# Performance Evaluation of a Long-Span Cable-Slayed Bridge Using Non-Destructive Field Loading Tests
## 3 Experimental Results and Analysis
### Cable Tension Increment Test Analysis for the Field Loading Test of Pingnan Xiangszhou Bridge  
There are 160 stay cables on Pingnan Xiangszhou Bridge. The cable force test was carried out for the stay cables of the whole Pingnan Xiangszhou Bridge. The test stay cables were numbered separately according to the upstream, downstream, and north-south ends. The outer stay cables of the tower are represented by \"A + No.\", and the inner stay cables are represented by \"B + No.\". The basic parameters of stay cables A8-A10 and B8-B10 after the completion of Pingnan Xiangszzhou Bridge are shown in Table 5.  
As shown in Figure 5a, in the process of the static load test, the cables with large cable force increments were tested using a wireless cable force tester. Under the loading cases No. 2 and No. 4, the cable force increment of six outer stay cables numbered A8-A10 at the upstream and downstream of pier cable tower #3 (north tower) were measured. Under the loading cases No. 7 and No. 8, the cable force increment of six inner stay cables numbered B8-B10 at the upstream and downstream of pier cable tower #3 (north tower) were measured. For the cable tension force test of Pingnan Xiangszhou Bridge, firstly, the deformation radar was used to measure the initial frequency of the stay cables when the bridge was unloaded. Then, the frequency of the stay cables was measured once for every loading case. The measured frequency of the stay cables was converted into stay cable tension force by the frequency method, as described in Section 2.3.2, and then the cable force increment could be obtained. The measured and calculated cable tension increment values  
\begin{table}
\begin{tabular}{c c c c c c} \hline \hline \multirow{2}{*}{**Cable No.**} & **Number per Bundle** & **Anchor Spacing (m)** & **Total Length (m)** & **Cable Elevation** & **Cable Density** \\ \hline A8 & 55 & 116.180 & 118.191 & 40.659 & 71.0 \\ A9 & 55 & 126.236 & 128.225 & 38.424 & 71.0 \\ A10 & 55 & 136.460 & 138.418 & 36.549 & 71.0 \\ B8 & 43 & 116.312 & 118.256 & 39.821 & 56.3 \\ B9 & 55 & 126.404 & 128.392 & 37.470 & 71.0 \\ B10 & 55 & 136.661 & 138.623 & 35.568 & 71.0 \\ \hline \hline \end{tabular}
\end{table}
Table 5: Basic parameters of stay cables after the completion of Pingnan Xiangszzhou Bridge.  
of the inner and outer stay cables, considering various loading cases, are shown in Figure 13, where \"Calculated-Upstream\" is the theoretically calculated cable tension increment value of stay cables at the upstream, \"Measured-Upstream\" is the experimentally measured cable tension increment value of stay cables at the upstream, \"Calculated-Downstream\" is the theoretically calculated cable tension increment value of stay cables at the downstream, and \"Measured-Downstream\" is the experimentally measured cable tension increment value of stay cables at the downstream.  
From Figure 13, it can be seen that under four loading cases (i.e., cases 2, 4, 7, and 8), the size relationships between the calculated values and the test results of cable tension increment at the corresponding upstream and downstream were the same. Taking case No. 2 as an example, the calculated and measured cable force increments of A8 at the upstream were 292.1 kN and 223.5 kN, respectively, while the corresponding calculated and measured cable force increments at the downstream were 477.2 kN and 344.1 kN, respectively. Overall, the measured cable tension increment values were less than the corresponding calculated values. These comparison results show that the measured displacement values of stay cables for Pingnan Xiangsizhou Bridge are smaller than the designed values, and the stiffness of the stay cables is competent.  
Figure 13: Measured and calculated cable tension increment values of inner and outer stay cables, considering various loading cases: (**a**) loading case No. 2; (**b**) loading case No. 4; (**c**) loading case No. 7; (**d**) loading case No. 8.