Not licensed in Ohio so, no, can't offer stamp. I'm also not anyones preeminent expert. I just want Jeffro to feel confident that a reasonable analysis of the floor structure is not unobtainable. I'm not offended by your comment in any way. You are correct to be skeptical.
Old buildings, especially barns that are open to weather and critters and insects and corrosive elements will degrade over time, weakening from their original design capabilities. Consideration must be taken, especially when upgrading the use to accommodate modern equipment, vehicles and operations.
Also, it's very important to check and see if there were any structural changes made over the years. A clever yet ignorant farmer might have thought a column or beam was in the way...
Also, past repairs could have been done incorrectly, or themselves become compromised (metal replacing wood and then rusting).
Your barn looks beautifully preserved.