this is just a thought (i am no expert in timber-farming) think of an octagon(diameter 18"-24" now extend the sides on the clockwise side(or the counter clockwise side) out to whatever your radius of your structure minus the radius of the octagon, and wallah that is the plan view of your "Bents" put in a skylight in the center. this would resemble many classic Greek/roman dome structures. I would imagine joinery would be similar to a 'hip roof rafter" meeting a ridge beam. getting this all together would require many hands.
