Unit Test Review

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BRIDGE BUILDING

• Unit Test Review

Updated 4/24/2012.
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FAMOUS BRIDGES
Bridge Name Location Importance
Brooklyn Bridge Brooklyn Manhattan, NYC crosses East River Designer John Roebling completed in 1883 Used caissons to build piers (caisson disease) Uses cable-stayed AND main cable designs
George Washington Manhattan, NYC Fort Lee, NJ crosses Hudson River First modern suspension bridge built after collapse of Quebec Bridge during construction, proved strength and safety of suspension bridges for very long crossings
Golden Gate Bridge San Francisco Marin County, CA crosses Golden Gate National icon
Oakland Bay Oakland San Francisco crosses Oakland Bay Collapsed in earthquake in 1989 Two bridges combined suspension beam On-ramp section melted in truck fire in 2007
Sunshine Skyway Bradenton St. Petersburg, FL crosses Tampa Bay Freighter hit it in 1980 Rebuilt with cable-stayed design Uses damage-sensing monitors (smart bridge), dolphins
Tacoma Narrows (Galloping Gertie) Tacoma Gig Harbor, WA crosses Tacoma Narrows Collapsed in 1940, ignored effect of constant 40 mph wind Rebuilt in 1950 using flexible, open design Parallel bridge completed in 2007
Verrazano Narrows Brooklyn Staten Island, NYC crosses Verrazano Narrows Longest suspension span in the United States
Akashi Kaikyo Kobe Awaji Island, Japan crosses Akashi Straight Longest suspension span in the world, built across a fault line
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PURPOSE of BRIDGES

• Bridges cross barriers (water, chasms, low areas,
  roads, other bridges)
• Primary purpose get people and their goods to
  the other side of barriers
• Roman bridges
• Move armies/troops to conquer land
• Move goods (trade) throughout empire
• Form function balance the beauty (shape) of a
  bridge with its purpose (usefulness, strength)
• Commerce carry trade and services between cities

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TYPES of BRIDGES
Main type Roadbed support Sub-type Example
Beam straight pieces triangles Truss Usher Park bridge
Beam straight pieces triangles Trestle
Beam straight pieces triangles Girder RR bridge over Spring Brook
Beam straight pieces triangles Draw Chicago River draw bridges
Beam straight pieces triangles King Post Morton Arboretum ped bridges
Arch curves Roman curved deck Irving Park ped. bridge
Arch curves Through
Arch curves Half-through
Arch curves Deck
Suspension suspended from cables Main (anchored) cable Golden Gate
Suspension suspended from cables Main (anchored) cable Akashi Kaikyo
Suspension suspended from cables Main (anchored) cable Verrazano Narrows
Suspension suspended from cables Cable-stayed Sunshine Skyway
Suspension suspended from cables Cable-stayed Brooklyn Bridge
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Beam Bridge Types
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Beam Bridges
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Arch Bridge Types
ROADBED
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Arch Bridges
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Suspension Bridge Types
PIERS (TOWERS)
ROADBED
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Suspension Bridges
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OTHER BRIDGES

• aqueduct bridge that carries water
• cantilever bridge with middle section supported
  by counterweights
• pontoon bridge that floats

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PARTS of a BRIDGE

• Roadbed carries the traffic
• Superstructure part of bridge above the roadbed
• Substructure part of bridge below the roadbed
• Pier primary vertical support
• Length distance from one end of bridge to the
  other, including access roadways
• Span
• Arch/beam distance from edge to edge of area
  crossed
• Suspension distance from one pier/tower to the
  other

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PARTS of a BRIDGE

• Caisson pier construction method where sections
  are sunk as the river bottom is dug out inside
• Dolphin bumper that protects bridge piers from
  boat traffic

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JOINTS

• Butt end of one piece attached to side of
  another at right angles
• Miter end of one piece attached to side at an
  angle, often 45 degrees
• Notch both pieces cut halfway through and
  joined, like Lincoln logs
• Lap end of one piece is hung over the side of
  another
• Lamination full length of two sides are attached
  to each other

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NATURAL MATERIALS

• No tools yet
• hanging vines
• piles of stones, rocks moved by water
• fallen trees

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FIRST BRIDGES

• Tools were needed
• woven vines, ropes
• stepping stones placed by humans
• wood

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MODERN MATERIALS

• Modern (since Roman times)
• stone (Roman arch)
• wood (covered bridges)
• iron (early railroad, cracked easily)
• steel (requires painting to prevent rust)
• steel-reinforced concrete

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STRESSES and FORCES

• compression squeezing or pressing together
• tension stretching or pulling apart
• neutral axis point in a beam where compression
  and tension are equal
• torsion torque or twisting motion
• oscillation bending or swinging back and forth
  in an even rhythm
• shear two parallel and opposing compression
  forces (think scissors)

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APPLYING STRESS

• shapes
• triangle strongest shape for resisting bridge
  forces
• racking collapse of a rectangle to a
  parallelogram corrected by bracing
• loads
• dead the weight of the bridge load itself
• live the weight of loads that change, e.g.,
  traffic, wind, ice, snow

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BRIDGE SAFETY

• civil engineer a design engineer who builds
  municipal infrastructure, i.e., bridges, roads,
  power plants, etc.
• bridge failures about 150 to 200 bridges,
  partially or totally each year in the U.S.
• inspections U.S. bridges over 20 feet require
  inspections every 2 years
• smart bridges use computer sensors to warn of
  damage before it gets serious