# Review of the Main Cable Shape Control of the Suspension Bridge
## 5 Conclusions  
The main cable erection and alignment control are the key problems in the construction of the upper structure of the suspension bridge. The key points for controlling the main cable shape include calculation theory, erection technology, and shape control. This paper reviews the research progress in the main cable shape control, from the aspects of main cable shape-finding, construction control technology, and construction control analysis. Figure 16: The stress-free assembly formats, constraint boundaries, and loads. Figure 15: Interactive framework. (1) Concerning the main cable shape-finding, both the analytical method and FEM focus on spatial cable suspension bridges and three-tower suspension bridges, which have special mechanical characteristics compared with traditional suspension bridges. Although the SCM and its derivative methods are the mainstream methods for shape-finding, there are also some new methods that are different from the SCM, which enrich the means of main cable shape-finding. The introduction of an intelligent optimization algorithm in the shape-finding process can greatly improve computational efficiency. By introducing the geometric relationship and physical relationship between the saddle and the main cable into the piecewise catenary equation, the main cable shape-finding calculation system was more accurate and perfect. This is despite the complex nonlinear equations being transformed into linearized equations in the shape-finding calculations via FEM, and iterative calculations still being required in the process of solving the element stiffness matrix due to the coupling of equations between the elements. The penalty factor search algorithm and the whole mechanical analysis method can improve the computational efficiency. Although the principle of simulating a cable saddle structure by a rod element is simple, the modeling process is complex and the accuracy is insufficient. The cable saddle element can efficiently analyze the influence of the cable saddle on the main cable, and the calculation accuracy is better than that of the rod element. It is a good idea to combine the analytical method with FEM to analyze the main cable shape, which can take advantage of the respective advantages of the two methods. The future research attentions are still focused on the application and improvement of the existing calculation methods, particularly in the calculation efficiency and refined analysis. However, these specific algorithms and elements are not extensively embedded in analytical software that is commonly utilized in current engineering practice. A large number of advanced calculation methodologies should be effectively applied to practical engineering. (2) Regarding the construction control technology, the constructional approaches of the main cable and the general principle of strand sag adjustment are summarized. Both the AS method and the PPWS method are focused on new technology, new equipment, and high-strength materials, which undoubtedly promote the rapid improvement of the suspension bridge construction level. The improved cable adjustment formula makes the cable strand erection calculation more efficient and accurate. The use of relative reference strands is the mainstream method for ensuring the quality of erection, but there are also interesting methods such as the use of the ruler cable and the mark method to erect cable strands, which enriches the means of cable strand erection. The measurement method based on machine vision undoubtedly provides a new idea for construction measurement. Although the relevant specifications stipulate the deviation range of cable erection, the error control standards of specific projects are still not uniform. However, quantifying the cable spacing to achieve cable pre-lifting is a commonly used method in current projects, but the quantitative values and control methods are different.