Designed and built more than 75 years ago and before the development of calculators, computers, CAD systems, or static and dynamic analysis software, the Golden Gate Bridge was an engineering marvel when it opened and remains so today. An in-person or virtual visit to the Golden Gate Bridge or the accompanying outdoor Golden Gate Bridge Exhibition in the visitor area at the San Francisco end of the Bridge provides many opportunities to reinforce math, science, statics, and dynamics concepts. Each of the exhibits described on the Golden Gate Bridge Exhibition web site link to additional resources and activities, many of which support Next Generation Science Standards (NGSS) and Common Core State Standards (CCSS).
The Next Generation Science Standards include engineering components that expect high school students to analyze a major global challenge to specify qualitative and quantitative criteria and constraints for solutions that account for societal needs and wants (NGSS HS-ETS1-1). Students must design a solution to a complex real-world problem by breaking it down into smaller, more manageable problems that can be solved through engineering (NGSS HS-ETS1-2). They also must learn to evaluate a solution based on prioritized criteria and tradeoffs ranging from cost to environmental impacts, and in particular use computer simulations to model the impacts of the proposed solutions (NGSS HS-ETS1-3, NGSS HS-ETS1-4).
In addressing the challenge of providing reliable transportation between San Francisco and counties to the north, Golden Gate Bridge engineers considered these and other design criteria and constraints during the initial design as well as after the bridge was in service.
- Engineers had to balance the advantages and disadvantages of tower height and cable size in the final design of the Golden Gate Bridge. Making the towers considerably taller to reduce the tension (pulling) force in the cables would have been a more difficult and expensive design alternative. (NGSS HS-ETS1-1)
- The aerodynamics of the bridge deck are an important design criterion for bridge stability when high winds blow through the Golden Gate. (NGSS HS-ETS1-1)
- The original design of the bridge deck needed to be changed because it performed poorly in large winds. A bracing system was added to the bottom of the deck to stiffen it so that it wouldn’t twist so much in the wind. (NGSS HS-ETS1-1)
- The wind, traffic, and earthquake loads excite the bridge to vibrate in various modes (swaying, twisting, vertical oscillation). A physical model of the bridge allows visitors to explore four of the modes of bridge vibration. Each of these modes has a unique shape and resonant frequency. Computer analyses of these vibrations are used to model the displacements and forces imposed on the bridge. (NGSS HS-ETS1-1, NGSS HS-ETS1-4)
- Fog often covers the bridge in a blanket of salty corrosive moisture that can rust the steel, causing damage to the bridge’s structural members and rivets. Engineers originally used special lead-based paint to protect the bridge from corrosion. Environmental constraints required the Golden Gate Bridge District to switch to zinc-based paints (NGSS HS-ETS1-1, NGSS HS-ETS1-3)
- The community wanted an aesthetically pleasing bridge. The original proposed cantilever-suspension hybrid design was considered unsightly and the design was changed to a suspension bridge. Later, architect Irving Morrow proposed the Art Deco details that improved the aesthetics of the bridge. (NGSS HS-ETS1-3)
- Funding the project during the Depression was a major obstacle. Voters approved $35 million in bonds to fund the design and construction. (NGSS HS-ETS1-1, NGSS HS-ETS1-3)
- The foundation of the south tower was built in water that is 110 feet (33 meters) deep. The safety of the divers was an important consideration in the construction of the bridge. (NGSS HS-ETS1-3)
- Engineers designed not only the bridge, but also temporary structures to allow for construction of the south tower in deep water with fast currents. (NGSS HS-ETS1-2)
Important design criteria relate to the gravitational loads as well as environmental loads such as wind pressure and earthquake shaking that the bridge must support.
