# A Review of the T-Stub Components for the Analysis of Bolted Moment Joints
## 6 T-Stubs of Non-Conventional Steel and Other Materials
During the welding process, the material reached high temperatures that affected the microstructure in the heat- affected zone (HAZ). Because of all the aforementioned, the researchers performed six tensile tests on double T-stub and demonstrated that the EC3 [1] formulae (Equation (1), which are accepted for determining the failure modes of conventional steel, cannot be used directly for design HSS T-stubs. Therefore, a FEM model that considered the effect of the HAZ, was employed to predict the behaviour of the T-stub, and the results showed that the alternative (Equation (2)) formula of the EC3 predicts with good accuracy the first yield resistance. Furthermore, the T-stub under combined axial and shear loads were investigated by the FEM. The results showed that the strain concentration is in the tensile side of the T-stub under combined loads, and the compression side of the T-stub did not achieve Mpl,1. Besides, the ultimate resistance and first yield resistance decrease with the decreases in the beam height. Moreover, the investigation proposed a formula, which considered a factor of the combined axial and shear load, to predict the T-stub behaviour. In 2019, [PERSON] et al. [95] studied T-stub components obtained by additive manufacturing (AM) using polymers. These T-stubs were printed by the fused deposition modelling (FDM) technique and made of four different materials: polylactide (PLA), acrylonitrile butadiene styrene (ABS), carbon fibre-reinforced polyamide (PA CF) and carbon fibre- reinforced polyethylene terephthalate (PET CF). This research aimed to study the behaviour of the components and compare the experimental force-displacement curves with the prediction of the Eurocode 3 [1]. As a result of this comparison, they determined that the code prediction was not accurate enough. In 2019, [PERSON] et al. [96] carried out 30 tests of extruded aluminium T-stubs specimens connected by sewage-locking pins under monotonic loads. The different specimens were designed by varying the distance between the pins and the web (m + 0.8r), the flange thickness, the sewage-locking pin collar type and the diameter and layout of the fasteners. Before the T-stub tests were performed, 42 experimental tests on the sewage-locking pins were carried out under tension, shear, and combined load (shear and tension) to assess their load-carrying capacity. The tests showed that the sewage-locking pins developed a new failure mode (compared to standard bolts) that was called collar pull-out. Additionally, the 42 tests were complemented by the tensile coupon tests on the T-stub plate and pin material. Afterwards, the 30 experimental tests on T-stubs were performed, and the four failures modes identified in EC9 were observed. The experimental tests result showed that the initial stiffness and the ultimate resistance increase significantly when the distance from the pin to the web or the thickness of the flange is increased. However, decreasing the distance between the pins and the web reduced the deformation capacity. Additionally, it was also noticed that the sewage-locking pins load-carrying capacity, the collar type and the pin diameter affected the structural behaviour. Finally, a new design method based on the continuous strength method (CSM) was proposed, which was validated with the experimental test results. Besides, the predictions of the EC9 method were evaluated, and It showed that the method underestimates the load capacity of extruded aluminium T-stub connections. In 2020, [PERSON] et al. [97] continued investigating the behaviour of extruded aluminium T-stubs connected by sewage locking pins. In the previous paper [73], the investigation developed experimental tests on 30 T-stubs, which was then used to validate the FEM models of this investigation. Before starting the T-stubs analysis, the researchers developed refined and simplified FEM models of the sewage-locking pins.