## 5 Conclusions  
This paper is focused on the pseudo-static responses of the shifting-girder system of the new erecting method of the main girders (i.e., RCSG technique) for the long span suspension bridge in a rural mountain area with poor transportation and no navigable rivers available for carrying large components. The global mechanical model of the double-layer cable system in the shifting-girder process is established. The solving program is developed to obtain the forces and deflections of the main cable, rail-cable, and slings when the shifting-girder system is undergoing the girder segments' weight. By taking the Aizhai suspension bridge as the engineering background, a global indoor reduced-scale model of a shifting-girder system is also designed to validate the presented theoretical method. The results for the presented method and model test are compared. The conclusions are drawn as follows:  
1. The theoretical results match well with the measured experimental results of the global model test for the 21 working conditions of the shifting-girder system undergoing girder loads. The differences of the forces and deflections from these two methods are small for most of the working conditions, except the maximum deviation of the measured force of rail-cable from the theoretical value reaches 6% in only a few working cases. 2. The main-cable's forces at the anchorage points on both sides are increasing in the erecting process of girder segments. The variation of the incremental cable forces is small in the erecting courses of the subsequent girder segments. 3. The vertical deflections of the main-cable at the locations of both 1/4 and 3/4 main span first decrease and then increase in the erecting process, and reach the maximum value when the erections of the girder segments are completed, due to the symmetry of the global structure along the mid-span. The deflection of the main-cable at mid-point first increases and then decreases in the erecting progress, and it reaches the maximum value when 1/4 of girders are completed. 4. The horizontal deflections of the two towers are increasing at all erecting times, and both point to the mid-span. The variations of these two deflections are small at the erecting stages of the last several girder segments. 5. The measured rail-cable force of the model test has a slight deviation from the theoretical value, while the variation is basically less than 5% and reaches a maximum of 6% in a few working cases. 6. The correctness and effectiveness of the presented theoretical method is validated by the experimental results of indoor model test. It is able to obtain the forces and the reflections of the double-layer cable system of the shifting-girder system undergoing girder loads. The accuracy and results satisfy the requirement of practical engineering application, and this simplified method is suitable to solve the RCSG system under load-condition for the long span suspension bridge adopting the RCSG technique for construction. Also, the modeling and studying of the presented theoretical method can supply references for the similar double-layer projects carrying loads. Conceptualization, Q.P. and D.Y. ; Methodology, Z.Y. ; Software, Q.P. and Z.Y. ; Validation, H.X. ; Formal Analysis, Q.P. ; Investigation, Q.P. and D.Y. ; Resources, D.Y. ; Data Curation, Q.P. and D.Y. ; Writing--Original Draft Preparation, Q.P. and Z.Y. ; Writing--Review & Editing, Q.P. and Z.Y. ; Visualization, Z.Y. ; Supervision, D.Y. This research was funded by the National Natural Science Foundation of China (Grant No.51678069); the Natural Science Fund of Hunan Province (Grant No. 2018 JJ2436); the Key Discipline Fund Project of Civil Engineering of Changsha University of Sciences and Technology (Grant No. 18 ZDXK02, 18 ZDXX14); Hunan Provincial Education Department Innovation Platform Fund (Grant No. 18K046); and the innovation team of the safety assessment theory and performance technology of the long span bridge of Changsha University of Science and Technology.