When the Tacoma Narrows Bridge opened to traffic on July 1, 1940, it was the world’s third longest suspension bridge by main span. Within a short time the bridge earned the nickname Galloping Gertie due to the fierce movements of the roadway that occurred during high wind events. Just a few months later, on this day in 1940, the Tacoma Narrows Bridge collapsed amid windy conditions, crashing into the Tacoma Narrows Straight down below. There were no human fatalities in the event, but one dog died when the abandoned car he was in fell into the water during the collapse.
Why did the Tacoma Narrows Bridge collapse?
Soon after the bridge opened in the summer of 1940 people noticed that even relatively mild wind caused the bridge to bounce up and down. Approaching drivers could see cars disappear and reappear as the bridge rolled like waves. Engineers believed the mass of the bridge to be sufficient enough to ensure it remained structurally sound in this event. However, the failure of the bridge occurred when a never before seen twisting motion overtook the bridge, causing half to twist one way and the other the reverse and vice versa over and over. A phenomena known as aeroelastic fluttering caused the twisting.
Ultimately a Federal Works Commission gave three main reasons for the collapse: 1. Aerodynamic instability by self-induced vibrations in the structure. 2. Eddy formations that might be periodic in nature. 3. Random effects of turbulence, that is the random fluctuations in velocity of the wind. Today, the collapse of the bridge serves as a common lesson for engineering and architectural students and professionals.
Video of Tacoma bridge collapse
Below is a video of the collapse filmed by Barney Elliot. He sold the footage and it has since been released into the public domain by the Prelinger Archives. You may be wondering, who is the man on the Tacoma Narrows Bridge before it collapses? That Leonard Coatsworth, who was an editor at The News Tribune in Tacoma. He was trying to save his dog Tubby from his car, which he abandoned on the bridge, making him the last person to drive on the bridge. He was unable to retrieve Tubby. According to Coatsworth’s eyewitness account:
Around me I could hear concrete cracking. I started back to the car to get the dog, but was thrown before I could reach it. 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 [1,500 ft; 460 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 … Towards 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.