The picture above is labelled “High Bridge Station, High Bridge, Ky.” in the Library of Congress. Part of what follows from that is straightforward, part is not. The Kentucky River follows an amazingly squiggly line through the central part of the state of Kentucky, running roughly northwest until it joins with the much larger and much straighter Ohio River. A portion of the river southwest of Lexington is in a deep gorge, and therefore presents an obstacle to constructing a road or a railroad to the south. The picture above shows the station on the Cincinnati Southern Railway in the tiny village of High Bridge, named after the adjacent 1879 rail bridge over the gorge.
The first bit of oddity is the presence of that arched stone tower. It does not seem to serve any purpose and railroads didn’t usually build ornamental towers. The explanation is that John Roebling started a rail suspension bridge here in 1851 for the Lexington & Danville Railroad, which was formed specifically to connect the railroad networks north and south of the gorge. The tiny railroad failed financially and the Roebling bridge was abandoned in 1855, but not until the towers and anchorages had been constructed. When the much larger Cincinnati railroad constructed its truss bridge twenty years later, they used the same alignment, so the track ran through the towers on both sides of the gorge.
The second oddity comes from the description of the truss bridge as the “first cantilevered bridge” constructed in the United States. This is not just in Wikipedia, where I expect the occasional mistake, but in engineering literature as well. Here’s a side view of the bridge, taken in the 1910s:
You get a good sense of the gorge and how shallow the cable curve of Roebling’s bridge would have been. Also, unless I’ve completely taken leave of my senses, that is not a cantilever truss, it’s three simple spans. The answer lies in the history of the bridge. In 1911 (after the top picture, before the second picture), the bridge was “rebuilt” for heavier trains by Gustav Lindenthal. Lindenthal was a great engineer, but not much for subtlety in design, and he effectively built a new bridge on the same site: he reinforced the foundations, replaced the towers, and replaced the trusses. The bridge was double-tracked in 1929, which is when Roebling’s towers were removed, since they were in the way of the second track. So what did the original bridge look like?
This view was taken the same time as the top picture. The extent of Lindenthal’s changes is obvious. The description of the original bridge was that the trusses were 37.5 feet deep and cantilevered 75 feet over the towers on each end. Here’s a close-up:
You can just make out that something’s going on. The verticals are spaced at half the truss depth, so that two panels are a square, and the diagonals typically cross that square. (That’s the definition of a “double-intersection” truss.) On the each side of the tower, in the main span, there’s an extra diagonal in each truss that crosses just the first panel. If the cantilever span was 75 feet, that’s four panels, and sure enough there’s something extra in the forth panel of the side span to the right: another single-panel diagonal. So it looks like the description is correct and the designer, C. Shaler Smith, decided to hide the distinction between the cantilever spans and the side spans, possibly because the cantilever form was new to the US and having a pronounced joint would have looked odd.
In order, a suspension bridge that was never completed, a cantilever truss that was hidden, and a simple truss.
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