It has been found that structural elements ideally suited for chemical pre stressing include pipes, thin walls and slabs, shells; folded plates and composite columns as well as pre cast beams and columns.

The Freyssinet anchorage system is widely used in Europe and India consists of a cylinder with a conical interior through which high tensile wires pass and against walls of which wires are wedged by a conical plug lined longitudinally with grooves to house wires.

After process of cooling, bars get shortened but which can be known with fixed arrangement at both ends and period of cooling is observed as 12 to 15minutes, a steel metal sheath of enlarged diameter and sufficient length is generally used to cover splice, screw threaded connectors are not recommended for splicing heat treated prestressing steels, which are highly suspectable for stress corrosion.

Freyssinet system of post tensioning anchorages which was developed in 1939, gave impetus to various new systems devised over years and at present, according to abeles re are over 64 patent post prominent systems used worldwide.

United beams more than 2 are hardened in Hoyer?s method of pretensiong in case of large distances between each beam, most commonly used devices are Weinberg clip developed in France and Dorland clip developed in united states se clips are clamped on to tensioned wires close on end diaphragms of units before concreting operations.

Thermo electric pre stressing has also been adopted in Germany for tensioning of oval section ribbed wires with an ultimate tensile strength of 1600n/mm², wrapping wire of 1mm diameter is generally used for splicing wires up to 6mm diameter and length of splice may vary from 20-30cm and splice formed in this manner has a strength almost equal to that of normal wire and this type of splice is generally used for wires of circular concrete tanks and anchorage loops.

In this system, forces are transmitted by bearing at end blocks while system eliminates loss of stress due to anchorage slip by screwing a nut and washer against end blocks and drawback of this system is that it cannot use curved tendons.

Screw connectors are normally employed to splice large diameter high tensile bars which can be threaded at ends, torpedo splice consists of triple wedges for securing wires and entire unit is covered and protected by a sleeve, clamp splices are equipped with bolts and nuts with a series of clamp plates to house tendons between m for splicing of small diameter wires of 3-6mm.

In case of heating bar gets elongated and shortens after heating and after anchorages are applied on both sides which stretch bar, clamp splices are equipped with bolts and nuts since re will be a considerable reduction in tensile strength of up to 50 percent, se type of splice can be used only in locations where prestressing force can be sufficiently reduced by curvature of tendon due to friction.

The stresses in wires are not similar, even though all wires are been stretched toger, Freyssinet system involves application of heavy jacks which are economical force applied for stretching is about 250kn to 500kn which is maximum and is still inadequate.