engineer for washington s department of transportation says the cause of the collapse was torsional flutter or aerodynamic instability. that was the vice that took the bridge down. this was a condition that no structure can maintain for a significant period of time. gertie is replaced by a stronger bridge in 1950, ten years after the collapse. but a part of it still survives. this is the side span, the approach span. this is the original galloping gertie s 1940 bridge. you can see the two eight-foot-deep open section. many lessons are learned from gertie s demise, including how critical aerodynamics are in building suspension bridges. there really wasn t another major suspension bridge after