Engineers want to take pride in their work, just like everybody else. We are sometimes forced by circumstances to create designs that are less than elegant – the fact that the word “kludge” was created fifty or sixth years ago to describe that kind of design suggests it may be less rare than we’d like to think. The thing to remember about kludges is that they work.
The picture above shows the Third Avenue Elevated at the Bowery circa 1900. At that time, the els were the best mass transit in New York, but the IRT subway that opened in 1904 was faster and had a higher capacity, and didn’t annoy the neighbors when it was in operation. The vast expansion of the subway system with the 1910s Dual Contract system doomed the els; the city-built IND system in the 1920s and 30s was designed to specifically replace a number of the el lines.
While I was looking for the paper open the Hell Gate Bridge in the Transactions of the ASCE, I stumbled across a paper titled “Manhattan Elevated Railway Improvements”, also published in 1918. The paper is 194 pages long, and given that the els were on their way out by 1918, I was curious what the improvements were. The short answer is that the IRT company, which had bought the els to complement the new subway, added a third track to each of the four main lines so that there could be express service (heading downtown in the morning, uptown in the evening). Here’s a map of the elevated system:
As you can see from the postcard above, some portions of the els had plenty of room to add new tracks. Connecting the two separate structures at the Bowery with cross-girders to support a center third track actually improved the overall lateral stability. But in many areas there was not enough room in the middle and that’s where the solutions got less elegant. Here are some of the track-structure sections:
In figure 36, the two local tracks remain where they were, on the lower level more or less centered on the columns. The station platform that had been between them has been removed and replaced by side platforms supported by new cantilevered trussed girders. The third track is supported on a new pedestal in the center and its platforms supported partially on the same pedestal and partially on the platforms below. In figure 37, new columns have been added outboard of the old columns and new girders run the full width. In figure 39, new girders cantilever to both sides of the old columns. And so on. There are a lot of different conditions described in the paper.
In some cases existing steel was replaced, but more often it was reinforced. Here’s an example of increasing the shear capacity on a trussed girder by drilling holes and riveting new lacing to double the trussing:
Increased loads on existing columns didn’t just require reinforcing or replacement of the columns, it required reinforcing the foundations. Here’s sheet-piling being used to create a new concrete pier around old wood piles:
Back to the Bowery, a photograph of the work in progress. The closest right-hand column has been shored:
And the center structure being installed:
On Greenwich Street, the third track fully in place in the center:
Finally, I want to emphasize something that I hope is obvious. Just because some of these designs are awkward doesn’t mean they were any easier for the designers. The article contains some good examples of how the additions were analyzed for train and wind loads:
Just because a designed is awkward doesn’t mean it doesn’t work.
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