Effects of prestressing at ULS: the values of γΔP,sup and γΔP,inf
Eurocode 2 part 1-1: Design of concrete structures 5.10.8 (3)
If the stress increase is calculated using the deformation state of the whole member the mean values of the material properties should be used. The design value of the stress increase Δσpd = Δσp⋅γΔP should be determined by applying partial safety factors γΔP,sup and γΔP,inf respectively.
The recommended values for γΔP,sup and γΔP,inf are 1,2 and 0,8 respectively for the design value of the increase of stress. If linear analysis with uncracked sections is applied, a lower limit of deformations may be assumed and the recommended value for both γΔP,sup and γΔP,inf is 1,0.