## 1 Introduction  
The ballastless track structure of high-speed railway refers to the track structure that replaces the ballast with a monolithic foundation such as a concrete or asphalt mixture. Due to its various advantages such as good stability, long-lasting geometric dimensions, low maintenance workload, high durability, small secondary dead load of bridges, small clear area of tunnels, and high comprehensive economic benefits [1; 2; 3], it has become the preferred choice for high-speed railway track structures worldwide. Currently, the primary method for ballastless track construction involves prefabricating track slabs in factories, while the base slab and filling layer are constructed on-site [4]. However, several issues exist in this method, including heavy on-site wet work, difficulty in precision control, poor quality stability, and high construction costs [5; 6; 7], which hinder the green and low-carbon progress of the railway industry. The new prefabricated track structure involves prefabricating track components in factories and transporting them to the construction site for rapid assembly. Compared to traditional ballastless track structures, it boasts advantages like convenient construction,a shorter construction period, better stability, and reduced labor force requirements. The structure comprises high-precision prefabricated track slabs, fastening systems, elastic pads, and other connecting components, facilitating efficient and precise track laying. Its defining feature is the utilization of prefabricated components for on-site assembly. This approach not only increases construction efficiency but also meets the rigorous demands of high-speed, heavy-duty, high-volume, and high-density railway transportation. Consequently, it significantly improves wheel-rail contact and optimizes stress and strain distribution across various track components, thereby effectively prolonging the lifespan of the equipment and postponing the maintenance cycles. Through a combination of factory production and on-site assembly, the application of prefabricated track structures is becoming increasingly widespread in modern railways [8], urban rail transit [9], and other related fields. The National Engineering Research Center of High-speed Railway Construction Technology (Changsha, China) has proposed a new track structure, namely, the modular assembled track structure, with built-in position retention [10]. This structure aims to tackle the issues inherent in traditional track structures, improve the assembly rate, stability, and safety of the track structure, and reduce labor costs, construction costs, as well as operation and maintenance costs on site. This promotes the further advancement of rail transit technology. Accurate analysis and prediction of the reliability of the new prefabricated track structure during the schematic design phase can help identify possible failure modes, causes, and impacts during use. This determination of reliability levels aids in selecting the optimal scheme, thereby enhancing the safety and durability of the rail transit system while reducing operational and maintenance costs. This promotes green and low-carbon development in the railway industry. Reliability refers to the ability of a product to perform its intended function under specified conditions and within a specified time interval [11]. The core of engineering structure reliability research is to solve the scientific measurement problem of structural safety under random conditions [12]. Traditional reliability analysis methods are mainly in two categories, probability-based methods and model-based methods [13]. 1. Probability-based methods: In 1926, [PERSON] first systematically discussed the idea of using probability theory to study the safety of structures in his book Structural Safety. Since then, related research has continued to emerge. Probability-based methods can be further divided into two categories: precise method and approximation method.