The rise in temperature causes a partial transfer of prestress due to elongation of tendons between adjacent units in long line process which may cause a large amount of creep if concrete is not properly cured.

The creep coefficient varies from a minimum value of 1.5(for wet conditions) to a maximum value of 4.0(for dry condition), for design purposes it is convention to differentiate between deformation due to externally applied stress generally referred as creep and deformation which occurs without externally applied stresses referred as shrinkage as increase in strain under a sustained stress is several times larger than strain on loading, it is of considerable importance in prestressed structural members.

In most bridge girders, cables are curved with maximum eccentricity in center of span in such cases loss of stress due to elastic deformation of concrete is estimated by considering stress in concrete at level of steel.

The British code for structural concrete recommends design values of ultimate creep strain of 48�10^-6 for pretensioning and 36�10^-6 for post tensioning and se values have to be increased in inverse proportion if compressive strength of concrete at transfer is less than 40n/mm².

A reasonably good estimate of magnitude of lines of prestress is necessary from point of view of design, if prestress present in steel is considered as force applied on concrete at ends and change is stress along with length of entire beam is not concluded as change in prestress.

Experiments have shown that a reduction in relaxation stress is possible by preliminary overstressing by 5-10percent for a period of 2 to 3minutes considerably reduces magnitude of relaxation and some codes permit temporary overstressing with corresponding lower magnitudes of relaxation stress.

The concrete members which are prestressed by providing tensioned tendons are termed as internally prestressed members due to bending moment in beam is developed and bending in beam results in change of unit stresses, unit strains in tendons.

The systems in which tendons are lopped around concrete anchorage blocks, as in case of Leonhardt-Baur system, loss of stress may take place, Baur Leonhardt system is included in third type of anchorages which work under principle of looping tendon wires at ends of concrete member, in this method double tendons are wrapped around end block.

The anchorage slip is observed in post tensioned members at time of transfer of prestress to concrete and friction wedges employed to grip wires, slip over a small distance before wires are firmly housed between wedges.

The loss of stress due to curvature effect, which depends upon tendon form or alignment which generally follows a curved profile along length of beam, curvature coefficient is expressed as ? and wobble coefficient is expressed as k/m.