Tacoma Narrows Bridge is the name of a modern pair of bridges in addition to an older bridge known for its spectacular collapse. The modern Tacoma Narrows Bridge is a pair of side-by-side suspension bridges west of Tacoma , Washington. The bridges span the Tacoma Narrows strait . Each bridge has a main span of about 2,800 feet (850 meters). The first bridge opened in 1950. It is 5,978 feet (1,822 meters) long, including its approaches. The second bridge opened in 2007 and is 5,570 feet (1,698 meters) long, including its approaches. The original Tacoma Narrows Bridge was built in 1940. It famously collapsed four months after completion.
Loading the player...Tacoma Bridge collapse
Suspension bridges are flexible compared to other bridge types. Long suspension bridges can sway 30 feet (9 meters) from side to side in high winds. Usually, a suspension bridge is strengthened by stiffening trusses (open frameworks) that extend below its roadway. The original Tacoma Narrows Bridge used stiffening girders (beams) rather than trusses. The girders were much shallower than trusses on other suspension bridges. The solid girders also caught the wind like sails.
As the original bridge neared completion, workers noticed oscillation (wavelike motion) along its length. The bridge’s remarkable up-and-down motion earned it the nickname “Galloping Gertie.” In spite of the oscillation, traffic still used the completed bridge.
On the windy morning of Nov. 7, 1940, the bridge’s up-and-down oscillation suddenly changed into a violent twisting motion. The bridge’s outer edges heaved back and forth nearly 30 vertical feet (9 meters) every few seconds. Within an hour, the twisting motion tore the bridge apart. No people were on the bridge when it collapsed.
