2.  Opened to traffic July 1 st 1940  Third largest suspension bridge in the world  Bridge nicknamed Galloping Gertie

3.  3 Span Suspension Bridge  Length 1810m -Mid span 853m  Engineers valued lightness, flexibility and slenderness  I beam used to support deck instead of truss

6.  I beams caught the wind  Wind Forced above and below  Vortex caused vertical forces on bridge Why did it collapse

7.  Aerodynamics not fully understood at the time  Led to further research

8.  Longitudinal resonance

9.  Torsional Resonance

10.  Determine and design for possible “freak” conditions  Understanding of aerodynamics  Using wind tunnel analysis  Testing models in “in-situ” conditions