P = 150kn, y = d/6 = 300/6 = 50mm, a = (100�300) = 3�10⁴, I = 225�10⁶, ?_e = 8, initial stress = 400n/mm², Stress in concrete, f_c = (150�10³/3�10⁴)+(150�10³�50�50/225�10⁶) = 6.66n/mm²,
Loss of stress due to elastic deformation of concrete = ?_ef_c = (8�6.66) = 53n/mm²,
Percentage of loss of stress in steel = (53�100/400) = 13.25% = 14%.

The rate of shrinkage is higher at surface of member and primary cause of drying shrinkage is progressive loss of water from concrete, phenomena of shrinkage being time dependant only total anticipated or residual shrinkage strain is considered in computation of loss of prestress to be used in design.

The loss of stress in steel due to creep of concrete is ?cc fc Es,
?cc = ultimate creep strain for a sustained unit stress, fc = compressive stress in concrete at level of steel, Es = modulus of elasticity of steel.

The term Es is defined as strain loss in steel, E_s = ?f_s/E_s,
?f_s = Loss of stress in steel, Es = strain loss in steel.

Initial stress in wires = (300�10³/300) = 1000n/mm²,
If beam is pretensioned total residual shrinkage strain = 300�10^-6,
Loss of stress = (300�10^-6)(210�10³) = 63n/mm², % loss 0f stress = (63�1000/100) = 6.3%.

The recommendations of Indian standard code (IS:1343) relaxation loss for prestressing steels at 1000 hours at 27?c and at time of initial prestress not to exceed 80% of characteristic tensile strength of tendons final stress not less than 45% of characteristic tensile strength of tendons.

b = 200mm, d = 450mm, l = 10m, r = 84m, d = 5m,
Angle between horizontal tangent drawn to cable at support sin? = (5/84) = 0.06radians,
Cumulative angle between tangents to cable at supports = (2�0.06) = 0.12radians.

A = 320mm², b = 200mm, d = 300mm, e = 50mm, p = 1000n/mm², l = 10m, E_s = 210kn/mm², E_c = 35kn/mm², Slip at anchorage = (1�210�10³/10�1000) = 21, Friction effect = (1000�0.0015�10) = 15.

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.