The Failure of the San Francisco-Oakland Bay Bridge
Group #14
Kimberly Konar
Marlborough High School
STEM ECHS
March 1, 2014
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A bridge is a structure used to create a passage over an obstacle such as a body of water
or a road. Bridges have many important jobs in the daily life of people. Although they are a
significant part of society, if designed or constructed incorrectly the flaws may become fatal. The
San Francisco/Oakland Bay Bridge collapsed on October 17, 1989 as a result of the Loma Prieta
earthquake causing one casualty.
The San Francisco/Oakland Bay Bridge connects San Francisco to Oakland traversing the
San Francisco Bay (San Francisco Attractions, n.d.). In order to travel across the bay one has to
take a ferry. With the amount of people coming and going from both major cities, the ferries
were extremely crowded. The state of California met and discussed how to fix the growing
problem. A bridge was their decision; this was decided because cars were gaining popularity and
being mass produced (San Francisco-Oakland, n.d.). There was only one problem; this problem
was the terrain around the bridge site. Varying soils and water depths along with potential
turbulent waters or winds were included in the list of geographical hurdles the engineers had to
overcome. After many years of discussion, President Herbert Hoover along with the
Reconstruction Finance Corporation decided to allow the state of California to build such a
bridge. With that news the state and its engineers began thinking of designs (California
Department, 2014).
Many ideas were thrown around during the brainstorming period; approximately fourteen
possible designs were submitted. Some of the designs that were vetoed were high steel trusses,
bascule spans and a suspension bridge in the eastern portion. The majority of the proposals were
denied due to the landscape, for instance the physical conditions of the bay made it unrealistic to
build a suspension bridge in the east. “Ultimately, a cantilever bridge was chosen to span
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Oakland to Yerba Buena Island and a suspension bridge from the island to San Francisco, with a
bore tunnel connecting the two” (California Department, 2014).
In the east there shall be a cantilever truss bridge. Many factors went into the final
decision of the truss bridge; one of the main aspects was safety. A truss bridge is a type of beam
bridge, reinforced by a frame of strong supporting beams in a triangular pattern. A cantilever
bridge is similar to a beam bridge and is supported from counterbalanced beams meeting in the
center (Bridges, n.d.). Truss bridges are able to span long distances due to their high strength to
weight ratio (Truss Bridge, n.d.).
Building a truss cantilever bridge across the western portion of the bridge was denied by
the many engineers; a suspension bridge better fit the surroundings. A suspension bridge is a
bridge were the desk hangs from wires, the wires are attached to cables which are then passed
over the top of towers and anchored into a concrete block at the end of the bridge (Bridges, n.d.).
The western half was projected to be 10,304 feet long; the type of bridge was chosen due to the
fact that the length does not greatly affect a suspension bridge; the bridge could be any length
and still work efficiently (California Department, 2004). As with every bridge the tension and
compression must be taken into account. Cables draped over the towers combats the tension
along with deck trusses for additional stability. The parabolic shape of the cables transfers the
compression forces into the towers taking it away from the bridge itself (Glydon, n.d.).
On July 9, 1933 they began construction on the San Francisco/Oakland Bay Bridge
(California Department, 2014). Three years after the construction began, on November 12, 1936
the American Bridge Company, who was in charge of the building, completed the last part of the
bridge (San Francisco Oakland, n.d.). It was an expensive project with the overall cost at $77
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million dollars, approximately $1.3 billion in today’s market (Dollar Times, n.d.). The opening
celebrations were very extravagant lasting for multiple days and included things such as parades,
ship racing and football games; the festivities of the completion pulled in a crowd of around 1
million people. One million people seemed like a colossal number at the time, but the bridge
carried about 9 million vehicles in the first year alone; the average in 2014 is around 102.2
million vehicles (California Department, 2014).
There were a variety of uses for the bridge. Ferries were one of the only ways to travel
across the San Francisco Bay until the bridge was built, “In 1928, ferries carried over 46 million
passengers between the two shorelines” (San Francisco, n.d.). Creating the bridge helped to
reduce the number of people riding on the ferry. Not only cars drove on the bridge, but The Key
System did as well. During 1958, the Key System was in action; the Key System was a method
of transportation compiled of local streetcars and bus lines that combined with a commuter rail
and bus lines to bring people to San Francisco via the lower deck of the bridge (California
Department, 2014). Tolls paid by the people using the bridge were an important source of
income for the bridge, it also helped pay back the loans and pay the workers (Pollak, n.d.).
The Bay Bridge stood as an iconic bridge for 53 years until disaster struck on October 17,
1989. A 7.1 magnitude earthquake named Loma Prieta hit the Bay area. The upper deck on the
East span collapsed and crashed into the lower deck resulting in the lower level failing. While
the East was damaged during the earthquake, the Western span stayed perfectly intact. There are
many theories on why the results that happened did occur. One of these theories is because a
truss bridge is more rigid than the suspension bridge which absorbed the shock of the quake
(California Department, 2014).
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NOAA or the National Oceanic and Atmospheric Administration discovered that during
the Loma Prieta earthquake the bearing shoe in the northeast corner and the bearing shoe in the
southeast corner of Pier E-9 failed. These bearing shoes were important to the bridge because
they provided support to 88-m truss. Each of the supports was attached to the pier with 20 2.54
cm bolts. Although even with all 20 bolts the bearing shoes shifted 14 centimeters north and 1.58
centimeters to the east. This was one of the reasons that the Bay Bridge deck collapsed (NOAA,
n.d.).
Daily life in San Francisco and Oakland were halted during the weeks after the disaster.
The bridge was a huge life line for many people who were traveling or worked on the other side.
