Design assumptions for prestressing tendons: the strain limit εud
Eurocode 2 part 1-1: Design of concrete structures 3.3.6 (7)
For cross-section design, either of the following assumptions may be made (see Figure 3.10):
- an inclined branch, with a strain limit εud. The design may also be based on the actual stress/strain relationship, if this is known, with stress above the elastic limit reduced analogously with Figure 3.10, or
- a horizontal top branch without strain limit.
The recommended value for the strain limit εud is 0,9εuk. If more accurate values are not known the recommended values are εud = 0,02 and fp0,1k/fpk = 0,9.