# Relaxation loss of prestressing steel, Δ`σ`_{pr}

_{pr}

## Eurocode 2 part 1-1: Design of concrete structures 3.3.2 (7)

The relaxation loss may be defined as the percentage ratio of the variation of the prestressing stress over the initial prestressing stress. Following the class of relaxation of prestressing steel, one of the Expressions below may be applied:

Class 1: | (3.28) |

Class 2: | (3.29) |

Class 3: | (3.30) |

where:

- Δ
`σ`_{pr} - is absolute value of the relaxation losses of the prestress
`σ`_{pi}- for post-tensioning, is the absolute value of the initial prestress,

for pre-tensioning, is the maximum tensile stress applied to the tendon minus the immediate losses occurred during the stressing process `t`- is the time after tensioning
`μ`- =
`σ`/_{pi}`f`, where_{pk}`f`is the characteristic value of the tensile strength of the prestressing steel_{pk} `ρ`_{1000}- is the value of relaxation loss (in %), at 1000 hours after tensioning and at a mean temperature of 20°C, see § 3.3.2 (6).

This application calculates
the relaxation loss Δ`σ _{pr}`
from your inputs.
Intermediate results will also be given.