Loft Construction in a Barn

My pole barn (81′ X44′) is constructed in the usual way with 6×6 or larger poles on the perimeter with 2X4 girts and T1-11 siding.

On the inside, the original builder put 4X6 treated posts about every 8 feet apart front to back and 10 feet from the outside walls. He also constructed some lofts supported by those poles. My project is to build another loft on the remaining unused poles. For putting flooring supported by posts, I am used to this type of construction:

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That is, the beams for the joists rest on top of the posts; joists can be on top of the beams or attached by joist hangers. In my barn, the builder simply nailed the beams to the face of the posts and used joist hangers from the beams. The beams are each a single 2X10 (span = 8 ft). This is looking down at the loft floor:

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It seems to me that the 2X10 that goes around the loft (maybe called a “rim” board by analogy to a deck) adds nothing to the weight bearing capacity of the loft. If the objective was appearance, that value is lost on me in a utility barn. The 2X10 sandwich does seem to help remove some of the twist in the support posts. Can anyone see a better reason for the construction actually used by the builder?

Is there any reason not to double the 2X10’s and position them on top of the 4X6 posts with steel plates and nails? Is the effect on counter-acting twist sufficient to offset the structural disadvantage on weight bearing? BTW, I plan on a safety rail using posts attached to the beams by lag bolts.

Regards, John

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