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GIRDER BRIDGES

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TRUSS BRIDGES ... The most common type is the Warren Truss ... Notice that the roadbed can be above or below the truss. Tacoma Narrows Bridge ... – PowerPoint PPT presentation

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Title: GIRDER BRIDGES


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GIRDER BRIDGES
  • Oldest and most common bridge type known. (Fallen
    logs were used)
  • In modern girder bridges, steel I-beams are used,
    but they are subject to twisting and are not
    good for bridges with any curve to them.
  • Box beams are stronger and used for curving or
    longer bridges.

3
ARCH BRIDGES
  • Second oldest bridge type.
  • Unlike girders, can be built from stone.
  • Because no center pier is required, can be used
    to cross valleys and rivers without interfering
    with river traffic.
  • Considered the most beautiful of bridge types.
  • Many ancient arches are still standing today!

4
CABLE-STAYED BRIDGES
  • Really just a continuous girder bridge with
    towers above piers
  • The cables are flexible and affected by the wind.
  • Longer spans require very complex computations
    and analysis.

5
SUSPENSION BRIDGES
  • Of all the types of bridges used today, the
    suspension allows for the longest spans.
  • Similar to a cable-stayed bridge except there is
    one main cable that runs between the towers with
    hanger cables below it.
  • The girder and roadbed are not resting on the
    piers as with other bridge types, but is hanging
    from the hanger cables!
  • Vulnerable to wind

6
TRUSS BRIDGES
  • Because of the use of the triangular shape,
    trusses only sustain compression and tension
    forces and not bending!
  • Can be built in small sections so are ideal in
    areas where large machinery wouldnt have access.
  • The most common type is the Warren Truss
  • For longer spans and for a stronger Warren Truss,
    vertical members are added. Notice that the
    roadbed can be above or below the truss.

7
Tacoma Narrows Bridge
  • Suspension Bridge that connects Tacoma and
    Seattle, Washington.
  • On the morning of November 7, 1940, the Tacoma
    Narrows Bridge twisted violently in
    42-mile-per-hour winds and collapsed into the
    cold waters of the Puget Sound.
  • Caused by self-excited vibrations the bridge
    took over the wind and destroyed itself.

8
TERMS OF BRIDGE CONSTRUCTION
  • TORSION- THIS IS A TWISTING FORCE
  • SPAN- A DISTANCE UNSUPPORTED BETWEEN 2 POINTS
  • LOAD-THE WEIGHT SUPPORTED BY THE BRIDGE
  • TENSION- STRETCHING A STRUTURAL MEMBER

9
  • DECK-THE ROAD BED OF A BRIDGE SYSTEM
  • SUSPENSION- A BRIDGE SYSTEM THAT USES CABLES TO
    SUPPORT THE DECK
  • COMPRESSION-DOWNWARD PRESSURE ON A STRUCTURE

10
  • GIRDER- A SUPPORT BEAM OF A BRIDGE
  • BEAM- A BRIGE TYPE THAT USES A SOLID GIRDER AS A
    DECK
  • TRUSS- A STURCTURAL SYSTEM THAT USES TRIANGLES TO
    EQUALIZE COMPRESSION AND TENDSION

11
  • WHICH COLOR REPRESENTS COMPRESSION AND TENSION?

12
Need to know
  • All 5 types of bridges (identify and sketch)
  • All 10 terms (define match explain)
  • Compare and contrast 2 types of bridges with AT
    LEAST 3 different UNIQUE qualities!!! (you choose
    the 2 types)
  • Questions- T/F, M/C, fill in the blank, short
    essay, Venn diagram
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