The most basic is stress under gravity load, because if that isn’t okay, the structure likely collapses. The short version is that there are many different possible analyses for a given structure, but they are not all equally easy to perform and they are not all equally useful. Given the talent and experience that went into the original the design, the big question is: what went wrong? Both the girders and the trusses are discontinuous at the towers, as they are not meant as primary supports, but rather to stiffen the deck. The trusses are fastened above the original plate girder stiffeners, with the girders serving as the bottom chord for the trusses. This picture obviously shows it after the 1943 side trusses were added for additional stiffness, and before they were removed in 2003 in favor of wind fairings. The fact that Othmar Ammann was involved is very much visible in the tower design, which is pretty much the tower used at every suspension bridge he worked on.
The picture above, from the 1991 HAER survey of the bridge, gives a good sense of its appearance. I want to expand on yesterday’s brief comment about the design issues with the Whitestone Bridge, because it illustrates not just a moment in the history info suspension bridges, but a never-ending tension in structural engineering.
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