Bay Bridge Wind Vortex Panels Fend off Swaying Disaster

Tom Warne Report, 13 August 2013

Contra Costa Times – August 5, 2013

OAKLAND – Efforts to keep the new Bay Bridge collapsing amid strong winds are underway as ironworkers are hanging 700 square steel plates beneath the deck. The panels are intended to fend off the strong forces that resulted in the collapse of the Tacoma Narrows Bridge in Washington. That span came down from a combination of the structure’s natural vibration frequency and the wind.

On Nov. 7, 1940, a new bridge nicknamed “Galloping Gertie” collapsed into the Puget Sound amid 35-knot winds, and the way engineers built bridges has never been the same.

According to Caltrans senior construction engineer Rob Kobal who gave a tour of the panels’ installation last week, “The panels create a vortex and disrupt the wind flow effect that could generate another Gertie,” he said. “After the Tacoma Narrows Bridge collapse, wind vortex panels became a common feature on suspension bridges.”

On the new Bay Bridge, the vortex panels will hang vertically in sets of 10 at angles alternating from the bottom of the deck. They will only be seen by boaters under the bridge. Kobal said the panels have been thoroughly tested at West Wind Labs in Monterey, on a scale model of a self-anchored span in a wind tunnel.

I believe it is required curriculum in every introductory college structures class to see the iconic video of the “Galloping Gertie.” It is enough to send shivers through the bones of any budding structural engineer. We have learned much from the bridge in Tacoma and have made great progress in understanding the nature of our creations. JN

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