# Experiments and Design of an Anti-Disaster Support System for Apple Orchards
## 3 Equivalent Static Test
### Fence Support System  
Figure 7 shows the test set-up of the fence support system. Assuming that the wind load acting on the apple tree was transferred from the wire supporting the tree to the line and end post, an equivalent static test was performed by pulling each post. Loading was applied while continuous monitoring of the load cell and LVDT was performed in order to prevent eccentricity. The collapse test of the fence support was carried out to induce the displacement of the apple tree collapse (over 238.59 mm). When the first test type collapsed, it was removed to subject the next support to the collapse test, and the procedure was repeated. Figure 8 presents the failure mode of the fence support right after the collapse test. It shows the collapse of the line post and end post due to loading.  
\begin{table}
\begin{tabular}{c c c c c} \hline \hline
**Type** & **Section** & \(A\) **(mm2)** & **S (mm3)** & \(I\) **(mm4)** \\ \hline Post & \begin{tabular}{c} e48.1 \(\times\) 2.1 \\ e59.9 \(\times\) 2.3 \\ \end{tabular} & \begin{tabular}{c} 303.48 \\ 416.20 \\ \end{tabular} & \
\begin{tabular}{c} 3344.6 \\ 5772.3 \\ \end{tabular} &
\begin{tabular}{c} 80,437.2 \\ 172,880.9 \\ \end{tabular} \\ \hline \hline \end{tabular}
\end{table}
Table 1: Section properties of members.  
\begin{table}
\begin{tabular}{c c c c c} \hline \hline
**Type** & \(F_{y}\) **(MPa)** & \(F_{u}\) **(MPa)** & \(E\) **(MPa)** & \(M_{y}\) **(N\(\cdot\)m)** & \(P_{y}\) **(N)** \\ \hline \(\omega\)48.1 \(\times\) 2.1 & 320.0 (295) & 367.7 & & 986.6 &
\begin{tabular}{c} 758.9 (fence) \\ 924.9 (matrix) \\ 1309.8 (fence) \\ 1596.4 (matrix) \\ \end{tabular} \\ \hline \hline \end{tabular}
\end{table}
Table 2: Section properties of post (SPVHS).  
Figure 7: View of the fence support system.  
Figure 9 shows the ground condition and the plastic hinge of the support after collapse. As loading increased, the support was damaged by the plastic hinge after yielding. The plastic hinge of the line post was more conspicuous in comparison to that of the end post, as shown by the test result.  
Figures 10-12 show load-displacement curves for the three fence support types. Using the yield loads of the line post (759 N) and end post (1310 N), each fence support system was examined for whether it had reached the yield load after the performance test.  
Figure 8: Test of the fence support system.  
Figure 10: Test result of fence support 1.  
Figure 9: Ground state and plastic hinge.  
Figure 10 shows that a line post (C3) reached the yield load at the displacement of the apple tree collapse, whereas other line posts (C2) and end posts (C1 and C4) did not. In particular, the first fence support test manifested a lack of bearing capacity of the ground. This is explained by the tractor compaction of the ground for the first test type not being satisfactory because the location was near drainage. Generally, the line and end posts of the first support test exhibited linear behavior up to 500 N. As the load increased, a second linear behavior was observed prior to reaching the yield load due to the aforementioned lack of bearing capacity of the ground. The test ended at the load above the yield load to observe the plastic hinge behavior of the support pipe. However, the displacement had already reached over the displacement at the time of apple tree collapse, requiring the consideration for reducing effect of the ground condition state during the design of the support system. Therefore, the linear trend around the load of 455 N (60% of the yield load for line post) was to be applied in consideration of the bearing capacity of the ground for the case of the line post. Although the end post manifested the same first linear trend as the line post, it exhibited a load of 786 N, which was 60% of the yield load for the end post, at the same displacement of the apple tree collapse. Therefore, the same reduction in the yield load as the line post was applied during the design of the end post system.