Study on the bending resistance performance of lightweight prefabricated frame tunnel components

Prefabricated frame tunnels have obvious advantages in terms of construction efficiency, space utilization and carbon emission reduction. However, when applied to large-span subway stations, municipal tunnels, and other projects, the heavy weight of prefabricated components increases the difficulty of transportation and lifting. A lightweight structural design is undoubtedly an important way to solve this problem. In this study, lightweight prefabricated tunnel components with circular, elliptical and round-ended open cavities were designed, and a bending performance test was carried out on the components. The dynamic failure characteristics of the components were tested by a noncontact measurement system. Moreover, the finite element method was used to evaluate the effects of the cavity ratio and axial force on the mechanical properties of the prefabricated tunnel components. The results show that under the same cavity ratio, the bearing capacity of the circular cavity component is the largest, while the bearing capacity of the round-ended cavity component is the smallest. In addition, the fracture toughness of the circular and elliptical cavity components is better than that of the round- ended cavity component. The cross-sectional deformation of the circular cavity is similar to that of the elliptical cavity, and the cross-sectional deformation of both is greater than that of the round-ended cavity. Under different cavity ratio conditions, reducing the cavity ratio can improve the bearing capacity of tunnel components, with the circular cavity component having the most significant improvement effect. When the cavity ratio is less than 15%, further reducing the cavity ratio significantly improve the bearing capacity of the component. By comprehensively considering the lightweight benefits, the cavity component has the greatest benefit when the cavity ratio is approximately 10%. Increasing the axial force can improve the bearing capacity and deformation resistance of cavity components, and the improvement in the bearing capacity of the round-ended cavity component is the most significant. This study provides reference information for the lightweight design of prefabricated frame tunnel structures.