# A Review of the T-Stub Components for the Analysis of Bolted Moment Joints
## 3 Experimental Testing
[18] carried out tests to study the one-side bolted T-stub through thread holes under tension strengthen with backing plates, and to propose a design method. These tests were performed in a universal servo-controlled hydraulic testing machine. The specimens used M20 8.8 bolts, the flange thickness varying from 6 to 20 mm, the backing plates had a thickness of 10 mm, and the T-stubs were connected to a T-stub base with a flange thickness of 30 mm and web thickness of 20 mm to ensure the elastic zone in the base. In this research, two new failure modes were proposed to might occur, and they should be investigated: (1) Mode 4 the hole thread failure, see Figure 20a, and (2) Mode 5, the T-stub flange yielding accompanied with hole thread failure, see Figure 20b. The results of the tests showed that two failure modes were observed during the test with the change of the flange thickness, which were Mode 1 (according to EC3) and Mode 5. Apparently, the backing plate increased the yield strength of the flange, see Figure 20c. However, the effect of increasing the flange thickness is of the utmost relevance, Figure 20c. Furthermore, The T-stub with a flange thickness of 16 mm is more ductile than the T-stub of flange thickness of 6 mm and backing plate of 10 mm, see Figure 20c. Figure 20: (**a**) Failure Mode 4; (**b**) Failure Mode 5; (**c**) T-stub with same flange thickness of 6 mm or thread length of 16 mm [18]. \"Reproduced with permission from [PERSON], [PERSON], [PERSON], [PERSON], Engineering Structures; published by Elsevier, 2017\". In 2019, [PERSON] et al. [46] studied the mechanical behaviour of bolts used to connect T-stubs. Six T-stubs made of Q235B steel were connected with grade 10.9 bolts to a base plate (T-stub with a quite thick flange) and tested while strain gauges acquired the data of the behaviour of the bolts. The experiments showed that the bending stress reached a value ranging from 13% to 45% of the total tensile stress when the bolts yielded. Therefore, it is not advisable to disregard the effects of bending moments in the design. Furthermore, the authors observed that the increment of the flange thickness change the failure mode from mode 1 to mode 2 (similar of EC3 failure modes). It should be mention that the data that was obtained from the experimental part was then used to calibrate the finite element model developed for this investigation. In 2020, [PERSON] et al. [47] studied the behaviour of T-stub connections connected to a rigid base, see Figure 21. The researchers carried out nine T-stub tests in the Laboratory of Structures at the University of Brasilia. These T-stubs were tested under monotonic loading, and the specimens had three different thickness flanges (7.9 mm, 9.5 mm and 12.7 mm). During the tests, the researchers recorded the applied load, the vertical displacement, and the reaction force on the bolts. The results of the experimental testing showed that 2 failure modes were observed, see Figure 22 and: (1) the bolt shank shear at the contact area with the T- stub flange; and (2) failure by the combination of the bolt shank shear at the contact with the flange and bolt tension failure in the thread. In 2020, [PERSON] et al. [48] studied a new type of self-centering connection which solved the common brittle damage problem of conventional steel connections under strong earthquake  
Figure 21: T-stub connection attached to a rigid base [47]. “Reproduced with permission from [PERSON], [PERSON], [PERSON], [PERSON], Journal of Constructional Steel Research; published by Elsevier, 2020”. Figure 22: (a) Force-displacement curve of T-stub specimens of thickness flange equal to 9.5 mm; (b) Reaction-force vs. applied load curves of the specimens of thickness flange of 9.5 mm [47]. “Reproduced with permission from [PERSON], [PERSON], [PERSON], [PERSON], Engineering Structures; published by Elsevier, 2020”. conditions (eg. Kobe and Northridge [49; 50]).