## 5 Results of Health Monitoring
### Influences brought by diurnal Temperature Difference  
The monitoring data measured at \(5\) a.m. and \(3\) p.m. in \(17\) October \(2015\) were chosen to analyze the structural changes that were caused by diurnal temperature difference. The ambient temperatures were \(20~{}^{\circ}\)C and \(35~{}^{\circ}\)C, respectively. The concrete S&C effects were neglected because the two moments were close to each other.  
The measured changes of structural alignments and girder compressive stresses are shown in Figure 10. The mid-span cables and girder dropped slightly, as shown in Figure 10a,b. The cable catenary sag increased along with the thermal expansions of steel wires and increases in cable length. In terms of the east side-span, the thermal expansion of concrete was caused by the ambient warming simultaneously besides the increases in cable catenary sag. The cable anchoring positions at girder ends moved towards the expansion joints. The cables and girder rose affected by the thermal expansion of mid-span girder and bidirectional sliding bearings between the east towers and girder. As for the west side-span, the bearings between the west towers and girder were transverse one-way sliding bearings. The additional movements of west cable anchoring positions that are caused by the thermal expansion of mid-span girder were relatively smaller when compared with the east ones. Thus, the structural alignments changed insignificantly.  
The measured changes of girder compressive stresses are shown in Figure 10c. In terms of the side-span girder, the compressive stresses increased affected by concrete thermal expansion and constrains brought by expansion joints. As for the mid-span girder, the top plate compressive stresses increased, and the bottom plate stresses decreased affected by the girder deflection. The uneven changes of the girder stresses between the side and middle webs of the same cross section caused by the temperature gradients reflect the significant spatial effect of the extra-wide girder.  
\begin{table}
\begin{tabular}{c c c c c c c} \hline
**Tower Location** & **Sensor** & \multicolumn{3}{c}{**Measured Tower Stress (MPa)**} & \multicolumn{3}{c}{**Variation Amount (MPa)**} \\ \cline{3-6}  & **15 April 2015** & **15 October 2015** & **15 April 2016** & **First Half Year Period** & **One-Year Period** \\ \hline \multirow{5}{*}{SUT1-S Southwest} & Northeast & \(-13.520\) & \(-13.100\) & \(-14.200\) & \(-0.420\) & \(0.680\) \\  & Southeast & \(-11.635\) & \(-12.760\) & \(-11.760\) & \(1.125\) & \(0.125\) \\  & Central south & \(-5.988\) & \(-5.810\) & \(-4.810\) & \(0.412\) & \(-0.588\) \\  & Southwest & \(-11.213\) & \(-11.680\) & \(-10.680\) & \(0.467\) & \(-0.533\) \\  & Northwest & \(-11.982\) & \(-11.380\) & \(-12.380\) & \(-0.602\) & \(0.398\) \\  & Central north & \(-9.295\) & \(-9.670\) & \(-10.270\) & \(0.375\) & \(0.975\) \\ \hline \multirow{5}{*}{ST1-N Northwest} & Northeast & \(-9.632\) & \(-9.740\) & \(-10.140\) & \(0.108\) & \(0.508\) \\  & Southeast & \(-10.433\) & \(-11.785\) & \(-10.385\) & \(1.352\) & \(-0.048\) \\ \cline{1-1}  & Central south & \(-10.010\) & \(-10.936\) & \(-9.336\) & \(0.926\) & \(-0.674\) \\ \cline{1-1}  & Southwest & \(-9.815\) & \(-10.730\) & \(-9.030\) & \(0.915\) & \(-0.785\) \\ \cline{1-1}  & Northwest & \(-8.353\) & \(-8.006\) & \(-8.606\) & \(-0.347\) & \(0.253\) \\ \cline{1-1}  & Central north & \(-7.863\) & \(-7.333\) & \(-8.030\) & \(-0.530\) & \(0.167\) \\ \hline \end{tabular}
\end{table}
Table 5: Measured tower root stress and variation amount.