Influential Parameter and Experimental Research on Compressive Bearing Capacity of Welded Hollow Spherical Joints Connected with Circular Steel Tubes

摘要

For the hollow spherical joint with the same specification, Design carrying capacity obtained from space truss specification is lower than that obtained from latticed shell. Especially when the material is Q345, calculation result will have 1 time difference. Hence, this article study deeply the failure mechanism and impact factor of load carrying capacity of spherical joint under compression.Firstly, Based on the linear hardening elastic-perfectly plastic model, a finite element model for the analysis of these joints is established, in which the effect of geometric nonlinearity is taken into account. The structural mechanical behavior, failure mechanism of joints is systemly investigated. It is revealed that for the compressed spherical joint that satisfy construction requirement in the last 2 technical specification, the failure mode is Due to the formation of cyclic plastic hinge that cause the load carrying capacity of hollow spherical joint to lose. At thelimit state, shear in failure key section is dominant stress and as 1/√3 times as failure Mises stress.Subsequently, based on orthogonal method, multi-parameter and single-factor significance analysis of compressive load capacity is performed by the F-inspection. The result indicates that yield strength of spherical material fy, are the critical factor that influence the load carrying capacity of hollow spherical joint, as well as wall thickness t, outer diameter of sphere D and outer diameter of steel tube D. Destructive experiments on 8 typical full-scale joints made from Q235B and Q345B, in which all parameters are same except material grade, were conducted to understand Directly the structural behavior and the collapse mechanism of the joint, and also to validate the finite element analysis and parameter study.Finally, the simplified theoretical solution is also derived for the loading-carrying capacity of the joint based on the punching shear failure model, and the basic form for the design equation is obtained. Moreover, by the regression analysis, the practical calculation method is established for the load-carrying capacity of the joints subjected to axial compressive forces. The calculation result obtained from this formula is consistent with experiment result, and the practical formula has safety reserve meeting the regulation in national codes. The achievements from this study can be directly applied for design and reference to the revision of relevant Design codes.