Bridges
Barry Biletch
Rachel Maillet
Naveena Shanmugam
Table of Contents
Introduction
3
History
4
Physics
5
Types of Bridges
10
Important Bridges
19
Bizarre Bridges
24
Build Your Own Bridge
29
Glossary
30
Picture Credits
31
About the Authors
32
Introduction
Since humans began to migrate, there has always been a
need to cross difficult terrain. One of the methods that our
ancestors designed to overcome these obstacles was the
bridge, which allowed them to pass over rivers, gorges, and all
manner of impediments with ease. Through the ages, society
has improved and refined the concept, which today has
blossomed into a wide assortment of different styles, each a
testament to modern engineering.
Arkadiko
One of the oldest bridges that still exists today is the
Arkadiko Bridge. It is an arch bridge in Greece, constructed in
the thirteenth century BC out of stone. It is 72 feet long and
13 feet tall. When it was made, it was part of a road between
the cities of Tiryns and Epidauros, used especially for chariots.
Even today, more than three thousand years later, many
people still use the Arkadiko Bridge for transportation.
Newton’s Laws
To understand how bridges can support themselves, we
must understand Newton's three laws of motion. The first law
states that an object can only stay stationary if all of the forces
on it sum to zero. This means that when gravity pulls a bridge
down, there must be a force that pushes upward to counteract
it. This force comes from the ground pushing up on the bridge.
Newton’s Laws
Newton's second law says that the force on an object is
equal to its mass times the acceleration that it experiences.
Gravity is an acceleration, so it produces a force on every
object. This force increases as the object becomes more
massive, so to keep the force that they experience low, bridges
must be as light as possible.
The third law says that for every action, there is an equal
and opposite reaction. This means that if a bridge pushes up
on a car, the car also pushes down on the bridge, which is an
additional force that must be countered.
Material Strength
The problem is that the materials used to build bridges
cannot withstand immense forces. There are limits, and in
order to design a successful bridge, an engineer must ensure
that the materials do not even come close to their limits. This
makes an interesting problem. To decrease the force on a part
of a bridge, an engineer can add more reinforcements to
distribute the forces. That way, each individual piece does not
need to support as much. The problem with this is that each
additional part has a weight, which also needs to be
supported. Engineers need to strike a balance between adding
support to a bridge and keeping it light.
Tension and Compression
Engineers also need to consider that forces on any
material will stretch or compact it. These effects are known as
tension and compression, respectively. They can be a problem
when designing a bridge because if materials distort, other
parts connected to them can bend and break.
There are multiple ways in which this problem can appear.
First, the bridge will experience different forces as it is being
built. Bridges do not simply spring into being after they are
designed. They are built from the ground up, so they must be
planned such that they can withstand both large and small
forces. Second, the load on a bridge can change. There are
fewer cars in the dead of night than there are hours before a
big game. Bridges must be designed to support a large range
of traffic to protect against tension and compression.
Wind
Another consideration in the construction of bridges is
wind. When this is not properly accounted for, the results can
be disastrous. In 1940, just 4 months after it was constructed,
the Tacoma Narrows Bridge succumbed to what is known as
aeroelastic flutter. This is a phenomenon that occurs when
wind hits a bridge in such a way that it harmonizes with the
bridge's natural resonance frequency, compounding the force
that it exerts. After 40 minutes of swaying back and forth, the
bridge reached its limits and collapsed. Luckily, nobody was
hurt except for an unfortunate dog. You can watch a video of
the collapse at http://vimeo.com/13323591.
Arch Bridges
Arch bridges are one of the oldest types of bridges that
support their own weight as well as the weight of the load on
top. The perfect semicircles equally spread compression on all
parts of the bridge. However, this also means that the material
used to build them must be strong and durable. In the ancient
times, stones were used for arch bridges, but now materials
such as steel and concrete are used.
The important parts of arch bridges are the deck, vertical
posts, cables, and abutments. The bridge below is the Pont de
Gard, an ancient Roman aqueduct bridge built in France.
Beam Bridges
Beam bridges are the oldest and most common bridges,
used for their strong and economical foundation. The design
can be as simple as a tree trunk put on two river banks. The
basic parts of a beam bridge are the columns, which support
the weight, and the beam, the overlay of the bridge. The
beam supports the traffic on top and resists the bending and
twisting of the bridge. However, the beam bridge is only
efficient for short distances; otherwise, the columns would not
be able to support the weight of the beam.
