Bridges are powerful entities that make a statement of connection between two places. They are part of the routine travel for some and a spot of tourist attraction for others. The success of a bridge is evidently linked to the engineering mastermind to support the different loads it withstands. They become part of history for they hold protests, movements and a day blocked across could lead to a lot of economic disturbances as people have places to be. One such bridge which became popular for its limited lifespan and made us rethink their existence is the Tacoma Narrows Bridge. 

1. Remained the world’s third-longest suspension bridge at one point | Tacoma Narrows Bridge

Proposed as a connector between the strait of Tacoma Narrows, Washington, the initiation of construction of Tacoma Narrows Bridge started around 1937 after twenty years of interest. Spanning over 2,800 feet the bridge had tall tower supports forming the vertical components held by cables to pass the tension forces over the horizontal deck panels. 

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Graphical representation of the force enactment in the suspension bridge ©

2. Toll made the project feasible 

To carry out the automobile traffic, the budget constraints for the Tacoma Bridge were resolved by proposing tolls at entry points to meet the monetary ends. However, after a survey, it was found that this would not balance the initial investments. With the push of political and economic agenda, the only feasibility they held was to alter the design of the bridge. This called out for replacing the 25 feet truss girders with 8 feet plate girders with depletion of stiffness. 

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The construction phase ©

3. The lifespan of four months

After 19 months of rapid construction of Tacoma Narrows Bridge, the structure saw its collapse on the morning of November 7th, 1940 just after being in use for four months. The documentation by the eyewitnesses, the press photographs have been able to capture the precise moment of ruin too. A 42 mile per hour wind storm is said to trigger it. 

4. Tacoma Narrows Bridge: No human casualties

As the sense of vibration of the swaying structure could be felt the commuters on site were able to flee the bridge minutes before the collapse. Leonard Coatsworth is documented as the last person able to move to safe premises after fleeing his car. However his dog, Tubby became the sole victim of this unfortunate event. 

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The experience of a survivor from an article on the event ©

5. Tacoma Narrows Bridge: The cause investigation | Tacoma Narrows Bridge

The downfall questioned the practice of construction and the engineering domains in existence.  After several factors were taken into consideration, some primary reasons were rounded.

The fluctuations and the increased wind velocity, eddy currents formed at the girders, and the self-induced vibrations due to the resonance of the bridge were narrowed down. 

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The cause investigation ©

6. The lesson of reflection

This turned out to be a turning factor where the theoretical calculations had to be perplexed with the practical challenges posed in the real existence. The need to prepare the structures for upholding various exceeding normal circumstances became the prominent key factor in designing the modern bridges henceforth.

10 Things you did not know about the Tacoma Narrows Bridge - Sheet
Theoretical Calculations ©

7. The aesthetic re-evaluation of Tacoma Narrows Bridge

The aim to build a slender, narrow, and eye-appealing massive structure was what gave the bridge its identity. However, the force components commanded a more logical explanation. Today we see high stress-bearing cable wires and steel structures taking prominence.

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Aesthetic Re – evaluation ©

8. Higher Flutter Resistance 

The unstable oscillation produced had the structure causing flutter to cope with the forces. Here, the maximum stress on the suspender cables is brought about. Once they fail to hold up, the central deck is the next and the most to bear the impacts thus splitting the bridge. Thus, the name “Galloping Gertie” stuck by.

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The photograph of the last man escaping ©

9. The reconstruction

After the first attempt, the project to reconcile was slowed down with the influence of World War II. The models with wind turbines testing the strength of the structure happened over the next 3 years. Some of the original piers were reused. Lightweight concrete made a replacement which helped in deflecting the 6% pressure is held on the foundation.

Modern-day twin bridge ©

10. The example it leads | Tacoma Narrows Bridge

The dream to combine a human’s imagination to explore something on a massive scale to build global connections saw a spark through the Tacoma Bridge. The lessons learned in its failure helped develop a new understanding of structural details, the software to support the calculation. The amalgam of architecture and engineering formed a closed bond over the structure. 

The example it leads ©

Harshitha K S is an avid reader, writer and student who believes that the simple habitual observations often spark exceptional ideas. She finds describing spaces through words to an unfamiliar to be engagingly vivid. With sustainability being the matchless shot forward, she hopes to make a worthwhile contribution.