The frictional losses and loss due to anchorage slip are observed in post tensioned members only because pretensioned members do not require anchorages for prestressing and in post tensioned beams which are unbounded loss and gain of prestress depends upon upward bending movement of beam and beam when loaded fully respectively.

The Indian standard code recommends a value varying from 0 to 90n/mm² for stress in wires varying from 0.5f_pu to 0.8f_pu and Indian standard codes for wires and bars prescribe 1000 hour relaxation test with no relaxation exceeding 5 percent of initial stress alternatively one can resort to 100 hour relaxation test with no relaxation exceeding 3.5 percent of initial stress similar provisions have also been made in British and American codes.

Force in each cable, p = (50×1200) = 60×10³n = 60kn, A = 3×10⁴mm², I = 225×10⁶mm⁴, e = 50mm, y = 50mm stress in concrete at level of steel f_c = (60×10³/3×10⁴)+(60×10³×50×50/225×10⁶) = 2.7n/mm².

The sustained prestress in concrete of a prestressed members results in creep of concrete which effectively reduces stress in high tensile steel and progressive inelastic strains due to creep in a concrete are likely to occur under smallest sustained stresses at ambient temperatures, shrinkage and creep of concrete are basically similar in origin, being largely result of migration of water in capillaries of cement paste.

If re is a possibility of a change of temperature between times of tensioning and transfer corresponding loss should be allowed for design, due to bending of a member prestress may vary depending upon line of bending, position of tendons(high strength steel cables which are flexible) number of tendons which are kept at different stages and also type of prestressing wher it is a post tensioned or pretensioned effect of bending may be eir a positive or negative in prestress.

Creep coefficient is generally low for post tensioned members and high for pre tensioned members, various factors influencing creep of concrete are relative humidity, stress level, strength of concrete, age of concrete at loading, duration of stress, water cement ratio, and type of cement and aggregate in concrete, for stress up to half of crushing strength of concrete.

The prestressing force at section is given by:
P_x = p?e^-(??+kx), Loss of stress (?f)_f = 1-(??+Kx),
P_x = Prestressing force at section x, P? = initial prestressing force, ? = coefficient of friction between cable and concrete, k = wobble effect, d = cumulative angle.

Typical values of total losses of stress that could be encountered under normal conditions of work were recommended by Lin, long term field studies on loss of prestress in post tensioned concrete bridge girders have been carried out by marks and Keifer, Neville gave losses in prestress considering various influencing parameters.

The total loss due to friction is divided into two types:
Loss of prestress due to effect of curvature, Loss of prestress due to wobble effect and frictional losses can be reduced by over tensioning tendons by an amount equal to maximum frictional loss and jacking tendons from both ends of beam adopted generally, when tendons are long or when angles of bearing are large.

The amount of anchorage slip generally depends upon type of wedge used at ends and magnitude of stress in wires, since loss of stress is caused by a definite total amount of shortening percentage loss is higher for short members than for long ones.