# Initial prestress force applied to the concrete: the values of `k`_{7} and `k`_{8}

_{7}

_{8}

## Eurocode 2 part 1-1: Design of concrete structures 5.10.3 (2)

The value of the initial prestress force `P _{m0}`

`(x)`(at time

`t`=

`t`) 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

_{0}`P`the immediate losses Δ

_{max}`P`

_{i}`(x)`and should not exceed the following value:

P_{m0}(x) = A⋅_{p}σ_{pm0}(x) | (5.43) |

where:

`σ`_{pm0}- is the stress in the tendon immediately after tensioning or transfer, = min {
`k`⋅_{7}`f`;_{pk}`k`⋅_{8}`f`}._{p0,1k}

## Recommendation

In this calculation of the initial prestress force applied to the concrete, the recommended value for `k _{7}` is 0,75 and for

`k`is 0,85.

_{8}