Cable-Stayed Bridges
Cable-stayed bridges have been around since 1840, but
have only been commonly used in the last 50 years. At first
glance, cable-stayed bridges may look like suspension bridges,
but the difference lies in how the cables are connected to the
central towers. The cables are like fishing poles attaching at
different points of the tower. They carry the tension of the
bridge, and the tower in the middle is under compression. The
Brooklyn Bridge is a cable-stayed bridge and one of the most
famous bridges.
Double-decked Bridges
Double-decked or double decker bridges have two
different levels, which are often used to separate the traffic.
Many times, the lower deck is used for the transportation of
automobiles and the top is used for the convenience of
pedestrians and bicyclists. The double-decked bridge is not
itself a style; it is a concept that is applied to other types.
Movable Bridges
Not all bridges are fixed to the ground. In fact, there are
three different types of bridges which are movable: the swing
span bridge, bascule bridge, and vertical lift bridge. The swing
span bridge is a movable bridge with a large pier in the middle
supporting it. It swings around in a semicircle when a boat
needs to pass by.
A bascule bridge has two sections separated at the middle
and are commonly referred to as leaves. These leaves open up
towards the sky in order to let boats pass through. Bridges with
only one leaf are called drawbridges, which were used in the
medieval times. The vertical lift bridge can be raised and
lowered by an elevator at either end. A famous example is the
Buzzard’s Bay bridge, which lays over the Cape Cod Canal.
Pontoon Bridges
A pontoon bridge is a floating bridge that is often used by
the army when it wishes to cross a stream or river. The
pontoons are bags of rubber filled with air so that they float in
the water. A wooden roadway is set so that soldiers and
equipment can be taken
across. Although most
pontoon bridges are used
by the military, the bridge
across Lake Washington is
used by civilians.
Suspension Bridges
The most famous suspension bridge is the Golden Gate
Bridge. It is a fixed bridge made of strong, long, steel cables
connected to the shore and high steel towers supported by
cables anchored in the banks. These two different sets of steel
cables then support the roadway that hangs in between. The
largest suspension bridge is the Bay Bridge that connects San
Francisco with Oakland, California. The entire bridge is 8 miles
long. That’s more than 100 times the length of a football field!
Tied Arch Bridges
Tied arch bridges are similar to arch bridges, but the arch
continues down past the roadway. Thus, the tension in the
bridge is similar to that of the string of a bow. Because of this,
tied-arch bridges are sometimes referred to as bowstring-arch
or bowstring-girder bridges. These are one of the more
sensitive bridges; they must be built very precisely. If not, the
entire bridge could collapse. The way that forces work allows
tied-arch bridges to be built with a less sturdy foundation; for
example, elevated piers or even unstable soil. Fremont Bridge,
located in Portland, Oregon, is a steel tied-bridge and the
longest bridge in Oregon. Interestingly, it is also a doubledecked bridge with four
lanes on each deck.
Truss Bridges
Truss bridges are the most popular of all bridges and were
first developed during the Industrial Revolution. The change
was tremendous and rapid; in fact, wooden bridges were
typically replaced with iron bridges. The truss is the section of
the bridge with triangles packed together. This truss can either
be above or below the roadway. The triangular structure
allows the force of a load to transfer from one point to a
considerably wider area. This structure of packed triangles can
also be used in
combination
with
other bridges to make
the other designs
stronger.
Brooklyn Bridge
While German born John Roebling was taking a ferry
across the East River in New York during the 1800s, the boat
was suddenly stuck in the ice. This dilemma gave him the idea
to design and engineer a bridge that would span across the
East River, connecting Manhattan Island to Brooklyn.
The actual building of the bridge began in 1869 by John
Roebling himself, but unfortunately, Roebling would not live to
see the completion of his work. Washington Roebling, John’s
son, would become the chief engineer of the project and, with
the help of his wife, commission the grand opening of the
Brooklyn Bridge in 1883.
