Tacoma Narrows Bridge Models Tested in NRC Wind Tunnel

Tacoma, Washington's original Tacoma Narrows Bridge was nicknamed 'Galloping Gertie' for its tendency to sway in windstorms. In 1940, the bridge collapsed due to aerodynamic instability during 65 km/h winds. As a result of this catastrophe, bridges routinely undergo wind tunnel testing during the design process to minimize wind-induced vibrations. NRC has extensive expertise in this area.

The current Tacoma Narrows Bridge, built in 1950, is now stretched beyond capacity. A new bridge, to be built parallel to the existing structure, has been proposed.

Models of the existing and proposed bridges in NRC's 9m x 9m wind tunnel

In spring 2003, researchers at the NRC Institute for Aerospace Research (NRC-IAR) and Rowan Williams Davies & Irwin Inc. (RWDI) used NRC's 9m x 9m wind tunnel to test aeroelastic models of the existing and proposed Tacoma Narrows Bridges. The side-by-side models respond to wind in exactly the same way as the real structures and will help researchers identify potentially significant wind interference effects arising from their proximity.

NRC Alumni and President of RWDI, Dr. Peter Irwin explained, "We came to NRC not only because of its excellent 9m x 9m Wind Tunnel, which is one of the largest in North America, but also because we can draw on the expertise of NRC's own wind engineering group. This is a great benefit in complex tests like these." RWDI designed and built the 1:211-scale aeroelastic models and then a team of RWDI and NRC-IAR staff tested the models under various wind conditions.

NRC-IAR bridge aerodynamicist, Dr. Guy Larose, noted the significance of the project, "This was the first time that two full aeroelastic models of a suspension bridge were ever tested side-by-side. The bridges were of similar span and design, and close to each other. We needed to evaluate how they would respond to the wind, and to each other."

The project also highlights NRC's collaborative approach to research and links to industry.

"This type of research collaboration with Canadian industry, while allowing us to develop new ideas and solutions to meet international engineering challenges, also strengthens Canada's position as an innovation leader", said Dr. Arthur Carty, NRC President.

Find out more about NRC Institute for Aerospace Research (NRC-IAR) and the Tacoma Narrows Project:

• NRC Institute for Aerospace Research (NRC-IAR)
• http://www.wsdot.wa.gov/projects/sr16narrowsbridge

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