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Bridge aerodynamics: past, present and future, London

Event organised by Wind Engineering Society

20 May 2015

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This meeting will be preceded by the WES AGM at 6.00pm (Refreshments available from 5.30pm in the Brasserie)

Allan Larsen

Tacoma Narrows Bridge – Still Resonating After 75 Years?

On 7 November 1940 the then newly built Tacoma Narrows Bridge collapsed in a 19 m/s gale creating some of the most spectacular footage in the history of civil engineering.

While the monumental University of Washington investigation following the collapse established the wind to be responsible for the collapse a clear understanding of the aerodynamic mechanism did not emerge. As a result myths and speculations as to the reasons for the collapse emerged.

At the 60 year anniversary of the Tacoma incident the present author proposed a physical model for the large amplitude wind induced torsional motions (sometimes referred to as one-degree-of-freedom flutter or A2* instability) which led to the bridge collapse.

This model has generally been accepted as providing a satisfactory physical explanation for the collapse. Now at the 75 year anniversary the model is cast in a simple but rigorous mathematical framework which allows the amplitude dependent nature of the torsional wind response to be predicted.

The WES presentation will cover the collapse and observations to be made from the original footage and the following investigations, some of the myths created and the development of the author's traveling vortex model.

Professor Mike Graham

Please note there is no charge and non-members of the Society are welcome to attend.

For more information please contact:

Pauline Arundel