People flocked from across the state to witness the events
of celebration for what was then the longest suspension bridge
in the world. Not only was this bridge a milestone in history
for engineers, but it
was also so for artists,
who produced poems,
photographs,
and
paintings featuring the
great Brooklyn Bridge.
Golden Gate Bridge
Joseph Strauss had incredible dreams, as well as several
doubts, as he began to build the suspension bridge that would
cross the Golden Gate in San Francisco, California in the
beginning of the 1900s. The waters of the Golden Gate leading
to the entrance of the San Francisco Bay were known to be
rapid and perilous. Although the engineering of the Golden
Gate Bridge was in popular demand, Strauss knew the risks
and dangerous waters that he was facing.
However, in 1937, the bridge was completed! After
blasting through rock thousands of feet below the surface of
rough waters, the largest suspension bridge of its time was
completed and measured to be a total 4,220 feet long.
Millau Bridge
The Millau Bridge in southern France, spanning the River
Tarn in the Massif Central mountain region, is the highest
bridge in the world. The pillar in the middle of the bridge is
taller than the Eiffel Tower.
Overseeing the construction of this bridge, Lord Foster
worked to complete this project in 3 years. Because the
roadway was very long (about 1½ miles), the builders had to
roll the actual roadway onto the pillars made from
concrete. This building technique had never been done before
at that time. As if floating on the clouds, the Millau Bridge was
built, as Lord Foster said, with the “delicacy of a butterfly.”
Tower Bridge
Not all drawbridges are only found in fairy tales
surrounding elegant castles. The Tower Bridge in London
connects the areas of Tower Hamlets with Southwark over the
River Thames. This bridge was built with a pedestrian walkway
that allowed tourists to cross the glass-covered passages while
the drawbridge was raised, permitting boats to sail through to
the other side. The pedestrian walkway was closed from 1909
to 1982 when it became a popular spot for unsavory
c
h
a
r
a
c
t
e
r
s
.
Today people are able to walk across the glass walkway
and admire the hydraulic pumps that once operated the
famous Tower Bridge.
Sydney Harbor Bridge
In 1815, Francis Greenway
expressed his desires to build a
bridge connecting the northern
and southern parts of the
Sydney
Harbor
in
Australia. This exact bridge
would become the largest steel
arch
b ridge
in
the
world. Today, tourists are able
to climb the bridge and
experience the unbelievable
views surrounding the harbor
during the daytime or the
night.
Bridges in Literature
Engineers and builders have
been working with bridges
for ages, along with authors
and writers. The tale of
“Three Billy Goats Gruff” is
about three goats trying to
cross a bridge guarded by a
troll. The book Bridge to
Terabithia, which has been
made into a movie, is about
two teenagers who discover
a bridge into an imaginary
land.
Whether
these
structures are figurative
or real, bridges have
been used throughout
history not only for
transportation
purposes, but for the
Rolling Bridge
Designed by Thomas Heatherwick, the Rolling Bridge in
London is a pedestrian walkway that curls up like a caterpillar
to allow for small boats to pass through. The bridge is
composed of eight triangular steel sections that are able to
collapse with the use of hydraulics. The innovation and
creativity used to create this “curling” bridge resulted in its
reward of the British Structural Steel Design Award in
2005. When the bridge is not laid out as a pedestrian walkway,
it’s rolled up into an octagonal shape that is exactly ½ of the
width of the waterway.
If you find yourself wandering around Paddington Basin,
London at noontime on a Friday, visit the Rolling Bridge and
you will be able to see it in action.
Wind and Rain Bridge
The Wind and Rain Bridge, also known as Chengyang to its
natives in China, is made entirely from wood (aside from the 5
large stone columns that support the bridge stretching across
the Linxi River). With brilliant flower engravings and wooden
pictures, the bridge looks like a piece of art. Both the natives
and the tourists can’t deny its beauty and its uncanny
resemblance to a school corridor as they walk through the
tunneled passageway. The most incredible thing about the
Wind and Rain Bridge is that it does not contain one single nail;
the wood was positioned so that all of the pieces are tightly
joined together.
Henderson Waves Bridge
This 899 feet long pedestrian bridge can be found in
Mount Faber Park above Henderson Road in Singapore. The
unique structure was designed by the IJP Corporation from
London and the RSP Architects and Engineers ltd. from
Singapore. The bridge has a surrounding structure with the
peaks and crests of waves that periodically rises over and
under the walkway of the bridge. Despite the technology that
was used to build this structure, the Henderson Waves Bridge
easily fits into the nearby park environment with an allweather timber that forms the walkway.
