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Throwback Thursday: Tacoma Narrows Bridge Collapse 1940

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Tacoma Narrows Bridge Image One
Image Credit: www.tacomanarrowsbridge.org

The caption above reads:

On July 1, 1940, the Tacoma Narrows Bridge was opened to traffic. This picture, taken from the air during dedication ceremonies, plainly shows three unusual characteristics of design: (1) Extremely narrow deck – 39′; (2) extreme length of suspension span – 2800′; (3) the solid stiffening girders used in the place of orthodox truss girders. Use of the solid girders is commonly blamed for the collapse.

Seventy-nine years ago, today, the Tacoma Narrows Bridge collapsed at approximately 11:00am PST due to a wind-induced aeroelastic flutter.

[A] suspension bridge in [Washington State] that spanned the Tacoma Narrows strait of Puget Sound, between Tacoma and the Kitsap Peninsula, [it] opened to traffic on July 1, 1940. The bridge’s collapse has been described as “spectacular” and in subsequent decades “has attracted the attention of engineers, physicists and mathematicians”. Throughout its short existence, it was the world’s third-longest suspension bridge by main span, behind the Golden Gate Bridge and the George Washington Bridge.

Tacoma Narrows Bridge Image Two
Image Credit: tacomanarrowsbridge.org
Notice the view of the car in the center of the twist.

Construction began in September 1938. From the time the deck was built, it began to move vertically in windy conditions, so, construction workers nicknamed the bridge Galloping Gertie. The motion continued after the bridge opened to the public, despite several damping measures. The bridge’s main span finally collapsed in 40-mile-per-hour (64 km/h) winds on the morning of November 7, 1940. Efforts to replace the bridge were delayed by the United States’ entry into World War II […]. The portion of the bridge that fell into the water now serves as an artificial reef.

The bridge’s collapse had a lasting effect on science and engineering. In many physics textbooks, the event is presented as an example of elementary forced resonance. [The] bridge collapsed because normal speed winds produced aeroelastic flutter that matched the bridge’s natural frequency. The collapse boosted research into bridge aerodynamics-aeroelastics, which has influenced the designs of all later long-span bridges.

[Source]

Tacoma Narrows Bridge Image Three
Photo Credit: tacomanarrowsbridge.org

I saw the Narrows bridge die today and only by the grace of God, escaped dying with it…

I drove on the bridge and started across. 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 on the roadway. I decided the bridge was breaking up and my only hope was to get back to shore. 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.

[Leonard Coatsworth, Tacoma News Tribune Editor]

[See also Tubby The Dog]

Some Bridge Facts:
♦ [The] entire 1940 bridge did not collapse into the water, though most of the center span did fall. The side spans were badly damaged and the 2 big towers got bent beyond repair […]. It would be 10 years before the bridge was replaced.
♦ [Due] to the undulating motions up and down […], you could be driving across it and, the car ahead of you might dip out of view. Sometimes the roadway would rise above the height of a car […].
♦ The 1940 bridge remains at the bottom of the water have provided a place for sealife [sic] that was not there, before and much of the life includes the giant Pacific octopus as well as lingcod, wolf eels and black seabass [sic].
♦ (Referencing the image at the very top…) Did a ship go under the bridge for opening day in 1940? Yes, it is true…the ship Atlanta was a Coast Guard Cutter. Ironically, not only was it the first ship to go under the bridge on opening day July 1, 1940, it was also the last ship to travel under the bridge before it collapsed […]. When the concrete started to crumble and fall off, the ship was underneath and pieces fell on her deck. Luckily, no pieces were big enough to cause any damage to the ship and the ship’s Commander was one of the first to report the collapse.

Link to the Armistice Day Blizzard
Harbor History Museum