Getting an accurate photo of a large structure can be difficult. With skyscrapers, for example, you have to get far away to reduce the effect of perspective, and that means you lose detail and likely have other structures blocking part of your view.
With bridges, it’s a bit easier, as you can use the river or valley that the bridge crosses over to provide a clear view. But even then, some aspects of the bridge may be impossible to capture. I’ve been looking for a picture of the Queensboro Bridge that shows its profile properly and I can’t find one. When I say “properly” I mean this: the bridge is badly asymmetrical, but it’s hard to show that.
The Queensboro is the only big bridge in the New York City area that is a cantilever truss, because most of our bridges couldn’t have intermediate piers. The East River is separated into two channels for about two miles by the long and narrow Roosevelt (originally Blackwell’s, later Welfare) Island, and that’s where this bridge crosses. There are towers in Manhattan, in Queens, and two on Roosevelt Island, leading to the following spans: Manhattan to Roosevelt Island (the west channel of the river) has a span of 1,182 feet, the span between the two Roosevelt Island towers is 630 feet, Queens to Roosevelt Island (the east channel) is 984 feet. The end spans are similar, at 460 and 470 feet.
The twenty percent difference between the two big cantilever spans is a reflection of the different width of the two river channels, but there are other issues in play. The land between the Queens tower and the end of the approach is nearly flat, while the land at the Manhattan end rises considerably between the river and approach end. At the time the bridge was constructed, the land at the Queens end was partially empty and of low value, while the land at the Manhattan end was crowded and of high value. The Manhattan approach is shorter and therefore steeper, which is not readily visible. (I know this in part because I occasionally biked over the bridge in 1981 and 1982, going to school, and pushing up the Manhattan approach was a chore.)
The Roosevelt Island span and the end spans are the anchor spans for the two river-channel spans. Because the channels are not so very wide, they consists only of the cantilever trusses, without suspended trusses between. Overall, the bridge is a bit ungainly compared to the suspension bridges north and south of it, but it’s the asymmetry that really sets it apart. Or would, if it could be seen.
