The Tacoma Narrows Bridge Collapse – 85 Years On

On November 7, 1940, just four months after it opened, the Tacoma Narrows Bridge in Washington State collapsed in spectacular fashion.

A steady 67km/h wind sent the elegant suspension bridge into violent oscillations until its mid-span tore apart and fell into the Narrows below.

No lives were lost that day, but the event shook the engineering world. The collapse became one of the most famous failures in modern history – captured on film, studied in classrooms, and referenced in every discussion of structural dynamics since.

What went wrong

The Tacoma Narrows Bridge was a marvel of its time – sleek, slender, and efficient. But those same qualities proved to be its undoing.

The bridge’s narrow deck and shallow girders made it remarkably flexible. In winds, the solid plate girders acted like the wings of an aircraft, generating lift instead of resisting it. When one of the main cables slipped slightly out of position, the bridge began to twist – not just up and down, but in a torsional flutter that fed on itself until the structure tore apart.

At the time, engineers had a “blind spot.” The leading suspension bridge designers believed failures were caused by heavy loads or poor materials, not by wind. Aerodynamics wasn’t part of standard bridge design.

What we learned

The Tacoma collapse was a turning point. It forced engineers to confront what they didn’t yet understand, and to study how air moves around large structures.

From this failure came fundamental advances in aerodynamic analysis, wind tunnel testing, and structural dynamics. Every modern bridge, from the Verrazzano-Narrows in New York to Japan’s Akashi Kaikyō, owes something to the lessons of the Tacoma Bridge collapse.

A legacy of progress

The rebuilt Tacoma Narrows Bridge, opened in 1950, was stiffer, heavier, and better designed to resist wind. By then, wind tunnel testing had become a standard step in design and remains mandatory for federally funded bridges today.

In the decades since, engineers have built ever-longer and more graceful spans, but with an awareness that form must follow physics.

Why we still study it

The Tacoma Narrows disaster reminds us that innovation isn’t just about moving forward, it’s about learning from what went wrong.

That mindset applies just as much to the infrastructure challenges we face today. Whether it’s delivering major projects, designing for resilience, or improving the way we manage risk, our industry continues to evolve because of what we’ve learned from the past.