Reinforced Concrete Arch
The reinforced concrete arch bridge has a short, but notable, history. At the turn-of-the-century, concrete was recognized as an excellent building material for bridges. Concrete is practical, inexpensive, and quite versatile. Alone it has enormous strength under compression, and when reinforced with steel or wire rods, its possibilities are endless. The bulk of Vermont's reinforced concrete arch highway bridges were constructed between 1908 and 1925, although a number of concrete arch culverts were constructed between 1902 and 1912. Construction was slow prior to 1916, at which time the Vermont State Highway Department forged ahead on highway bridge-building. The majority of Vermont's concrete arch bridges are solid-spandrel, meaning their walls are constructed of solid concrete. A few notable examples are open-spandrel, meaning their structure consists of vertical columns and cross girders.
The most common type of reinforced-concrete arch bridge was the solid-spandrel arch. Seen below, solid-spandrel arch bridges had solid walls of concrete.
Many concrete arch bridges were ornamented with raised or recessed panels, pilasters, stringcourses, or decorative finishes.
Railings were also quite decorative. Balustrades were sometimes constructed, as seen on the left, but solid walls with recessed panels, seen on the right, were the most common type of railing.
Open-spandrel reinforced-concrete arches are the most structurally sophisticated bridges. Colchester, Westminster, Windsor, and Bellow's Falls all received these engineering marvels, most of which were constructed in the early 1930s. Below are several excellent examples of open-spandrel construction.