Analysis of T-stub component under combined shear and axial loads

Abstract

Structural robustness has gained prominence following historical collapses triggered by local damage. Modern design approaches increasingly account for catenary effects, which require significant rotational capacity in structural joints. In this context, the present thesis focuses on the specific behaviour of T-stub components subjected to combined shear and axial loads, due to their critical role in joint performance under extreme conditions.

Experimental reference data from Mancini's tests at the University of Trento, involving inclined loading angles on a T-stub specimen, were analysed to understand boundary conditions and load configurations. Analytical predictions from Eurocode and other standards (AISC, Australian, Song's proposal) were evaluated against these tests. Significant discrepancies highlighted the limitations of current codes in capturing T-stub behaviour under combined actions.

To improve understanding, a finite element model was developed in Abaqus. As material damage was excluded from the constitutive laws, the model was limited to capturing the pre-damage response. Validation showed good qualitative agreement with Mancini's results, though stiffness differences arose due to modelling simplifications and unavailable parameters (e.g. bolt threading and interaction details).

Rotational boundary conditions and a refined model including load-transmitting pins were analysed. The pin model revealed stress concentrations and detachment areas that simplified models could not capture. Stress analyses showed non-uniform distributions along the bolt, varying significantly with load inclination. Intermediate angles did not behave as linear combinations of pure shear and tension but displayed unique interaction effects.

Finally, moment effects in the bolt were investigated. Asymmetric contact stresses at the washer indicated bending moments about both X and Y axes - these effects are ignored in current design standards.

The present thesis demonstrates the sensitivity of T-stub performance to loading configurations and modelling assumptions. It underscores the need for refined numerical models and improved design criteria to account for complex stress states and moment effects in bolted connections under combined loading.