Analysis of the dynamic mechanism of square tubular t-joints with chord flanges subjected to impact loading

This study examines the dynamic mechanical properties of square tubular T -joints with impact loads acting on the chord surface in the joint area. The study first verified the failure modes and behaviors of the specimens under a brace axial force and impact, respectively, where the simulation results demonstrated good agreement with the experimental results. A total of 138 square hollow section tubular T -joint finite element models were divided into T1, T2, and T3 groups based on different tube diameter ratios. The failure modes, displacement -time history curves, and impact force -time history curves were obtained. The results revealed that the joint deformation modes were primarily characterized by significant local indentation at the impact site and junction of the chord and brace, as well as a certain degree of deformation at both ends of the chord. Within a certain range, the preloaded axial force could mitigate the development of plastic deformation, whereas an increased ratio of the drop hammer length to chord diameter exacerbated it. Finally, theoretical analysis was simplified by defining the plastic element set, and the energy dissipation coefficient psi was proposed to evaluate the impact resistance of square tubular T -joints by analyzing the specific energy changes in the intersecting region (El) and at the ends of the chord (Ee).