Ohio Rev. Code § 5591.21
Except as provided in section 5501.49 of the Revised Code, the board of county commissioners shall construct and keep in repair necessary bridges over streams and public canals on or connecting state, county, and improved roads.
The board may submit to the electors the question of issuing county bonds for the construction of bridges on proposed state or county roads or connecting state or county roads, one or more of which may be proposed, but such bonds shall not be issued or sold until the proposed roads are actually established.
When the board determines it unnecessary in the construction of any bridge and the approaches thereto to acquire the entire land upon and over which the same shall be located, it may acquire such part of the land and easements and rights in the remainder thereof as are necessary and sufficient for such construction.
R.C. §5591.21