# Effects of prestressing at SLS and limit state of fatigue: the values of `r`_{sup} and `r`_{inf}

_{sup}

_{inf}

## Eurocode 2 part 1-1: Design of concrete structures 5.10.9 (1)P

For serviceability and fatigue calculations allowance shall be made for possible variations in prestress. Two characteristic values of the prestressing force at the serviceability limit state are estimated from:

P = _{k,sup}r _{sup}P_{m,t}(x) | (5.47) |

P = _{k,inf}r _{inf}P_{m,t}(x) | (5.48) |

where:

`P`_{k,sup}- is the upper characteristic value
`P`_{k,inf}- is the lower characteristic value.

## Recommendation

The recommended values of `r _{sup}` and

`r`for the effects of prestressing at SLS and limit state of fatigue are:

_{inf} - for pre-tensioning or unbonded tendons: `r _{sup}` = 1,05 and

`r`= 0,95

_{inf}- for post-tensioning with bonded tendons:

`r`= 1,10 and

_{sup}`r`= 0,90

_{inf}- when appropriate measures (e.g. direct measurements of pretensioning) are taken:

`r`=

_{sup}`r`= 1,0.

_{inf}