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1940: The Tacoma Narrows Bridge Failure

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The 1940 Bridge nearing completion:
You can still see the catwalks along the
main cables.
Its already oscillating in this picture.

On November 7, 1940, at about 11 a.m., the Tacoma Narrows Bridge collapses in a high wind. The bridge spanned the Tacoma Narrows, a deep, narrow section of Puget Sound that separates Pierce County from the Kitsap Peninsula. The bridge collapses four months and seven days after it is dedicated. It had severely oscillated even as it was being built: Workers on the bridge sucked lemons to combat seasickness and dubbed it "Galloping Gertie."

The structure's wave-like motions made it a thrill to drive across -- joyriders increased traffic on the bridge from the beginning -- but no one expected it to collapse. The bridge disaster was a tragedy for Tacoma, which lost the retail trade from Kitsap County and a connection to the Bremerton Navy Yard during the years of World War II. The engineering failure became a textbook case and revolutionized designs and procedures for building suspension bridges.



Realizing a dream
The Tacoma Narrows is the single point in the 20,000 square miles of Puget Sound where the Washington mainland and the Olympic Peninsula are close. For years, it had been clear to State officials that the Narrows would have to be bridged in order to open up the spectacular and thinly populated Peninsula.

Aware of this situation, the Washington State Legislature created the Washington Toll Bridge Authority in 1937, with a mandate to finance, construct and operate toll bridges.

Between the time the state legislature authorized the money to study the proposal and the completion of that study, Lacey Murrow, Director of the Washington State Department of Highways, had given Clark Eldridge, a bridge engineer with the department, the green light to design a bridge to span the Narrows.

Eldridge’s plan called for a 5,000 foot, two-lane suspension bridge. When completed, the structure would be the third longest suspension bridge in the world.

After examination of Eldridge's plans in May of 1938, the Public Works Administration agreed to finance 45 percent of the construction, provided that the State of Washington retain a board of independent engineering consultants to reexamine Eldridge's design. The State complied and employed the firm of Moran and Proctor to study the plans for the substructure.


Caisson Plan, revolutionary at the time

Furthermore, the State retained Leon S. Moisseiff, the world-renowned suspension bridge builder to examine the plans concerning the superstructure. Both Moran and Proctor and Moisseiff made significant alterations to Eldridge's original design. Specifically, Moran and Proctor wanted an entirely different substructure. As to Moisseiff, he substituted the 25 foot deep open stiffening truss with an eight foot, shallow plate girder, resulting in a much lighter bridge.

Prior to the opening of the construction bids, a group of contractors notified the engineers they could not meet the specifications for the substructure. As a result, Moran and Proctor's plans for the substructure were scrapped, and Eldridge's original plans for the substructure were reintroduced. After consultation with Moisseiff, it was agreed that Eldridge's design for the substructure would be used in conjunction with Moisseiff's plans for the superstructure.

This modified plan was approved by the Public Works Administration and bids for construction were opened on September 27, 1938. The Pacific Bridge Company's low bid of $5,594,730.40 was accepted. The Bethlehem Steel Company was an associate contractor that supplied and erected the steel and wire.

Vertical oscillations of the roadbed occurred even during the construction phase and raised questions about the structure's stability. Some breezes as low as four miles per hour caused oscillations, while stronger breezes often had no effect. Prior to the bridge's opening, hydraulic buffers were installed at the towers to control the stresses.

The undulations continued, however, and further studies were undertaken at the University of Washington. Their recommendation of the installation of tie-down cables in the side spans were implemented, but to little effect.

Work on the bridge began in early 1939 and on July 1, 1940, the $6.4 million bridge opened and the link between the Washington mainland and the Olympic Peninsula was complete.

The City of Tacoma and Pierce County Board of Commissioners asked the State to construct a bridge across the Narrows. The legislature appropriated $25,000 to study the request.

Satisfied with the results of the study, on May 23, 1938, the State of Washington submitted an application to the Public Works Administration (PWA) requesting funds for construction of a bridge.

Building the First Bridge


600 ton anchor being dropped for caisson mooring


The west tower begins to rise out of the water


The completed towers


Completed Catwalks with guy wires for the spinning sleds


Ceremony marking the first run of the wire spinning sled


Reels of wire waiting to be loaded onto the spinning sled for the main cables


Spinning the wires for the main cables
A Dream Come True

On July 1, 1940, a clear day with blue skies, some 10,000 people turned out for the dedication and opening of the bridge. Washington Governor Clarence Martin extolled the economic and military progress that it would spur. Tacomans saw the bridge as a dream come true -- it would open Tacoma to shoppers previously dependent on Bremerton, and enable access from Pierce County to the Bremerton Navy Yard. The bridge was slender (too slender as it turned out) and beautiful. The 2,800-foot span strung between the towers was the third longest span among the world's suspension bridges. "Everyone marveled," writes historian Murray Morgan, "at the gossamer grace of a structure so long" .


