Bridges
Arches are commonly used in bridge construction and so spandrels may also appear in those structures. Historically, most arch spans had solid spandrels, meaning that the areas between arches were completely filled in — usually with masonry — until the advent of steel and reinforced concrete in the 19th and 20th centuries.
Where a river is prone to repeated flooding, the increased pressure of flowing water against the spandrel may cause the bridge to be washed away. Some bridges thus had deliberate openings, usually tubular, in their spandrels to allow floodwater to pass through.
Open-spandrel bridges later became fairly common, where thin ribs were used to connect the upper deck to the bridge arches, resulting in significant savings in material and weight, and therefore in cost. The Roman Trajan's Bridge across the Danube is one of the oldest examples. Reinforced-concrete open-spandrel bridges were fairly common for crossing large distances in the 1920s and 1930s.
Read more about this topic: Spandrel
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—H.G. (Herbert George)
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