Undersea Concrete Spherical Structures
Harvey H. Haynes and Lawerence F. Kahn
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biaxial loads: buoyancy: concretes: cracking (fracturing): deep submergence; hydrostatic pressure: long time study: marine atmospheres: permeability: seawater:shells (structural forms): strength: stresses: underwater
An experimental test program was conducted on plain concrete spherical shells of size 16 and 66 in. (40.6 and 167.6 cm) outside diameter (OD) subjected to short- and long-term hydrostatic loading. Two stages of failure were observed for the spheres; crack development in the plane of the wall thickness followed by implosion. A direct relationship was found between implosion pressure, concrete strength, and the ratio of wall thickness to outside diameter. Results from long-term loading tests showed that spheres under sustained pressure implode with time in a similar manner to that known for uniaxially loaded prisms and that the permeability rate of seawater through concrete decreases with time. Test findings support the utilization of buoyant spheres to a maximum operational depth of 3000 ft (approx. 900 m); deeper depths are feasible for negatively buoyant spherical structures.