With the continuous development of the social economy and the increasing service life of bridges, in-service bridges generally face multiple challenges such as safety decline, durability deterioration, and insufficient traffic capacity. Demolition and reconstruction have become an important way for some old bridges to achieve functional renewal and ensure traffic safety. This paper takes the first concrete self-anchored suspension bridge in China that has undergone demolition—the Zicai Bridge in Qinzhou—as the specific engineering basis. In response to the safety requirements and smooth progress of its demolition construction, after a comprehensive comparison and optimization of multiple demolition schemes, the core technical solution of reverse sequence removal of the hangers was finally determined. To fully verify the technical applicability, structural safety, and feasibility of this demolition scheme, this study adopts a core research method combining theoretical calculation and numerical simulation, and systematically and deeply analyzes the entire process of bridge system transformation, the evolution law of structural force, and the mechanical responses of key parts during the hanger removal process. The study found that the maximum stress of the hangers in the system during the hanger removal process was much lower than the material breaking stress. The tilt of the bridge tower and the deformation of the main cables were all within the controllable range. Only the local tensile stress at the lower edge of the main beam had a cracking risk exceeding the material’s tensile limit. Based on this, specific construction optimization suggestions and control measures were proposed. This research not only solved the core technical problems of this type of special bridge demolition, but its research ideas and quantitative analysis results can also provide important theoretical references and technical support for the subsequent demolition construction of similar cable-bearing system bridges, and has positive significance for promoting the scientific and standardized development of complex bridge demolition construction.
Yuan et al. (Thu,) studied this question.