No abstract

No abstract

No abstract

No abstract

Three series of novel tensile and flexural creep tests on partially-damaged concrete specimens were carried out in order to gain some insight into creep crack growth and failure of strain-softening materials. In the tests, each specimen was initially loaded to a given point in the descending branch and thus had a lower load-carrying capacity than that at the peak-point. Then, the specimen was unloaded and reloaded to sustain a load which was from 70% to 95% of its current load-carrying capacity. Experimental creep curves display a three-stage process, consisting of primary, secondary and tertiary stages, with a decreasing, constant and increasing creep rate, respectively. The secondary stage dominates the whole failure lifetime, whereas both the secondary and tertiary stages are important in terms of creep deformation. Failure lifetime seems to be more sensitive to the change of load level in flexural tests rather than in tensile tests. The decrease in load-carrying capacity due to damage tends to result in a shorter failure lifetime and a lower critical load level for creep rupture. The descending branch of the static loaddeflection or load-CMOD curve may be used as an envelope criterion for creep fracture. RrSUME Trois s&ies d'essais innovants de fluage a la traction eta la flexion ont (t( effectu&s sur des @rouvettes de b(ton partiellement endommag&s pour (tudier la propagation de la fissuration et la rupture des mat&iaux radoucis. Chaque @rouvette a d' abord ~t( charg& jusqu'h un point donn( de la branche descen