Classic Engineering Disaster: THe Tacoma Narrows Bridge collapse

The last post I put up was about a chemistry-related disaster: Here's a physics/engineering related disaster, and a good reason why you need to make sure that you do your calculations correctly!

At a mile long, the Tacoma Narrows bridge was the third longest bridge in the world at the time it was built.

The first version of the bridge, nicknamed Galloping Gertie, was designed by Clark Eldridge and altered by Leon Moisseiff. In 1940, it became famous for a dramatic wind-induced structural collapse, an event that was caught on motion picture film. The replacement bridge opened in 1950.

The guy who designed this first bridge asked for $11 million but only recieved $6 million so he had to cut a few corners. And in the video that you're about to see you can see what happens when you do that (physics is not only about getting the questions right in the exam - if you get them wrong in real life then THIS could happen. Seriously.)



The wind-induced collapse occurred on November 7, 1940, due to a physical phenomenon known as mechanical resonance. From the account of Leonard Coatsworth, a driver stranded on the bridge during this event:

" Just as I drove past the towers, the bridge began to sway violently from side to side. Before I realized it, the tilt became so violent that I lost control of the car… I jammed on the brakes and got out, only to be thrown onto my face against the curb… Around me I could hear concrete cracking… The car itself began to slide from side to side of the roadway.

On hands and knees most of the time, I crawled 500 yards [450 m] or more to the towers… My breath was coming in gasps; my knees were raw and bleeding, my hands bruised and swollen from gripping the concrete curb… Toward the last, I risked rising to my feet and running a few yards at a time… Safely back at the toll plaza, I saw the bridge in its final collapse and saw my car plunge into the Narrows. "

The final destruction of the bridge was recorded on film by Barney Elliott, owner of a local camera shop. The Tacoma Narrows Bridge Collapse (1940) is preserved in the U.S. National Film Registry, and is still shown to engineering, architecture, and physics students as a cautionary tale.

No human life was lost in the collapse of the bridge. Theodore von Karman reported that the State of Washington was unable to collect on one of the insurance policies for the bridge, because its insurance agent fraudulently pocketed the insurance premiums. The agent, Hallett R. French who represented the Merchant's Fire Assurance Company, was charged with grand larceny for withholding the premiums for $800,000 worth of insurance. The bridge, however, was insured by many other policies that covered 80% of the $5.2–million structure's value. Most of these were collected without incident

On November 28, 1940, the U. S. Navy's Hydrographic Office reported that the remains of the bridge were located at geographical coordinates 47°16′00″N, 122°33′00″W, at a depth of 180 feet (55 m).

More on the Tacoma Narrows collapse can be found on Wikipedia