## 8 Discussion and Conclusions  
Using field monitoring data collected for over a year, this research investigates the static behavior of a typical span of a large tied-arch aqueduct under variations of air temperature and water load in an effort to predict the deformations and strains of the aqueduct during operation in order to set up a baseline for the structural safety evaluation. It serves as a feasibility study for the implementation of an SHM system for the entire aqueduct and can also provide a valuable reference for the structural monitoring of other large-scale aqueducts under similar operating conditions. Through the evaluation of the structural monitoring data over a year and the 3D model analysis for the aqueduct, the following conclusions can be drawn:  
1. The variation in the longitudinal deformation of the composite tied-arch closely follows the trend of the air temperature fluctuation during both the non-operation and operation periods of the aqueduct, with its daily maximum and minimum values occurring almost simultaneous with the daily highest and lowest air temperatures, respectively. 2. The daily extreme longitudinal deformation of the composite tied-arch \(\Delta L_{dex}\) not only has a good linear relationship with the daily extreme air temperature change \(\Delta T_{dex}\) during the non-operation period but also a good multiple linear correlation with \(\Delta T_{dex}\) and the \(\Delta L_{dex}\)-related water level \(W_{dex}\) during operation. However, it is impractical to  
Figure 28: Analytical \(\varepsilon\) versus monitored \(\varepsilon\) of the left rod under water load during operation. Figure 29: Analytical \(\varepsilon\) versus monitored \(\varepsilon\) of the right rod under water load during operation. isolate the temperature effect from the multiple linear regression due to the resulting poor correlation between \(\Delta L_{dxc}\) and \(W_{dxc}\). The multiple linear regression can provide good estimations for the longitudinal deformation of the composite tied-arch under different combinations of temperature and water level. 3. During the non-operation period, the air temperature has an insignificant effect on the vertical deformation of the composite tied-arch, and the two sets of monitored data also show a very poor relationship. The multiple linear regression of the daily average vertical deformation \(\Delta V_{dxc}\) versus the daily average temperature change \(\Delta T_{dxc}\) and daily average water level \(W_{dxc}\) exhibits a fairly good correlation during operation, which can give reasonable predictions for the vertical deformation of the composite tied-arch. 4. The measurement of vibrating-string strain gauges is greatly influenced by the air temperature, particularly for those installed on the right side of the composite tied-arch exposed to solar radiation. During the non-operation period, the correlations between the daily average strain \(\varepsilon_{dxc}\) and daily average air temperature \(T_{dxc}\) of all gauges are generally weak, especially for those on arch rings. During operation, the multiple linear regressions of \(\varepsilon_{dxc}\) versus \(\Delta T_{dxc}\) and \(W_{dxc}\) for gauges on tension rods, in particular, those on the left side not exposed to solar radiation, present more consistent correlations than those on arch rings, which can be used to provide fair approximations for the strains of the tension rod. 5. It is found that the 3D FE model can make fair predictions on the vertical deformation of the composite tied-arch under water load, whereas the consistencies between the temperature-excluded monitored data and model analysis results for the longitudinal deformation and strains of the composite tied-arch seem not quite as promising. 6.