A segmental bridge is usually a concrete bridge that is put together in small sections. The concrete can be cast at the location where the bridge is being built or premade elsewhere and brought in. When completed, such a bridge typically appears to have numerous division lines on it where these sections are connected together. These are often connected with epoxy and a steel support system.
A main benefit of the segmental bridge design is that it can help builders more easily construct bridges over areas where it is difficult to transport large sections of concrete. This can include deep valleys, wide waterways and heavily traveled highways. Building a segmental bridge, as opposed to a traditional one, can also limit the amount of disruption to the environment and to users' daily commutes.
To build a segmental bridge, the construction crew usually first erects the support towers. These towers will hold the weight of both the bridge itself and the traffic crossing over it. The crew generally builds these towers up from the ground below the bridge, layering concrete to reach the underside of the actual overpass.
Once the towers are in place, the crew normally begins work on the superstructure, which is a kind of frame that sits on top of each tower. This will hold the deck, or span, of the bridge. For bridges that are cast on-site, the construction crew usually installs the steel frame and supports before pouring the concrete for the span. For precast bridges, the workers can build the steel frame piece by piece as they attach each segment, like a puzzle.
Segmental bridges are a relatively new invention. The idea for this design originated in Europe. The first segmental bridge in the world was built in Baluinstein, Germany, in 1950 to span the Lahn River. It was cast onsite. The first precast bridge was built across the Seine River in France in 1962.
It took another decade for the segmental bridge to come to the United States. The first one built in the U.S. was the Corpus Christi Bridge in Texas. It was constructed in 1973 using precast concrete girders. The first U.S. bridge cast onsite was constructed in San Diego in 1974.
Other well-known segmental bridges are the Seven Mile Bridge, located in the Florida Keys; The Manwel Dimech Bridge in Malta; and the Four Bears Bridge in North Dakota. This type of bridge continues to be a popular one. The segmental design can be a convenient one that can save both time and money.