# Performance Evaluation of a Long-Span Cable-Slayed Bridge Using Non-Destructive Field Loading Tests
## 3 Experimental Results and Analysis
### Strain Analysis for the Field Loading Test of Pingnan Xiangszhou Bridge  
Figures 8-12 show the experimentally measured values and theoretically calculated values of strain of the main girder for Pingnan Xiangszhou Bridge at different sections (as shown in Figure 5b), considering various field loading cases (as listed in Table 1). Among them, strain measuring points 1-6 are distributed at the bottom of the bottom plate of the main girder, while strain measuring points 7-15 are distributed at the bottom of the top plate of the main girder, for Pingnan Xiangszhou Bridge.  
Figure 8: Measured and calculated strain values of the main girder at section A, considering loading cases 1 and 2: (**a**) 1–6 at the bottom of the bottom plate; (**b**) 7–15 at the bottom of the top plate.  
Figure 9: Measured and calculated strain values of the main girder at section B, considering loading cases 3 and 4: (**a**) 1–6 at the bottom of the bottom plate; (**b**) 7–15 at the bottom of the top plate.  
Figure 11: Measured and calculated strain values of the main girder at section D, considering loading cases 7 and 8: (**a**) 1–6 at the bottom of the bottom plate; (**b**) 7–15 at the bottom of the top plate.  
Figure 12: Measured and calculated strain values of the main girder at section E, considering loading cases 9 and 10: (**a**) 1–6 at the bottom of the bottom plate; (**b**) 7–15 at the bottom of the top plate.  
It can be seen from Figure 8a,b that the measured strain values of the bottom plate section, which has maximum positive moment in all first-span cross-sections, are less than the calculated strain values under symmetrical loading and eccentric loading, and the corresponding calibration coefficient is between 0.5 and 0.86. Similarly, the measured strain values of the top plate are less than the corresponding calculated values, and the corresponding calibration coefficient is between 0.57 and 0.91. The results show that the strength of the first span of Pingnan Xiangszhou Bridge meets the design requirement, and that the design is proved reasonable.  
From Figure 9a,b, under the action of symmetrical loading, it can be seen that the calibration coefficient of the top plate strain for Pingnan Xiangszhou Bridge is between 0.52 and 0.75 at the maximum positive moment section of the second span, and the calibration coefficient of the bottom plate strain is between 0.33 and 0.78. Under the action of eccentric loading, the calibration coefficient of the bottom plate strain for Pingnan Xiangszhou bridge is between 0.52 and 0.81, and the calibration coefficient of the bottom plate strain is between 0.55 and 0.85. The strain values of the girder at the second span are less than the designed values. The results show that the strength of the second span for Pingnan Xiangszhou Bridge meets the design requirement.  
Similarly, according to the strain analysis in Figures 10-12, the measured strain values of the maximum negative moment section, the \(L/4\) section, and the maximum positive moment section at the third span for Pingnan Xiangszhou Bridge are less than the calculated strain values. Moreover, the calibration coefficients are less than 1, which indicates that the strength of the third span meets the design requirement. Therefore, the whole bridge has adequate resistance to external loadings, and the design is reasonable.