I am thinking of building a barn with a 16' center aisle. I would like the option of finishing a loft space on top of the center aisle. I will have 6x6 vertical posts on a concrete pad. I want the wide center aisle ideally to allow vehicles, tractors etc to drive in/through and plenty of room so I don't want a support post in the middle of the aisle.. I'm having trouble imagining how in the world I would correctly support a wood beam set on top of 6x6 posts that is 16' long... especially considering that I will want the beam to support joists and a floor on top of it. Any suggestions?