Peter Lambert
03-11-2005, 03:45 PM
Suitable for Physics courses. (Waves; Resonance)
(Two b/w photos and a short mpg video attached)
TACOMA BRIDGE COLLAPSES:
November 7, 1940
Only four months after its completion, the Tacoma Narrows Bridge in Washington State suffers a spectacular collapse.
When it opened in 1940, the Tacoma Narrows Bridge was the third-longest suspension bridge in the world. The bridge spanned 2,800 feet and took three years to build. To save cost, the principle engineer, Leon Moisseiff, designed the bridge with an unusually slender frame that measured 39 feet and accommodated just two vehicular lanes.
At the time, the engineering community was perplexed about how a bridge designed to withstand winds of up to 120 mph could collapse in a wind of 42 mph. Experts still disagree on the exact cause of the bridge's destruction, but most agree the collapse was related to resonance, a phenomenon that also comes into play when a soprano shatters a glass with her voice. In the case of the Tacoma Narrows, the wind resonated with the natural frequency of the structure, causing a steady increase in amplitude until the bridge was destroyed.
(Two b/w photos and a short mpg video attached)
TACOMA BRIDGE COLLAPSES:
November 7, 1940
Only four months after its completion, the Tacoma Narrows Bridge in Washington State suffers a spectacular collapse.
When it opened in 1940, the Tacoma Narrows Bridge was the third-longest suspension bridge in the world. The bridge spanned 2,800 feet and took three years to build. To save cost, the principle engineer, Leon Moisseiff, designed the bridge with an unusually slender frame that measured 39 feet and accommodated just two vehicular lanes.
At the time, the engineering community was perplexed about how a bridge designed to withstand winds of up to 120 mph could collapse in a wind of 42 mph. Experts still disagree on the exact cause of the bridge's destruction, but most agree the collapse was related to resonance, a phenomenon that also comes into play when a soprano shatters a glass with her voice. In the case of the Tacoma Narrows, the wind resonated with the natural frequency of the structure, causing a steady increase in amplitude until the bridge was destroyed.