Even in a low wind, the bridge would oscillate

People enjoyed Galloping Gertie tremendously. They would wait until the wind was "right," drive up to Tacoma Narrows, then wait in line to "ride the bridge." Everyone was sure it was safe. A bank put up a billboard on the Tacoma side, proclaiming itself to be just as safe as the bridge. (The bank rushed to remove the billboard the day the bridge collapsed.)

No one thought the bridge would fail, but there were worries about its propensity to gallop. The wave-like motions of the bridge went up and down in the direction of the roadspan, and only during collapse did the bridge begin to move laterally. F. Bert Farquarson, a civil engineering professor at the University of Washington, began making measurements and suggesting alterations to reduce the movement. He was present at the collapse, and his astonishment was as great as anyone's.

The Collapse

On the day of the collapse -- known as the Pearl Harbor of Bridge Engineering -- Gertie was galloping fast and hard.  A steady 40-mile and hour wind was howling through the Narrows, which was a common event.   The wave motion changed from an up and down motion to a twisting motion.  As air passed over and under the bridge, depending on the twist, the effect would increase.  At its height, one side of the bridge would be about 28 feet above the other side, and the road-bed would be at a 45 degree slope!

When Leonard Coatsworth, a Tacoma reporter, was driving across the bridge with his dog Tubby in the car.   The bridge's oscillation changed from an up and down motion (about a 30-hertz transverse wave) to a twisting motion, with two opposing waves (about a 14-hertz  double transverse).

Here is his account of what happened:

"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" (quoted in Tacoma Narrows Bridge Information Center).

Professor Farquarson was there doing his measurements and ran out and tried to save Tubby, but the dog bit him and he gave up the effort. Tubby was the only fatality.

For about 30 minutes, the center span endured the twisting, then things started falling apart.


Wind Storm Damage photographed prior to the collapse

 

 

At about 10:30 A.M., a center span floor panel dropped into the water 195 feet below. The roadbed was breaking up, and chunks of concrete were raining into the Sound.

At 11:02 A.M., 600 feet of the western end of the span twisted free, flipped over, and plunged down into the water. Engineers on the scene hoped that once this had happened, the remainder of the span would settle down.


The main section falling is 600 feet long, the single section of roadway that's falling is 25 feet long.

 

The twisting continued, and at 11:09 A.M., the remaining bridge sections ripped free and thundered down into the Sound. When this happened, the 1,100 foot side spans dropped 60 feet, only to bounce up and then settle into a sag of 30 feet.

As for the center span, it rested on the dark and tide-swept bottom of the Narrows..

The cause of the failure was solid girders, which took wind and acted like sails (girders with perforations would have let the wind pass through). Also, the bridge was not stiff enough or heavy enough to withstand the wind of the Tacoma Narrows.

Full map from sidescan data
These days most are aware of the location, identification and recoveries from the Titanic. The Titanic was a large ship but in comparison it would take 5.56 Titanic’s end for end to occupy the space that Galloping Gertie now occupies. In raw materials the bridge contained 5.0 times that of Titanic. These figures make Galloping Gertie the largest man made structure ever lost at sea. In addition the current swept bottom of the Narrows has now become the largest single man made reef supporting an abundance of marine life.

The sunken remains of "Galloping Gertie" were placed on the National Register of Historic Places in 1992 to protect her from salvagers.

Reconnecting Gig Harbor
The new bridge in 1950, with Mt Rainier in the back ground.

 

For the next 10 years, Tacoma and Gig Harbor/the Olympic Peninsula were once again unconnected by bridge. Then after 29 months of construction, a new, much safer Tacoma Narrows Bridge opened on Oct. 14, 1950.

The new bridge spans 5,979 feet -- 40 feet longer than "Galloping Gertie" -- and is part of Hwy. 16.

The new bridge rocks a bit in heavy winds (I felt it), but it safely stands to this day (2003).

Some 50,000 vehicles drive across the bridge every week day.  Daily, especially on Friday afternoons, long lines develop on both sides of the bridge, the traffic volume much larger than the bridge was designed for. 


The Tacoma Narrows Bridge, in 1999.

Starting this year (2003) a new bridge is being built, next to the existing bridge... Its not expected to be done until 2009.


An artist's rendition of the two bridges.