Study on the longitudinal equivalent bending stiffness of quasi-rectangular assembled subway stations

The longitudinal equivalent bending stiffness (EI)eq of quasi-rectangular assembled subway stations is a critical parameter in assessing mechanical behavior and plays an essential role in both the structural design of components and verification of bending bearing capacity. In order to analyze the longitudinal bending performance of an assembled subway station and its influencing factors, implicit expressions for the longitudinal equivalent bending stiffness (EI)eq and effective ratio of the longitudinal bending stiffness (η) were presented based on the corner calculation formula of an equivalent continuous beam. The influence of component length on the distance from the neutral axis to the x-axis, effective ratio of the longitudinal bending stiffness (η), and maximum stress on the cross-section were discussed through the analysis of section parameters. Furthermore, an in-depth analysis was conducted on the impact of thickness, radius of curvature, central angle of top and bottom plates, as well as semi-short axis length (b) on the maximum stress experienced by assembled components. In order to reflect the actual action range of the circumferential joint of the assembled station, the impact factor of circumferential joint (λ) was proposed, which extends the longitudinal equivalent continuity model of quasi-rectangular assembled linings. The findings indicate that the state of stress distribution in the cross-section and the value of η remains constant across different component lengths, with negligible impact from the direction of the bending moment. The maximum cross-sectional stress was greatly influenced by the semi-short axis length (b) when subjected to a constant bending moment. When the thickness of the top plate (t1) falls within the range of 0.6～2 m, an increase in semi-short axis length (b) results in a decrease of maximum tensile stress by 6.8% to 9.3%. When the thickness of the bottom component (t3) is between 0.6 m and 2 m, an increase in semi-short axis length leads to a reduction of maximum compressive stress by 62.5% to 63.6%. As λ increases from 0 to 1, effective ratio of the longitudinal bending stiffness (η) exhibits a progressively decreasing trend, declining from 1% to 0.05%. This result is consistent with the calculation conclusion of the longitudinal equivalent continuity model. The research findings offer valuable insights into the structural design and bending bearing capacity verification of prefabricated components for assembled subway stations. © 2024, Central South University Press. All rights reserved.