PSI - Issue 64

Veronica Bertolli et al. / Procedia Structural Integrity 64 (2024) 1111–1117 Veronica Bertolli , Tommaso D’Antino , Christian Carloni/ Structural Integrity Procedia 00 (2019) 000 – 000

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4

CMOD. The test was carried out by controlling the CMOD. The initial CMOD rate was 0.0002 mm/s, which was increased up to 0.0010 mm/s during the softening branch, when the CMOD value reached approximately 0.10 mm. When the CMOD value reached approximately 0.50 mm, the rate was set at 0.0020 mm/s until specimen failure (for control and group NBT-2.6, NBT-3.9, and NBT-5.2) or completion of the test (for group NBT-5.2-12 and NBT-5.2 15). It is worth noting that the test procedure and specimen dimensions used in this work comply with EN 14651 (European Committee for Standardization (2007)), except for the values of a 0 (50.8 mm instead of 25 mm) and S (456 mm instead of 500 mm).

Table 1. Notched beams tested.

Specimen

Microfibers [kg/m 3 ]

Macrofibers [kg/m 3 ]

F L [kN] 9.29 9.00 8.92 8.53 8.67 8.20 9.36 8.31 8.91 7.95

f L [MPa]

f R 1 [MPa]

f R 2 [MPa]

NBT-1

-

- - - - - -

-

-

- - - - - -

NBT-2.6-1 NBT-3.9-1 NBT-3.9-2 NBT-5.2-1 NBT-5.2-2

2.6 3.9 3.9 5.2 5.2 5.2 5.2 5.2 5.2

3.89 3.86 3.69 3.75 3.55 4.05 3.59 3.85 3.44

1.47 1.46 1.50 1.42 1.48 2.42 2.65 2.66 2.39

NBT-5.2-12-1 NBT-5.2-12-2 NBT-5.2-15-1 NBT-5.2-15-2

12 12 15 15

2.40 2.65 2.44 2.17

Fig. 2 Three-point bending test set-up.

3. Results and discussion The nominal properties that characterize the concrete post-cracking tensile tests are usually determined following the prescriptions of EN 14651 (European Committee for Standardization (2007)), which computes the nominal stress  N starting from the load applied by the testing machine as:

3 2

FS

(1)

σ

=

N

2

Dh

sp