Mechanical properties analysis of joints for prefabricated metro station structure based on Whole-process in-situ monitoring

Abstract

Changchun Metro Line 2 implemented the whole-process monitoring and measurement of prefabricated metro station for the first time. This paper analyzes the mechanical behavior and deformation of the joints of vault and arch springing, which bear high bending moments, in order to study the mechanical properties of these joints, which play a key role in the bearing capacity of prefabricated structure. In addition, it also discusses the trend of the joint stress, relative deformation and relative rotation angle as it changes with the construction process and after opening for traffic. Furthermore, it analyzes the performance of the joints in different construction stages, and compares it with the numerical calculation results based on the long-term in-situ monitoring and survey data carried out at the prefabricated station of Changchun Metro during the whole construction period. As indicated by the result, at the beginning of the assembly and arching into a ring of the components at the top, the structure undergoes a self-adaptation period, where the joints are subject to heavy stress and deformation. After backfilling and water level recovery, the joints are subject to increased axial force and reduced stress and deformation, resulting in a positive effect on the bearing capacity of the joints. The overall change range in joint stress is rather small. During the construction period, the two tenons of double-tenon joint of vault bear external force by mutual engagement, which are subject to two types of stresses, namely, tensile stress and compressive stress. The concave-convex tenon of single-tenon joint at the arch springing is markedly engaged with each other, with the tenon subject to a bending effect. The test results are relatively stable, and the overall deformation at the joint of vault and arch springing is relatively small, with sufficient safety margin from the end of construction disturbance through the operation stage till today. The research results demonstrate great practical guiding significance for the joint and structure design of prefabricated metro station.