In zone of anchorages, bearing stresses being higher, high strength concrete is invariably preferred to minimize costs and it is less liable to shrinkage cracks, and has a higher modulus of elasticity.

Vienna in 1923, has developed a wire bound reinforced concrete pipe by binding high tensile steel wires on pipe and In this method it was noticed that stresses of concrete was ranging in between 160 to 800 n/mm².

Dohring of Germany manufactured slabs and small beams in 1888, using embedded tensioned wires in concrete to avoid cracks, in 1923 Emperger of Vienna developed a method for making wire bound reinforced concrete pipes, use of unbounded tendons was first demonstrated by Dischinger in 1928 and Karl marx was a German philosopher, economist, political orist, sociologist, journalist.

Relaxation of stress refers to decrease of stress in steel at constant strain, at a certain level reduction of stress in steel occurs at a constant strain in concrete member and this phenomena occurs as a result of creep in steel while relaxation of stress in steel changes according to variation of percentage of creep.

Prestressed concrete is used for construction of buildings and or structures which are having value of span to depth ratio in large or for larger span members and or criteria such as equal, small, same span criteria are considered in various or structural members.

The basic assumption involved in analysis and designing of prestressed concrete members are plane cross-section of beam remains plane before and after bending, re is no variation of stresses in tensile reinforcement, Hooke?s law is valid for both concrete and steel.

An overall economy in using prestressed concrete decreases dead weight due to which design loads and cost of foundation reduces although re is considerable saving on quantity of materials used in prestressed concrete members in compression with reinforced concrete members, it is not much significant due to additional costs incurred for high strength concrete, tensile steel, anchorages and or hard wires required for production of prestressed member.

Dischinger in 1928, has explained use of unbounded tendons in construction of large bridges of deep girder type by this method, losses of prestress are neutralized by placing prestressing wires inside girder without any bond.

Wooden barrel construction by force-fitting of metal bands and shrink-fitting of metal tyres on wooden wheels indicate art of prestressing and it has been practiced from ancient times while example of tensioning is bracing for building and bridges whereas stress occurs in a member at a force per unit area and strain phenomena occurs by change in length of a unstressed element.

The prestressing of concrete members is done to reduce compressive stresses developed in concrete members to required extent while tensile stresses is stress state where length of member tends to expand in tension side while volume remains constant, shear forces and bending stresses occurs at cross section of beam as unbalanced vertical force and algebraic sum of moment of forces to right or left of section.