Study on the Compression Performance of Prefabricated Reinforced Welded Hollow Sphere Joints

To address the challenges encountered during the in situ welding reinforcement process of hollow spherical joints, including complex construction, limited quality control, and low efficiency, this study proposed a prefabricated reinforced hollow spherical joint. A three-dimensional finite element (FE) model was developed and validated against experimental results to quantify the effects of T-rib web width (b), web thickness (t1), ferrule thickness (t2), hollow-sphere diameter (D), and bolt pretension (fv) on the bearing capacity of the prefabricated joint. Based on these analyses, a predictive model was established for the axial compressive bearing capacity of the prefabricated joint. The results showed that, under compression, the reinforcing components primarily provided a supporting role to the hollow sphere, thereby improving the buckling resistance of the prefabricated joint under compression. The reinforcement mechanism primarily relied on friction between the ferrule and the steel stub for load transfer, with the available frictional resistance governed primarily by bolt pretension and the stiffness of the reinforcing components. When sufficient friction existed between the ferrule and the steel tube, increasing the T-rib web width from 0 mm to 80 mm improved the bearing capacity of the prefabricated joint by 33%. At a T-rib flange height (h)-to-web width ratio of h/b = 1.0, the T-rib satisfied the reinforcement requirement through its inherent strength and stiffness. As the hollow-sphere diameter-to-thickness ratio decreased, the incremental gain in bearing capacity diminished. A predictive model was proposed for compressive bearing capacity by accounting for the support provided by the reinforcing components and the effects of hollow-sphere diameter, steel-tube diameter, and the tube-to-sphere diameter ratio. The proposed model predicted the FE results with errors within ±10%, and the findings can provide a practical reference for designing the compressive bearing capacity of prefabricated reinforced hollow spherical joints.