# Automated Real-Time Assessment of Stay-Cable Serviceability Using Smart Sensors
## 4 Experiment
### Test of Automated Real-Time Cable Serviceability Assessment System  
A series of laboratory experiments were carried out to test the developed automated real-time serviceability assessment system. These experiments were designed to assess the serviceability level of the stay-cable in mid-span every 5 s. The test results are displayed in Figure 5. The gateway node commanded the leaf node to measure the cable vibration in terms of the acceleration every 5 s, as shown in Figure 5a. The leaf node automatically computed the acceleration-based displacement conversion algorithm to estimate the dynamic displacement every 5 s (Figure 5b). Finally, the maximum absolute amplitude of the converted dynamic displacement was used to assess the serviceability level, which can be either allowed or disallowed depending on the serviceability criterion (the amplitude should be less than twice the diameter of the target cable; Figure 5c). The serviceability level was evaluated based on the \"Max Abs Amp\", which denotes the maximum absolute amplitude of the estimated displacement for 5 s. From the results depicted in Figure 5, this study verified that the developed system functioned well to measure the cable response in terms of acceleration, estimate the displacement from the measured acceleration, and assess the serviceability level based on the defined threshold. Furthermore, the wireless communication between the gateway node and the leaf node was tested to verify the system for serviceability assessment. The result of the wireless communication test between the two nodes is depicted in Figure 6. Because the fan was not sufficiently strong to induce vibrations greater than the failure level of 20 mm, the serviceability threshold was adjusted to 1 mm just for the purpose of verification. As shown in Figure 6a, wireless communication can be activated after the gateway and leaf nodes are connected through Bluetooth communication by pressing the \"Scan for devices\" button and selecting the \"raspberrypi\" as the pairing device in the \"Select a \begin{table}
\begin{tabular}{c c c c c c} \hline \hline
**Length (m)** & **Inclination (\({}^{\circ}\))** & **Tension (N)** & **Mass (kg/m)** & **Diameter (mm)** & **Break Load (Ton)** & **Cable Type** \\ \hline
6.95 & 43 & 457.8 & 0.314 & 10 & 5.46 & IWRC \\ \hline \hline \end{tabular}
\end{table} 
Table 1: Properties of laboratory-scale cable. Figure 4: Laboratory setup for monitoring serviceability. device to connect\" list of the _BT Chat_ application. After the activation of wireless communication, the gateway node commanded the leaf node to measure the acceleration of the stay-cable under the fan vibration, estimate the displacement from the measured acceleration, and assess the serviceability level every 5 s. The serviceability status as well as the maximum absolute amplitude of the estimated displacement for 5 s were communicated to the gateway node through wireless communication, as shown in Figure 6b. Note that \"ua_max\" denotes the maximum absolute amplitude of the estimated displacement for 5 s and the serviceability level is printed as either \"Allowable\" or \"Not allowable\" based on the defined threshold of 1 mm. The stay-cable experienced both serviceability allowable and not allowable conditions depending on the assessment cases. For example, in the third assessment case (Figure 6c), the maximum absolute displacement was 0.909 mm at 1.33 s, which indicates allowable serviceability. In the second example, the maximum absolute displacement was 0.914 mm at 0.24 s, which is also within the serviceability threshold (Figure 6d). The third example, however, indicated that the serviceability of the stay-cable was a failure because the maximum absolute displacement was 1.230 mm at 1.68 s, which exceeds the defined threshold (Figure 6e). Thus, this study verified that the developed wireless system can assess the serviceability of the stay-cable automatically and in real time under the defined serviceability threshold through wireless communication between the gateway and leaf nodes.