Bridge aerodynamics: past, present and future, London

20 May, 2015 | 18:15 - 20:00

Bridge aerodynamics: past, present and future, London

About this event

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.

Allan Larsen

(COWI Consulting Engineers, Lyngby, Denmark)
Tacoma Narrows Bridge, still resonating after 75 years?

Allan Larsen received his MSc in Mechanical Engineering from the Danish Technical University in 1979, the Von Karman Diploma in Fluid Dynamics in 1981 and a PhD in Flow Induced Vibration in 1984.

Since 1989 he has been employed by COWI as a wind engineer for major bridge projects including the Storebælt Bridge - Denmark, Höga Kusten Bridge - Sweden, Chacao Bridge - Chile, Stonecutters Bridge - Hong Kong, Messina Bridge Project - Italy and Izmit Bridge - Turkey.

Prof. Mike Graham

(Imperial College, London)
Aerodynamic control of long span bridges.