Bridge Description West Union Covered Bridge, West Union Indiana

The West Union Covered Bridge is a two-span bridge. Each span, from abutment to pier essentially behaves as its own bridge, connected to the other only by a metal tension rod connecting the two end posts over the pier, about 2' below the top chord on either side. Each span is composed of a double Burr arch and a sixteen-panel multiple king-post truss. The multiple kingpost design centers around strong, vertical posts (in tension), set at 9 1/2' intervals that are connected to an upper and lower chord that run the length of the truss. Diagonal braces (in compression), connect the posts to each other from bottom to top toward the center of the truss.

The top chord is made of a single string of timber segments that are simply set end-to-end across the bridge. The lower chords each are composed of two parallel chords. Where the various segments of the individual lower chord members are joined, a "double headed hook" shear block secures the union. Match marks are still visible on the ends of the chord segments, indicating the pre-fabrication or pre-arranging and matching of the members.

The vertical posts are mortised into the top chord. They are then sandwiched between and bolted to the arches. The lower chords are notched around the posts. Diagonal braces are notched into the posts at both ends between the chords. The arches are doubled, with two sets of concentric arches on each truss side. The arch timbers are 5 1/2 x 10". The arch timber segments join at every other post, meeting end-to-end and secured with a double bolt assembly through the corresponding post. The segments of the upper arch are never spliced at the same post as are the segments of the lower arch. The arches are incrementally pushed away from the posts by wooden spacers to make the required distance to sandwich the lower chord. Near the center of the span, wooden blocks reinforce the space between the inner and outer arches.

An iron tie rod connects the top chords above each post. There are, then, sixteen overhead panels across each span of the bridge (mirroring the truss panels). Timber cross braces form X's (one resting inside the other) in the panels between the ties. Cast iron shoes are secured to the top chord to receive the upper lateral cross braces and the tie rods. The roof rafters sit on the upper chord and support longitudinal stringers. The roof is of plywood, covered with shingles.

Board and batten siding, painted barn red, cover the bridge. There is a 10' overhang at the north entrance and a 17' overhang at the south. There is a small window slit running the length of the sheathing beneath the eaves. Daniels wrote of this feature that it was "to admit light." It also helps allow wind to pass through the structure, relieving some of the transverse stress. There are two windows in each span on the west side. These have sills and awnings, supported by three two-by-fours. The trim is painted white. On the east side, a single, small window breaks each span.

The portal faces are of vertical planks, painted white. Each portal has four signs attached. In the tympanum, "1876 / J.J. DANIELS / WEST UNION / CROSS THIS BRIDGE AT A WALK" is painted in black. The vertical clearance is 14'-6" and the opening is 16' wide. The road deck is made of longitudinal planks nailed to a layer of lateral planks. A guardrail runs the length of each side, but runs behind, rather than in front of, the arches.

The decking sits on longitudinal stringers that rest on floor beams, which in turn are supported by the lower chords. Iron rods tie the lower chords. Between the tie rods, timber cross braces fit into iron shoes in the same manner as the upper lateral braces.

According to covered bridge historian Joseph Conwill, "It appears that [Daniels] is attempting to mimic the function of continuous trusswork in having the live-load deflection of one span partly relieved by the dead load of the other; if so, a sophisticated feature."

The timber bridge rests on hewn stone abutments and one pier. The upstream side of the pier is angled to form a point that helps to break up ice and debris flowing downstream. The concrete approach walls were built in 1914 after a flood damaged the existing walls. The south approach has the date "1914" and the names of the county officials at that time stamped into it.

At the abutments, the arches bear on cast iron plates that were built into the stone. Daniels included these plates to "give a solid bracing and prevent the timber from taking moisture from the rock" and rotting. This element prolonged the life of the arch ends, one of the most vulnerable spots in a timber bridge. Daniels also built iron eyehooks into the abutment face to anchor a "stay rod" coming down from the bottom chords. This feature was meant to secure the superstructure of the bridge to the abutments in an attempt to prevent the truss from being washed downstream in a flood.