Energy-based assessment of the influence of the nonlinearities on T-stub ultimate behaviour

Exceptional loadings, such as those from impact or blast events, induce significant rotations in structural joints through catenary actions in the connecting beams, leading to large displacements in the T-stubs. Current regulations on structural robustness necessitate experiments to demonstrate that joints possess sufficient deformation capacity. A valid and cost-effective alternative to experiments is finite element (FE) modelling. This study presents an accurate FE model for simulating the force-displacement (F-∆) response of bolted T-stubs undergoing large displacements, validated against available literature data. The model accounts for geometric non-linearities and material damage in both the flange and bolts. To characterize the materials of the flanges experiments on unnotched, pre-notched, and shear specimens are conducted while tensile and shear tests on bolts are performed. The investigation into the presence of catenary actions in the flange aims to elucidate the relationship between geometric non-linearities and the development of a 2nd hardening branch in the F-∆ response. A preliminary criterion for determining the significance of catenary actions in the flange is proposed based on the strain energy dissipated in the flange through membrane force. Comparisons in terms of energy are made between T-stubs that do and do not develop a 2nd hardening branch. The study reveals that the development of catenary effects depends on the boundary conditions of the T-stubs and the initial position of the bolt within the hole.