The load on structural element corresponding to first visible crack is called as cracking load and transfer refers to phase in which prestress is transferred to concrete, transfer load occurs at pretensioned members when prestress is released from bulk heads while in post tensioned members, transfer occurs after tensioning of tendons.

Prestressing of concrete improves ability of material for energy absorption under impact loads and working loads proved to be good in prestressing than in reinforcing and it is done in concrete members to reduce compressive stresses developed in members to required extent.

In pre-tensioning system, tendons are tensioned first and n casting of concrete is carried out and edge of tendon at its eir side is fixed to an abutment and its or edge is pulled with application of jack and n reinforcements are set free after curing and hardening.

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.

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.

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.

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.