Movies - Tacoma Narrows Bridge

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The Tacoma Narrows Bridge is a mile-long (1600 meter) suspension bridge with a main span of 2800 foot (850 m) (the third-largest in the world when it was first built) that carries Washington State Route 16 across the Tacoma Narrows of Puget Sound from Tacoma to Gig Harbor, Washington. The first version of the bridge, nicknamed "Galloping Gertie," was designed by Clark Eldridge and altered by Leon Moisseiff. It became famous for a dramatic filmed structural collapse in 1940. The replacement bridge opened in 1950.

First bridge

Desire for a bridge at this location dates back to 1889 with a Northern Pacific Railway proposal for a trestle, but concerted efforts began in the mid-1920s. The Tacoma Chamber of Commerce began campaigning and funding studies in 1923. Several noted bridge architects, including Joseph B. Strauss, who went on to be chief engineer of the Golden Gate Bridge, and David B. Steinman builder of the Mackinac Bridge, were consulted. Steinman made several Chamber-funded visits culminating in a preliminary proposal presented in 1929 but by 1931 the Chamber decided to cancel the agreement on the grounds that Steinman was “not sufficiently active” in working to obtain financing.

The road to Tacoma’s doomed bridge continued in 1937, when the Washington State legislature created the Washington State Toll Bridge Authority and appropriated $5,000 to study the request by Tacoma and Pierce County for a bridge over the Narrows.

From the start, financing was the issue; revenue from tolls would not be enough to cover construction costs. But there was strong support for a bridge from the U.S. Navy, which operated the Puget Sound Naval Shipyard in Bremerton, and from the U.S. Army, which ran McChord Field and Fort Lewis in Tacoma.

Washington State engineer Clark Eldridge came up with a preliminary, “tried and true conventional bridge design,” and the toll bridge authority requested $11 million from the federal Public Works Administration (PWA). But, according to Eldridge, prominent “Eastern consulting engineers” — led by New York engineer Leon Moisseiff — petitioned the PWA to build the bridge for less.

Preliminary construction plans had called for 25-foot-deep (7.6 m) girders to sit beneath the roadway and stiffen it. Moisseiff, respected designer of the famed Golden Gate Bridge, proposed shallower supports — girders 8 feet (2.4 m) deep. His approach meant a slimmer, more elegant design and reduced construction costs. Moisseiff’s design won out. On June 23, 1938, the PWA approved nearly $6 million for the Tacoma Narrows Bridge. Another $1.6 million was to be collected from tolls to cover the total $8 million cost.

Collapse

The collapse occurred on November 7, 1940. From the account of Leonard Coatsworth, a driver stranded on the bridge during this event:

: 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 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.

The final destruction of the bridge was recorded on film by Barney Elliott, owner of a local camera shop. The Tacoma Narrows Bridge Collapse (1940) is preserved in the U.S. National Film Registry, and is still shown to engineering, architecture, and physics students as a cautionary tale.

No human life was lost in the collapse of the bridge. Theodore von Karman reported that the State of Washington was unable to collect on an insurance policy for the bridge, because its insurance agent fraudulently pocketed the insurance premiums.

Exactly where were Galloping Gertie's remains? On November 28, 1940, the U. S. Navy's Hydrographic Office reported that the remains of the bridge was located at geographical coordinates , at a depth of 30 fathoms.

Video of collapse

In the Internet Archive you will find a longer version: "Footage of the Tacoma Narrows bridge wobbling and eventually, collapsing" from Stillman Fires Collection. http://www.archive.org/details/Pa2096Tacoma

Cause of collapse

The bridge was solidly built, with girders of carbon steel anchored in huge blocks of concrete. Preceding designs typically had open lattice beam trusses underneath the roadbed. This bridge was the first of its type to employ plate girders (pairs of deep I beams) to support the roadbed. With the earlier designs any wind would simply pass through the truss, but in the new design the wind would be diverted above and below the structure. Shortly after its construction in July 1940 (opened to traffic on July 1), it was discovered that the bridge would sway and buckle dangerously in windy conditions. This resonance was longitudinal, meaning the bridge buckled along its length, with the roadbed alternately raised and depressed in certain locations — one half of the central span would rise while the other lowered. Drivers would see cars approaching from the other direction disappear into valleys which were dynamically appearing and disappearing. From this behavior the bridge gained the nickname "Galloping Gertie." However, the mass of the bridge was considered sufficient to keep it structurally sound.

[ Visit the complete Wikipedia entry for Tacoma Narrows Bridge ]

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Movies - Tacoma Narrows Bridge

First bridge

Collapse

Video of collapse

Cause of collapse

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