Prestressed concrete poles are currently mass produced and are widely used in most countries for railway power and signal lines, lightening poles, antenna masts, telephone transmission, low and high voltage electric power transmission and substation towers main advantage resistance to corrosion in humid and temperature climate and to erosion in desert areas, freeze throw resistance in cold regions.

Longer spans exceeding 30m necessitate lapping or wielding of reinforcement in addition, structure may be rendered unfit for its intended use at serviceability limit states due to excessive deflections and objectionable cracking and most of se problems are eliminated by prestressing edge beams of long span shell structures.

Tanks have been built for storing liquid oxygen at 230 degrees with capacities up to one million liters and prestressed concrete, although water tight, it is not gas tight were vapours under pressure are to be stored and in such cases, a thin membrane linear of steel provides rigidity and increases steel tensile capacity of pretressed concrete.

f_c = 8.2, stress = 1000, diameter = 150mm
F = (8.2 x 1000 x 150)/1000 = 1230kn.

The main advantages according to Gerwick of prestressed concrete piles over traditional reinforced concrete and steel piles are high load and moment carrying capacity, standardization in design for mass production, excellent durability under adverse environmental conditions, crack free characteristics under handling and driving, resistance to tensile loads due to uplift combined load moment capacity, particularly advantages for deep foundations to carry heavy loads in weak soils.

In fixed base joint junction is between tank wall and footing is most vulnerable location as far as leakage is concerned and hence in case of tanks storing penetrating liquids, it is necessary to form wall and footing in monolithic construction and this type of connection is generally well suited for shallow tanks with diameters up to 30m, where fixing moment developed at wall base does not result in excessively high stresses and congestion of reinforcement.

In general, concrete shells have thin cross sections, which prectude use of large diameter Cables and tendons consisting of 5 to 8mm diameter wires accommodated in narrow sheaths are conveniently used in post tensioning lower parts of shell membrane to overcome problem of correctly positioning curved cables along space curves at junction of shell and edge beam, it is general practice to impart prestress by post tensioning curved cables that housed entirely in deep edge beams and edge beams being invariably deep, it is convenient to arrange cables one over or so that maximum eccentricity is available at centre of span.

According to Ooykaas prestressed concrete pipes may be classified depending upon method of manufacture under following groups:
Monolyte construction based on principle that a mix of fresh concrete subjected to triaxial pressure behaves in some respects like a solid body, two stage construction method of manufacturing a non cylinder pipe (without steel cylinder) was developed by Lewiston pipe corporation around 1930.

Cylindrical tanks are by far most commonly used types from structural and constructional consideration and some of largest prestressed concrete tanks constructed are circular in shape and a cylindrical shape is well suited for circumferential wire wrapping, which constitutes major prestressing operation in tanks and square or rectangular tanks spanning eir vertically or horizontally, are required for industrial use and square tanks are advantageous for storage in congested urban and industrial sites where land space is a major constraint.

? = 0.075, t = 120mm, internal diameter is 30�10³, N_d = 840
S = 2�840/0.075x1000x20/10.75x30x103x120 = 11.6mm.