Design assumptions for reinforcement steel: the strain limit εud
Eurocode 2 part 1-1: Design of concrete structures 3.2.7 (2)
For normal design, either of the following assumptions may be made (see Figure 3.8):
a) an inclined top branch with a strain limit of εud and a maximum stress of kfyk/γS at εuk, where k = (ft/fy)k,
b) a horizontal top branch without the need to check the strain limit.
The recommended value for the strain limit εud is 0,9εuk.