It Was Sixty-five Years Ago Today. . .That The Tacoma Narrows Bridge Collapsed Into Puget Sound, Four Months After Opening

You may have seen the movie of the Tacoma Narrows Bridge collapsing in science class. It is often used to demonstrate resonance. Even during construction, they noticed that breezes as low as four miles per hour caused oscillations, while stronger breezes often had no effect. The $6.4 million Tacoma Narrows Bridge opened in July, 1940, linking the Washington State mainland with the Olympic Peninsula. Click here to download a clip of the movie.

Locals named the bridge "Galloping Gertie." People would drive hundreds of miles to cross the bridge and experience the rolling and undulating. The disappearance and reappearance of cars in the concrete swells was a highlight.

On Thursday, November 7, 1940, the center span had been undulating three to five feet in winds of 35 to 46 miles per hour. They closed the bridge. Soon, the motion dramatically changed from a rhythmic rising and falling to a two-wave twisting motion with the road tilting 45 degrees from horizontal one way and then 45 degrees from horizontal the other.

The roadbed broke up, and finally the center span of the bridge fell into the Sound. 600 feet of the western end of the span twisted free, flipped over, and plunged into the water. At 11:09 A.M., the remaining bridge sections ripped free and thundered down into the Sound. The 1,100 foot side spans dropped 60 feet, bounced up and settled into a sag of 30 feet. The center span rested on the bottom of the Narrows.

Leonard Coatsworth, a Tacoma newspaper editor, somehow talked the guards into letting him cross after the bridge had closed. He was the last person to drive on the bridge:

"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. I started to get my dog Tubby, but was thrown again before I could reach the car. 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 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."

---o0o---