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

It is well known that the application of the principle of superpositio n in the service stress range yields an inaccurate prediction of concr ete creep when unloading takes place. It appear that after a period of compression creep, the experimental creep recovery is significantly l ess than predicted by the principle of superposition. In the present s tudy, this non-linear behaviour, attributed to the sustained compressi ve preload, is modelled by a two-function method. In this approach, a creep function is used for modelling the time-dependent deformations d ue to increasing stress and a separate creep recovery function represe nts the behaviour under decreasing stress. Good agreement with test da ta is achieved.