The colorful bridge with tall towers is a world-renowned symbol of California as famous as the Hollywood sign.
The Golden Gate Bridge is iconic in the Golden State and beyond, but here are a few things you may not know about one of the world’s most beloved bridges.
November is National Historic Bridges Month, and San Francisco’s Golden Gate Bridge turned 90 this year. The much longer, 4 1/2-mile Bay Bridge from Oakland to San Francisco was completed a year before the Golden Gate.
But the colorful bridge with tall towers is a world-renowned symbol of California as famous as the Hollywood sign. The Golden Gate was the tallest suspension bridge in the world when it opened. Impressive as that sounds, the incredibly complicated engineering masterpiece was built in a little more than four years and was finished under budget.
Construction began Jan. 5, 1933, when workers started excavating 3.25 million cubic feet of dirt for the structure’s huge anchorages.
The anchorages took 1 million tons of concrete to make. They are massive blocks that grip the bridge’s main cables and are fastened to bedrock. While the anchorages were being made, the piers that the towers would go on were being built. The north pier has a bedrock ledge 20 feet below the water. The south pier is 100 feet below the surface, and a football field-size, watertight cofferdam was built so concrete could be pumped in.
By 1935, the towers were complete, and two years later, the bridge was finished.
Bridge basics
It was supposed to be blue and yellow
The span is called the Golden Gate Bridge because the entry into San Francisco Bay is known as the Golden Gate. In the 1930s, the U.S. Navy had lobbied that the bridge be painted in blue and yellow stripes to increase its visibility. But when the steel arrived in San Francisco coated with burnt red primer, the consulting architect decided the color was both highly visible — and more pleasing to the eye. The color has two names, orange vermilion or international orange.
CMYK colors are: cyan: 0%, magenta: 69%, yellow: 100%, black: 6%.
The original paint contained lead, and it took 30 years to remove all the lead-based coating. The cleanup effort started in 1965 and ended in 1995. Zinc-based primer was used as a replacement.
It was expensive to cross
The initial toll for the bridge was 50 cents each way — roughly equivalent to $18 today. Now, tolls are collected in the southbound direction only and are about $9 with a FasTrak pass for a two-axle car.
The bridge moves a lot
At a 50th anniversary event, about 300,000 people were on the bridge and its curve in the center flattened out. At the center of the bridge, the span can move downward about 10 feet and upward about 5.8 feet. For very strong winds, the deck is designed to bow horizontally at the middle of the center span 27.7 feet.
You can learn a lot more about its history and construction here.
The main cables
Each cable is composed of 27,572 wires. If the wires were one continuous length, they could wrap around the earth over three times.
The wires in the cable were grouped together and then tightly compressed into their final form by a hydraulic press. A main cable is 7,650 feet long.
Main cable bands are located every 50 feet, and the vertical suspender ropes are hung from the cable bands.
Suicide prevention
Between 2000 and 2019, the bridge averaged between 30 and 40 suicides per year.
Construction of a suicide prevention barrier, a horizontal net of steel cables that runs 20 feet below the walkways on both sides of the bridge, began in 2017 and is expected to be finished soon. The original estimate was $79 million but the cost has risen to more than $300 million.
If you are having suicidal thoughts, call or text the Suicide and Crisis Lifeline at 988, or go to 988lifeline.org.
You can read more about the net here.
The foggiest idea
San Francisco is really foggy, especially during the summer.
During construction, the south tower was hit by a ship trying to navigate the fog, so foghorns have been on the bridge since 1937. There are three horns in the middle of the bridge and two larger horns on the south tower. Each horn emits a different tone at different times to help guide ships safely through dense fog.
The south tower foghorn sounds a deep, loud note for 2 seconds, then it repeats in 18 seconds. The horns at midspan sound a pair of high-pitched notes.
A movie star
The bridge is a popular star in — and target for mayhem — in the movies. Here’s a link to a YouTube video that shows the bridge being destroyed in the movies many times.
Source: Golden Gate Bridge Highway and Transportation District, History.com, Structure Magazine
