Experimental and numerical simulation study of mechanical properties of inner sleeve T-joint in modular gymnasia.

• A new modular building and its all-bolt internal sleeve connection joints are introduced. • The mechanical properties of the all-bolt internal sleeve joints are investigated by tests. • The FE model that can accurately simulate the joints' mechanical properties is established using a reasonable simulation technique. • The test-validated FE model carried out the parametric analysis of the all-bolt inner sleeve joints. • The properties of the gap and inner sleeves' properties are critical to the mechanical properties of the joints. In response to the contradiction between the insufficient number and unreasonable distribution of stadiums in cities and the increasing demand of people for fitness, the authors propose movable modular gymnasiums. This gymnasium takes advantage of the modular building, which can be quickly built, dismantled, and reassembled to fully utilize the temporary empty land in the city to meet the fitness demand of the people. However, the box modules bear a huge roof load, which puts higher demands on the performance of the modular units and their connecting joints. This study proposes a novel joint using an inner sleeve and bolted connections. The proposed connection uses an inner sleeve and bolts to connect the upper and lower columns of the modular unit to give it a higher bearing capacity. Bolts connect the lower unit's ceiling beam and the upper unit's floor beam to provide a better overall performance of the modular unit. The authors conducted experimental studies of 2 full-scale models and 24 finite-element parametric analyses. The results show that the welding quality determines the beam-ward bearing capacity of the joints, while it has little effect on the column-ward bearing capacity. In practical engineering, the authors suggest that the initial stiffness of the joints does not consider the contribution of the inner sleeve. The setting of stiffening ribs forces the inner sleeve to deform and force, improving the joints' mechanical properties, with the initial stiffness in the column direction increase of 25 %, the initial stiffness in the beam direction increase of 31 %, and a bearing capacity in the beam direction increase of 38 %. The design thickness of the inner sleeve and stiffening ribs should be close to the wall thickness of the modular beam and column. The results of this paper contribute to the development of fitness for the whole population and the expansion of the application of modular buildings. [Display omitted] [ABSTRACT FROM AUTHOR]