## 4 Discussion on Results
Moreover, as shown in Figure 10c, the variation of the deflection for the main-cable at the mid-point of the main span increases first and then decreases, with the progress of erecting of the girder segments. The deflection for the main-cable at the mid-span reaches the maximum when the erections of B25-27 and B23'-25' are completed, i.e., 1/4 of the girders of the global suspension bridge is completed. Next, this deflection gradually decreases, while the variation rate is small. When the number of completed girder segments is bigger, the gravity stiffness of the main-cable is greater. And the influence of the installation of the subsequent girder segments on the main-cable's deflection at mid-point becomes smaller and smaller. Figure 11 illustrates the comparison of the horizontal displacement of the tower between the presented theoretical results and measured values at both sides for the 21 working cases. With the erection of girder segments, the tower deflections at both the Chadong and Jishou sides are increasing. And the two horizontal deflections are both pointing to the mid-span at all the erecting time. Moreover, the variations of the two towers' horizontal deflections are small at the erecting stages of the last several girder segments. Figure 12 shows the comparison of the rail-cable forces between the presented theoretical results and measured values for the 21 working cases. With the erection of the girder segments, the measured rail-cable force has a slight deviation from the theoretical value in each working case. While the variation range is not large, the deviation is basically less than 5%, and, in a few working cases,  
Figure 12: Comparison of rail-cable forces by the presented theoretical result and experimental result on different shifting-girder working cases: (**a**) Jishou side; (**b**) Chadong side. it reaches the maximum deviation of 6%. This difference is acceptable from engineering viewpoint, which indicates these two methods match well with each other. Besides the forces of the main-cable, displacements of the main-cable, horizontal deflections of the two towers, and forces of the rail-cable mentioned in Figures 9-12, the theoretical results of the shape of the rail-cable, sling force, etc. are all in good agreement with experimental results for the 21 working cases. The compared results show the calculated values by the presented method for the deflection and force of main-cable, sling force, deformation of rail-cable match well with the tested values during the construction of girder segments. Therefore, the presented theoretical method can correctly and effectively obtain the forces and deflections of the RCSG system undergoing girder loads, and the systematical responses are conform to the prediction values, thus the correctness of the presented method is validated. Furthermore, in the shifting-girder process undergoing girder loads, the theoretical results and the measured results for the vertical deflection of rail-cable and the force at anchor points are basically consistent. This indicates that the presented method truly reflects the actual mechanical performance of the structure, and the deformation and force of rail-cable can be studied and solved by the proposed theory in this research. Additionally, with the erection of the girder segments, the measured force of the rail-cable has a slight deviation from the theoretical value in each working case. Nevertheless, the deviation range is not large and the deviation value basically stays within 5% with a maximum deviation of 6% in only a few of the working cases. When the gravity center of the girder segment reaches the mid-point of inter-node, the relative deformation of the rail-cable is the largest. While the increase of the erected girder segments will not directly affect the local deformations of the rail-cable.