# Evaluation of Shear Effect on Deflection of RC Beams
## 3 Experimental Results
### Crack Patterns  
Figure 5 shows the crack patterns at the peak load for each specimen. The crack patterns were sketched after pictures taken during the test. In all specimens, flexural cracks first occurred at the mid-span of the specimens, and the cracks progressed to both ends as the load increased. After the peak load, concrete crushing occurred between the loading points, exhibiting a flexural failure mode.  
Figure 4: Load vs. displacement relationships of tested specimens: (**a**) B3-2.5 Series; (**b**) B6-2.5 Series; (**c**) B6-4.0 Series.  
\begin{table}
\begin{tabular}{c c c c c c c c c c} \hline \hline \multirow{2}{*}{**Specimens**} & \multicolumn{3}{c}{**At First Crack**} & \multicolumn{3}{c}{**At First Flexural Yield**} & \multicolumn{3}{c}{**At Peak Load**} \\ \cline{2-10}  & \(P_{cr}\) & \(\Delta_{cr}\) & \(P_{y}\) & \(\Delta_{y,L}\) & \(\Delta_{y,G}\) & \(\Delta_{y,G}\) & \(\Delta_{y,G}\) & \(\Delta_{y,G}\) & \(P_{w}\) & \(\Delta_{u}\) \\  & **(kN)** & **(mm)** & **(kN)** & **(mm)** & **(mm)** & **(mm)** & \(\Delta_{y,G}\) & \(\Delta_{y,G}\) & \(\Delta_{y,mm}\) & **(kN)** & **(mm)** \\ \hline B3-2.5a & 31.2 & 0.51 & 285.3 & 9.9 & 6.1 & 1.62 & 1.44 & 0.89 & 356.6 & 52.0 \\ B3-2.5b & 33.3 & 0.57 & 299.7 & 9.8 & 6.9 & 1.42 & 1.43 & 1.01 & 350.7 & 44.7 \\ B3-2.5c & 31.2 & 0.62 & 296.1 & 9.5 & 6.6 & 1.44 & 1.38 & 0.96 & 344.4 & 30.5 \\ B6-2.5a & 30.4 & 0.52 & 451.6 & 11.9 & 7.6 & 1.57 & 1.56 & 1.00 & 507.7 & 22.1 \\ B6-2.5b & 37.9 & 0.65 & 446.8 & 11.5 & 7.7 & 1.49 & 1.51 & 1.01 & 489.8 & 21.9 \\ B6-2.5c & 37.4 & 0.54 & 467.0 & 11.4 & 8.0 & 1.43 & 1.49 & 1.05 & 520.2 & 19.0 \\ B6-4.0a & 25.0 & 1.17 & 275.1 & 19.8 & 14.7 & 1.35 & 1.27 & 0.94 & 301.3 & 30.4 \\ B6-4.0b & 24.8 & 1.18 & 268.7 & 20.1 & 16.1 & 1.25 & 1.29 & 1.03 & 299.1 & 29.4 \\ B6-4.0c & 24.9 & 1.13 & 274.1 & 19.9 & 14.9 & 1.34 & 1.27 & 0.95 & 308.9 & 34.9 \\ \hline \hline \end{tabular} Note: \(P_{cr}\), \(P_{y}\), and \(P_{u}\) = applied loads at first cracking, first yielding, and peak load, respectively, \(\Delta_{cr}\), \(\Delta_{y,L}\), and \(\Delta_{u}\) = measured deflections using LVDT installed on the mid-span of specimens at first cracking, first yielding, and peak load, respectively, \(\Delta_{y,G}\) = deflection obtained using strain gauges attached on the mid-span of specimens, \(\Delta_{y,min.}\) = analytical deflection using ACI equation.  
\end{table}
Table 3: Load and deflection capacities of specimens obtained from this study.  
From Figure 5, it is evident that the B3-2.5 series specimens, which have a lower tension reinforcement ratio than the B6-2.5 series specimens, have more progressed flexural and shear cracks to the top. This is because the lower the tension reinforcement ratio, the higher the position of the neutral axis. In addition, the B3-2.5 series specimens had a smaller number of shear cracks and a wider crack spacing than the B6-2.5 series specimens because the shear stress applied to the specimen was smaller, owing to its low load-resistance capacity for flexure.  
Because the B6-4.0 series specimens had a higher shear-to-span ratio than the B6-2.5 series specimens, flexure was remarkably more dominant than shear. The cracks also illustrated these characteristics, and as illustrated in Figure 5, the crack spacing of the B6-4.0 series specimens was wider than that of the B6-2.5 series specimens. In the B6-2.5 series specimens with relatively large shear effect, as the spacing of the shear reinforcing bars narrowed, the shear crack spacing gradually narrowed. However, for the other series specimens, the effect of the spacing of the shear reinforcement on the cracks was not founded.