In recent earthquakes some BEAM-COLUMN joints have shown undesirable brittle mode of failure by developing a fracture line at their welded CONNECTION between the BEAM and the COLUMN. The main reason for this type of behavior is the formation of dominate three dimensional state of tension stresses around the CONNECTION lines. Such confinement at weld materials reduces the ductility of the weld and provides the condition for brittle fracture at the CONNECTION line. The onset of fracture is, therefore entirely dependent on the magnitude of the state of stress. As a remedy, many researchers propose to reduce the distance far from the face of the COLUMN. In this study, a new type of BEAM-COLUMN joint with the same rational is developed. While possessing all the required features for such CONNECTIONs, it is considered a practical solution for BEAM-COLUMN joints by solving some other related issues surrounding the problem. Analytical and experimental studies, carried out in this work, verified the potential of the proposed BEAM, COLUMN CONNECTION in preventing brittle mode of failure. The joint has also shown a remarkable cycle behavior by representing a large number of loops with low rate in degradation of sectional properties.

Composite special moment frames represent a novel type of special moment frames (SMFs) where a combination of concrete COLUMNs and steel BEAMs is used. This paper evaluates the modeling of composite special moment frames and the behavior of the steel BEAM-concrete COLUMN CONNECTION. Due to the focus on hinge formation, the behavior of the CONNECTION with a hole drilled on the BEAM flange was analyzed. Numerical simulations were carried out in ABAQUS. The BEAM-COLUMN CONNECTION was subjected to one-five rows of holes. It was observed that the BEAM-COLUMN CONNECTION with three rows of holes had the optimal hinge formation behavior, stress distribution, and load. The CONNECTION with five rows of holes showed plastic strains in the first four rows, while the fifth row had no plastic strain. This suggests an increased drilling space since the fifth hole row did not contribute to the improvement of stress distribution uniformity. It was numerically found that the bending moment change varied from 8% to 46%; the model with three rows of holes had the lowest bending moment change, whereas the model with a single hole row showed the highest change in the bending moment. Moreover, energy absorption changed by 4-20%.

The aim of this research work is to study the flexural behaviour of steel BEAM-COLUMN CONNECTION with gusset plate under static loading condition. CONNECTIONs are normally the focal points of receiving damage due to overload including earthquake. The main reason for the failure of CONNECTION is, their inability to deliver large rotation. Gusset plates are used for connecting two or more members together. While gusset plates are used as the connecting element of bracing to the BEAM-COLUMN joint, the load carrying capacity and stiffness of BEAM-COLUMN joints are possible to increase. To know the increasing capacity of BEAM-COLUMN CONNECTION with gusset plate are determined by conducting the experimental and analytical program. An experimental research demonstrates the actual behaviour of steel BEAM-COLUMN CONNECTION with gusset plate. There are four number of specimens are tested under static loading condition. Each specimen is fabricated by changing the CONNECTION parameter like gusset plate thickness, angle leg length. Finite element analysis was done using ABAQUS. Using the finite element model, a parametric study was conducted to determine the changes in the CONNECTION and initiation of damages. The contact element which is used as a surface to surface instead of node to node. Accurate results can be obtained by validating the results of experimental work with FEM analysis. The comparison is made for the deflection and strain occurred on the experimental program with the analytical results.

Steel COLUMNs composed of hollow structural section filled with concrete are one of the best solutions for providing the required strength and stiffness through the composite action of steel and concrete. The HSS COLUMN and steel BEAM CONNECTIONs proposed so far have included complex details and extensive welding in most cases, which complicates the construction of the CONNECTION and also its behaviour. Hence, in this research, an attempt is made to avoid these complexities and to employ a CONNECTION with high efficiency and easier implementation by passing a continuous steel BEAM through tubular CFT COLUMNs. The influence of the steel tube diameter, the thickness of the steel tube, the thickness of the BEAM flange and web and also the amount of axial load applied to the COLUMN are investigated by numerical modeling using finite element method. The results of the pushover analysis show that the ratio between the bending moment capacity of the COLUMN and that of the BEAM (Mpc/Mpb) plays a significant role in the effect of the other studied parameters. In the range of Mpc / Mpb < 0. 6, variation of the the steel tube wall thickness directly influences the ultimate moment of the CONNECTION and its ductility. On the other hand, in the range of Mpc / Mpb > 0. 6, the ultimate moment and ductility of the CONNECTION are directly linked to the thicknesses of the flange and web of the steel BEAM.

The importance of welded CONNECTIONs on the behavior of steel moment resisting frames was the reason of researchers focus on welding details. In this paper result on 32 pilot tests indicate moment CONNECTION behavior are presented. In this experimental research, in order to CONNECTION strength evaluation, complete joint penetration (cjp) weld strength with different welding procedure, double side fillet weld out of plane strength, one side fillet weld out of plane strength and amperage intensity effect on welding quality, have been studied. Also in order to CONNECTION rehabilitation, rib stiffener effect on CONNECTION strength, T-stiffener effect on CONNECTION strength, electrode toughness effect on welding quality and grinding and rewarding effect on welding quality have been studied. Maximum strength of cjp weld is observed in welding with backing. Out of plane strength of double side and on side fillet weld have been determined. CONNECTION strength increase amount with stiffener strengthening of CONNECTION have been proposed. It has also been proposed constructional recommendations about electrode toughness, rewelding and amperage intensity.

Most of the steel moment resisting frames, damage at the BEAM-to-COLUMN CONNECTIONs during seismic loads. Application of passive dampers in order to prevent damages to the main components of structure has been an interesting subject for many researchers recently. In this present study, performance of the metallic yield damper is slit steel damper (SSD) on the steel BEAM-to-COLUMN CONNECTION is carried out using finite element model. