The torsional motion began small and built upon its own self-induced energy. In other words, galloping Gertie’s twisting induced more twisting, then greater and greater twisting. This increased beyond the bridge structure’s strength to resist. Failure resulted.
Why Did Galloping Gertie Collapse?
Galloping Gertie, the iconic bridge that spanned the Tacoma Narrows in Washington State, is one of the most famous engineering failures ever. Completed in July 1940, the bridge quickly developed an unsettling vibration and sway, earning it the nickname “Galloping Gertie”. Just four months later, the bridge collapsed into Puget Sound. The spectacular failure of the bridge has intrigued engineers and physicists ever since and has become a subject of intensive research.
So, why did Galloping Gertie collapse? The explanation is a combination of several factors. First, the bridge was designed with a deck that was too flexible. The deck was supported by eight steel girders connected to each other using a series of diagonal suspender cables. This design was prone to excessive oscillation, which is what caused the bridge to sway and vibrate.
Second, the bridge was built in a location especially prone to strong winds. The bridge was in the middle of the Tacoma Narrows Strait, known for its strong winds. The winds blowing across the bridge created an aerodynamic force known as a “Galloping Gertie”, which added to the oscillations caused by