The prestressed concrete members develop deformation under influence of two usually opposing effects, which are prestress effects and transverse loads and deflections caused are to be changed first because loss incurred due to prestress which in turn decreases deflection and effects of creep which increases deflection are suggested in method for long term deflections.

The principle of reduced modulus involving creep coefficient is used to amplify initial deflections and according to this method, final long time deflections are expressed as:
a_f = (a_il ? a_ipxp_t / p_i) (1+?).

In bilinear method recommended by 1963 European concrete Committee moment curvature is approximated by two straight lines, Experimental investigations have shown that a closer approximation to actual load deflection behavior is possible by assuming bilinear moment curvature relationships.

In post cracking stage, a prestressed concrete beam behaves in a manner similar to that of a reinforced concrete beam, se beams undergo cracking under working loads, y undergo large deflections and reinforced concrete beam require shear reinforcement in this testing of steel and concrete cannot be done.

The FIP-1984 recommends following suitable deflection limits for floors, roofs and or horizontal members in building as total deflection below level of supports is Span/200 to Span/300.

In post cracking stage, behavior of beam is similar to that of reinforced concrete members, instantaneous deflections in post cracking stage is obtained as sum of deflections up to cracking load based on gross section and beyond cracking load considering cracking section.

More complicated problems involving unsymmetrical loading may be solved by combining both moment area orems Mohr?s first orem and second orem, since bending moment at every section is product of prestressing force and eccentricity tendon profile itself will represent shape of bending moment diagram.

A straight tendon at a uniform eccentricity below centroidal axis is given as:
If camber of beam with straight tendons upward deflections are considered as negative and
a = -(PeL) (L/4)/EI = -PeL²/8EI, P = effective prestressing force, e = eccentricity, L = length of beam.

?Lin? suggested a procedure which is not exactly accurate but it helps in calculating long term deflections in a very simplified manner, this procedure helped in calculating long term deflections.

Short term deflections of prestressed members are also known as instantaneous deflections governed by distribution of bending moment throughout span and flexural rigidity of member, se orems are applied for determining deflections due to prestressing force, imposed loads and self weight.