The Tacoma Narrows bridge collapse

The Tacoma Narrows Bridge, built in 1940, was the first Tacoma Narrows Bridge. It 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. Opening for traffic on July 1, 1940 it dramatically collapsed into the river on November 7 of the same year. In 1940 it was the third longest suspension bridge in the world in terms of main span length, behind the Golden Gate Bridge and the George Washington Bridge.

The bridge's collapse had a lasting effect on science and engineering. The actual cause of the bridge failure was aeroelastic flutter. This bridge is a good example of how a Bluff Body placed within a fluid flow can affect the dynamics of the system and effect significant energy within the system. The failure of this bridge boosted research in the field of bridge aerodynamics-aeroelastics, the study of which has influenced the designs of all the world's great long-span bridges built since 1940.

In fluid dynamics, aeroelastic flutter, vortex shedding and vortex-induced vibrations (VIV) are motions induced on bodies interacting with an external fluid flow like air or water. Vortex Shedding around a bluff body at specific Reynolds numbers causes the flow to becomes asymmetric and the Kármán vortex street occurs.

A natural and very powerful phenomenon, Vortex shedding occurs throughout the natural world. In the case of the Tacoma Narrows bridge once the wind maintained a 40 mile per hour flow it was only a matter of time before structural failure occurred. Starting after this spectacular failure, the science of fluid dynamics has specialized in suppression techniques for industries as varied as: bridges, stacks, transmission lines, aircraft control surfaces, offshore structures, thermowells, engines, heat exchangers, marine cables, towed cables, drilling and production risers in petroleum production, mooring cables, moored structures, tethered structures, buoyancy and spar hulls, pipelines, cable-laying, members of jacketed structures, and other hydrodynamic and hydroacoustic applications. The most recent interest in long cylindrical members in water comes from the off-shore oil and gas industry where drilling in depths of 1000 m or more now occurs.

© CC- (?) 2005 Cesareo de La Rosa Siqueira

Theodore von Kármán was a Hungarian-American mathematician, aerospace engineer and physicist who was active primarily in the fields of aeronautics and astronautics. He is responsible for many key advances in aerodynamics, notably his work on supersonic and hypersonic airflow characterization. He is regarded as the outstanding aerodynamic theoretician of the twentieth century.[1]

Credited with contributing to a number of concepts like the von Kármán vortex street (flow past cylinder), von Kármán integral equation (boundary layers), Kármán-Pohlhausen parameter (boundary layers) and many more, Theodore von Kármán was awarded the National Medal of Science "For his leadership in the science and engineering basic to aeronautics; for his effective teaching and related contributions in many fields of mechanics, for his distinguished counsel to the Armed Services, and for his promoting international cooperation in science and engineering."[2]

1) I. Chang, Thread of the Silkworm. Perseus Books Group (1995). ISBN 0-465-08716-7.

2) "The President's National Medal of Science: Recipient Details".