A bridge is like an aerial road'

1
Bridges

• A bridge is like an aerial road.
• It lets our traffic be capable of striding across
  natural obstacles such as straits, rivers,
  valleys
• In some big cities, bridges are used frequently
  as an overhead road to reduce traffic jam and
  raise transportation efficiency.

2

• The load mainly acts on the desk of the bridge.
• The bridge must be deigned to pass the load to
  the ground efficiently.
• Different designs of bridges are applied under
  different conditions.

3
Arch Bridge

• the vertical force acted on the desk would pass
  to the supporting points on both sides of the
  bridge through the designed arch-shaped curve
• The desk can be either under or above the arch.
• The entire arch bridge structure is under
  pressure. Therefore, materials that can bear high
  pressure, such as natural rocks, are the best
  materials for building arch bridges.

4

• eg. Anji Bridge, built at Zhaozhou in China in
  the 7th century (Stone Bridge)

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eg. Sydney Harbour Bridge in Australia (Steel
Bridge)
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Continuous Bridge

• the bridge desk was supported by many bridge
  piers.
• Continuous bridge is usually built over shallow
  water areas or places where large ships cannot
  pass through.
• eg. Seven Mile Bridge (Florida , U.S.) The
  Island Eastern Corridor (Hong Kong)

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eg. Seven Mile Bridge (Florida , U.S.)
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Cable-Stayed Bridge

• Pylon/Bridge towers are built on the bridge pier.
• Cables from both sides of the pylon/bridge tower
  are suspended to the bridge desk.
• The load is passed to the pylon/bridge tower
  through the cables and then to the ground through
  the pylon/bridge tower.
• Steel cables with high tensile intensity are
  chosen as they have to sustain strong tension.
• The length of the cable-stayed bridge is usually
  between 160 and 900 meters.
• eg. Kap Shui Mun Bridge (Hong Kong)

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eg.Kap Shui Mun Bridge (Hong Kong)
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Suspension Bridge

• The main suspending cables are hung on the
  pylon/bridge towers.
• Then connections are made between the main cables
  and the bridge desk with vertical steel cables.
• The ends of the main cables are anchored to the
  ground by concrete to hold against the great
  tension acting on it.
• The span can reach to more than 2000 meters.
• eg. Tsing Ma Bridge (Hong Kong) Golden Gate
  Bridge (San Francisco, California)

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eg. Tsing Ma Bridge (Hong Kong)
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Golden Gate Bridge (San Francisco, California)
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NOVA Online Super Bridge

• http//www.pbs.org/wgbh/nova/bridge/

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Acknowledgment

• Hong Kong University of Science and Technology
  (HKUST)
• Dr. Christopher K.Y. LEUNG Associate
  Professor, Department of Civil Engineering,
  Hong Kong University of Science and Technology