2-FUNCTION METHOD FOR THE PREDICTION OF CONCRETE CREEP UNDER DECREASING STRESS

It is well known that the application of the principle of superposition in the service stress range yields an inaccurate prediction of concrete creep when unloading takes place. It appear that after a period of compression creep, the experimental creep recovery is significantly less than predicted by the principle of superposition. In the present study, this non-linear behaviour, attributed to the sustained compressive preload, is modelled by a two-function method. In this approach, a creep function is used for modelling the time-dependent deformations due to increasing stress and a separate creep recovery function represents the behaviour under decreasing stress. Good agreement with test data is achieved.