PSI - Issue 28

Zuzana Marcalikova et al. / Procedia Structural Integrity 28 (2020) 957–963 Author name / Structural Integrity Procedia 00 (2019) 000–000

960 4

Fig. 3. Three-point bending test; (a) load-displacement diagram, (b) beam with crack after test.

From the values ordered in Tab. 2 an increase in fracture energy with increasing fiber dosing is apparent. The fracture energy for displacement of 8 mm increased for the dosing of fibers 75 kg/m 3 by 60 % compared to the dosing of 40 kg/m 3 . In the case of dosing 110 kg/m 3 , this fracture energy increased by 49 % compared to dosing 75 kg/m 3 . The ratio of fracture energies (displacement 8 mm/5 mm) was very similar for all dosages.

Table 2. Fracture energy.

Fracture energy for displacement

Fracture energy for displacement

Fracture energy ratio (8 mm/ 5 mm) [-]

Specific fracture energy for numerical modelling of shear capacity beam [N/m]

s / f y / f u / f res for numerical modelling [-]/[MPa]/[MPa]/[MPa]

Dosage [kg/m 3 ]

5 mm [N/m]

8 mm [N/m]

40 75

1227 2018 3007

1569 2508 3746

1.28 1.24 1.25

73

-

- -

0.00110/1200/1400/200 0.00136/1200/1400/200

110

Note: s is reinforced ratio f y is yield strength, f u is tensile strength and f res is residual tensile strength

Research into basic material properties (Marcalikova et al., 2020b) was followed by experimental testing of beams with a size of 150 x 150 x 700 mm, which were reinforced with two bars of reinforcement with a diameter of 10 mm at the lower bottom, concrete cover was 20 mm. Two beams were tested for each fiber dosage, i.e. total of 8 RC beams. The test scheme is shown in Fig. 4 (a). The test results are given in the form of the functional dependence of the maximum load achieved in the test on the amount of fiber (Fig. 5). Regression linear function shows a good agreement of 97 %. The value P max is the load in the press at which the sample was broken. It can be observed that with increasing amount of fiber, the maximum load P max increases. In the case of lower dosing, i.e. 40 kg/m 3 , there was increase of 24 % compared to plain concrete. A more significant increase up to 65 %, respectively 80 % can be observed in case of dosing of 75 and 110 kg/m 3 . 3. Numerical modelling The numerical modeling of a fiber reinforced concrete beam simulated a three-point bending test. The ATENA computer system (Cervenka et al., 2007) was used for numerical modelling. A 3D computational model was used for numerical modelling, where the mesh of finite elements is shown in Fig. 4 (b). An eight-node isoparametric element