Study on rigidity and bilinear model for improved hub-shape inlay joint

Original hub-shape inlay joint constitutes a crucial joint kind for reticulated shell. However, due to its relatively low joint rigidity and design tend to be conservative, limits its application in single-layer reticular shell with smaller spans. Based on this, this study improves the original hub-shape inlay (OHI) joint, and proposes an innovative semi-rigid joint, namely improved hub-shape inlay (IHI) joint. FE models are created for the OHI and IHI joints using ABAQUS package, with a total of 126 numerical joint models investigated. This study systematically examines IHI joint’s mechanical properties under five types of single loads as well as coupled action of axial load along with moment, followed by parametric analysis. Subsequently, nonlinear fitting of key joint parameters established a bilinear model for IHI joint’s strong axis load-displacement relationship. Computational results indicate: (i) Compared with the OHI joints, the IHI joints exhibit significantly enhanced bending capacity about strong axes, with initial rigidity increasing by 97% as well as ultimate moment rising by 29%; (ii) As the depth of the inlay tenon decreases, various joint rigidities improve to different degrees, with the most pronounced effect observed when the joint undergoes axial tension; and (iii) Under coupled action of moment along with axial load, IHI joints’ bending resistance gradually decreases with increasing axial tension, and initial stiffness as well as ultimate moment are inferior to their corresponding values under pure bending.