Engineering And Art At The Manhattan Bridge

I’ve talked about the Manhattan Bridge before, and here it is again. First, it’s a great bridge and is often overlooked because its immediate neighbor is the Brooklyn Bridge. Second, thanks to the Federal Art Project that was part of the New Deal, we have the photo above, federally-owned (and therefore copyright-free) and taken by Berenice Abbott.

Even among professional photographers, Abbott was unusually skilled at framing shots, so the formal artistic quality of the photo is no surprise. But it’s important to mention that there’s no fakery here. That is a real view of one of the towers of the bridge that can be replicated by anyone standing on the pedestrian walkway. Even in an arty photo like this, you can pick up some of the engineering design: the tower structure is built up of riveted steel sections with plates at the exterior; the ornament is partly cast metal. This angle gives a good sense of the load path: the suspender cables in tension carrying the deck load up to the main cables, which are pressing down on the tower.

Here’s a less artistic view of a tower, from the HAER survey:

The curved bulge where the deck passes the tower is the walkway, and that’s where Abbott was standing for her photo. You can just make out the band of cross-bracing up the narrow side of the tower, matching the more-prominent cross-bracing on the main faces. This picture makes the distinction between the structure of the tower and the ornament clear: the ball finials, the cornice below the cables, and the upper walkway are add-ons, while the four main verticals and the cross-bracing connecting them are the working parts of the tower. The four verticals are located, unsurprisingly, directly in line with the four main cables, to carry the load straight down, so the cross-bracing is there to join the verticals so they work together for lateral wind load.

In short: the engineering design hides nothing, and so allows the design intent to be read. You can debate whether the added ornament is a distraction or not, but an artistic shot like Abbott’s is based on the lines of the structure more than anything else.