# Revisiting Cracking in Reinforced Concrete Beams: An Updated Analysis
## 4 Test Results
### Crack Position
Regarding Beams B09 and B10 (stirrups spacing 180 mm apart), Figure 4e,f show that the main cracks are positioned in the location of the stirrups. Secondary cracks form (posteriorly) between the main cracks. A conclusion can already be drawn: cracking position does not depend on the type of reinforcement, whether of the ER type or of the NR type. In Figure 5a, the cracks formed in Beam B11 are shown, which, as we recall, did not have any kind of transverse or compression reinforcement in the central zone. When the first cracks were detected, the locations of the first stirrups placed in the lateral zones had started cracking. In any case, an almost uniform distribution of formed cracks is visible, with an average spacing of around 100 mm (almost coinciding with the position of the demountable mechanical strain gauges DEMECs). This value is lower than the predicted average value (\(\sim\)120 mm). In Figure 5b,c, the stirrups are spaced 60 mm apart and the cracks are positioned according to the stirrups. In the case of Beam B13, there is no crack in the position of the first visible stirrup on the left. In Figure 5d, the stirrups are spaced 180 mm apart. It is possible to locate the cracks in the positions of the two visible stirrups. Among these, the secondary crack is in the middle. In Figure 6 are the images relating to Beams B15-B18. In Beam B15, it is possible to visualize the centerline of the beam--the only one placed among the DEMECs, 100 mm apart. In this line, there is no crack corresponding to the central stirrup. Three cracks on the left and two cracks on the right are located in the positions of the following stirrups, spaced 60 mm apart. In Beams B16 and B17, the coincidence of the cracks with the location of the stirrups is notorious. In Beam B18, with stirrups spaced 180 mm apart, the location of the central crack is visible, plus two main ones on each side. Among these are secondary cracks. At the time of testing, Beams B19 and B20 were about 2 years old. Both with stirrups spacing 180 mm (in the center of the beam there is no stirrup), it is possible to confirm in Figure 7 that all stirrups (6) in the central zone had an associated (main) crack. The secondary cracks were positioned between these, with some irregularity. Beams B21 and B22 were tested without active axial restraint. In the central zone, Beam B21 contains five stirrups spaced 180 mm apart. As before, in the position of the stirrups, the main cracks appeared and, among these, the secondary ones as well (Figure 8a). Beams B22 and B23 (Figure 8) have stirrups spacing 60 mm apart; there is a stirrup in the center of the beam. From the center of the beam, it is possible to verify the coincidence of the cracks  
Figure 5: Crack position of Beams B11–B14. formed in relation to the positioning of the stirrups. On only Beam B23, just to the right of the central crack, two cracks are identified, instead of just one, close to the next stirrup. Figure 9 shows the positions of the cracks formed in the central zone of Beams B24-B26. Figure 9a shows the coincidence between the position of the cracks and the shear reinforcement. In Figure 9b,c, this coincidence is also almost complete for the seven stirrups in the central zone. It is important to note the double crack (instead of just 1) immediately to the right of the central crack. This double crack, which formed in Beams B25 and B26, results from the device used in the beams to ensure the cover (a small piece of steel \(\upphi\)10). The records relating to Beam B27 were lost on an SSD (solid-state drive) card. The authors ensure that the cracks were also located in the positions of the stirrups. Figure 8: Crack position of Beams B21–B23. Figure 6: Crack position of Beams B15–B18. Figure 7: Crack position of Beams B19–B20. In fact, this finding that the main cracks are formed preferentially in the position of the stirrups has been confirmed for a long time. In addition to these beams, the authors have already tested many others and have not been able to find any cases that suggest any other conclusion.