The lateral-torsional buckling of BEAM is a disadvantage for connections with REDUCED BEAM SECTION (RBS). One effective method for preventing such buckling is to reduce web SECTION (RWS) instead of flange. This, not only eliminates the disadvantage of RBS, but also, provides better behavior and more ductility. This paper investigates the effect of longitudinal and transverse web/flange slits on the behavior of bolted steel moment frames. The investigated frames include: frame with full BEAM SECTION and frames with BEAMs REDUCED by: radial cut in flange, longitudinal slits in flange, transverse slits in flange, longitudinal slits in web, transverse slits in web, mixed web slits, and, cruciform web slits. These one-story one-bay frames are analyzed using nonlinear finite-elements method with shell elements of type S4R and solid elements of type C3D8R in ABAQUS. The quasi-static cyclic loading according to Supplemental Access Control protocol is applied to the frames. The results show that by using RWS BEAMs, the location of plastic hinge can move from column face to an appropriate distance at the reduction region. According to the results, the maximum rupture index (RI) occurs in frame with full (not REDUCED) SECTION; while, the minimum RI belongs to RWS frame with longitudinal web slits. The larger the RI, the greater is the probability of rupture at low drifts. The hysteresis curves of frames show that the strength of frames with longitudinal or transverse flange slits decreases at final step of loading, i.e. at the last two cycles with greatest rotation angles. The frame with longitudinal web slits with 31.8% more load-carrying capacity and 30.9% more energy dissipation, shows better performance compared to the other RWS or RBS frames.

One of the drawbacks of the mentioned connections after Northridge and kobe earthquakes was the destruction of BEAM after earthquake, difficulty and non economical displacement of the BEAM. Several studies are being carried out on a variety of materials and systems that dissipate the seismic loading effects in order to improve the seismic performance of steel frames. By placing dampers in the BEAM column connections, damage to the BEAMs and columns, which are very difficult to replace after an earthquake, was prevented during an earthquake. During the design process of dampers, in order to concentrate the earthquake loads on the damper, it was manufactured intentionally with a lower strength than the BEAMs and columns. Through this, BEAMs and columns are protected from damage by utilizing the energy absorption capacity of the damper. Slit damper is a plate or a standard SECTION with a number of slits in the web. The damper is attached to the BEAM by bolting a plate on the damper under the flange of the BEAM. In this study first compared slit steel damper connection and connection with the REDUCED BEAM SECTION (RBS) under cyclic loading. Some suggestions were provided for improvement of the performance of slit steel damper connection and for making its behavior similar to that of REDUCED BEAM SECTION connection and transforming it to a connection which can be used in the special bending frame; and these suggestions include increase in the thickness and number of stripe and decrease in the height. the results and simulations showed that increasing in the number of strips, the increase in thickness and decrease in the height of the SSD damper affects significantly the performance of SSD connection.

In this research, the effect of the elliptical web reduction, the effect of the radial flange reduction and also the effect of the use of stiffener, on the behavior of BEAM, on the behavior of connection and on the performance of steel moment frame is studied. By using Finite-Elements Method and 3D elements in ABAQUS, the nonlinear-static analyses of the frame under cyclic loading are carried out and the Von-Mises criterion is checked. The results show that in the BEAM with no reductions, maximum stresses and strains occur in the web. By reducing the web SECTION of the BEAM, maximum stresses and strains are transferred to the location of the REDUCED SECTION. The ratio of maximum strength to the strength at the final step of loading, and also, the value of dissipated energy, show that, in comparison with the connections with radial-shaped reductions, the connections with elliptical-shaped reductions have less strength degradation and more ductility.

