## 4 Experimental Results and Discussion
### Specimens Cracking  
The pattern of crack development of all monotonically tested specimens made with smooth reinforcement is characterized by the occurrence of two dominant cracks. The first crack is a crack of the previously mentioned end cross-section. The second crack occurs in most specimens near the first stirrup (125 mm from the bottom of the column).  
A monotonically tested specimens showed a crack at a height of 200 mm, which differs significantly from all other specimens (the ratio of moment and cross-sectional rotation of this specimen also showed differences compared to other tested specimens). These two cracks at the bottom of the column have a constant change in width as the displacement of the top of the column increases and have a significant effect on the amount of element rotation around the plastic joint. Other cracks along the height of the column do not show significant width growth during the test (in some cases it even decreases). The crack width measurements of each specimen are shown in Figure 10. The results given apply to monotonic (designation M) and cyclic (designation C) specimens.  
The cracks shown are located on the plastic joint itself, but also in the immediate vicinity. The crack designations contain the distance of the observed crack from the bottom of the column. The figure shows the dominance of the crack at the end cross-section and the smaller but still significant influence of the first crack from the bottom of the column of all monotonically tested specimens. For monotonically tested specimens (AB-NS-004-1) made with ribbed reinforcement, the crack width at the end section is almost half of the crack width of specimens made with smooth reinforcement. The crack in the end cross-section is also significantly less pronounced compared to the first crack from the bottom of the column. The occurrence of cracks in the sample with ribbed reinforcement was observed up to a height of 1.2 m from the bottom of the column, whereas in the samples with smooth reinforcement the height of the crack reached only 0.65 m. In total, two specimens made with a larger amount of longitudinal reinforcement (AB-NS-002-1 and AB-NS-003-1) also show a smaller crack width in the end section and thus a lower dominance of the crack in relation to the adjacent crack. It should be noted that a larger amount of reinforcement was achieved by increasing the reinforcement diameter, while the position and distribution of the reinforcement over the cross-section remained almost the same (the only difference is the position of the center of gravity due to a larger bar diameter).  
Figure 11 shows the width and distribution of cracks at the location of the plastic joint and in its vicinity for cyclically tested specimens. For almost all cyclically tested specimens, the dominance of the crack is visible at the end cross-section. In contrast to the monotonous tests, these tests show that the second crack from the bottom of the column is significantly less dominant and does not deviate much from the other cracks above. According to the measured crack sizes at the location of the plastic joint and in its immediate vicinity, the specimens with ribbed reinforcement behave in the same way as specimens with smooth reinforcement. The difference is only visible in the height at which cracks occur. In the case of the cyclically tested specimen with ribbed reinforcement, cracks appear up to a height of 1 m, whereas in the case of specimens with smooth reinforcement the crack height is the same as in the monotonously tested specimens and is about 0.65 m.  
Figure 10: View of the crack in the area of plastic hinges.