The seismic design of nuclear power plants not only needs to meet the requirements for structural safety but also ensure the safe operation of nuclear facilities in extreme situations such as earthquakes and prevent accidents like radioactive material leakage. Therefore, studying the seismic performance and against progressive collapse of the main plant in the conventional island has important practical significance. This article is based on the alternate path method and identifies the key columns in the gable structure using node displacement and bearing capacity methods. These key columns play a crucial role in the stability of the entire structure under earthquake action. If a key column fails, it may cause the progressive collapse of the structure, posing a serious threat to the safe operation of the nuclear power plant. After identifying the key columns, a detailed analysis of the plastic hinges of the gable structure, as well as the vertical displacement and rotation changes of the failed columns, was conducted using static and dynamic nonlinear analysis methods. A plastic hinge is a nonlinear deformation form that may occur in structures under earthquake action, and its formation and development have a significant impact on the seismic performance of structures. By analyzing the vertical displacement and angle changes of the failed column, the against progressive collapse performance of the remaining structure can be more accurately evaluated. The results indicate that the failure of the edge columns of the key columns has a greater impact on the against progressive collapse of the remaining structure, which is consistent with the results of the component importance analysis.

In addition, the results of static nonlinear and dynamic nonlinear analyses were compared. The amplification effect of the load is considered in static analysis, so the predicted against progressive collapse is generally higher than the results of dynamic analysis. This discovery suggests that in practical engineering, we cannot solely rely on the results of static analysis. Instead, we should comprehensively consider dynamic effects to more accurately evaluate the progressive collapse performance of structures. Finally, three different optimization methods were proposed to enhance the overall safety margin of the structure. Using traditional methods, such as increasing the amount of reinforcement and enlarging the cross sectional size, to enhance the structure’s against progressive collapse can lead to an increase in material usage and construction difficulty. In addition to applying traditional methods, diagonal braces were also added and the support layout of the structure was optimized. It was found that adding diagonal braces can more effectively enhance the against progressive collapse and deformation ability of the frame and bent structure of the main plant in the conventional island. This optimization measure not only enhances the overall against progressive collapse performance of the structure but also offers better economic efficiency and construction convenience. Therefore, in the seismic design of nuclear power plants, multiple factors need to be comprehensively considered, including structural form, material selection, construction quality, etc. By optimizing the structural design and reinforcement measures, the seismic performance of the main plant in the conventional island can be significantly enhanced, thereby ensuring the safe operation of nuclear power plants under extreme conditions such as earthquakes.

In summary, this study employed the alternate path method to identify key columns and adopted static and dynamic nonlinear analysis methods to comprehensively explore the against progressive collapse ability of the gable wall structure of the main plant in the conventional island. The impact of key column failure on structural performance was revealed, and effective structural optimization measures were proposed, providing an important theoretical basis and practical guidance for seismic design and reinforcement in nuclear power plants. Research on the seismic performance of future nuclear power plants will pay more attention to the in depth integration of structural engineering, seismology, materials science, and intelligent technology. This is to comprehensively optimize the seismic design of nuclear power plants, further enhance their seismic safety, and provide strong guarantees for the sustainable development of nuclear energy.