What is the on -board bridge?

The on -board bridge is a design in which the road or sidewalk of the bridge, called decks, sits purely at the top of supporting structures, which are usually made of concrete, steel or wood. Various supportive designs are used, but the advantage of the on -board bridge does not have visible support over the road. This design gives an open road without steel work to prevent or create no danger to helicopters or nearby aircraft. These bridges are built of rectangles made of steel -reinforced concrete connected to the end and placed on vertical supports called columns. Less steel is used on preliminary designs for deck and columns must be placed relatively close to each other to provide support. It is best suited for pedestrian bridges or short connecting sections where there is space for multiple columns. This bridge is built using a reinforced concrete cox with a flat road at the top. Construction of concrete box beams can bridge more distances than a flat concrete deck as the box will beto support greater load without wearing or failure.

Another type of on -board bridge is beam style design. Horizontal rays, usually steel, are associated with end-to-end along the entire length of the bridge and supported by columns located under each connection. The steel and concrete roads can then be placed. Steel beams can bend up and down if the span is too long, which will weaken the bridge. The bridges of the beams are useful for pedestrian or road bridges, where more pillars do not create any problems with space or will.

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lattice deck uses a range of steel beams with square or triangular design to create a box that rests on the columns at each end. The steel support of the lattice system can be more difficult to build than the beam bridge, but can be built on the ground and then rises to a crane place. Can bridge more distanceBefore the beam deck, which makes them useful where the will is needed. The drop -down bridge for truss decks requires more height than the deck of the beam for check -in needed, because the lattice system has a height of about 12 percent of the bridge length.

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arches can be used in the on -board bridge design if the arch is placed under the road. This design is built a steel arch, which is supported by the basis at both ends of the arch. The road is built above the arch, with the highest point of the arch in the middle of the road span. The arc suggestions are useful where there is higher will, such as rivers, port roads or other roadways.