Optimal limit state design with unbonded prestressing tendons

This paper explores the theoretical behaviour of concrete structures prestressed by means of unbonded tendons according to the CEB-FIP ‘Model Code for concrete structures’. The subject matter is dealt with analytically. The study comprises two parts: the first deals with sections containing unbonded prestressing steel only, the second investigates structures having traditional bonded reinforcement in addition to unbonded tendons. In both cases, diagrams and tables have been provided to facilitate optimal design. To make the scope of the investigation as general as possible, the calculated values have been obtained, or at least presented, in non-dimensional terms. A detailed design example is given in the Appendix.