Bridge IdentificationHome Up Bridge Identification Bridge Design Bridge Construction Bridge Project Ex. A answers Ex B answers EX C answersBdg Iden. Answers

As we said earlier, anything that has shape has structure. Bridge structures allow us to
us to see how the structure works. They are like living skeletons. There's no doubt you've
seen a bridge, and it's even more likely that you've traveled over one. In fact most of us
have even constructed a bridge. Who hasn't laid a plank or log down over a small stream
to keep from getting wet?

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Bridges are a natural part of everyday life. A bridge provides passage over or around
some sort of obstacle.
The obstacle may be as large as a river, a valley, a road or a set
of railroad tracks, or something as small as a ditch or puddle.

tunnel.jpg (62901 bytes)


 

Bridges are not a new idea by any means, for a matter of fact; our prehistoric ancestors built
bridges before they built houses. Nature had provided the first
bridges with trees that had fallen across streams, rocks stepping
stones, and hanging vines which provided passages for animals
and man over obstacles such as rivers or valleys. Man soon began
to imitate nature by constructing primitive bridges of his own using
these examples. As our prehistoric relatives wandered around
looking for food, they didnít even think about building houses.
However, to wonder very far, they did need to build bridges across
rivers and streams.
For a bridge timeline: http://www.nireland.com/bridgeman/Chronology.htm

We have certainly come along way in regards to bridge construction. Today, when we refer to
bridges, we are mainly referring to a structure used by people and vehicles to cross areas that
are obstacles to travel. Without bridges, people would need boats to cross waterways and would
have to travel around such obstacles as canyons and ravines. Engineers build bridges over lakes,
rivers, canyons, and dangerous highways and railroad tracks not just as a means of getting
people places, but more for the purpose of providing economic stability. If you have ever been
on either bridge in Halifax during rush hour, you would quickly experience the magnitude of their
importance between Halifax and Dartmouth. The Oakland Bridge in the U.S. sees over 260,000
people cross over it each day, in fact, the U.S. is believed to average over 3 billion bridge
crossings per day. Big bridges don't come cheap. The Brooklyn bridge spanning over 6,000 ft
in New York cost over $25 million in 1883. The Seto-Ohashi bridge completed in 1988 in Japan
spans over 43,000 ft and cost over $8.3 billion to build. Obviously, in order to justify such an
investment, the goal is much more than to see what is on the other side. These engineering feats
of achievement link vital components of a healthy economy by permitting the necessary transfer
of people, information, goods and materials from one place to another. During war time, bridges
are considered as strategic targets as they are truly life lines for the same reasons mentioned
above.

This is a good time to watch the Bridge video.

BRIDGE TERMINOLOGY

Bridge components:

Most modern bridges have a concrete, steel, or wood framework and an asphalt or concrete
roadway
. The roadway is the part of a bridge on which people, animals and vehicles travel.
Bridges also provide pathways that carry power-lines and pipelines.

The structure of a bridge which extends above the road is called the superstructure. The portion
below the roadbed is referred to as the substructure.
The majority of bridges are held up by at least two supports that are set in the ground at either
end of the bridge called abutments. The above is a picture of an abutment on
one end of an arch bridge in North Sydney N.S.
The distance between two adjacent supports is called a span of a bridge.

Supports that stand between the abutments are called piers.

The total length of the bridge is the distance between the abutments. Most short bridges are
supported only by abutments and are called single-span bridges. Bridges that have one or
more piers in addition to the abutments are called multi-span bridges. Most long bridges are
multi-span bridges. The main span is the longest span of a multi-span bridge. The longest multi
span bridge in the world is the "Confederation Bridge" joining P.E.I. and New Brunswick.
"Click" here: http://www.capejourimain.com/qtvr/ , then "click" on a picture. After it loads up,
hold in a left "click" to scan the 360 degree view.
There are many kinds of bridges.

Bridges that carry canals or water conduits are called aqueducts. A bridge built over dry land or over a wide valley and consisting of a number of small spans is referred to as a viaduct.

 

The term overpass is applied to relatively short bridges crossing highways and railroads. Causeways are low
road bridges over swamps or shallow lakes and bays. Some bridges utilize boats
instead of fixed piers to produce the pontoon bridge.

http://science.howstuffworks.com/bridge-pictures.htm

Types of bridges- http://www.rpi.edu/~brawi/frame_ft_jbt/bforces12.htm

Although there are many different kinds of bridges, they usually fall into these
three types or styles of bridges: beam, arch, and suspension. The biggest
difference between the three is the distances they can each cross in a single
span. A span is the distance between two bridge supports, weather they are
columns, towers or the wall of a canyon. A modern beam bridge, for instance,
is likely to span a distance of up to 200 feet, while a modern arch can safety
span up to 800 or 1,000 feet. A suspension bridge, the pinnacle of bridge
technology, is capable of spanning up to 7,000 feet.

To check out the longest spanning bridges according to type: http://www.hut.fi/Units/Departments/R/Bridge/longspan.html

Beam:
The oldest type of bridge. A tree, plank, or girder system supported between
two piers or abutments. P.E.I. is home to the longest Beam Bridge in the world,
"The Confederation Bridge". The beam bridge is the easiest and cheapest to build.
The weight is transferred along the beams to the supports.

Beam bridges can be subdivided into 3 categories :

  • GIRDER BRIDGES- are made using solid beams / girders of various shapes.
     

