CT's Historic Concrete Arch Bridges

(click on images for larger view)


Construction of a reinforced concrete bridgeConcrete is a mixture of sand, stone and cement that hardens into a rock-like mass when mixed with water. Although known to the ancient Romans, concrete was not widely used for bridges until methods of reinforcing it with steel were developed. Like stone, concrete has tremendous resistance to compressive forces but relatively little tensile (bending) strength. Imbedding steel in the concrete, however, gives it tensile strength as well.

The first reinforced-concrete bridge in America was built in 1889, but the material remained in an experimental phase until the early 1900s. Bridge engineers found that varying the proportions of the ingredients affected the strength of the concrete, and they tried several methods of reinforcement, including steel beams, twisted bar, and cable, before settling on the ridged rod still in use today.

Reinforced concrete had many advantages. The material itself was inexpensive, consisting mostly of locally available sand and stone. Since concrete was also being introduced for dams, roads, and Construction of a reinforced concrete bridgebuildings in the early 1900s, many Connecticut contractors quickly gained experience working with the new material. Concrete also promised lower maintenance costs compared with metal trusses, which required frequent painting and replacement of rusted components. The State Highway Department recommended concrete for town bridge construction and built most of its own early bridges using concrete.

Not all reinforced-concrete bridges were arches. Most of Connecticut's bridges from the 1920s and 1930s consisted of a single thick slab or a series of concrete beams. Arches, however, were used for the State's larger bridge projects and for the many "City Beautiful" bridges erected in urban areas in the early 20th century.

Take a virtual tour of Connecticut's historic concrete bridges via the links in the sidebar to the left.



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