Bridging The Gap
Engineering 1
2009 - 2010
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Bridge Defined
• Bridge
– A structure built to span a valley, road, body of
water, or other physical obstacle, for the
purpose of providing passage over the obstacle.
– Designs of bridges vary depending on the
function of the bridge and the nature of the
terrain where the bridge is constructed.
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Civil Engineers
• People who design and build bridges, roads,
canals, dams, and buildings are called called
civil engineers.
• Fun and exciting career.
Famous engineers
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Types Of Bridges
• 4 Main types of Bridges
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Beam
Cantilever
Arch
Suspension
• Each type of bridge can be made of a variety of
materials.
• Each type of bridge can be composed of trusses
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Bridge Material
• Materials
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Wood
Steel
I beams
Box Girders
Concrete
Bridge Forces
• Forces
– Tension
• Pulling apart
– Compression
• Pushing together
– Bending
• Bends
– Torsion
• Twisting
– Shear
• Two opposing forces
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Beam Bridges
• Turn to your neighbor and describe what
you think the first bridge was like.
• Beam bridges consist of one horizontal
beam with 2 supports usually on either end.
• Simplest type of bridge
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Beam Bridge Types
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Beam Bridges
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Beam Bridges
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Beam Bridge Diagram
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Truss Beam Bridge
• A truss bridge is basically a fancy beam
bridge.
• The truss is a triangular design used for
support to hold up more weight and span
more distance.
• Trusses were added to beam bridges to hold
more weight and span longer distances
• Span distances are still limited.
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Types of Truss Beam Bridges
All of the types of truss bridges can either be a through
truss or a deck truss
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Types of Truss Beam Bridges
Allen Truss
Brown Truss
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Types of Truss Beam Bridges
Fink Truss
Howe Truss
Pegram Truss
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Types of Truss Beam Bridges
Post Truss
Pratt Truss
Warren Truss
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Truss Beam Bridges
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Truss Beam Bridge Diagram
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Arch Bridges
• Perfected by the Romans
• Very strong. Many ancient and well known
examples of stone arches still stand to this day.
• The weight of an arch bridge is carried outward
along the curve of the arch to the supports at each
end. These supports, called the abutments, carry
the load and keep the ends of the bridge from
spreading out.
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Arch Bridge Diagram
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Arch Bridge Types
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Arch Bridge Types
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Arch Bridge Types
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Arch Bridges
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Cantilever Bridges
• Structures that project horizontally into
space, supported on only one end
• Solved the problem of increasing the span
distance.
• A good example of a cantilever is a diving
board.
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Cantilever Bridge Diagram
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Cantilever Bridges
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Suspension Bridges
• A type of bridge in which the deck (the
load-bearing portion) is hung below
suspension cables on vertical suspenders.
• 2 types
– Suspension bridge
– Cable-stayed bridge
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Suspension Bridges
• Cables are suspended between towers, plus
vertical suspender cables that carry the
weight of the deck below.
• Suspension cables must be anchored at each
end of the bridge.
• The main forces in a suspension bridge of
any type are tension in the cables and
compression in the pillars.
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Suspension Bridge Diagram
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Cable-stayed Bridge Diagram
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Suspension Bridges
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Bridge Building
• Caisson
– a watertight chamber used in construction work
under water.
– Very important part of bridge building.
– Used to lay the foundations for piers
– Very dangerous
– Caisson’s disease – AKA the bends!
• Many people died from this.
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Bridge Building
Caisson Diagram
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Bridge Building
• Piers are constructed after the foundation is
built.
• Piers
– Vertical structures which bear a great deal of
compressive force.
– Hold up the deck
– Built on top of a foundation
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Bridge Building
• After the piers are built, the deck supports
and the road deck are constructed.
• The Deck
– The surface where we drive or walk.
– Continuous and may be a truss, box girder, or a
plate girder.
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Bridge Vocabulary
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Truss
Deck
Load
Member
Foundation
Tension
Compression
Abutment
Pier
10. Joint
11. Arch
12. Beam
13. Cable stay
14. Caisson
15. Cantilever
16. Cement
17. Concrete
18. Bridge
Bridge Vocabulary
19. Drawbridge
20. Span
21. Suspension bridge
22. Tensile strength
23. Dead load
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24. Live load
25. Dynamic load
26. Torsion
27. Shear
28. Force