Ponte Vecchio Bridge
Ponte vecchio translates to old bridge in Italian. Taddeo
Gaddi, its builder, produced a bridge that was like none other
during the Middle Ages in Europe. Not only was this bridge the
first segmental arch bridge in the west (a type of bridge with
an arch built in a different way than other bridges with arches),
but it was the first bridge to stretch across the Arno River in
Florence. The most unique part about this structure is that
there are essentially two stories; the lower story is a collection
of shops, and the upper story is a group of buildings that
connect to neighboring palaces.
Magdeburg Water Bridge
The Magdeburg Water Bridge in Germany is the longest
navigable aqueduct in the world. Ships are able to travel from
the Elbe-Havel Canal to the Mittelland Canal by crossing over
the Elbe River. This bridge is able to support tons of water and
ships because there is an equal and opposite force pushing
away from the bridge as there is one pushing into the
bridge. This will always be the case, even when there are five
ships all lined up to sail above the Elbe River. As long as the
ships are buoyant, able to float, the forces will simply cancel
each other out and equal 0. This bridge does not defy the laws
of physics and gravity, but it surely does amaze.
Build Your Own Bridge
Now that you’ve read all about bridges, it’s time that you
engineer your own. Think about all the different designs that
exist and the different materials that were used. Now gather
your own materials and give it a try. Here’s a good start. Make
a bridge that spans 10 inches and can support its own weight
as well as the weight of a load, such as pennies.
Materials:

Plain paper

Paper clips

Ruler

Books

Pennies

Scissors
Build:
1. Think of some ideas as to how you want to build your
bridge. Design it and construct it.
2. Place the bridge across the 10 inch distance and make sure it
stands up.
3. Place pennies on top and see how much weight it can hold.
4. Make adjustments to your bridge to make it better!
Glossary
Abutment: Abutments are structures at the end of a bridge
which supports the arch.
Aqueduct: Aqueducts are man-made channels used to
transport water.
Compression: Compression is the application of force on an
object to make it smaller in volume.
Deck: The deck is the roadway of a bridge.
Engraving: Engraving is a piece of art that is made by cutting on
a metal or wood surface.
Hydraulic: Hydraulics are devices that are operated, propelled,
or moved by liquids in motion or pressure.
Industrial Revolution: The Industrial Revolution was the
introduction of machinery during the late 18th and early 19th
century.
Pier: A pier is a structure or tower in a body of water.
Segmental: Segmental refers to something that is divided into
pieces that make up a whole.
Tension: Tension is the application of force on an object to
make it stretch.
Timber: Timber is wood that forms one structure with the
combination of other materials.
Picture Credits
Cover
http://fc04.deviantart.net/fs71/i/2010/039/e/9/
Bridge_Wallpaper_by_tonvanalebeek.jpg
Background
http://www.wallpapersland.net/wp-content/uploads/2011/05/GoldenGate-bridge.jpg
Tied Arch Bridges
http://www.vermontbiz.com/files/images/
VermontNewYorkpickdesignfornewChamplainB_C5CA/
ModifiedNetworkTiedArchBridge.jpg
http://www.ciorba.com/structural/conceptstudies/1/1a.jpg
Arkadiko Bridge
http://images.ookaboo.com/photo/m/Arkadiko2_m.jpg
Truss Bridges
http://www.sci-experiments.com/BayBridgeTutorial/
cascade_teft_truss_bridge_476_1971_ampprn.jpg
http://
images.brighthub.com/31/3/313bd3e13443525459781438ca78f0264a4628c