REDUCED BEAM SECTIONs (RBS) provide ductility for rigid connections in steel moment frames by reducing the load imposed on the panel zone and driving the location of the plastic hinge away from the column. Despite these advantages, RBSs are accompanied by a number of drawbacks, among which are the impracticality of some of the proposed models, early local buckling in the BEAM’s flange/web, and lateral torsional buckling brought on by the transverse reduction in the flange’s width. The objective of the present study is proposing a new RBS detail that has the minimum number of these weaknesses, while benefitting from the advantages of REDUCED SECTIONs. In the first step, a number of numerical models were constructed inside the ABAQUS finite element software. After analyzing the models using pushover analyses and interpreting the results, three BEAM models were selected. One of these models was an AISC-approved RBS model, which was used as the basis of comparison to evaluate the performance of the proposed specimens. In the three models proposed, the reduction was in the form of decreasing the thickness of the BEAM’s flange. In one of the models, thickness reduction in the flange was done by creating shallow grooves. In the remaining sample, a rectangular area on the surface of the flange was shaved off to create the REDUCED SECTION. The plastic SECTION moduli of the proposed samples are equal to the thinnest SECTION of the RBS specimen. The experimental RBS samples were full-scale, and tested under cyclic loading. The results of all of the samples showed that plastic hinge was created in the expected region. The seismic criteria for the special moment connection were satisfied by all of the proposed samples. The sample with the shaved flange was superior to the RBS specimen in terms of ductility and energy dissipation.

Nowadays, the use of innovative methods such as cross-SECTIONal reduction method in designing moment connections of steel structures has become widespread among designers. The method of reducing the cross SECTION by deliberately weakening the BEAM in a part close to the connection of the BEAM and column reduces the plastic strains of the joint and the formation of a plastic hinge in the BEAM. In this paper, the effect of REDUCED BEAM SECTION (RBS) on joint strength by removing the plastic hinge from the column and also the optimal performance of various REDUCED BEAM SECTION shapes through different indicators such as hysteresis curve, pushover diagram, energy dissipation of connection and …,are checked. In this research, modelling and nonlinear analysis of 10 examples of REDUCED BEAM SECTION with and without BEAM SECTION reduction using ABAQUS software has been investigated under cyclic loading. The results showed that all models with REDUCED BEAM SECTION have the ability to transfer the place of formation of plastic strains or the same plastic hinge into the BEAM and away from the column. Among all the methods of reducing the crossSECTION, the method of reducing flange BEAM SECTION with uneven holes and enlarging inward to the BEAM has shown a better performance than other samples. The energy dissipation of this method is increased 68% versus the reference sample without REDUCED SECTION. The flexural capacities of sample with reducing flange BEAM SECTION with uneven holes and enlarging inward to the BEAM has shown better cyclic performance. The values of flexural capacity in the mentioned sample is decreased 33% versus the reference sample without REDUCED SECTION. This subject causes plasticization faster and as a result, more energy dissipation is obtained versus other samples.

Connections play a crucial role in structures, including steel structures, and have a significant impact on the seismic behavior of the structure. One particular type of connection commonly used in steel structures is the REDUCED BEAM SECTION (RBS). This connection reduces the moment strength of the BEAM near the column, which in turn results in less moment being transferred to the column at the final moment. The study involved 30 numerical analyses conducted using ABAQUS to examine two cases. The first case involved investigating a connection with a BEAM that had a hole in the flange area. The variables examined included the area of the flange holes and the axial force of the column. In the second case, a yield ring was utilized in the flange area of the BEAM. The radius of the yield ring was considered as a variable insix different cases. Equations for calculating the maximum strength moment and analyzing the linear region of a BEAM were presented in the study. The yielding damper must yield earlier than other members, and an equation was provided to ensure that it does. Finally, the cyclic behavior of the two models was also compared. Numerical analysis revealed that if the area of the flange holes is half that of the BEAM flanges, the BEAM's strength does not significantly decrease withincreasing axial force. The elastic stiffness and ductility of the SRD-equipped connection were higher than the RBS model, with the SRD model achieving 1.8 and 2.6 times greater ductility and elastic stiffness, respectively, in the most optimal state.

