BRIDGES

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BRIDGES
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BRIDGE EXPLORATIONS

• What makes bridges stay up
• What makes bridges fall down
• Different types of bridges
• You will design and construct a bridge
• You will test your bridges load capacity

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Beam Bridges
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The Tarr Steps England Circa 1000 B.C.
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KOCHER VIADUCT, AUTOBAHN, GERMANY 185 m HIGH,
1128 m LONG
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Top of beam is in compression and bottom is in
tension. The middle of the beam is neutral the
middle is in neither compression or tension.
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Making a beam stiffer
I Beams move most of the beams material away from
the neutral axis which is underutilized. This
results in a stiffer beam.
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Arch Bridges
PONT DU GARD, FRANCE, 63 BC-13 BC 47.4 m HIGH
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Arches are made of wedge-shaped stones in
compression. Without the keystone the two sides
of the arch will fail. The wedged stones at
the bottom must be prevented from moving outwards
using abutments (stones anchored into the soil).
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MOSTAR BRIDGE, YUGOSLAVIA 1566-1567 27.3 m SPAN,
19 m HIGH
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Cabin John Bridge, Washington D.C.
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RHINE RIVER, BONN- BUEL, 1948
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FRANCIS SCOTT KEY BRIDGE, WASHINGTON, DC
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HEILBRONN, AUT0BAHN, GERMANY
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Truss Bridges A truss is a hinged triangle
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TENMON BRIDGE, KUMAMOTO PREFECTURE, JAPAN SPAN
100 300 100 m 42 m CLEARANCE, 1966
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Why are trusses so common? The members are in
either experiencing compression or tension the
members are not bending. Trusses can be arranged
into many shapes.
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Truss Bridge with a moveable center section.
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Cabin John Bridge, under construction using
timber false work
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Cantilever Truss Bridge
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Cantilever Bridges
Cantilever is a beam supported at only one end.
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The Forth Rail Bridge c.1882-1889 Scotland One
the worlds most massive bridges.
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Suspension Bridges
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Akashi-Kaikyo Bridge 3911 m
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Cable is made by running spools of smaller cable
back and forth across the towers. This is called
spinning the cable.
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Cable Stay Bridges
Kaohsiung County, Taiwan
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Øresund Bridge between Denmark and Sweden
Relatively inexpensive to construct no large
cables need to be spun over towers. Able to span
large distances.
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What kind of Bridges?
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MARACAIBO BRIDGE, VENEZUELA, 1957
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FEHMARNSUND BRIDGE, 248 m SPAN
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Combination arch and beam.
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GANTER BRIDGE DESIGNED BY CHR. MENN
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Engineering Design Process

• Problem Statement
• Problem Analysis
• Design Specifications
• Brainstorming / Idea generation
• Idea Selection
• Implementation

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Problem Statement

What is the maximum load a short paper bridge
can carry?
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Problem Analysis

• How will structure carry loads?
• How is failure likely to occur?
• What can be done to prevent failure?

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Design Specifications

• 10 minimum span
• 1 max. bearing at abutment
• Tape is connector only.
• Bridge cannot be taped to the abutment.
• Materials Three 2X12 strips (cut from heavy
  poster paper)

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Idea Generation Selection

• Brainstorming
• Minimize judgment
• Combine ideas
• Select final idea based on best fit for Design
  Specifications

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Implementation

• Construct bridge
• Test bridge
• Review and evaluate design