## 4 Experimental Results and Discussion
### Comparison between Results of Analytical and Numerical Analysis  
By measuring the relative deformations at the location of the extremely loaded cross-section (at the bottom of the column), the amount of cross-section rotation at which the yield strength of the reinforcement was reached was determined. The results obtained were compared with the values of the cross-section rotation when the yield strength obtained by analytical and numerical methods was reached. As the analytical and numerical results do not include the effect of slippage of the smooth reinforcement, a significant difference of the experimentally obtained cross-section rotation when reaching the yield strength is visible. Figure 14 (above) shows the moment and rotation ratios for the end cross-section of the two monotonically tested specimens. Experimentally, analytically, and numerically obtained curves are compared in the diagram. The first specimen was made with smooth reinforcement (Figure 14 top left) and the second with ribbed reinforcement (Figure 14 top right). The point of reaching the yield strength obtained by experimental tests is shown by a rhombus marking, while the point of reaching the analytically and numerically obtained yield strength is shown by cross and triangle markings. The cross-sectional rotation at the point of reaching the analytically and numerically obtained yield strength almost coincides, while the difference of the experimentally obtained rotation angle in comparison with the two previous analyzes is marked with the notation \(\Delta\varphi\). The given diagrams clearly show the differences in the angle of rotation of the cross-section when reaching the yield strength of the specimen made with smooth reinforcement and the specimen made with ribbed reinforcement. Specimens with smooth reinforcement show a significantly greater deviation of the experiment results from the numerical or analytical analysis. The values of the angle of rotation angle when reaching the yield strength of other monotonically tested columns are shown in Figure 15. A comparison of the results for the end section and two sections where relative deformations were measured in relation to the results obtained analytically and numerically is given. The results of the tested specimens with smooth reinforcement show on average a five-times higher rotation of the experimentally obtained end section when reaching the yield point compared to the results obtained with analytical and numerical methods which do not take into account the effect of slippage from the anchoring area (Figure 15). For specimens with ribbed reinforcement (AB-NS-004), the rotation angles of the end cross-section when reaching the yield point in the experiment have a significantly smaller difference from the results obtained by analytical and numerical analysis (two-times the rotation of the experimental result). After opening the first crack, specimens made with smooth reinforcement also show a greater deviation of the experimentally obtained moment to rotation curves compared to specimens with ribbed reinforcement. The effect of slipping of the smooth reinforcement from the anchorage area on the side of the anchor block and the column body itself influences the rotation of the cross-section as soon as the first crack occurs. Figure 14: Moment to section rotation ratios: (**a**) monotonous specimen with smooth reinforcement; (**b**) monotonous specimen with ribbed reinforcement; (**c**) cyclical specimens with smooth reinforcement; (**d**) cyclical specimen with ribbed reinforcement. The greater distance between the anchoring points of the smooth reinforcement leads to a greater relative deformation of the bar and thus to a greater rotation of the cross-section, which then accumulates at the end cross-section. From this it can be concluded that the  
Figure 15: Section rotation when reaching yield point for monotonously (M) and cyclically (C) tested specimens.