Increase of concrete compressive stress at time of transfer of prestress by pre-tensioning: the value of k6
Eurocode 2 part 1-1: Design of concrete structures 220.127.116.11 (5)
The concrete compressive stress in the structure resulting from the prestressing force and other loads acting at the time of tensioning or release of prestress, should be limited to:
|σc ≤ 0,6⋅fck(t)||(5.42)|
For pretensioned elements the stress at the time of transfer of prestress may be increased to k6⋅fck(t), if it can be justified by tests or experience that longitudinal cracking is prevented.
The recommended value of k6 for the increase of concrete stress is 0,7.