Few bridges are as iconic as the Golden Gate Bridge. Spanning across the strait of the Golden Gate, the massive structure stands as a testament to the power of American ingenuity. The 75 year old structure stretches from an impressive 1.7 miles. The bridge span is supported by suspension cables anchored in a pair of towers that stand 746 feet tall. Two 7,000 foot long cables stretch over top of the towers and are anchored in bedrock at either end of the bridge.
The span, one of the seven wonders of the modern world, has become the number one land mark of the city of San Francisco. It has appeared in movie and television shows and attracts tourists from all over the world. San Francisco is understandably proud of its landmark. In 1987, the city held a massive celebration to celebrate the 50th anniversary of the bridges’ opening. That day, a frightening occurrence on the Bridge burned the celebration into the public memory as the day the Golden Gate Bridge (supposedly) almost collapsed.
A day of celebration turns scary
On May 24, 1987, the Golden Gate was closed to vehicular traffic and opened for pedestrians. Proud locals flocked to the bridge, eager for the rare chance to cross the span on foot. About 300,000 people swarmed to the bridge, with another half million or so waiting for a chance to have their turn.
However, a the masses of people jammed on the bridge made it impossible for many at the center to move. Unbeknownst to people on the bridge, but obvious to onlookers from afar, the sheer weight of so many people caused the Golden Gate to sag about seven feet and flatten out. Folks on the bridge only noticed that the wind was making the bridge sway, making some folks feel sick, and starting the panicked notion that the bridge might collapse. City officials closed the bridge and gradually broke up the human gridlock at the center of the bridge. Relieved of the massive weight, the Golden Gate resumed its original shape.
But could it have really collapsed?
Legend has it that the Golden Gate came “this” close to collapsing that day, and that some combination of luck and the actions of city officials prevented what would have been the greatest engineering disaster in human history. The horror of hundreds of thousands of people plummeting to their deaths in the icy waters of the San Francisco Bay hundreds of feet below is certainly dramatic, but was there any chance for it to happen?
It turns out the odds of that happening weren’t too likely. All bridges, but especially suspension bridges, are designed to move both vertically and horizontally. The Golden Gate was designed to move 16 feet vertically and 27 feet horizontally, which you will notice is far more than the seven feet the bridge dipped that day. In addition, by the time of the 50th anniversary celebration, upgrades to the bridge structure allowed it to support 5700 pounds per foot, with an additional safety factor of 150%. In other words, the bridge could support at least 5700 pounds (bridges and other structures are always over-engineered, to account for possible unknown or extreme circumstances.)
So, while there is no doubt that seeing the Golden Gate flatten out under the weight of hundreds of thousands of people, there was very little danger of the bridge collapsing. The legend is just that, a legend.
Rosenbaum, Dan. “Golden Gate Bridge.” San Francisco Travel. http://www.sanfrancisco.travel/icons/golden-gate-bridge.html
Tung, Stephen. “The day the Golden Gate Bridge flattened.” MercuryNews.com. San Jose Mercury News. September 13, 2014. http://www.mercurynews.com/breaking-news/ci_20695953/day-golden-gate-bridge-flattened