Previous studies have demonstrated the occurrence of brittle and early stage cracks in the connection between the link BEAM and the column, specifically in the vicinity of the groove welds  that connect  the flanges of the link BEAM to the column, when subjected to seismic activity. A similar type of rupture has also been observed in the end-plate connections of the link BEAM to the external link BEAM. This research explors the consept of utilizing a box-shaped link BEAM with a REDUCED cross-SECTION in the Abaqus finite element software to magnitude the plastic strain demand generated at the flange ends of the box link BEAM. The objective is to prevent rupture in this specific region. The results indicate that the maximum equivalent plastic strain at the end of the link BEAM flanges can be REDUCED by up to 38% for short link BEAMs, up to 41% for intermediate link BEAMs, and up to 68% for long link BEAMs. Consequently, this approach effectively prevents premature ruptures in the area adjacent to the groove weld connecting the BEAM flange to the end plate. The magnitude of the equivalent plastic strain at the end of the box link BEAM decreases as parameters "a" and "b" decrease, and parameter "c" (geometric parameters of the REDUCED cross-SECTION) increases. Parameter "c" exhibits the most significant influence on this parameter, while parameter "b" has the least significant impact. Additionally, the adoption of a REDUCED cross-SECTION in the box link BEAM results in an increase of up to 35% in the energy dissipation of the link BEAM due to enhanced participation of the flanges in energy dissipation for short link BEAMs, up to 158% for intermediate link BEAMs, and up to 250% for long link BEAMs.

In 1994, Northridge, California, an earthquake created brittle fractures and cracks near the BEAM-to-column connection welds in more than 170 steel MRF buildings. In many cases, these fractures and cracks were observed in the BEAM without any signs of plastic deformation. Since connections are one of the most important components of a building frame, a good understanding of the structural behavior of connections and sufficient knowledge of how it is transmitted is a prerequisite for designing a safe connection. Steel moment frame structures to resist the earthquakes are designed based on the assumption that they can resist yield or plastic deformation without reducing strength. The plastic deformation involves the plastic rotations of the BEAMs at their connection to the columns and theoretically resulting in the loss of seismic energy applied to the structure. All the modifications proposed in recent years for the moment connections are aimed at shifting the maximum plastic capacity or ductility demand from the end of the BEAM or connection zone and transferring the ductility demand to an area within the BEAM and away from the column. On the other hand, the details of seismic moment connections provided in FEMA351 can be classified into two groups: a- Connection zone strengthening methods; b- REDUCED BEAM methods. There are different types of the connections presented with the idea of ​​strengthening the connection zone; for example, we can refer to the connection with welded cover plates to the flange, the connection with the side plate, the connection with the screwed seat, the connection with the welding muscle, etc. However, the connections provided and used with the idea of ​​reducing the BEAM are more limited, such as RBS or REDUCED SECTION BEAM connection, free-flange BEAM connection, sheared BEAM-to-web connection, and REDUCED BEAM-to-web connection. RBS connections form a plastic hinge outside the connections site and reduce force and moment at the connection, and is one of the pre-confirmed rigid connections after the 1994 Northridge earthquake. One method of building RBS connections is to use a connection of BEAM with a REDUCED SECTION by replaceable links. The use of these replaceable links is one of the methods to increase the ductility and transfer the plastic hinge into the REDUCED area of ​​the BEAM. In these connections, the goal is to displace the plastic hinge into the REDUCED area of ​​the BEAM at a certain distance from the column, so in these connections, moving the plastic hinge away from the column reduces the concentration of strain in the welded zone. As a result, it reduces the weld cracking rate and thus reduces brittle failure in the connections.Connection of the REDUCED BEAM SECTION was proposed after damage to structures in the 1994 Northridge earthquake. This connection reduces the damage caused to the panel zone by forming a plastic hinge outside the BEAM-to-column connection area. In this research, we investigate in a laboratory a new type of BEAM SECTION connection, which in recent years has been named as replaceable links. Among the links designed in the first laboratory sample, the semicircular cutting method on the flange of the replaceable BEAM was used to reduce the finding, and in the second sample, circular holes in the flange of the sample were used to reduce the BEAM SECTION. Studies have shown that high stress concentration occurs in the REDUCED area and other parts of the BEAM and column elements will remain without significant stress, which makes the BEAM replaceable after an earthquake. Analytical results show that the link with reduction by creating a hole in the flange has more energy absorption and ductility than the link with reduction by cutting a semicircle in the flange of the link BEAM. Also, according to the maximum amount of time recorded in the samples and referring to the existing regulations in the design of structures, it can be stated that both samples are among the allowable connections in a special moment frame.