c_large.jpg
Newton’s Laws
http://www.nireland.com/bridgeman/Canal%20Bridge.jpg
http://farm5.static.flickr.com/4015/4245451177_92bc0cc032.jpg
Brooklyn Bridge
http://www.photohome.com/pictures/new-york-pictures/new-york-city/
brooklyn-bridge-1a.jpg
Material Strength
http://img.ehowcdn.com/article-new/ds-photo/getty/
article/178/247/87713685_XS.jpg
Golden Gate Bridge
http://www.sftravel.com/images/goldengate/golden-gate-bridge-3.jpg
Introduction
http://www.nireland.com/bridgeman/Butterfly%20Bridge.jpg
Tension and Compression
http://teachers.egfi-k12.org/wp-content/uploads/2009/07/
LightningVolt_Mackinac_Bridge.jpg
Wind
http://content.lib.washington.edu/farquharsonweb/images/FAR017.jpg
Arch Bridges
http://www.makingthemodernworld.org.uk/learning_modules/
maths/02.TU.03/img/IM.1470_zl.jpg
Beam Bridges
http://s3.hubimg.com/u/1719498_f520.jpg
Cable-Stayed Bridges
http://farm2.static.flickr.com/1423/623981238_be67462776.jpg
Double-Decked Bridges
http://farm3.static.flickr.com/2648/4118652342_28936a67f5.jpg
Movable Bridges
http://cache.gawker.com/assets/images/jalopnik/2009/05/
Military_Land_Bridge.jpg
http://mtidry.files.wordpress.com/2009/12/rbridgel5.jpg
http://web.me.com/lusterb/A_Movable_Bridge/Logbook/
Entries/2008/7/4_Intro_files/shapeimage_2.jpg
http://2.bp.blogspot.com/_0uokoJaOhrs/SaPzMm5irgI/
AAAAAAAABKI/3pNt0-2nLZw/s400/Swing+Bridge+in+Sydney.JPG
Pontoon Bridges
http://rmparchive.com/images/hosting/600Border/LC720-600Border.jpg
http://www.psgtech.edu/ncc/images/Wings/EP/Bridges/Pontoon%
20Bridge02.jpg
Suspension Bridges
http://misterholbrookschallengeprogram.edublogs.org/
files/2011/06/902635594_501f527997-28ac5y8.jpg
http://listsoplenty.com/pix/wp-content/uploads/2010/03/Cliftonsuspension-bridge-Bristol-completed-in-1864-500x375.jpg
Millau Bridge
http://whatafy.com/storage//2012/02/2012/02/15/23344/The-MillauViaduct.jpg
Tower Bridge
http://www.london-attractions.info/images/attractions/tower-bridge.jpg
Sydney Harbor Bridge
http://www.sydneyharbourbridgeclimb.org/Sydney-Harbour-Bridge-Climb
-Images/sydney-harbour-bridge-climb.jpg
Rolling Bridge
http://farm5.staticflickr.com/4129/5003048916_2c48e03efb_z.jpg
Wind and Rain Bridge
http://2.bp.blogspot.com/-Qd4G8y_NXz8/ThxszvskvdI/AAAAAAAAAu0/
iJG8b56qf8A/s640/Wind-and-Rain-Bridge-tour.jpg
Henderson Waves Bridge
http://www.worldtoptop.com/wp-content/uploads/2011/05/
henderson_waves_bridge_2.jpg
Ponte Vecchio Bridge
http://www.destination360.com/europe/italy/images/s/italy-pontevecchio.jpg
Magdeburg Water Bridge
http://amazingtourismtraveling.com/wp-content/uploads/2011/04/
Magdeburg-Water-Bridge-Germany-3.jpg
Build Your Own Bridge
http://3.bp.blogspot.com/_yFBVrbWRrEc/S_NqMLgtdYI/AAAAAAAAABM/
cPl0JU99lK0/s1600/Penny+Bridge+2010-05-04+08.49.14%282%29.jpg
About the Authors
Naveena Shanmugam is wrapping up her
year as a junior at the Massachusetts Academy of Math and Science. She enjoys playing basketball, practicing her skills for
speech and debate, and participating in
mock trial. When she’s not busy with all of
this, she loves to listen to music, dance,
and spend time with her family and
Rachel Maillet is a student at the Massachusetts Academy of Math and Science who absolutely loves music. She plays the guitar
and the ukulele and loves collecting records. During the summer she enjoys lifeguarding at her town pool and relaxing with
her dogs Jack, Cocoa, and Cooper.
Barry Biletch is a student at the Massachusetts Academy of Math and Science. He enjoys reading books, doing math (yes, really),
and programming computers. In addition,
he also likes playing chess with his friends.