1950: (Bridge Hunter; Historic Bridges; HAER; 3D Satellite, northern)
2007: (Bridge Hunter; 3D Satellite, southern)
(Update: RoadTraffic-Technology article)
 |
Photo from WASH,27-TACO,11--32 from wa045337. ORIGINAL UNREPLACED APPROACH FROM FIRST SUSPENSION BRIDGE - Tacoma Narrows Bridge, Spanning Narrows at State Route 16, Tacoma, Pierce County, WA |
The 1940 Bridge Hunter link above is well worth clicking because it contains photos of the construction, as well as the destruction, of the bridge.
 |
| Photo from Bridge Hunter
Spinning the first wire of the bridge
Photo taken on January 10, 1940
[You can tell this is an old photo because they did not require that the dignitaries to put on hard hats before they entered the work zone. (I noticed that Historic Bridges selected the same construction photo that I chose. Great minds think alike.)] |
 |
| Bridges Now and Then posted "Tacoma Narrows Bridge under construction showing men on the footwalk leading to the tower, January 3, 1940". (Seattle Post Intelligencer) Mike McCormick: Jan 3 they are spinning the cables (looks like it just started) and 5 months later the bridge was opened? Seems incredibly fast. And four months after opening the bridge is down. |
 |
| Bridges Now and Then posted "Workers clamping the cable wire, Tacoma Narrows Bridge construction, January, 1940." (University of Washington Libraries) |
The engineer of the Tacoma bridge deliberately used a light deck structure of steel girders rather than a heavy truss to save money and to give the bridge a sleek, modern look. Engineers now understand that this was a double-whammy because it was not only weak compared to a truss, the 8' high girders severely disrupted the wind flow over the deck. The girders deflected the wind and caused vortices to form above and below the deck causing aeroelastic flutter forces that caused torsional waves in the deck. The size and duration of those twisting waves broke the bridge. [Ethan Siegel]
(new window) The obligatory video of the destruction
Using a light deck structure was an engineering fad around the 1940s. Fortunately, the 1939 Deer Isle Bridge was stiffened before it suffered damage. [HistoricBridges]
 |
Tacoma Narrows bridge collapse, November 7, 1940, Courtesy WSDOT via historylink.org
|
The replacement bridge opened Oct. 14, 1950.
 |
| Photo from WASH,27-TACO,11--7 from wa0453 7. ROADWAY AND WESTERN TOWER AS SEEN FROM EASTERN TOWER WOLFGANG MAYR SUMMER ICOMOS INTERN ON CABLE FOR SCALE - Tacoma Narrows Bridge, Spanning Narrows at State Route 16, Tacoma, Pierce County, WA |
The replacement design used a truss for stiffness. It was also the first bridge tested in a wind tunnel.
 |
| Photo from WASH,27-TACO,11--11 from wa0453 11. OVERALL VIEW OF THE ROADWAY TRUSS LOOKING EAST - Tacoma Narrows Bridge, Spanning Narrows at State Route 16, Tacoma, Pierce County, WA |
Today, the 1950 bridge handles westbound traffic, and the 2007 bridge carries the eastbound traffic.
 |
| Photo taken by Royce and Bobette Haley in August 2014 from 2007 Bridge Hunter Looking NW-Four towers [The more modern looking towers on the right would be the 2007 bridge. At first, I could not figure out why the trusses of the cross beams are "filled in." But now I suspect the towers are made with reinforced concrete instead of steel.] |
 |
| Nickey.com Tacoma Narrow Bridges Photographed from the top of the 1950 bridge, the bridge is under construction on the left. See More: https://nickeyscircle.com/aerodynamic-designed-bridge/ Express Way Explorers posted with the same comment |
 |
| Atamic Aerials posted "Deep Breaths" A humpback whale spouts in the fading sunlight beneath the Tacoma Narrows Bridges. Bridges Now and Then shared |
 |
| James Torgeson posted One of the cable saddles for the 2nd Tacoma Narrows Bridge ("Sturdy Gertie") that were fabricated at the Bethlehem home plant. |
 |
| Bridges Now and Then posted "Men working in the interior of a caisson for the Tacoma Narrows Bridge showing reinforcing rods, approximately 1939." (Seattle Post-Intelligencer) Jack Hart: Galloping Gertie. The Tacoma Narrows Bridge is a ten minute drive from my door. w https://www.youtube.com/watch?v=XggxeuFDaDU [1:12 video of newsreel clips] |
 |
| Bridges Now and Then posted A look at an anchorage, Tacoma Narrows Bridge, 1949. (Earl White) |
 |
| Dave Frieder commented on the above post My section of Hand Rope and a Rivet from Tacoma-Narrows Bridge. |
(new window) I learned about the Practical Engineer when he noticed my YouTube videos are copyleft and wanted to use a clip from one of my videos in one of his videos with acknowledgment. I was flattered and granted him permission even though he did not need it. I've since learned that his videos are well worth watching. He explains there were resonance forces, but they cause longitudinal waves in the deck. He agrees with Ethan Siegel that the bridge was torn apart by torsional waves caused by flutter forces. In fact, he elaborates that it is aeroelastic flutter. My conclusion is that it must be aeroelastic flutter forces that makes a flag wave.
