Flexural performance of high strength grouted SHS tube-sleeve connection for modular construction

Prefabricated prefinished volumetric construction divides traditional buildings into room-sized modules that are manufactured off-site and assembled on-site. This construction method offers improved construction speed, superior quality control, and reduced environmental impact compared to traditional construction. In high-rise modular construction, the connections between modules may experience significant bending moments due to wind loads or earthquakes. Therefore, the flexural performance of these connections becomes a critical factor that affects the overall stability and robustness of the modular structures. The present study combines the advantages of high strength grout and square hollow section tube sleeves to develop a robust grouted connection for prefabricated structures without compromising assembly efficiency. Firstly, the study conducts three-point bending tests on eight full-scale specimens to investigate the flexural behavior of the connection. The load transfer mechanism, failure modes, moment-curvature relationship, and strain development of the tube-sleeve connection under lateral load are analyzed in detail. The study also quantifies and discusses the effects of different shear key spacing, grout length, inner tube width, and steel fiber content on the strength and stiffness of the connection. In addition, the study utilizes ABAQUS to simulate the bending responses of the connection, including inner tube fracture, grout crack development, and internal complex strain state. The finite element analysis results demonstrate good agreement with the experimental results, with an average ratio of 1.04 between numerical results and test results for flexural resistance, and a standard deviation of 0.04. Furthermore, based on elasto-plastic mechanics and the actual cross-sectional stress distribution of the connection, three analytical models are proposed to predict the flexural resistance of the connection. Finally, the moment-shear interaction relation is verified against the finite element and test results using the elastic-plastic analytical model and the ultimate state shear model.