Here are the last 2 of 3 monumental engineering failures which imparted stern lessons upon engineers of the time and spurred on advancements within the field.
2. St Francis Dam
Purpose: Intended to serve as a water reservoir for the city of Los Angeles.
Location: San Francisquito Canyon
Constructed between: 1924 to 1926
Height: 185 feet
Modelled after: The Mulholland Dam
Catastrophic failure: The dam failed on March 12, 1928. It flooded the San Francisquito Canyon 140 metres above the stream bed and the water continued travelling down into the Santa Clara River Valley, flooding it as well.
Failure due to: The dam was built in the wrong area, right on top of a Pleistocene-age landslide and the problem was exacerbated by chief engineer, William Mulholland, adding 20 feet to the dam’s original planned height.
The failure led to: This engineering failure resulted in the passing of new federal dam safety legislation, as well as the necessity to take into account geological factors.
In the aftermath: 827 existing dams were thoroughly inspected after the incident and 1 third were found to be in need of repairs and maintenance.
3. Tacoma Narrows Bridge
Purpose: The third largest in the world at the time, the Tacoma Narrows Bridge, nicknamed ‘Galloping Gertie’ was intended to serve as an economic and military pathway to the Olympic Peninsula during WWII.
Location: The bridge spanned the Tacoma Narrows straight between Tacoma and Kitsap Peninsula
Constructed between: 1938 and 1940
Catastrophic failure: 4 months after being opened to the public, high wind speeds resulted in the bridge collapsing into the Puget Sound (an inlet of the Pacific Ocean). It twisted up to 48 feet on one side, hitting angles of 45 degrees on the other, all while waving up and down before it snapped-off from its cables, flipped and plunged into the water
Failure due to: Wind speed was a minor factor taken into consideration during suspension bridge design of the time.
The failure led to a design breakthrough: Suspension bridge designs from thereafter considered wind speeds and aerodynamic effects, carried out wind tunnel studies and measured stresses resulting from wind loads.
In the aftermath: A sturdier, broader and heavier bridge completed construction in 1950 replacing the failed ‘Galloping Gertie’.
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