(m4bridge-concrete-or-glennjackson-memorial) The Glenn Jackson Memorial Bridge
Unreinforced concrete has been used to build bridges construction for millennia, likely starting with the building of masonry bridges and aqueducts as well as by spanning water conduits using concrete. Too, bridges built with cast iron in the 1700s likely had concrete decks, some could have even had their structure encased in concrete. In 1873, a Frenchman, Joseph Monier obtained a French patent for a method of iron-wire reinforced concrete bridge construction.
Concrete bridges are a type of bridge, constructed out of concrete, and began to appear widely in the early twentieth century.
Reinforced Concrete
Concrete bridges are a type of bridge used widely today and while haveing their roots in ancient Roman construction, was not used in the modern time until the mid-nineteenth century. The modern form of concrete contruction, that with steel reinforcement, began to be built some time in the 1850s by the Frenchmen Josepth Lambot and Joseph Monier, who used the steel reinforcement for building garden structures. Patents were taken by both men during the 1850s and 1869s
Later, with the establishment of the construction industry, most were skeptical about the mixing of concrete with steel with theoretical experiments not initiating until the late 1880s. Then, in the early years of the twentieth century, the theories began to be proven and accepted by the construction industry, which was followed by standard practices and the first codes.
Types of Concrete Bridges
However, historically, wood, stone, and iron were used for building bridges, but steel and concrete are the primary construction materials used today for modern bridges and most of these concrete bridges used reinforced and pre-stressed concrete.
When reinforced concrete is used to build bridges, there are a number of designs. However, two types that are most common are the Beam Bridges and the Segmental Bridges.
Beam Bridge
A concrete bridge, in its basic form is a horizontal concrete beam that is supported at each end by vertical supporting piers with the weight of the concrete together with any load exerting downward pressure of the two supporting piers. The concrete must be strong enough so that it does not bend under its own weight nor the added weight of the load.
Also called a girder bridge, this type of bridge is the simplest and least expensive kind of bridge to build.
Pre-stressed concrete is the best material for concrete bridge construction and is usually the least expensive material in constructing concrete bridges. However, the biggest limitation of a concrete bridge is the length. Concrete bridges is normally limited to 250 feet or less between piers but when longer spans are necessary, the piers must be daisy-chained together to create what is known by bridge engineers as a continuous span.
Lake Pontchartrain Causeway:
The best example of a continuous span concrete beam bridge is the Lake Pontchartrain Causeway which crosses Lake Pontchartrain north from Metairie, Louisiana, a suburb of New Orleans to Mandeville, Louisiana. This bridge is listed as the longest continuous bridge over water in the world,
Segmental Bridge
A segmental bridge is a type of concrete bridge which is very economical for spans of more than one hundred yards (100 meters), especially when access to the construction site is restricted, such as over wide rivers.
A segmental bridge is a bridge built in short sections (called segments), i.e., one piece at a time, as opposed to traditional methods that build a bridge in very large sections. The bridge is made of concrete that is either 1. cast-in-place (constructed fully in its final location) or 2. precast concrete (built at another location and then transported to their final location for placement in the full structure).
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