Open concrete reservoir walls are designed upon similar principles to those applied to re taining walls. Expansion joints and water tightness are important. They are lined with a i concrete bottom 4 inches to 8 inches thick, pre ferably reinforced with a mesh of metal.
Covered reservoirs have concrete bottoms carrying the upward pressure to columns that also support the concrete roof. Roof and bottom may be groined arches or slabs. Reser voirs of groined arches in the United States have spans from 10% feet to 16 feet, a rise of from 1 foot 6 inches to 4 feet, and a crown thickness of 6 inches. Since the exterior walls are supported by the roof, thinner sections are needed than for open reservoirs. A circular reservoir wall supporting a domed roof needs a ring of reinforcing at the top.
Reinforced concrete water tanks must be constructed of impervious concrete, and are gen erally built in one operation of wet concrete. They should be reinforced, not only for mechan ical stress, but for shrinkage. The tank of the filtration plant at Merrimack, N. H., is 40 feet high, and 144 feet in diameter. The walls are 10 inches thick at the top. Rings of deformed round bars h-inch in dimension, are spaced 6 inches vertically in centre of wall, intersected with h-inch vertical rods, spaced 5 feet centres.
Examples of reinforced concrete stadia and grandstands are found at Harvard, Tacoma, Syracuse, Yale. These offer a suitable appear ance, require no repairs and prevent accidents that arise from lack of maintenance of wooden structures. The following statistics show seat ing capacity of well-known stadia: Stadia, Circus Maximus, Rome, estimated 380,000; Colosseum, Rome, estimated 45,000 to 100,000; Yale Bowl, 125,000; Athens Stadium, 50,000; College of City of New York, 10,000; Syracuse, 20,000; Tacoma, 20,000i Harvard, 45,000; Princeton, 41,500. Construction cost per seat ranges from $36 for the stadium of the City of New York, $8.50 for the Princeton Stadium to $7.35 for the Yale Bowl.
Grain and ore bins, coal pockets are other containers that are common. • Hool, (Reinforced Concrete Construction) (New York 1912) •, Morsch, (Concrete Steel Construction) (Engineering News, New York 1910) ; Sabin, L. C., 'Cement and Concrete) (New York 1907); Taylor and Thompson, (Concrete: Plain and (New York 1908); Turneaure and Maurer, Principles of Reinforced Concrete Construc tion) (New York 1909).