•The production of precast pre-stressed beams is made in several steps. T4 time is the reference time and is always equal to zero. Thus, the times T1 to T3 times are negative and the times T5 to T7 times are positive.
•Tensioning of strands (T1) :The pre-stressing steel is put in tension and is retained by jacks and other mechanisms of steel retention. At this step, no concrete is present. The losses by relaxation starts at this time.
•Concrete casting (T2) : The concrete is cast in place and the concrete cure begins. This data is considered in the calculation of concrete age for the calculation of creep losses.
End of cure, beginning of shrinkage (T3) : When the cure is stopped, the surrounding humidity drop provokes the start of the shrinkage of concrete. The shrinkage occurring between time T3 and time T4 will not induce pre-stressing losses.
•Transfer of pre-stress (reference time) (T4): At this step, the concrete is sufficiently resistant to support the pre-stressing forces. The pre-stressing strands are released and transfer the forces to the concrete beam. Due to the arrangement of the strands in the beam, the beam tends to camber under the effect of the pre-stressing forces. From this time, the losses caused by creep and remaining shrinkage begins.
Casting of slab and stiffener beams (T5): At this time, the loads induced by the self weight of the slab and the stiffener beams are held by the pre-stressed beam only. Once hardened, the slab acts in a composite manner with the beam to support the additional loads added later to the structure. Once the concrete slab has hardened, the program assumes the continuity at the interior supports which affects the effect of additional loads.
•Add. dead loads 1 (edges, sidewalks and curbs) (T6): The time at which the additional loads are applied to the structure has an effect on the losses. The intensity of these loads are specified for each span.
Add. dead loads 1 (asphalt) (T7): The time at which the additional loads are applied to the structure has an effect on the losses. The asphalt is considered as a dead load which has a load factor larger than other dead loads. It has thus been separated from other additional dead loads. The intensity of these loads are specified for each span.