Thin Concrete Shells Research Articles

A new method of experimental buckling of circular cylindrical roof shell models with free edges subjected to external pressure

Non-linear snap-through behavior of a thin concrete shell roof characterized by free edges, or free edge members supported by several columns, is considerably influenced by the boundary conditions and the edge disturbances developed in the prebuckling state. This paper presents a method of realizing all four natural boundary conditions along a free edge of a roof shell model subjected to external pressure. The experimental method is shown to be useful for investigating non-linear behaviour of circular cylindrical roof shell models with free generator edge beams. The method has a wide applicability to a variety of roof shell models with free edge members lying on a horizontal plane.

A method, of design for shell concrete roofs using prestressed edge beams

Summary: In a beam provided with prestressing cables which follow a continuous curve between supports, the prestressing force resolves itself into two components: firstly, a horizontal compressive force, which remains very nearly constant throughout the span and secondly, a vertical distributed load, acting upwards and balanced by two downward reactions at the anchorages over the supports. By selecting a suitable curve for the cables, this vertical distributed load can be made uniform throughout the span: it can also be made to equal in value the uniformly distributed permanant loads acting on the beam, thereby cancelling all deflections caused by such loads. Prestressing forces are usually designed to counteract tensile stresses, the effect of such forces on the deflection being purely incidental. In the case however of thin concrete shells, the vertical prestressing forces provide an effective means of cancelling the edge disturbances caused by deflections in edge beams, thereby enabling the thin shells to be regarded as membranes wirhout any appreciable bending stresses. In the following article, an attempt is made to analyse the efreCI on thin shell structures of the prestressing forces resulting from suitable arrangement of cables. Some reference is also made 10 polygonal shell structures. Incidentally, it may be noted that the provision of curved cables inducing upward vertical loads may lead 10 reasonably economical design in other types of structure not mentioned in this article, such as continuous girders or large span rectangular slabs.