As encouraged, the following text by Priscilla Long was copied verbatim from historylink.org.
65 photos
As encouraged, the following text by Priscilla Long was copied verbatim from historylink.org.
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 Tacoma from Gig Harbor and the Key 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.
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" (South on the Sound).
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 day the bridge collapsed, the bank rushed to remove the billboard.)
A Lighter, Cheaper Bridge An original design for the Tacoma Narrows Bridge was the work of Washington Department of Highway's leading bridge engineer, Clark Eldridge (1896-1990). But Eldridge's design was compromised when Washington State Highway Director Lacey V. Murrow took his estimate of $11 million to the federal government (the Public Works Administration), which agreed to loan Washington the money but only for a modified, cheaper bridge designed by Leon Salomon Moisseiff (1872-1943). Moisseiff was a renowned suspension-bridge engineer involved in virtually every suspension-bridge design in the United States during the 1920s and 1930s. He believed that suspension bridges could be built much lighter. Moisseiff modified Eldridge's design in part by removing the truss intended to stiffen the deck; "Galloping Gertie's" deck had no supporting truss and was upheld by steel girders that were a mere eight feet high. Not coincidentally, Moisseiff's design required considerably less steel and cost $4 million less to build. Eldridge remained in charge of construction.
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 design 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. Leonard Coatsworth, a Tacoma reporter, was driving across the bridge with his dog Tubby in the car. 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.
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.
The collapse terminated Moisseiff's career and he died less than three years later. Clark Eldridge, who accepted some of the blame, took work with a San Francisco contractor working for the U.S. Navy on Guam. At the outbreak of World War II, he was taken captive by Japan and became a prisoner of war for three and a half years. After the war Eldridge returned to Washington state and resumed work as a consulting engineer and contractor. The collapse reverberated as a personal tragedy in the lives of both men.
The second Tacoma Narrows Bridge, incorporating all lessons learned, was built in 1950.
Sources:
Murray and Rosa Morgan, South on the Sound: An Illustrated History of Tacoma and Pierce County (Woodland Hills, CA: Windsor Publications, Inc., 1984), 116-119; "A Tale of Two Gerties," Gig Harbor Peninsula Historical Society and Museum (http://www.gigharbormuseum.org); Tacoma Narrows Bridge Information Center (http://www.firebirdz.net/tnb); "History of the Tacoma Narrows Bridge," Online Exhibits, University of Washington Libraries, Manuscripts, Special Collections, University Archives (http://www.lib.washington.edu/specialcoll); Bob Carson, Masters of Suspension, Second Edition (Tacoma: News-Tribune, 2007); Craig Holstine and Richard Hobbs, Spanning Washington: Historic Highway Bridges of the Evergreen State (Pullman: WSU Press, 2005); "People of the 1940 Narrows Bridge," Tacoma Narrows Bridge, Washington Department of Transportation website accessed November 15, 2008 (http://www.wsdot.wa.gov/tnbhistory/People/people1.htm#3). See also Richard S. Hobbs and Gerry Coatsworth Holcomb, “Life and Death at the Tacoma Narrows,” Columbia: The Magazine of Northwest History, Vol. 21, No. 2 (Summer 2007), 3-8.
Note: This essay was expanded on November 15, 2008, and corrected on November 12, 2014.
[Priscilla Long on historylink.org, License: CC BY-NC-ND]
No comments:
Post a Comment