Bridges are a part of everyday life; a part of the landscape that is often taken for granted until a natural disaster or wear and tear cause them to be closed for rehabilitation.  The resulting detours are never as convenient as taking that bridge.

There are numerous types of bridges such as beam bridges, cantilever bridges, arch bridges, suspension bridges, cable-stayed bridges, truss bridges, movable bridges, and double-decked bridges.  In this post we will take a closer look at the some of the most  innovative kinds of bridges – the movable kind.

Movable bridges are generally found spanning waterways, providing land traffic with a safe means of crossing water while at the same time serving to allow water traffic, such as large freighters, passage in situations where a fixed bridge would not.  Movable bridge design also offers the advantage of lower price, due to the absence of high piers and long approaches.  The principal disadvantage to movable brides is that the traffic on the bridge must be halted when the bridge is opened for passages.

Some bridges are operated by the users, especially those with allowing boat traffic, others by a bridgeman (or bridge tender); a few are operated remotely using video-cameras and loudspeakers.  Movable bridges are often powered by electric motors.  While moveable bridges in their entirety can be quite long, the length of the moveable portion is restricted by engineering and cost considerations to a few hundred feet.

Types of Movable Bridges

  • Drawbridges – the bridge deck most often with a hinge on one end enabling the other end to be raised and lowered
    • Bascule bridge – a drawbridge hinged on pins with a counterweight to facilitate raising and lowering
    • Folding bridge – a drawbridge having multiple sections that collapse together horizontally
    • Curling bridge – a drawbridge having multiple sections that curl vertically
  • Rolling bascule bridge – an unhinged drawbridge lifted by the rolling of a large gear segment along a horizontal rack
  • Vertical-lift bridge – the bridge deck is lifted by counterweighted cables mounted on towers
    • Table bridge – a lift bridge with the lifting mechanism mounted underneath it
  • Retractable bridge (Thrust bridge) – the bridge deck is retracted to one side
  • Submersible bridge – the bridge deck is lowered down into the water
  • Tilt bridge – the bridge deck, which is curved and pivoted at each end, is lifted at an angle
  • Swing bridge – the bridge deck rotates around a fixed point, usually at its center; may resemble a gate in its operation
  • Transporter bridge – a structure high above the water, canyon, etc that moves a suspended section of road back and forth across the span

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