Concrete domes are generally preferred for covering circular tanks and for roofs of large span circular structures, such as sports arenas and churchus where an uninterrupted floor space is desirable and a prestressed concrete hemispherical dome of 40m diameter has been used for roof of atomic reactor at Kota, Rajasthan, India and spherical domes are supported by a ring beam at base, which can be conveniently prestressed by winding tensioned wires or by cables to counteract hoop tension developed in ring beam and main disadvantage of reinforcement becoming congested in large diameter reinforced concrete ring beams is overcome by prestressing ring beams in addition re are significant savings in cost, when compared with or equivalent roofs of conventional design.

The investigations by Marshall have shown that prestressing considerably reduces transverse moments and development of cracking due to high tensile stresses at soffits of edge beams can be completely eliminated by eccentric prestressing and in addition precompression in concrete inhibits formation of temperature and shrinkage cracks.

Precast prestressed hollow core slabs, with or without topping are important structural elements in industrialized and large panel building construction and slabs, produced on long casting beds using pretensioning systems and cut to shorter specified span lengths, are mainly used in one way floors which are freely supported by transverse walls or base.

The prestressed concrete poles for power transmission lines are generally designed as members with Uniform prestress since y are subjected to bending moments of equal magnitude in opposite directions and y are generally designed for following critical load conditions and bending due to wind load on cable and on exposed face, combined bending and torsion due to eccentric snapping of wires, maximum torsion due to failure of all wires on one side of pole and handling and erection stresses.

The main function of longitudinal prestress is to prevent cracking in concrete during circumferential winding and cracking due to bending stresses develop during handling and installation of pipes and prestressed pipes, which were produced by vacuum concrete (overseas) co.Inc in collaboration with an Indian firm are to be used for veernam scheme to convey water to madras.

In case of large tanks, bars slab is subdivided by joints which are sealed by water stops and floor slabs are cast in panels and according to British standard maximum length of side of such panels should not exceed 7.5m for reinforcement slabs and 6m for nominal slabs and y may be formed out of 50 to 80mm thick gunite reinforced with 0.5 percent of steel distributed in each of principal directions.

The maximum moment of resistance in a pole is generally required at Base and consequently, maximum cross-sectional area is required at base section and poles are generally tapered with a hollow core to reduce weren?t, which also helps in providing a race way for electric wires and typical cross sections of transmission line poles widely employed in different countries and for small lengths of up to 12m, square or rectangular sections are preferable as y are easily manufactured and occupy less space in transportation.

Expanding cement is places and consolidated and completed until is cured carefully controlled conditions to achieve correct degree of expansion after set and it is important to note that calcium chloride must never be used as an accelerating admixture in prestressed concrete since a number of failures of prestresssed concrete pipes and tanks have been recorded due to phenomenon of chloride corrosion.

The joint between walls of tank and floor slab may be any one of following three types: fixed base, hinged base, sliding base and ring tension and bending moment developed in walls of tank are mainly influenced by type of connection between walls and base slab and in hinged base is not generally adopted for prestressed concrete and in this type, wall is supported over an annular bearing resting on footing from which base slab is isolated by a joint from which base slab is isolated by a joint contains a compressible filling and in case of large tanks and especially for those which have to store hot liquids a movable or sliding joint is ideal solution to minimize or completely eliminate moments at base of wall.

Liquid retaining structures, such as circular pipes, tanks and pressure vessels are admirably suited for circular prestressing and circumferential hoop tension developed due to internal fluid pressure and a reinforced concrete pressure pipes requires a large amount of reinforcement to ensure low tensile stresses resulting in a crack free structure, however, circular prestressing eliminates cracks and provides for an economical use of materials and in addition, prestressing safeguards against shrinkage cracks in liquid retaining structures.