Right? (Also, the bolts in the center might be helpful in some other sense but they serve no real purpose in this analysis in my opinion.)

If the bolts are snug tight, can you look at the moment caused by the full tension in the bolts x the moment arm?

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-Dik

I would use the rated maximum load on the bolts as their maximum contribution to the opposing moment.

Hi JD PE
I would solve the issue by this method.- https://roymech.org/Useful_Tables/Screws/Bolted_Jo...

Scroll down to you see the sub heading “bolts withstanding bending forces”

“Do not worry about your problems with mathematics, I assure you mine are far greater.” Albert Einstein