PSI - Issue 25

Zuzana Marcalikova et al. / Procedia Structural Integrity 25 (2020) 27–32

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Author name / Structural Integrity Procedia 00 (2019) 000–000

Fig. 3. Test schema for bending tension strength (three - point bending test).

The resulting mechanical properties are shown in Tab. 3. The evaluation of the three - point bending test included determination of load-displacement (LD) diagrams, which are shown in Fig. 6 and Fig. 7. From the LD diagram the difference between the selected types of fibers is clearly visible.

Table 3. Mechanical properties for dosing 75 kg/m 3 .

Type fibers

Mechanical properties

Dramix® 3D 65/60 BG Dramix® OL13/20

Compressive strength – cubic f c,cube [MPa]

28.17

40.19

Splitting tensile strength – perpendicularly to the filling direction f ct,sp, ┴ [MPa]

3.64

3.08

Three-point bend test f ct, fl,3B [MPa]

5.02

4.98

3. Numerical modeling

For the numerical modelling it is possible to use finite element methods and nonlinear analysis within the ATENA computational system (Cervenka et al. 2007). The created 3D numerical models simulate the three - point bending test and use the fracture - plastic material model (Cervenka and Papanikolaou, 2008). The finite element mesh is well visible in Fig. 5. Was used eight-node isoparametric finite elements.

Fig. 4. (a) Relationship between stress and crack width – concrete; (b) Stress-strain diagram.

The fibers were taken into account in the concrete by two concepts. For Dramix® OL 13/20 fibers (series 2) was used typical concrete tension softening in Fig. 4 (a). However, tensile strength and fracture energy were modified. This is possible designation, in this case modelling, as effective tensile strength and fracture energy. For the model case it was f tef = 0.95 MPa and fracture energy 900 N/m. In the case of Dramix® 3D 65/60 BG (series 1) fibers, a concept combining a smeared reinforcement model and plain concrete model was chosen to illustrate.