Two Bridges

That’s the Black River in Wisconsin, with a rail bridge in the background and a small road bridge in the foreground. To be more specific, this is at a dammed rapids in the river – the Black River Falls – and adjacent to the town of Black River Falls. Here’s a close-up of the rail bridge:

I really like both bridges, which is unfortunate, as both were short-lived and disappeared long ago. The rail bridge was constructed in 1880 and taken out of service after being damaged by flooding in 1911. The Chicago & Northwestern Railway rerouted the line to Eau Claire to avoid this river crossing, and the abandoned bridge was taken down in 1915. Sic transit… The bridge was a deck lattice truss and seemingly well-braced; if it had been a through-truss, it would have been substantially higher above the river and less likely to have been damaged by flooding, although possibly exposed to higher wind loads. (As always with this kind of thing, the Bridgehunter website is invaluable.)

The road bridge is, to my taste, even better. We don’t build many truss bridges any more because of the relatively large amount of maintenance and because of changes to the relative costs of steel material and connection fabrication. As a result we don’t get little gems like this any more. The bridge carried Harrison Street in the town of Black River Falls across the river by way of an island that cut down the required span length. It’s hard to tell from the angle of the photo, but it looks to be one or two lanes wide. The visible truss was not the only span – you can see the pony truss of an approach off to the left in the top picture. It is technically a Parker truss, but I’m not sure that Parker, whoever he was, deserves credit for simply using a segmental top chord on a Warren truss. You can see the lattice-truss girders connecting the last connection nodes of the top chords, forming rigid portals with the sloped end segments of the chords. The portal on the right has a sign, no doubt with the name and construction date of the bridge. The hangers from the top-chord connections down to the mid-span of each lower-chord segment (used to cut the lower-third spans in half) are rods and almost invisible in the photo.

The Harrison Street bridge was constructed in 1869, was damaged in the same 1911 flood that damaged the rail bridge, and was repaired and put back in service. It was demolished in 1929 after the parallel Main Street bridge was opened a block away, designed for the load of trucks. The Main Street bridge was a plate-girder deck bridge, which meant that there was nothing but the pedestrian handrail above the roadbed, which was, depending on your taste, either a good way to provide an unobstructed view or boring. That bridge was replaced by a similar one in 1980.

There are good reasons why a plate-girder deck bridge is better suited to this site than a through-truss, but aesthetics is not among them.

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