# Revisiting Cracking in Reinforced Concrete Beams: An Updated Analysis
## 4 Test Results  
### Crack Position  
We start by mentioning that the title of this point is not \"crack spacing\". In fact, the cracks occur in the position of the stirrups. It does not mean that there will be cracks in all stirrup positions, nor does it mean that cracks between stirrups cannot occur. It means that the cracks, if they appear, occur first in the positions of the stirrups, if any. In Figure 3, it is possible to visualize the positioning of the cracks in relation to the stirrups in the central zone (\(\mathrm{L_{2}}\)) of Beams B01-B04. The failure of these beams occurred in the tensile reinforcement. Using the positioning of the LVDT (Linear Variable Differential Transformer) placed laterally to the beam (but in the center of the beam), it can be seen that the central crack is located about 5 mm to the left in the case of Beams B01 and B04; about 20 mm to the right in the case of Beam B02; and is centered on Beam B03. Two particularities to note: the line that identifies the position of the crack is drawn by hand slightly to the side (\(\sim\)10 mm) of the crack; remember that these beams were not produced in the laboratory, so any small deviations from the central stirrup must be assumed. Anyway, the remaining main cracks (two on each side) are located in the following stirrups, 180 mm spaced apart. Two important aspects should be highlighted: (i) the splitting of the cracks; (ii) the extra (secondary) cracks, arising between the main cracks of Beams B02 (2 nd crack starting from the center to the right) and B03 (in the vertical direction of the right force point). For Beams B05-B10, Figure 4 shows the cracks in the central zone (\(\mathrm{L_{2}}\)). The failure of these beams occurred due to crushing of the compressed concrete and/or instability of the compressed reinforcement. Remember the absence of stirrups in central zone of Beams B05 and B06, a spacing of 60 mm apart between stirrups in Beams B07 and B08, and a spacing of 180 mm apart in Beams B09 and B10. For these beams, EC2 [1] determines a maximum spacing between cracks greater than 160 mm (80 mm minimum; average of 120 mm). Taking into account the number of spacings (10) between the main cracks of Beams B05 and B06 (beams without stirrups in central zone), and the value \(\mathrm{L_{2}}=975\) mm, the experimental (average) value of the spacing between cracks is less than 100 mm, i.e., much less than predicted (average) value. \begin{table}
\begin{tabular}{c c c c c c} \hline \hline
**Group** & **Steel** & \(\mathrm{\Phi}\) & \(\mathrm{f_{y}}\) **(MPa)** & \(\mathrm{f_{u}}\) **(MPa)** & \(\mathrm{\epsilon_{u}}\) **(\%)** \\ \hline  & ER & 8 & 585 & 631 & 4.74 \\ I & NR & 8 & 532 & 635 & 14.5 \\ I & ER & 10 & 617 & 666 & 5.96 \\ II & NR & 10 & 551 & 648 & 12.8 \\ III & ER & 12 & 604 & 653 & 6.14 \\ IV & NR & 12 & 541 & 632 & 13.7 \\ VI & ER & 16 & 552 & 647 & 4.8 \\  & NR & 16 & 575 & 684 & 13.6 \\  & NR & 12 & 559 & 664 & 8.1 \\ VII & NR & 12 & 550 & 655 & 13.6 \\  & ER & 6 & 577 & 828 & 6.49 \\  & NR & 8 & 634 & 726 & 11.1 \\ \hline \hline \end{tabular}
\end{table} 
Table 3: Mechanical characteristics of reinforcement steel. If due attention had been paid at that time, it would have been very interesting to verify whether or not the first crack had occurred in the first stirrup of the lateral zones; in the first stirrup, the curvature is (a little) lower than the curvature in the central zone. In fact, these stirrups having (principal) cracks placed there, and thereafter an almost uniform spacing in the central zone; it is almost certain that this happened. Figure 4c,d, relative to Beams B07 and B08 (stirrups spacing 60 mm apart), show that the cracks are preferentially positioned in the location of the stirrups. In the case of Beam B08, note the absence of the crack in the alignment of the 4 th visible stirrup to the right. It is most likely that the crack has displaced too much (\(\sim\)30 mm) to the left. Figure 4: Crack position of Beams B05–B10. Figure 3: Crack position of Beams B01–B04.