# A Review of the T-Stub Components for the Analysis of Bolted Moment Joints
## 1 Introduction  
Over the decades, steel structures have been the preferable option to construct building ranging from small houses to skyscrapers. This predilection is because of the overwhelming benefits of the material such as strength, uniformity, elasticity, ductility, toughness, etc. These benefits give steel structures the advantages of being lighter (in weight per length) than concrete or wood and making it easy to modify or make amplifications. Nevertheless, steel structures have the disadvantages of quickly corroding in the typical environment and susceptibility to fatigue or buckling, etc. According to Eurocode 3 [1], steel structures can be classified into braced frames and unbraced frames. Braced frames have a system of stiff elements called bracings, which is provided to withstand the sum of the lateral forces. In the other case, the unbraced frame is adopted [2]. Additionally, the standard provided a further classification based on the sensitivity to second order effects in the elastic range. The term non-sway frame is used when the lateral-stiffness is sufficient to allow the geometrical second order effects to be neglected. On the other hand, when the lateral stiffness is not enough to neglect the geometrical second order effects, whether for braced or unbraced frames, the term sway frames is used [2]. Another type of classification divides them into steel trusses and steel portal frames, where the principal differences between them are the arrangement of elements and the type of connection. Usually, the trusses have triangular units of straight elements connected by pinned joints; they do not have rotational stiffness. On the other hand, the portal frames are made of shape profiles connected by joints traditionally considered rigid. The most common portal frames moment connections are the T-stub connection (see Figure 0(a)), and the end-plate bolted connection (see Figure 0(b)). The T-stub connection is a type of connection where T profiles are connected from its web to the beam flange and from its flange to the column flange. The T-stub connection was first studied by [PERSON] and [PERSON] [3]. On the other hand, the end-plate bolted connection is a type of connection where a plate is welded to the cross-section of the beam, and then it is joint to the column flange employing bolts. Moreover, the end-plate bolted connection has more structural advantages because of the greater lever arm and because it permits placing a greater number of bolts near to the tension zone, which reduces the bending moment in the end-plate [3]. This type of joint is studied by the component method, Eurocode 3-1.8 [1], which considers the joint as a set of single basic components located in three different single zones: the tension zone, the compression zone and the shear zone, see Figure 2. These components of the joint can be represented in a mechanical spring model (see Figure 2b), where the characteristic of each spring are obtain from the properties of each component (Column Web in Tension CWT, Column Web in Compression CWC and Column Web in Shear CWS). The T-stub is the component that characterises the behaviour of the tension zone. The T-stub has an elastic behaviour at the beginning, see Figure 3b, because its elements do not reach the yield stress of the constitutive law, see Figure 3a, and the force-displacement curve of this zone is linear. However, when the stresses are superior to the yield stress, the T-stub elements begin to plasticize and the knee zone is observed before the slope of the curve changes, see Figure 3b. Figure 1: (**a**) T-stub connection; (**b**) End plate connection. Figure 2: (**a**) Components; (**b**) Spring model. Different authors have been studying the T-stub component since 1965 in three different manners: analytical, experimental and numerical simulations. As a result of these investigations, researchers got to the conclusion that the T-stub component can fail in three modes.