audioVid Brooklyn Bridge   |  

Alex Gendler

The Visionary Proposal

In the mid-19th century, suspension bridges were collapsing all across Europe. Their industrial cables frayed during turbulent weather and snapped under the weight of their decks. So when a German-American engineer named John Roebling proposed building the largest and most expensive suspension bridge ever conceived over New York’s East River, city officials were understandably skeptical. But Manhattan was increasingly overcrowded, and commuters from Brooklyn clogged the river. In February of 1867, the government approved Roebling’s proposal.

A New Kind of Bridge

To avoid the failures of European bridges, Roebling designed a hybrid bridge model. From suspension bridges, he incorporated large cables supported by central pillars and anchored at each bank. This design was ideal for supporting long decks, which hung from smaller vertical cables. But Roebling’s model also drew from cable-stayed bridges. These shorter structures held up their decks with diagonal cables that ran directly to support towers. By adding these additional cables, Roebling improved the bridge’s stability, while also reducing the weight on its anchor cables.

Engineering on an Unprecedented Scale

Similar designs had been used for some other bridges but the scope of Roebling’s plan here dwarfed them all. His new bridge’s deck spanned over 480 meters—1.5 times longer than any previously built suspension bridge. Since standard hemp rope would tear under the deck’s 14,680 tons, his proposal called for over 5,600 kilometers of metal wire to create the bridge’s cables. To support all this weight, the towers would need to stand over 90 meters above sea level—making them the tallest structures in the Western Hemisphere.

Tragedy and Transition

Roebling was confident his design would work, but while surveying the site in 1869, an incoming boat crushed his foot against the dock. Within a month, tetanus had claimed his life. Fortunately, John Roebling's son, Washington, was also a trained engineer and took over his father’s role. The following year, construction on the tower foundations finally began.

Trials Beneath the River

This first step in construction was also the most challenging. Building on the rocky river bed involved the use of a largely untested technology: pneumatic caissons. Workers lowered these airtight wooden boxes into the river, where a system of pipes pumped pressurized air in and water out. Once established, air locks allowed workers to enter the chamber and excavate the river bottom. They placed layers of stone on top of the caisson as they dug. When it finally hit the bedrock, they filled it with concrete, becoming the tower’s permanent foundation.

Working conditions in these caissons were dismal and dangerous. Lit only by candles and gas lamps, the chambers caught fire several times, forcing them to be evacuated and flooded. Even more dangerous was a mysterious ailment called "the bends." Today, we understand this as decompression sickness, but at the time, it appeared to be an unexplainable pain or dizziness that killed several workmen. In 1872, it nearly claimed the life of the chief engineer. Washington survived, but was left paralyzed and bedridden.

A Family’s Determination

Yet once again, the Roeblings proved indomitable. Washington’s wife Emily not only carried communications between her husband and the engineers, but soon took over day-to-day project management. Unfortunately, the bridge’s troubles were far from over. By 1877, construction was over budget and behind schedule. Worse still, it turned out the bridge’s cable contractor had been selling them faulty wires.

Completion and Legacy

This would have been a fatal flaw if not for the abundant failsafes in John Roebling’s design. After reinforcing the cables with additional wires, they suspended the deck piece by piece. It took 14 years, the modern equivalent of over 400 million dollars, and the life’s work of three different Roeblings, but when the Brooklyn Bridge finally opened on May 24, 1883, its splendor was undeniable.

Today, the Brooklyn Bridge still stands atop its antique caissons, supporting the gothic towers and intersecting cables that frame a gateway to New York City.

audioVid Golden Gate Bridge   |  

A Distant Beginning

In the mid-1930s, two familiar spires towered above the morning fog. Stretching 227 meters into the sky, these 22,000-ton towers would help support California’s Golden Gate Bridge. But since they were currently in Pennsylvania, they first had to be dismantled, packaged, and shipped piece by piece over 4,500 kilometers away.

Moving the bridge’s towers across a continent was just one of the challenges facing Charles Ellis and Joseph Strauss, the project's lead engineers.

Doubts and Opposition

Even before construction began, the pair faced all kinds of opposition. The military feared the bridge would make the important harbor an even more vulnerable target. Ferry companies claimed the bridge would steal their business, and residents wanted to preserve the area's natural scenery.

Worse still, many engineers thought the project was impossible. The Golden Gate Strait was home to 96-kilometer-per-hour winds, swirling tides, an endless blanket of fog, and the earthquake-prone San Andreas fault.

Rethinking the Design

Despite the obstacles, Strauss was convinced the bridge could be built—and that it would provide San Francisco’s commuters more reliable passage to the city. He was, however, a bit out of his depth.

Strauss’s initial plans to span the strait used a cantilever bridge. This kind of bridge consists of a single beam anchored at one end and extended horizontally like a diving board. Since these bridges can only extend so far before collapsing under their own weight, Strauss’s design used two cantilevers linked by a structure in the middle.

But Ellis and his colleague Leon Moisseif convinced Strauss to pursue a different approach: the suspension bridge. Where a cantilever bridge is supported from one end, a suspension bridge suspends its deck from cables strung across the gap. The result is a more flexible structure that’s resilient to winds and shifting loads.

Engineering Innovation

This kind of design had long been used for small rope bridges. And in the 1930s, advanced steel manufacturing could create cables of bundled wire to act as strong steel rope for large-scale construction.

At the time, the Golden Gate Bridge was the longest and tallest suspension bridge ever attempted, and its design was only possible due to these innovations. But cables and towers of this size could only be built at large steelworks on the country’s east coast.

While the recently completed Panama Canal made it possible to ship these components to California, reassembling the towers on site didn’t go quite as smoothly.

Building Against Nature

It was relatively easy to find a stable, shallow foundation for the north tower. But building the south tower essentially required erecting a ten-story building underwater. Since the strait’s depth prevented drilling or digging the foundations, bombs were dropped on the ocean floor, creating openings for pouring concrete.

A seawall was built to protect the site from powerful currents, and workers operated in 20-minute shifts between tides. The towers had so many compartments that each worker carried a set of plans to prevent getting lost. At one point, an earthquake rocked the south tower nearly five meters in each direction.

Safety and Sacrifice

Strauss took worker safety very seriously, requiring hard hats at all times and stretching a safety net below the towers. But not even these precautions could prevent an entire scaffolding platform from falling in 1937, carrying ten workers to their deaths.

Once the towers were complete, workers spun the cables in place, hung suspenders at 50-foot intervals, and laid down the concrete roadway.

A Finishing Touch: The Color Debate

The bridge was finished, but there was still one more task ahead: painting it. After production, the steel had been coated with a reddish paint primer it maintained throughout construction. But the Navy had been pushing hard to paint the bridge a tactical black and yellow.

Consulting architect Irving Morrow actually thought the primer itself paired nicely with the strait’s natural backdrop—and he wasn’t alone. Citing numerous letters from locals, Morrow’s 30-page pitch to paint the bridge “international orange” beat out the Navy’s plans.

An Iconic Landmark

Today, this iconic color still complements the strait’s blue water, green hills, and rolling fog—serving as a striking reminder of human ingenuity, perseverance, and design.