Study on the Influence of Geometric Parameters and Shape Optimization of Single Tenon Joint in Assembled Subway Station

The various components of fully prefabricated metro stations are mainly connected using grouted tenon and mortise joints. Therefore, studying the mechanical properties of the joint locations is of significant importance for the overall safety and stability of the station. This paper focuses on the single tenon-long joint as the research object and applies an orthogonal experiment plan to investigate the relationship between the lower bottom length, upper bottom length, and height of the joint and its flexural load carrying capacity. After comparing various loading methods, uniformly distributed loads are chosen as the method for applying axial forces and bending moments. The objective is to determine the dimensions of the tongue and groove that exhibit optimal mechanical properties based on the law of opening displacement and maximum deflection variation with bending moment. The influence of geometrical parameters on the flexural strength of tenon joints is analyzed by means of range analysis in order to find the combination of geometrical parameters with the best mechanical properties. The degree of influence of each geometrical parameter was also ranked. Using these insights, the authors proposed a modified cross-shaped tenon based on the optimal combination of geometrical parameters, which was verified by comparing the M-theta curves of the optimal combination and the optimum working condition. The main conclusions are as follows: (1) the ranking of the geometric parameters of the joint in terms of their influence on the flexural capacity is as follows: height has a greater impact than the bottom length, and the bottom length has a greater impact than the top length. Among these parameters, the influence factor of the height is significantly greater than the other two. (2) The optimum geometry for the tenon and mortise joint is 385 mm for the lower bottom length, 230 mm for the upper bottom length, and 200 mm for the height; the joint's ratio of height to total width should be 25%, the ratio of lower bottom length to total width should be 48%, and the ratio of upper bottom length to total width should be 29%. (3) The load carrying capacity of the cross-shaped tenon is significantly higher than that of the optimal combination and optimum working condition, providing a significant improvement. This research's results will serve as a valuable reference for designing assembly nodes in prefabricated assembly metro stations.