Monotonic behaviour of 4-bolt row connections: Analytical and numerical analyses

The present work aims to numerically investigate the performance of 4-bolts T-stubs and the influence of geometrical parameters, such as the flange thickness, on both 4-bolts T-stubs capacity and ductility, which have not yet been investigated in the existing literature. Advanced numerical models were properly developed, and their effectiveness was verified against experimental tests performed on a 4-bolts T-stub that had previously been presented in the literature. Sixty 4-bolts T-stubs specimens were designed and modelled, featuring variations in flange thickness and width, the distance between the internal bolt and the web, the spacing between the bolts and the distance between the outer bolt and the edge of the plate. Moreover, the response of all the specimens investigated was compared against two analytical models that had already been presented in the literature. Finally, in order to better understand the influence of the additional external bolts on the overall performance of the T-stubs, the numerical results were compared to those obtained on traditional 2-bolts T-stubs properly introduced. The results demonstrate that the flange thickness exerts a significant influence on the T-stub capacity and ductility, while the influence of the other geometrical parameters, such as the flange width and bolt positioning, is determined by the T-stub failure mode. Finally, in function of the awaited failure mode, the use of 4-bolts T-stubs could allow an increase in specimen resistance and/or ductility with respect to the traditional 2-bolts T-stub.