San Francisco was hosting the World Series that year and the game had to be postponed due to
the destruction (Encyclopedia Britannica, 2013). Engineers along with many of the people
involved in the planning of the bridge decided that the bridge was to be used as a way to transfer
emergency vehicles from Oakland to San Francisco in case of an earthquake. When the bridge
collapsed this safety method could not be used because the bridge was broken. This possibly led
to more deaths than the earthquake should have caused (Knowles, 2013).
Redesigns of the Bay Bridge commenced almost immediately after the disaster occurred.
The engineer’s job was to design and create a bridge that was structurally sound and
“earthquake-proof.” Out of the many ideas submitted the engineers thought that a Self-Anchored
Suspension bridge would work for a third of the span while the other two-thirds would consist of
a skyway. According to the designers, the bridge was designed to endure within a 1500 year
period the strongest earthquake on the site of the Bay. The new design construction ended on
September 3, 2013. Engineering are hopeful that the bridge will hold up to the future quakes.
(Stanglin, 2013).
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On October 17, 1989 the Loma Prieta earthquake struck the San Francisco Bay area. The
earthquake caused major damage to the surrounding people and infrastructures. Traversing the
bay lay the Bay Bridge, during the quake the upper deck of the eastern span caved in resulting in
the lower level collapsing. This event caused an enormous amount of issues in daily life and led
engineers to wonder what went wrong in their design.
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References
Bridges. (n.d.). Retrieved March 1, 2014, from
http://www.ohio.edu/people/gb885811/531%20Final%20Site/Gina%20Bruce%20Site/In
formation/Technology%20Education/Drafting%203%20and%204/Bridges.pdf
California Department of Transportation (2014). Bay Bridge History Timeline| Bay Bridge
Info. Retrieved March 1, 2014, from http://baybridgeinfo.org/timeline#c1872
California Department of Transportation (2014). Bay Bridge History | Bay Bridge Info.
Retrieved March 1, 2014, from http://baybridgeinfo.org/history
Dollar Times Inflation Calculator. (n.d.). Retrieved March 1, 2014, from
http://www.dollartimes.com/calculators/inflation.htm
Encyclopedia Britannica (2013, October 7). San Francisco-Oakland earthquake of 1989
(United States). Retrieved March 19, 2014, from
http://www.britannica.com/EBchecked/topic/1505843/San-Francisco-Oaklandearthquake-of-1989Glydon (n.d.). Suspension Bridges - Math Central. Retrieved March
1, 2014, from http://mathcentral.uregina.ca/beyond/articles/Architecture/Bridges.html
Knowles, D. (2013, February 11). As San Francisco’s Bay Bridge redesign nears completion,
architect Marwan Nader reflects on his feat of earthquake and aesthetic engineering. New
York Daily News [New York]. Retrieved from
http://www.nydailynews.com/news/national/bay-bridge-architect-prepares-unveil-redesignarticle-1.1259395NOAA- National Oceanic and Atmospheric Administrator (n.d.). Damage
to Truss Support Bearing Shoe, San Francisco Oakland Bay Bridge | NGDC Natural
Hazard Images | ngdc.noaa.gov. Retrieved March 15, 2014, from
http://ngdc.noaa.gov/hazardimages/picture/show/280
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Pollak, D. (n.d.). Timeline of the San Francisco-Oakland Bay Bridge Seismic Retrofit:
Milestones in Decision-Making, Financing and Construction. Retrieved from California
Research Bureau website: http://www.library.ca.gov/crb/04/13/04-013.pdf
San Francisco Attractions – Golden Gate Bridge Facts, Alcatraz Tours, Fisherman’s Wharf
San Francisco – Worldatlas.com. (n.d.). Retrieved March 1, 2014, from
http://www.worldatlas.com/webimage/countrys/namerica/usstates/casanfrancisco.htm
San Francisco Oakland Bay Bridge - HistoricBridges.org. (n.d.). Retrieved March 1, 2014,
from
http://www.historicbridges.org/bridges/browser/?bridgebrowser=california/baybridge/
San Francisco-Oakland Bay Bridge. (n.d.). Retrieved 1, 2014, from
http://www.dot.ca.gov/hq/esc/tollbridge/SFOBB/Sfobbfacts.html
Stanglin, D. (2013, September 3). S.F. Bay Bridge re-opens with new 'quakeproof' span. USA
Today. Retrieved from http://www.usatoday.com/story/news/nation/2013/09/03/sanfrancisco-bay-bridge-reopens/2756741/
Truss Bridge. (n.d.). Retrieved March 1, 2014, from
http://apriencia.files.wordpress.com/2012/02/puente.pdf
Kim,
Your writing provides clear organization, smooth transitions from one idea to the
next, and strong use of logical reasoning to convey the results of this infrastructure failure;
WELL DONE!!! Now, work to address factors other than the earthquake that may have
contributed to the bridge’s collapse and work to find information regarding what has been
done since this disaster to solidify the bridge and, hopefully, avoid such calamities in the
future. Also, work to vary diction and syntax; at times your voice is redundant and greater
variety of sentence structure will not only enhance your voice, but convey your grasp of the
English language. Lastly, work to develop the few areas in which I asked for further
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clarification; stay away from ambiguity and use your research as a tool to develop your
thoughts and defend your claims.
EXCELLENT WORK!
ASSESSMENT CRITERIA & SCORE
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INTRO/PURPOSE-------------4/4
TOPIC DEVELOPMENT----3/4
USE OF EVIDENCE----------4/4
CONVENTIONS---------------4/4
DICTION/SYNTAX-----------3/4
TOTAL---------------------------18 = A