## 4 Numerical Analysis
### Model Geometry, Material Models and Finite Element Mesh
It was confirmed that the default value provides satisfactory results [42; 45];
* ratio of biaxial and uniaxial compression flow stress of \(\sigma_{\text{b0}}/\sigma_{\text{c0}}\), whereby the adopted value in the paper is \(\sigma_{\text{b0}}/\sigma_{\text{c0}}=1.16\) (default value). It was confirmed that the default value provides satisfactory results [43; 45];
* ratio of the magnitude of deviation stress in tension and compression K, whereby the adopted value in the paper is K = 0.666 (default value). It was confirmed that the default value provides satisfactory results [43; 45]. In [43] the impact of this parameter was analyzed and it was demonstrated that its impact on the results is small, and that a higher K provides a stiffer model;
* viscosity parameter \(\mu\), which is implemented for the purpose of achieving a solution convergence, whereby the adopted value in the paper is \(\mu=0.0002\). This parameter should be around 15% of the time increment [43]. Concrete damage plasticity model is characterized by the possible inclusion of the reduction of the modulus of elasticity due to the materials damage, with the aid of damage parameters d\({}_{\text{c}}\) for the compression and d\({}_{\text{t}}\) for the tension. Damage parameters, d\({}_{\text{c}}\) and d\({}_{\text{t}}\), can be defined by the relation [41]:  
\[\text{d}_{\text{c}}=1-\frac{\sigma_{\text{c}}}{\text{E}_{0}\Big{(}\epsilon_{ \text{c}}-\epsilon_{\text{c}}^{\text{pl}}\Big{)}};\;\text{d}_{\text{t}}=1- \frac{\sigma_{\text{t}}}{\text{E}_{0}\Big{(}\epsilon_{\text{t}}-\epsilon_{ \text{t}}^{\text{pl}}\Big{)}} \tag{2}\]  
Variation of damage parameters in the function of strains in concrete for the analyzed model is presented in Figure 10. It should be mentioned that in the software, the parameters are defined in relation to the inelastic strain, whereby the limit of elastic behavior of the analyzed concrete under compression is 0.4f\({}_{\text{c}}\) = 20.11 MPa (corresponding strain 0.0009), and the limit of elastic behavior in tension is f\({}_{\text{t}}\) = 3.42 MPa (corresponding strain 0.000153). The experimentally determined splitting tensile strength of concrete is f\({}_{\text{ct,sp}}\) = 3.80 MPa (Table 4). The bearing capacity to axial tension was determined indirectly through the splitting tensile strength using the relation defined in the European standards [37]:  
\[\mathrm{f_{ct}}=0.90\cdot\mathrm{f_{ct,sp}}=0.90\cdot 3.80=3.42\;\mathrm{MPa} \tag{3}\]  
The concrete beam is meshed with solid finite elements C3D8R. An element has 8 nodes (nodes at the corners of the element), whereby linear interpolation functions are used and the reduced integration is implemented. The reinforcement mesh element is the finite element T3D2 which represents a member with two nodes at the ends of the element [41]. Finite elements used for the mesh of concrete beam have dimensions \(12.5\times 12.5\times 40\) mm, while the length of the member finite elements of the reinforcement is 25 mm. With so adopted dimensions of finite elements, B-1 and B-2 models have 17,976 finite elements and 20,753 nodes, while the B-3 model, has 18,108 finite elements and 20,888 nodes. The only difference between the models B-1 and B-2 is in the diameter of reinforcement cross section so the number of finite elements is the same. On the other hand, the model B-3 has additional reinforcement so the number of finite elements is slightly higher compared to the models B-1 and B-2.