Issue 60

T. Messas et alii, Frattura ed Integrità Strutturale, 60 (2022) 102-113; DOI: 10.3221/IGF-ESIS.60.08

load. At this point, the resistance drops abruptly. For fiber reinforced concretes, three stages are observed: a linear trend characterized the first stage, whereas in the descending branch (second stage); the fibers limit the cracks and their opening by sewing. Finally, in the third stage, the load tends to be constant and is vanished only after a large deformation. This decreasing is due to the presence of fibers at the level of the crack. The failure then occurs either by tearing or by fiber breakage.

Fiber length 8 cm

Fiber content 1,8 %

10 12 14 16 18 20 22

10 12 14 16 18 20 22

BT BFV3 (0,6%) BFV6 (1,2%) BFV9 (1,8%)

BT BFV7 (L=2.5 cm) BFV8 (L=5 cm) BFV9 (L=8 cm)

0 2 4 6 8

0 2 4 6 8

Load (kN)

Load (kN)

0 0.5 1 1.5 2 2.5 3 Deflection (mm)

0 0.5 1 1.5 2 2.5 3 Deflection (mm)

(a) (b) Figure 10: Load-deflection curve: (a) for a fiber content of 1.8 % and (b) for a fiber length of 8 cm.

10

10

Maximum deflection (mm) Load (kN)

10 12 14

Maximum deflection (mm) Load (kN)

10 12 14

8

8

6

6

0 2 4 6 8

0 2 4 6 8

4

4

Load (kN)

Load (kN)

0.60 %

2

1.20 %

2

Maximum deflection (mm)

Maximum deflection (mm)

0

0

0 1 2 3 4 5 6 7 8 9 10 Fiber length (cm)

0 1 2 3 4 5 6 7 8 9 10 Fiber length (cm)

(a)

(b)

10

10 12 14

8

6

0 2 4 6 8

Maximum deflection (mm) Load (kN) 1.80 %

4

Load (kN)

2

Maximum deflection (mm)

0

0 1 2 3 4 5 6 7 8 9 10 Fiber length (cm)

(c) Figure 11: Maximum deflection versus fiber length for fiber content: (a) 0.60 %, (b) 1.20 %, and (c) 1.80 % by volume. Figs. 11a-c show the improvement of the ductility of concrete. For the length of Alfa fibers more than 5 cm, the deflec- tion is negatively affected by the presence of fibers. The mechanical behavior in tensile bending of the different types of concrete is better by using short fibers 2.5 cm in length. By considering the fibers content, a content of 1.20 % leads to good results in terms of deflection.

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