Issue 30

A. Fernández-Canteli et al., Frattura ed Integrità Strutturale, 30 (2014) 383-393; DOI: 10.3221/IGF-ESIS.30.46 385 with the same meaning of the parameters  , a and W as above. Figure 2 : Characteristic specimen’s dimensions in [mm].  cs [mm]  sb [mm] W [mm] a [mm] b [mm] e [mm] A lig [mm 2 ] α [-] Specimen 1 153 8 116.4 40.2 63.5 4 4838.70 0.3454 Specimen 2 153 8 114.3 32.9 68.6 4 5584.04 0.2878 Table 1 : Measured dimensions of the two specimens tested. E XPERIMENTAL PROCEDURE he fabrication of the specimens is as follows: firstly, concrete is prepared as a mixture of the components. Then, the concrete is poured into the mold, in this case a PVC pipe of internal diameter  d = 153 mm, i.e. the required for the specimen. The curing process lasted for 21 days after which the bars are allocated into the drill holes and glued to the specimen using a strong epoxy adhesive. Lastly, the notch is mechanized. This procedure can be also applied for fracture characterization of concrete when drilling cores are extracted from real structures. All tests were performed with a servohydraulic test machine MTS Bionix 25 kN of load capacity, see Fig. 3. One of the bars is anchored to the lower clamps, which stay fixed. The other bar is anchored to the upper clamps, which move vertically up and transmit the load to the specimen . Thus, as the displacement of the upper clamp increases, a crack is generated starting in the tip of the notch, until the complete rupture of the specimen. Tests are performed by displacement control of the machine with a rate of 0.5 mm/min. N UMERICAL SIMULATION umerical simulations are performed using two different codes based on the finite element method. The first one is the ATENA software [16, 17] developed for specific applications in concrete structures. The second one is the ABAQUS software [18]. The results from the compression test provide an average value of 32 MPa for the cylindrical compressive strength, which corresponds to a cubic compressive strength of 37 MPa. According to table 7 from European standard EN 206-1 (page 20), the concrete mixture was classified as C 30/37. A cubic compressive strength of 37 MPa was used as input value for the material model of concrete (SBETA) and after that the values of tensile strength and Young’s modulus, etc. are calculated from empirical equations implemented in the ATENA software. The characteristic input parameters of steel and concrete used in both cases of numerical simulations in ATENA and ABAQUS are listed in Tab. 2, where: T N