PSI - Issue 31

F. Kheloui et al. / Procedia Structural Integrity 31 (2021) 140–146

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F. Kheloui et al. / StructuralIntegrity Procedia 00 (2019) 000–000

Fig. 3. Evolution of stress

The unconfined element has stress field concentrations in the central region causing the opening of cracks, which will subsequently cause the rupture of the element. These constraints are limited by the presence of confinement, in the case of partial confinement; they are concentrated in unconfined regions. The high stresses in the composite create additional pressure on the cylinder which increases the stresses of confined concrete.

Fig. 4. Confrontation of the curves (σ–ε)

The unconfined concrete reaches a maximum stress of 32.66MPa with a deformation of 2.2 ‰, beyond this value there is a degradation of the stress until failure. The total confinement of the concrete develops a resistance of 48.27 MPa by comparing it with the resistance of the unconfined concrete; we will have a contribution in terms of resistance of 47.79%. On the other hand, the partially confined model with hoops reaches a resistance of 36.20MPa with an intake of 10.84%. The partially confined concrete with a propeller reaches a resistance of 34.95MPa with a contribution of 7.011%. Helicoidally confinement generates a small increase in resistance and deformation at rupture compared to other types of confinement. The Fig.5 presents the stress-strain curves of the unconfined and confined cylinders with a variation of the width of the bands for a spacing of 10mm and a thickness of 1mm. The analysis of the results clearly shows the improvement in terms of compressive strength and ductility of the confined specimens compared to the unconfined specimens and this for the four variations of the width. However, the cylinder confined with strips of a width of 30mm has a maximum strength of 42.343 MPa with a contribution of 29.65% while the cylinder confined with bands of 25mm width presents a minimum resistance value which is 39.066 MPa with a contribution of 19.61%.