A girder bridge is a simple and inexpensive type of bridge made of a horizontal beam supported by posts or pillars. It works on the principles of compression and tension and is commonly made of reinforced concrete or steel beams. The biggest limitation is its length, but longer spans can be achieved by daisy chaining bridge sections. The Lake Pontchartrain Causeway is one of the longest girder bridges in the world, measuring nearly 24 miles in length and supported by 9,500 concrete piers.
A girder bridge, sometimes called a girder bridge, is a rigid structure consisting of a horizontal beam supported at each end, usually by some sort of post or pillar. In structural terms, it is the simplest type of bridge and is a popular choice due to its inexpensive construction costs. It began as a felled log supported by opposing river banks that was used to cross a river or other body of water. Today it is commonly made of reinforced concrete or steel beams for everything from pedestrian bridges to highway overpasses.
This type of bridge works on the principles of compression and tension, so a strong beam is needed to resist twisting and bending under the weight it has to bear. When a load, such as a group of moving cars, pushes down on the beam, the weight of the beam pushes down on the piers. The top edge of the beam is pushed together as a result of the compression, and the tension causes the bottom edge to stretch and stretch. This works in the same way that a wooden board supported by blocks on each end can only support a certain amount of weight before warping. The top reaches its maximum compression and the bottom cracks from too much tension.
Many girder bridges used in road construction are made of concrete and steel because these materials are strong enough to withstand compressive and tensile forces. The distance a beam can travel is directly related to its height, because higher beams offer more material to dissipate the stress. To create taller beams, you can add reinforcement trusses. A truss is a truss construction that supports a beam, creating stiffness and increasing the beam’s ability to dissipate compression and tension. This technique only works to a certain extent, because eventually the weight of the bridge and trusses will be too heavy to support.
Despite reinforcements such as concrete, steel, and trusses, the biggest limitation of this type of bridge is still its length, so it rarely spans more than 250 feet (76.2m). Greater distances can be achieved by daisy chaining bridge sections to create a continuous span. One of the longest bridges in the world is a continuous span girder bridge that was created in this way. Located in Louisiana, the Lake Pontchartrain Causeway is a pair of parallel bridges measuring nearly 24 miles (38.5 km) in length and supported by 9,500 concrete piers.
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