An unfortunate number of the bridges I’ve discussed are no longer around, so it’s nice to have a happier story to report. The 1869 Waco Suspension Bridge over the Brazos River is not only still present, it’s about to get a full rehab from friend of OSE (and friend of many others) Patrick Sparks and Sparks Engineering.
The Waco bridge is another good example of normalization: there was a time when a 475-foot main span for a suspension bridge was groundbreaking, but it was well before this bridge was built. While this suspension bridge wasn’t a record breaker, but it was impressive enough in its context that some mythology seems to have grown up around it. That’s unfortunate, since the reality is good enough. It was designed by Thomas Griffith, an engineer who had designed at least one suspension bridge already, over the Mississippi at Minneapolis, and who had a connection to John A. Roebling & Sons, the company hired to build the Waco bridge. (There are references, including in the HAER survey, that Griffith had worked for the Roebling Company, but it’s not clear when that would have been or which projects are the overlap between his career and the company’s.) Thomas’s design used the Roeblong system for the main cables and their anchorages, but not the Roebling diagonal stays. In 1914-1915, the towers were reinforced by the addition of upper arches connecting the pylons and the wood deck structure was replaced by a steel one. Here’s a close-up on the newer stiffening trusses:
Even with the improvements, the bridge is not strong enough for modern traffic and is now used only for pedestrian traffic.
A suspension bridge was not needed at this location, because the Brazos River was not used for heavy shipping. In the top pictures you can see the mid-river piers that once carried a truss bridge for interurban streetcars. The suspension bridge was used, rather, because it was efficient: in the 1860s it provided a cost-effective way to build a connection over the river. It was renovated over a hundred years ago because that was, again, a more cost-effective way to keep the connection than demolition and construction of a new bridge. Only in its latest incarnation as a footbridge has its historic nature played a role.
I look forward to Pat’s write-up of the rehab after it is complete.
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