- The gravitational loads acting on the bridge include its own weight as well as the weight of the vehicles and people that cross the bridge. The bridge deck trusses, towers, cables, suspenders, foundations, and anchorages all act together to support these loads and keep the system in a state of equilibrium. (NGSS HS-PS2-1)
- The wind blows through the Golden Gate pushing sideways on the towers and the deck. Faster winds cause larger forces to act on the bridge. Bridge designers needed to consider the fastest winds that could blow when they calculated the strength and size of the members on the bridge. (NGSS HS-ETS1-1)
- The Bay Area experiences very large earthquakes, such as the M7.8 1906 San Francisco earthquake. Bridge damage and closure would have a major impact on the economics of the region. Special devices called seismic isolators have been installed on the bridge to minimize damage during future earthquakes. (NGSS HS-ETS1-1, NGSS HS-ESS3-1)
Science and Math
- Mathematical models of cable force versus tower height exist to calculate and compare possible bridge geometries. The outdoor exhibit contains a physical model that allows students to feel the force in the cables for three different bridge geometries. Download this Excel file to experiment with a simplified mathematical model of cable geometries. (CCSS.Math.Content.HSF-IF.B.4, CCSS.Math.Content.HSF-IF.B.5)
- Bay Area faults, melting ice from the ending of the most recent ice age, and ancient rivers created San Francisco Bay, the geologic formations, and the deep (115 m, 337 ft) underwater channel beneath the Golden Gate Bridge. (NGSS HS-ESS2-1, NGSS HS-ESS2-5)
- On foggy days, fog horns are used to guide ships safely under Golden Gate Bridge. The fog horns, located at the bridge mid-span and south tower, each have their own tone and blast pattern. The south tower horns emit a lower tone with a longer wave length than the mid-span horns. (NGSS HS-PS4-1)
- The wind pressure on the bridge (and the wind force that the bridge must resist) increase as the square of the wind speed. When the wind blows twice as fast, the force is four times as great. (CCSS.Math.Content.HSF-IF.B.4)
- The Golden Gate Bridge is built of steel, which is an alloy made up of iron and carbon atoms. Painters continually paint the bridge to prevent rust from corroding and weakening the structural members. Corrosion is a chemical reaction of the form: Iron + water + oxygen → rust. (NGSS HS-PS1)
- As the sun beats down on the bridge it absorbs energy and heats up. As the steel cables heat up they expand and lengthen, causing the bridge to sag. A telescope pointed at the bridge allows visitors to see how much the center of the bridge has moved up or down with temperature. This video explains how the scope works and what you will see. (2:14 minute video) (NGSS HS-PS3-2)
History and Social Sciences
The state history and social sciences standards expect students to apply chronological and spatial thinking, use primary and secondary sources for research, explain the context of historical events, and interpret the impact of history on the physical and social character of a place.
The Golden Gate Bridge was an extraordinary science and engineering accomplishment of its time that forever changed the development of the Bay Area. The bridge, its exhibits, and surrounding artifacts provide a rich source of information about the history of technology and the history of the Bay Area.
- The History Exhibit, which consists of a mural and nine companion interpretive panels, chronicles the history of the design and construction of the Bridge. It includes political hurdles and creation of the Golden Gate Bridge District, economic considerations including the impact of the Great Depression, people responsible for the success of the project, engineering innovations, and the sequence of the construction of the Bridge.
- Because the Golden Gate Bridge is an international icon, seismic retrofits and other improvements have focused on retaining the art deco style and architectural features that define the Bridge. Maintaining the unique historical character of the Bridge has been a top priority in projects to replace Bridge members and add base isolators.
- Visitors can walk across the Bridge and imagine what it was like on May 27, 1937, Pedestrian Day, of the Opening Fiesta Week when 200,000 people each paid 25 cents to walk across the Bridge.
- Pedestrians on the Bridge can compare the vehicles zooming across the Bridge today to the Golden Gate Ferry system, which until 1937 was the only way to travel between San Francisco and the counties to the north.
- The Bridge is located next to several historic seacoast fortifications including Fort Scott, Fort Point, and the Civil War era East and West batteries. Portions of the outdoor Golden Gate Bridge Exhibition are housed in Battery Lancaster, where students can get a close up view of the large iron rings that were used to maneuver the guns in the battery.