1. ‘Galloping Gertie’ The Tacoma Narrows Bridge Failure November 21, 2006 Max Walker Robby Poshusta Robby Poshusta Jan Kubicka Jan Kubicka Aaron Aslin Aaron Aslin

2. History ► Started November 23, 1938 ► Opened to the Public July 1, 1940 ► Designed by Clark Eldridge ► Altered by Leon Moisseiff ► Pacific Bridge Company, General Construction Company, Columbia Construction Company

3. Location

4. Random Facts ► Greatest Span 2,800ft ► Total Length 5,979ft ► Cost – $8 million ► 17.25” Diameter Cables ► 6,308 wires spun one at a time to make the large cables. ► Third largest suspension span in the world at the time.

5. Engineering Design Included: ► Suspension bridge ► Two Towers ► Two Main Cables ► Two Anchorages ► One Lane Highway

6. Anchorages Engineering

7. Engineering ► False Bottom Caisson ► 600 ton blocks of concrete were used to anchor the caisson

8. Collapse

9. Collapse ► 11am on November 7, 1940 ► 42 M.P.H. wind ► No one died in the collapse ► Several cars were thrown into the water

10. Collapse Mechanical Resonance ► When the natural frequency of vibration matches the frequency of oscillation ► A swing set ► The 42 mile and hour winds caused the resonance ► Soldiers marching in lockstep over a bridge can destroy it by creating resonance

11. Collapse ► The force of the wind when contacting the thick garter on the bridge matched the natural frequency or ‘critical speed’ of the bridge creating bigger and bigger horizontal oscillations

12. Collapse

13. Outcome ► Incorporated the force from wind into the design of bridges ► Used a vented garter and roadway ► Reinforced existing bridges ► Made bridges thicker and wider

14. Outcome ► “The consulting designer, Leon Moisseiff felt the fall occurred because engineers did not know enough about aerodynamics, and that lack of funds had forced the building of a bridge unprecedently narrow for its length. (University of Washington- Special Collections)”

15. Bibliography ► University of Washington Special Collections- Tacoma Narrows Bridge. November 16, 2006. ► University of Washington Special Collections- Tacoma Narrows Bridge. November 16, 2006. http://www.lib.washington.edu/specialcoll/ exhibits/tnb/default.htmlhttp://www.lib.washington.edu/specialcoll/ exhibits/tnb/default.html ► WSDOT- Tacoma Narrows Bridge: Extreme History. November 16, 2006. ► WSDOT- Tacoma Narrows Bridge: Extreme History. November 16, 2006. http://www.wsdot.wa.gov/TNBhistory/

16. Videography Tacoma Narrows Bridge Collapse Tacoma Narrows Bridge Collapse