Bridges of Yesterday, Today, and Tomorrow
... new bridge, also called Tacoma Narrows Bridge, was built 29 months after construction on the “Galloping Gertie.” This new, safer bridge is 5,979 feet long, which was 40 feet longer than the old “Galloping Gertie” bridge. After the “Galloping Gertie sank, the remains of this bridge were taken to the National Register of Historic Places in 1992 to protect this bridge from rotting and disappearing. There are a few different kinds of bridges that are built, all different shapes and sizes. Beam bridges, or girder bridges, are supported at each end by the ground with the weight of the bridge going downward. Cantilever bridges are an easy form of beam bridges, or girder bridges. However, cantilever bridges differ from beam bridges, or girder bridges because cantilever bridges are only supported by one end. Another type of a bridge are arch bridges. These bridges stick out forward and backwards at their ends. Suspension bridges use cables for weight to pull inward against anchorages on both sides of the span so that the roadway hangs from the main cables by the network of vertical cables. The cable-stayed bridge depends on the diagonal cables connected directly between the bridge deck and holds up towers at each end. Some bridges are very low that they allow traffic to pass under easily, so they are designed with parts that can move, similar to swing and draw bridges. Some history about bridges is that in the Middle East, they used arched structure bridges that were made out of stone and/or brick in 4000 BC. Many of these bridges are still standing today. In 1779, cast iron bridges were made and introduced. In prehistory, people used things like logs or vines for bridges. Clapper bridges were made from flat stones easily laid across or supported by piles of stones. These bridges were some of the earliest bridges. Most engineers think about what forces are put on a bridge before they build, design, or construct a bridge. Most bridges consider the following forces: vertical, longitudinal, and transverse. Vertical forces are...