Static performance of welded hollow sphere joints with trapezoidal ribs under both axial compression and bending moment

Welded hollow spherical joints (WHSJs) are prevalent in spatial reticulated structures throughout China. Adding external trapezoidal ribs is an effective strategy for enhancing strength of WHSJs. These joints often bear not just axial forces but also bending moments, such as in single-layer reticulated shells and suspended-dome structures. This study investigates the static behavior of WHSJs reinforced with external trapezoidal ribs subjected to both axial compression and bending moment. Eccentric compression is employed to simulate this combination, effectively integrating axial compression with bending moments. Experiments are conducted on 13 specimens, focusing on the influence of the number of external ribs, load eccentricity and load angle, to reveal the failure mechanism, load-bearing capacity and strain development. It is found that the load-bearing capacity decreases as the load eccentricity and load angle increase, with reductions of up to 70 %. The specimens failed due to the development of plastic hinges in the hollow sphere. Subsequently, a refined finite element model is developed using ANSYS and calibrated against the experimental results. The calibrated model is served to perform a parametric study on the load-bearing capacities of the reinforced WHSJs. The lower envelope method is employed to propose a practical calculation method for load-bearing capacities of WHSJs with trapezoidal ribs under both axial compression and bending moment. Experimental results demonstrate that the actual loadbearing capacities are consistently higher than the proposed predictions, confirming the safety and reliability of the method.