PaintballJim:
Your and Charlie’s calc. for ultimate shear cap’y of the side pl. looks about right under the bolt, assuming nicely finished pl. edges, no nicks, notches, etc., no stress raisers. But, this is going to be loaded many times, thus some pin or pinhole wear; and there is a very high bearing stress in the side pl. immediately under the pin (a Hertz Stress problem). And, the high tri-axial stress picture there is the point at which a failure will start. The failure is actually a mix of high shear and tensile stresses. And, as WillisV suggested AISC 360-10, I wonder if the more appropriate equation isn’t J3-6c, a slightly lower available bearing strength. I’d have to look a little deeper to try to understand how AISC accounts for the Hertz stress problem in their approach to the pin/bolt bearing problem. A FoS of 3 or 4 (your 3k load to calc’ed. 13.2k cap’y.) is reasonable for this type of equipment. There is some good discussion on this problem in various literature and text books related to lifting pin-plates and eye-bars, and the like.
I’ll add something more for you to think about..., since the flange on the I-beam is sloped, and I assume the treads on the rollers are sloped to match, what prevents the two side plates from spreading apart under load and with movement down the beam? Draw a free body diagram of the trolley looking down the beam axis, and study this problem a bit. Can the bolt and side plates resist this tendency for the rollers to try to move outward? Or, should you have pipe spacers and through bolts btwn. the side plates, immediately under the I-beam bot. flg.?