Issue 35

T. Holušová et alii, Frattura ed Integrità Strutturale, 35 (2016) 242-249; DOI: 10.3221/IGF-ESIS.35.28 245 The ligament area, marked as A lig (area marked by red dash lines Fig. 1), is defined as the fractured area and is calculated as the product of the length of the ligament and specimen thickness ( B ). The parameter  (relative notch depth) from Tab. 1 is defined as follows:  = a/W (1) In Fig. 2 a schematic diagram of a modified compact tension specimen is shown together with the aforementioned dimensions of the specimens. For a better visualization of how the attachment of the specimen to the apparatus would look during a real experimental procedure, specimens with both types of attachment are shown in Fig. 3. N UMERICAL S IMULATION umerical simulations are performed with ATENA software [16], which is based on the finite element method (FEM). This software has been specifically developed for applications connected with concrete structures. This program is used for numerical support in the experimental testing of the MCT test. The MCT dimensions used to create the numerical models are listed in Tab. 1. The MCT specimen is created from two material components, concrete and steel. In the numerical simulations the numerical material called 3D Non Linear Cementitious 2 (3DNL) was used in plane stress conditions for the concrete part. As regards the steel bars, the numerical material called Plane Stress Elastic Isotropic (PSEI) was used. The selected input parameter for the numerical study is the cubic strength f cu [MPa] in the case of 3DNL. It was used 8 various f cu values ( f cu  {10, 25, 37, 45, 55, 67, 75, 85} MPa) corresponding to the cubic strengths of different classes of plain concrete. The program calculates the other mechanical parameters for material model (the values of other relevant input parameters are left as default values generated by the program). The input parameters of the 3DNL numerical material are summarized in Tab. 3; those for PSEI are in Tab. 2. The typical length of the element sides of the finite element mesh of the numerical models is 2 mm; the length is refined to 1 mm around (in the vicinity of) the starting notch. The finite element mesh, boundary conditions and numerical models of the MCT test – with the specimen held by grips and with the eye nuts in the ends of the steel bars – are shown in Fig. 4. Figure 4 : Numerical models of the modified compact tension test with boundary conditions: a) current grips; b) with eye nuts. N Applied load Boundary conditions a) b) Pin