For service conditions, RAM Concept assumes that unbonded tendon stresses are not affected by cross section strains.

For ultimate resistance moment calculations, RAM Concept 's general approach to unbonded tendon stress-strain curves is detailed in Chapter 51, "Section Design Notes". For IS 456-2000, the maximum unbonded tendon stress (called f_limit in Chapter 51, "Section Design Notes") is defined by IS 1343-1980 Appendix B, Table 12. For IS 1343: 1980, the value used as a strain reduction factor for unbonded tendons is 0.1.

RAM Concept assumes that each tendon is placed on the more beneficial side of the cross section centroid (the same limiting stress value is used for both positive and negative moment capacity calculations at each cross section). This assumption typically has no impact on the ultimate stress in the tendon as when the tendon is on the "wrong" side of the cross section centroid, the stress in the tendon is less than f_pb, due to the small tension strains (possibly compression strains) in the cross section at the tendon elevation.