Initial prestress force applied to the concrete: the values of k7 and k8
Eurocode 2 part 1-1: Design of concrete structures 5.10.3 (2)
The value of the initial prestress force Pm0(x) (at time t = t0) applied to the concrete immediately after tensioning and anchoring (post-tensioning) or after transfer of prestressing (pre-tensioning) is obtained by subtracting from the force at tensioning Pmax the immediate losses ΔPi(x) and should not exceed the following value:
| Pm0(x) = Ap⋅σpm0(x) | (5.43) |
where:
- σpm0
- is the stress in the tendon immediately after tensioning or transfer, = min {k7⋅fpk; k8⋅fp0,1k}.
Recommendation
In this calculation of the initial prestress force applied to the concrete, the recommended value for k7 is 0,75 and for k8 is 0,85.
