Golden Gate Bridge

Golden Gate Bridge and Fort Point, San Francisco, CA

The Golden Gate Bridge – More than 60 years after its completion, the Golden Gate Bridge remains the world’s tallest suspension bridge. Hanging from two 746-ft-high towers, its cables — each a yard thick — are the biggest ever to support a bridge. In fact, the Golden Gate Bridge contains enough cable to encircle the earth three times. To leap across the mouth of an ocean harbor, something never before accomplished, civil engineers planted one pier in the open sea, 1,000 ft. from the shore. Construction crews braved biting cold, 70-mph gusts and dizzying heights to complete the bridge in only four years. Details…(video 3:23)

A century ago, building the Golden Gate Bridge seemed like an impossible task. Any bridge in this location would have to withstand brutal winds, tide, and fog. It would also sit less than eight miles from the epicenter of the most catastrophic earthquake in history. Only one engineer was willing to gamble that his bridge could withstand such destructive power. more…

Suspension bridges are suspended from cables. The earliest suspension bridges were made of ropes or vines covered with pieces of bamboo. In modern bridges, the cables hang from towers that are attached to caissons or cofferdams. The caissons or cofferdams are implanted deep into the floor of a lake or river. Sub-types include the simple suspension bridge, the stressed ribbon bridge, the underspanned suspension bridge, the suspended-deck suspension bridge, and the self-anchored suspension bridge.

The most spectacular bridge in the world

The dream of spanning the Golden Gate Strait had been around for well over a century before the Golden Gate Bridge opened. It took just over four years to build the Golden Gate Bridge. Construction commenced on January 5, 1933 and the Bridge was open to vehicular traffic on May 28, 1937. Pedestrian Day was held on May 27, 1937.

Building the Golden Gate Bridge was a significant engineering challenge in its day. But with hard work and determination, it was completed in only four years – an amazing feat of engineering.

  • Ask – From the specifications, there are a wide range of requirements that were included in the bridge. Why was the bridge necessary? What kind of weather does San Francisco have? What changes occur in the structure of the bridge with temperature changes? How much load must it support?
  • Imagine – Bridges aren’t the only way for cars to get from one side of the San Francisco Bay to the other. Although it was built many years later, everyday, thousands of cars go through the tunnel known as the Transbay Tube between the cities of Oakland and San Francisco. What type of bridge could be built in this location? How can the bridge design handle the possibility of earthquakes? What other ways can cars get from one side to the other?
  • Plan – During the design phase the type of bridge changed from the original cantilever-suspension hybrid bridge design—a suspension span design. Why was the bridge so hard to build? What are the differences in properties for the original and final bridge designs?
  • Create – Strauss insisted on the use of the most rigorous safety precautions in the history of bridge building. What were some of the big challenges faced during the actual construction? What precautions were taken to ensure worker safety?
  • Improve – Several modifications, additions and replacements have been made over time. New materials including paint formulation have be adopted to extend the life of the bridge. What Improvements have been made since the bridge was built?

That’s engineering

  • tensile strength – The Golden Gate Bridge deck is supported by steel cables. A single steel cable can not support the entire weight, but many cables working together can. Engineers calculate the load and the tensile strength of the cable to determine how many cables are required to support the bridge. They add in a margin of safety – some extra capacity to be on the safe side.
  • geology of the bridge foundations
  • the study of the wind forces on the bridge
  • metal strengths,
  • load carrying abilities and transferring to the foundations

Engineering ideas

  • concrete, anchorages, piers, bedrock, suspension bridge, cable-spinning, cofferdam

Do it
Here are some challenges for you to work on…

  • Using the Bridges activities resources – online, app or hands-on, experiment with designing and building a suspension bridge.

Learn more…