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    wpe1.jpg (32051 bytes)

    TRUSS BRIDGES- The truss beam utilizes triangular shapes to distribute
    the weight to the supports.

  • bailey.jpg (62476 bytes) (Bailey Bridge) truss.jpg (62108 bytes)
  • CANTILEVER BRIDGES- Comprised of a center beam supported by two outer
    beams that work together to balance the weight over the supports.
    wpeA.jpg (34106 bytes)Quebec Bridge  

Beam bridge technology is often utilized for special bridge purposes ranging from
portable bridges used by wood contractors to cross brooks and steams to pontoon bridges used by the military and in the Artic to cross swamplands. They are often
used in the design of movable bridges such as
Drawbridges, also called bascule bridges, can be traced back to the timber drawbridges used to cross the moat of
a castle. These bridges could be drawn up from the inside to prevent the enemy
from crossing the mote. Today These bridges are today are most often made of
steel. Some may be double decked, or double leafed and so on, but as far as
bridges go, they are all used for relatively short spans (a few hundred feet). The
most famous draw bridge is probably The Tower Bridge (1894) in London. For
longer spans ( up to 500 feet or so), Vertical-lift bridges are used. These bridges, as well as Swing bridges, are designed to accommodate heavy traffic across short
canals or rivers and on occasion
permit tall vessels to pass through.
DRAWBRIDGES and SWING BRIDGES- http://science.howstuffworks.com/bridge.htm

http://www.rpi.edu/~brawi/frame_ft_jbt/bforces11.htm

Arch Bridges: http://www.howstuffworks.com/bridge3.htm

Very old designs. Used by Roman engineers to build stone aqueducts as far back
as 312 B.C.. The arch distributes the load down the curving path to the abutments
. Abutments are the points the arch meets the ground.
In 312 B.C. the Romans began
building aqueducts: a man-made channel carrying water. Although most of the
aqueducts were built underground, the parts that heeded to be above were held
in place with arches. The tops were covered to shield the water from the sun and
make it harder to contaminate the water.

Seal Island Brdg.

Interesting Facts:

An arch made of stone doesnít even need mortar. Ancient Romans built arch
bridges (and aqueducts), which are still standing, and structurally sound, today.
These bridges and aqueducts are real testaments to the natural effectiveness
of an arch as a bridge structure.

Suspension:
Jungle vines have been replaced by steel cables. The cables are supported from
towers. Suspension bridges are used for spanning distance. Today there are two categories of suspension bridges; traditional and the modern cable stayed
bridges
.

  • TRADITIONAL SUSPENSION BRIDGES
    MacKay Bridge, Halifax, N. S.

Traditional or original suspension bridges that have the road surface is held from steel cables
with connecting suspenders. As you can see in the pictures below of the "Mac Kay Bridge" in
Halifax Nova Scotia.

The cables are hung from towers and are anchored at the ends of the bridge. Modern cables are
made of thousands of strands of wire that are woven together into one cable. While suspension
bridges are used to span long distances, steel trusses are often used to stiffen up the road surface.

 

Traditional Suspension Bridge

SUSPENDERS and CABLES are under tension

http://www.howstuffworks.com/bridge4.htm
 

CABLE-STAYED BRIDGES

The Millau Viaduct above the River Tarn is the world's tallest bridge creates a direct route between Paris and the Mediterranean coast.

Cable-stayed bridges are a form of suspension bridge first designed by German engineers to be built in Sweden in 1956. Single towers can be used to suspend the road. This design uses fewer piers than that of beam bridges, and works better than regular suspension bridges for short distances.

 

http://www.howstuffworks.com/framed.htm?parent=bridge.htm&url=http://www.hsba.go.jp/bridge
/e-akasi.htm

Looking back, once again at our prehistoric ancestors, we can see that the basic principles of bridge building have withstood the test of time. The single-span bridge is an expansion of the primitive beam bridge made by dropping a tree or log across a stream or gully. The stepping-stone crossing, improved by logs laid on the stones to connect them is the prototype of the multi-span bridge. Wooden piles driven into the river bottom to form bridge supports made it possible for the log or beam structure to span wider streams .
Canadian bridges: http://collections.ic.gc.ca/civileng/eng/sites.asp?type=5

Questions:
 

1.) What are the cheapest type of bridge to build?

2.) What 3 special kinds of beam bridges often made to span canals?

3.) The Romans developed what type of style bridge for a kind of bridge to carry water ?

4.) How do the types of bridges differ between the New Margaree Bridge, the Seal Island Bridge and the Angus L. Bridge in Halifax?

5.) Check out this "Build a bridge GAME". Take the time to go through each of the three steps as you will be responsible for this information.
http://www.pbs.org/wgbh/nova/bridge/build.html

Bridge Identification Puzzle



 
Across
2. Bridge supports on either end of a bridge.
5. Supports located between the 2 ends of a bridge.
6. __________ provided the 1st bridges.
7. The biggest consideration when choosing between different bridge types deals with
   ___________
10. Road bridge over swamps and shallow bodies of water.
11. Bridge designed to carry water.
13. The type of bridge designed to span the greatest distances.
Down
1. Another name for a solid beam.
3. The portion of the bridge extending above the road way.
4. Very old, strong and long lasting bridge type introduced by the Romans.
8. The oldest type of bridge.
9. Kind of beam composed of triangular shapes.
12. Bridges are not just built for convenience but for the great role they play in 
    our__________
13. Anything that has shape has this:______________
 

 

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