## 4 Shear Test Results and Discussion  
### Test Results and Failure Mode  
Figure 7 shows the load and displacement curves measured in the shear tests of the anchors installed in the plain and SFRC. The load and displacement curve can be divided into pre-cracking and post-cracking regions based on a point when a concrete crack occurs on the top surface of the concrete block. Before the crack occurs, the tensile stress generated in the concrete block is below the cracking strength of the concrete. Thus, all of the materials including concrete linearly and elastically resist the external shear loads, and the load and displacement curve of the anchor in the SFRC is similar to that in the non-reinforced plain concrete, as shown in Figure 7.  
Figure 6: Energy absorption capacities \(T_{600}\) and \(T_{150}\) with increasing fiber volume percentages from zero to 1.00%. Figure 7: Typical load and displacement curves measured from the shear tests of anchors in the plain concrete and SFRC. When a crack occurred on the top surface of the concrete block, the slope of the load and displacement curve decreased due to the strength reduction of the concrete. Cracks initiated almost simultaneously on the left and right sides of the steel anchor on the top surface of the concrete block. The left and right cracks occurred at an angle on the top surface and proceeded to the edge of the block. The inclined cracks reduced the stiffness of the anchor block, which resulted in the lower slope of the load and displacement curve. The load, at which the inclined cracks occurred on the top surface of the anchor block, is defined as the cracking shear load of the anchor, \(V_{cr}\). While the inclined crack propagated to the edge of the top surface, another new vertical crack was generated from the top to the bottom on the front side of the anchor block. The vertical crack proceeded to a depth a little longer than the embedded depth of 240 mm. Then, the anchor reached its ultimate shear load, \(V_{u}\). The inclined crack, which reached the edge of the block, was directed to the end tip of the vertical crack and thus formed into a semi-circular crack shape on the front surface of the block. Table 3 summarizes the cracking and ultimate shear loads, \(V_{cr}\) and \(V_{u}\), and the displacement at the maximum shear load, \(d_{c,u}\) for the anchor specimens in the plain and SFRC. Figure 8a shows a typical example of crack distributions of anchors in the plain concrete upon concrete breakout failure. The steel fibers mixed in concrete changed the crack distribution and shape of the concrete anchor under shear load. The anchors in SFRC showed a great improvement of the shear load and displacement resistance after cracking, while the strength of the anchor in the plain concrete quickly decreased and reached the final brittle fracture. This is because the steel fibers distributed in the concrete control the growth of the cracks and greatly improve the tensile capacity of the concrete block. \begin{table}
\begin{tabular}{c c c c} \hline \hline
**Name of** & \(V_{cr}\) **(kN)** & \(V_{u}\) **(kN)** & \(d_{c,u}\) **(mm)** \\ \hline \multirow{6}{*}{V000} & 29.6 & 38.0 & 2.55 \\  & 30.3 & 35.2 & 2.17 \\  & 40.5 & 45.8 & 1.52 \\  & 23.6 & 26.4 & 1.66 \\  & Mean & 31.0 & 36.3 & 1.98 \\  & (Std.) & (7.01) & (8.01) & (0.48) \\ \hline \multirow{6}{*}{V033} & 35.2 & 42.9 & 3.78 \\  & 29.5 & 38.2 & 3.81 \\  & 35.3 & 41.8 & 4.06 \\  & 28.1 & 30.5 & 2.76 \\  & Mean & 32.0 & 38.3 & 3.60 \\  & (Std.) & (3.78) & (5.63) & (0.58) \\ \hline \multirow{6}{*}{V067} & 34.8 & 48.7 & 8.58 \\  & 34.6 & 55.9 & 9.56 \\ \cline{1-1}  & 33.4 & 48.7 & 8.64 \\ \cline{1-1}  & 29.8 & 43.6 & 7.59 \\ \cline{1-1}  & Mean & 33.1 & 49.2 & 8.59 \\ \cline{1-1}  & (Std.) & (2.31) & (5.05) & (0.80) \\ \hline \multirow{6}{*}{V100} & 37.4 & 52.1 & 12.27 \\  & 30.7 & 59.4 & 9.72 \\ \cline{1-1}  & 28.8 & 53.8 & 13.76 \\ \cline{1-1}  & 30.7 & 43.7 & 9.56 \\ \cline{1-1}  & Mean & 31.9 & 52.2 & 11.33 \\ \cline{1-1}  & (Std.) & (3.77) & (6.48) & (2.04) \\ \hline \hline \end{tabular}
\end{table}