Farquharson continued wind tunnel tests. He concluded that the “cumulative effected of undampened rhythmic forces” had produced “intense resonant oscillation.” in other words, the bridge’s lightness, combined with an accumulation of wind pressure on the 8-foot solid plate girder and deck, caused the bridge to fail.
Why Did the Tacoma Narrows Bridge Collapse?
The Tacoma Narrows Bridge collapse of 1940 remains an iconic example of the destruction that can be caused by a phenomenon known as aeroelastic flutter. This type of failure occurs when the wind causes an oscillation in the bridge’s structure, creating a self-sustaining wave pattern that eventually leads to its destruction. The Tacoma Narrows Bridge was the first major suspension bridge in the United States when it opened in 1940, spanning the Tacoma Narrows strait of Puget Sound in Washington state. Less than four months later, the bridge collapsed due to aeroelastic flutter.
Engineer Leon Moisseiff designed the Tacoma Narrows Bridge. The bridge was meant to be an engineering marvel, featuring the longest span of any bridge in the world at the time of its construction. The bridge’s unique design was meant to make it more flexible, allowing it to withstand windy conditions better. However, this design also made the bridge more susceptible to aeroelastic flutter. The bridge’s flexibility caused it to move in the wind, creating a self-sustaining cycle of oscillation that eventually caused the bridge to collapse.
The morning of the collapse, the wind was blowing at a speed
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