page_title: Tacoma Narrows Bridge (1940)
section_title: Design and construction
hierarchical_section_title: Tacoma Narrows Bridge (1940) / Design and construction
caption_attribution_description: Cover of the 38-page program for the opening ceremonies for the Tacoma (WA) Narrows Bridge and McChord Field (USAAF), now McChord AFB, part of Joint Base Lewis-McChord, Lakewood, WA.
context_page_description: The 1940 Tacoma Narrows Bridge, the first Tacoma Narrows Bridge, was a suspension bridge in the U.S. state of Washington that spanned the Tacoma Narrows strait of Puget Sound between Tacoma and the Kitsap Peninsula. It opened to traffic on July 1, 1940, and dramatically collapsed into Puget Sound on November 7 the same year. The bridge's collapse has been described as "spectacular" and in subsequent decades "has attracted the attention of engineers, physicists, and mathematicians". Throughout its short existence, it was the world's third-longest suspension bridge by main span, behind the Golden Gate Bridge and the George Washington Bridge.
  Construction began in September 1938. From the time the deck was built, it began to move vertically in windy conditions, so construction workers nicknamed the bridge Galloping Gertie. The motion continued after the bridge opened to the public, despite several damping measures. The bridge's main span finally collapsed in 40-mile-per-hour winds on the morning of November 7, 1940, as the deck oscillated in an alternating twisting motion that gradually increased in amplitude until the deck tore apart.
context_section_description: The desire for the construction of a bridge between Tacoma and the Kitsap Peninsula 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 engineers, including Joseph B. Strauss, who went on to be chief engineer of the Golden Gate Bridge, and David B. Steinman, who went on to design 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. Another problem with financing the first bridge was buying out the ferry contract from a private firm running services on the Narrows at the time.
  The Washington State legislature created the Washington State Toll Bridge Authority and appropriated $5,000 (equivalent to $84,000 today) to study the request by Tacoma and Pierce County for a bridge over the Narrows.
  From the start, financing of the bridge was a problem: revenue from the proposed tolls would not be enough to cover construction costs, but there was strong support for the 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 near Tacoma.
  Washington State engineer Clark Eldridge  produced a preliminary tried-and-true conventional suspension bridge design, and the Washington Toll Bridge Authority requested $11 million (equivalent to $185 million today) from the Federal Public Works Administration (PWA). Preliminary construction plans by the Washington Department of Highways had called for a set of 25-foot-deep (7.6 m) trusses to sit beneath the roadway and stiffen it.
  However, according to Eldridge, "Eastern consulting engineers"—by which Eldridge meant Leon Moisseiff, the noted New York bridge engineer who served as designer and consultant engineer for the Golden Gate Bridge—petitioned the PWA and the Reconstruction Finance Corporation (RFC) to build the bridge for less. Moisseiff and Frederick Lienhard, the latter an engineer with what was then known as the Port of New York Authority, had published a paper that was probably the most important theoretical advance in the bridge engineering field of the decade. Their theory of elastic distribution extended the deflection theory that was originally devised by the Austrian engineer Josef Melan to horizontal bending under static wind load. They showed that the stiffness of the main cables (via the suspenders) would absorb up to one-half of the static wind pressure pushing a suspended structure laterally. This energy would then be transmitted to the anchorages and towers. Using this theory, Moisseiff argued for stiffening the bridge with a set of eight-foot-deep (2.4 m) plate girders rather than the 25-foot-deep (7.6 m) trusses proposed by the Washington Toll Bridge Authority. This approach meant a slimmer, more elegant design, and also reduced the construction costs as compared with the Highway Department's design proposed by Eldridge. Moisseiff's design won out, inasmuch as the other proposal was considered to be too expensive. On June 23, 1938, the PWA approved nearly $6 million (equivalent to $109 million today) for the Tacoma Narrows Bridge. Another $1.6 million ($29.1 million today) was to be collected from tolls to cover the estimated total $8 million cost ($145.3 million today).
  Following Moisseiff's design, bridge construction began on September 27, 1938. Construction took only nineteen months, at a cost of $6.4 million ($116.2 million today), which was financed by the grant from the PWA and a loan from the RFC.
  The Tacoma Narrows Bridge, with a main span of 2,800 feet (850 m), was the third-longest suspension bridge in the world at that time, following the George Washington Bridge between New Jersey and New York City, and the Golden Gate Bridge, connecting San Francisco with Marin County to its
caption: Program for the opening of the Tacoma Narrows Bridge, June 30, 1940
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