The Tacoma Narrows Bridge

November 7, 2017

Last week we explored the world of horseracing and author Dick Francis. This week we will be discussing galloping. But unlike how a horse gallops, this galloping took place on November 7, 1940 and has since become a text-book example of what NOT to do when building a bridge.

We are talking, of course, about the Tacoma Narrows Bridge which sank on this date. It was dubbed ‘Galloping Gertie’ as even the most gentle of breezes would cause the roadway to sway. I can only imagine the feeling of unease one had when driving over the structure.

For a local newsman it proved terrifying. From the infallible Wikipedia:

“Leonard Coatsworth, a Tacoma News Tribune editor, was the last person to drive on the bridge:

‘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 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 bridge had opened only four months earlier! In reading about everything that went wrong the biggest mistake seemed to have been that in a desire to save money on what was perceived as a bridge which would be lightly used, the design was flawed from the beginning.

Ultimately they determined the bridge failure was due to ‘aeroelastic flutter’. Unless, of course, you are an engineer the term means little. The film of the event for us laypeople, however, reveals a structure bucking like an unbroken stallion during its first ride.

Although I was not around in 1940, I was going to school in Tacoma on February 13, 1979 when another bridge met the same fate as Galloping Gertie. It was then when I grasped the power of a Pacific Northwest windstorm. During the night prior to its sinking, sustained winds of 85 mph buffeted the Hood Canal floating bridge . They estimated gusts up to 120 mph (called a ‘hurricane’ most anyplace else as any sustained wind over 72 mph is classified as such) had occurred. The structure was swamped and at 7 a.m. that dark, windy and rainy morning, the bridge sank.

Fast forward to November of 1990 and yet a third Washington state bridge met a similar doom. We watched in fascinated horror live TV news on the morning of November 25^th as the floating bridge – being resurfaced to continue carrying traffic while a new span was constructed – which connected Mercer Island to Seattle was inundated. As my husband no doubt said at the time: “surf’s up!”

In the 30 plus years I’ve lived in Western Washington there are a couple things you can count on me doing. First, I will do anything I can to avoid driving in windstorms. I’ll drive in rain, snow, sleet and dark of night but the wind stops me. Second, I will move to the northeast corner of any structure, especially one with nearby tall trees. The worst winds hale from the southwest so if a tree is going to come down it will fall from that direction. When we still lived in Kirkland, my family knew that a heavy wind meant ‘going to the mattresses’ and sleeping on the floor of the living room as far from the trees as possible.

Now that we are in windstorm ‘season’ remember to batten your hatches when the wind blows and you just might want to avoid driving on bridges.

As always some interesting links PLUS a video from the Washington State History museum which tells the entire Galloping Gertie story.

https://en.wikipedia.org/wiki/Tacoma_Narrows_Bridge_(1940)

https://en.wikipedia.org/wiki/Pacific_Northwest_windstorm

http://www.wsdot.wa.gov/TNBhistory/Connections/connections3.htm

https://www.youtube.com/watch?v=KqqyAZDpV6c