vertical lift bridge.pdf

 A vertical-lift bridge or bridge or just lift bridge is bridge is a type of movable bridge in bridge in which a span span rises  rises vertically while remaining parallel with the deck. The vertical lift offers several benefits over other movable bridges such as the bascule bascule and  and swing[1] span bridge. bridge. Generally speaking they cost less to build for longer moveable spans.  The counterweights in a vertical lift are only required to be equal to the weight of the deck, whereas bascule bridge counterweights must weigh several times as much as the span being lifted. As a result, heavier materials can be used in the deck, and so this type of bridge is especially suited for heavy railroad use.  Although most vertical-lift bridges use towers, each equipped with counterweights, counterweights, some use hydraulic jacks located jacks located below the deck. An example is the 52-foot (16 m) span bridge at St Paul  Avenue in Milwaukee[2] (see also table bridges). bridges). Another design used balance beams to lift the deck, with pivoting bascules located on the top of the lift towers. [3] An example of this kind was built at La Salle in Illinois, USA. The biggest disadvantage to the vertical-lift bridge (in comparison with many other designs) is the height restriction for vessels passing under it. This is a result of the deck remaining suspended above the passageway.