Iconic structure: The Golden Gate Bridge

One of my best friends lives in San Francisco and is a consultant to the National Park Service which runs Alcatraz, The Presidio and the Golden Gate Bridge. She’s an architect and an engineer and even qualified for the Olympic swim team once. Given her accomplishments and her expertise I trust in her intellectual instincts. I told her I wanted to write a paper about ALCATRAZ. She had once taken me there early in the morning with the crew that runs the old prison-turned-tourist site and I thought it be an interesting subject to learn more about. I even had the chance to meet a former prisoner there who spoke compellingly about his life on “The Rock”, which is how locals and others refer to ALCATRAZ. But she persuaded me that THE GOLDEN GATE BRIDGE was a much better choice.  Who knew that a suspension bridge could trump the one time home of gangsters Al Capone, Machine Gun Kelly, The Birdman of Alcatraz and even Whitey Bulger who happens to hail from my hometown of Boston and was recently captured by authorities after a slip up by the one person in the world he thought he could trust: A dame, of course.

My engineer friend said to me, “Alcatraz is interesting and has mystery of course, but The Golden Gate Bridge is simply beautiful, don’t you think?” Yes, I said.  The bridge also had special appeal to her because, as an architect and engineer, she always loved seeing man’s intervention in a landscape. ”It’s more interesting to look at” she said. And that is what this bridge provides. A marriage between nature and man.

Make no mistake. I am impressed by the Golden Gate Bridge too. I love looking at it. And I wondered why. Then it struck me. I also love prehistoric creatures and I realized the bridge sort of reminded me of the huge but elegant “Diplodocus.”

Diplodocus lived 150 million years ago and was the largest creature to ever walk the earth. It is easily recognizable because of its long neck and tail. Measuring 115 ft long with four sturdy legs, it was gargantuan. 5 million people come to London’s Natural History Museum every year to see the skeletal remains of that dinosaur. It never fails to fascinate. Perhaps it is because we cannot fathom that something that was quite that huge ever walked our planet …albeit thousands of years before we arrived. But proof is proof. English auctioneer James Rylands who is married to Bermudian Jen Cox recently acquired a Diplodocus for his auction house. He  says this  about the awesome creature: “Yes it’s definitely a size thing.”!

He’s right. Anything huge is stunning.

But when I spoke with the manager of the bridge, Kary Witt, he said size was not the first thing he notices about the bridge when he looks at it from a distance. “I think it looks graceful. Delicate even.” It is not until you get very close to it, which is his job, that you really understand the sturdy enormity of it. “The central cable is 36 inches thick,” says Witt. “That scale is impressive,” he adds.

The sheer expanse of the Golden Gate Bridge is what strikes most of us first. Bridges are measured in a number of ways. By spans or by feet. Feet produce the most impressive numbers, so that is the yardstick I will use here. Built over 4 years and opened in 1937 the Golden Gate Bridge was once the longest suspension bridge in the world measuring almost 9-thousand-feet long.  It now ranks 8th. The longest suspension structure is called the Akashi Kaikyō Bridge in Japan which is just over 12-thousand feet long.

There are many types of bridges. For perspective’s sake I will tell about the longest bridge of ANY kind. It is the “Danyang–Kunshan Grand Bridge” which runs along the Yangtze River and is part of the Beijing-Shanghai, High-Speed Railway. It approximately measures an astounding 5-hundred thousand feet long. Or, 102-miles.

Like the Golden Gate Bridge, it took 4 years to build. Which is a stunning accomplishment  given the difference in the size of the two structures.  The Chinese bridge opened in 2011 and cost a whopping 8.5-Billion dollars to construct. A huge sum compared to the Golden Gate Bridge. As a matter of interest, a decade ago the cost to construct a new Golden Gate Bridge was estimated at $1.2 billion dollars.

A far cry from the actual cost of 35-million dollars, which,  came in under budget and and ahead of schedule. On the day it opened in 1937 the San Francisco Chronicle referred to it as “A thirty-five million dollar steel harp!” The bridge cables looked like a harp. And the “harp” reference was made again in the description of a  terrifying incident which happened on the bridge during its 50th anniversary celebration.

Harvard University Professor Spiro Pollalis writes in a research paper that in 1987, 50,000 spectators were predicted to attend the celebration. But 16 times that many showed up. That was 8-hundred-thousand people in all. Pollalis explains that all bridges are built with a “specific maximum load which is not to be exceeded during the lifetime of the bridge.” But on that day the bridge was clearly overloaded. The roadway actually deflected or sank by almost ten feet at the center. In addition, “according to witnesses, the cables supporting the roadway were stretched as tight as the strings of a harp. The situation was compounded by the 17-mile per hour winds blowing across San Francisco Bay,” .

He goes on, “While the bridge was swaying from side to side because of the winds and flattening under the heavy live load, near panic conditions resulted. People were suffering from nausea and claustrophobia” and the dense crowd make evacuation a nightmare.”

Bridge Manager Kary Witt says the “harp” references also have something to do with the sounds the bridge makes as winds pass through it. Those sounds are recorded by seismic devices which are installed along the structure .  The former drummer for the Grateful Dead, Mickey Hart,  referred to the structure this way: “The bridge is a giant wind harp.” Hart then used a process he called “sonification: to actually compose music made from the sounds coming from the bridge for its 75th anniversary in 2012.

Technology writers for the website HOW STUFF WORKS Robert Lamb and Michael Morrisey define the bridge construction this way. “As the name implies, suspension bridges, like the Golden Gate Bridge or Brooklyn Bridge, suspend the roadway by cables, ropes or chains from two tall towers. These towers support the majority of the weight as compression pushes down on the suspension bridge’s deck and then travels up the cables, ropes or chains to transfer compression to the towers. The towers then dissipate the compression directly into the earth.

In addition to the cables, almost all suspension bridges feature a supporting truss system beneath the bridge deck called a deck truss. This helps to stiffen the deck and reduce the tendency of the roadway to sway and ripple.” This is especially important in  San Francisco where the potential for earthquakes is always a threat.

The writers say “Suspension bridges can easily cross distances between 2,000 and 7,000 feet (610 and 2,134 meters), enabling them to span distances beyond the scope of other bridge designs. Given the complexity of their design and the materials needed to build them, however, they’re often the most costly bridge option as well.”

But not every suspension bridge is an engineering marvel of modern steel,” say the writers. “In fact, the earliest ones were made of twisted grass. When Spanish conquistadors made their way into Peru in 1532, they discovered an Incan empire connected by hundreds of suspension bridges, achieving spans of more than 150 feet  across deep mountain gorges. Europe, on the other hand, wouldn’t see its first suspension bridge until nearly 300 years later

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Of course, suspension bridges made from twisted grass don’t last that long, requiring continual replacement to ensure safe travel across the gap. Today, only one such bridge remains, measuring 90 feet. And that is in the Andes,” say Lamb & Morrisey”

 Although the idea of a bridge spanning the Golden Gate was not new, the proposal that eventually took hold was made 2 decades before its actual construction.  But the cost was estimated at an impossible $100-Million. Joseph Strauss was an ambitious engineer who stood only 5-foot-3-inches tall but who had big ideas. He had wanted to be an artist but then became obsessed with bridges building 400 of them. He said the job could be done for $17-million.

 He was half right and the project was a go.

But, how to actually get this project of engineering marvel and human sacrifice and courage done…Next…