# A Review of the T-Stub Components for the Analysis of Bolted Moment Joints
## 6 T-Stubs of Non-Conventional Steel and Other Materials
The simulations were compared with experimental data, and they showed that the refined model reproduced with good accuracy the behaviour of the pins but with a high computational time of processing. Therefore, the simplified model was developed through the application of a four-step calibration methodology. This methodology allowed to reduce the computational time without lost sufficient accuracy. Afterwards, the FEM models, which used 8-node bricks elements with reduced integration and hourglass control (C3D8R), of the extruded T-stubs was validated by comparing the numerically derived load-carrying capacities, load-displacement curves and failure modes with those obtained from the 30 experiments [73]. Then a parametric study was performed to provide insight influence of four key parameters (the preloaded in sewage-locking pins, pin diameter, filler radius at the web-to-flange junction and pitch distance of the pins) on the structural behaviour. The simulation results showed that the T-stub's initial stiffness increased when the preloading and the filler radio increased, but the deformation capacity was not influenced. Furthermore, load-carrying was not influenced by the preloading level. The pin diameter affected the T-stub failure mode directly due to the change in the resistance area. Finally, the authors proposed a design method that was more accurate than the EC9 formulae due to the improvement in the prediction of 13%. In 2020, [PERSON] et al. [98] aimed to achieve a damage-controllable and earthquake-resilient steel frame with more feasible and simple dissipative devices. Therefore, the authors studied an innovative moment-resisting bolted connection, employing FEM, that used double replaceable T-stub fuses made of low yield point steel (LYP). Because of the higher ductility dissipation capacity and the fatigue performance [99] of the LYP steel, the connection ductility and energy dissipation capacity are enhanced. The finite element model, which was used to study the cyclic behaviour, was calibrated with available experimental data that were obtained by [PERSON] et al. [100] and [PERSON] et al. [101]. Then the seismic response (hysteresis curves) of the connection, with different weakening strategies in the T-stub, were studied and optimise by considering the most relevant parameters, the weakened degree and the free deformation length, which should be simultaneously analysed. Furthermore, the authors proposed relevant suggestions for designing this kind of connections to behave as structural fuses that can dissipate more than 90% of the system energy and how to avoid the buckling in the T-stub stem. In 2020, [PERSON] et al. [102] tested a total of 13 austenitic and duplex stainless-steel T-stubs connected with A4-70 and A4-80 stainless steel bolts to study the T-stub behaviour. These experimental tests were replicated by employing a 3D FEM model. After the 13 simulations reproduced with good accuracy the behaviour of the T-stubs, that were obtained in the experimental testing, a parametric study was performed to predict the behaviour of 168 configurations and to investigate the importance of key parameters such as the material grade, bolt preloading, bolt diameter and flange thickness on the structural response. The test result data and the simulation results were used to determine the suitability of the design standard EC3 and JGJ 82-2011 (Chinese standard) for steel and was determined that the stainless T-stubs had the same three failure modes of steel T-stubs, but the resistance prediction was quite conservative. Therefore, the nominal yield strength value used in the design standards to predict the T-stub behaviour was replaced by the 3.0% proof strain (due to strain hardening) and the prediction were more accurate. Additionally the method of Faella predicts more precisely the initial stiffness than the other standards method.