Concrete Funicular Shells for Floors and Roofs
Research is described in which a concrete funicular shell, 35 x 40 feet in plan with a 2-inch thickness and a 30-inch rise, was tested to define its behavior under various loadings. The shell sustained a uniformly distributed load of 135 psf before failing in local buckling. In a subsequent test on an undamaged portion, it sustained a concentrated load of 10,800 pounds over an area 6 inches square before failing in punching shear. In addition to the test, pertinent construction and analysis techniques are discussed. It was found that double-curved shallow shells may be easily cast over an earth mound. When combined with the lift-slab technique, this mode of construction is expected to provide an inexpensive method for fabricating large shells for floors and roofs. Approximate limit analyses can be used to proportion shallow shells for ordinary purposes; however, no completely satisfactory method is available for treating such members. Elastic analysis provides a reasonable representation of behavior only at low loads. Despite the limitations in current analysis, the technology has developed sufficiently to permit use of shallow shells in military and civilian construction. Naval Shore Establishment uses include decks of docks and floors and roofs of warehouses. (Author).
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