Architecture and Engineering of the Pentagon
The Pentagon, considered the largest office building in the world, has many distinctive design features, while being rather ordinary in its construction. The vast building, nearly a mile in circumference, has a footprint in the shape of an equilateral pentagon. In keeping with the theme of five, it has five concentric wings, each of which is five stories high.
The five wings, named Rings A, B, C, D, and E, with E being the outermost, are less distinct than appears from the building's roof. Only the lightwells between Rings B and C go to the ground. The lightwells between Rings A and B, C and D, and D and E descend only to the base of the third floor.
|These figures from FEMA's Pentagon Building Performance Report show a radial section through one of the Pentagon's wedges (above), and a perpendicular section along one of the light wells (below).|
The Arlington Farms area was selected for the Pentagon so that the enormous new building would not detract from the classical architecture of the buildings on the Mall. Ground breaking was on September 11, 1941.
The original plans called for three, and then four stories. The plans were modified several times during construction to provide more space, partly in response to the attack on Pearl Harbor.
Various squabbles relating to matters such as the choice of masonry facing slowed the construction. The selection of steel-reinforced concrete for the building's structure saved an estimated 43,000 tons of steel, in great demand because of the war effort. 1 The Pentagon's construction included 42,000 15-inch-wide square steel-reinforced concrete pillars.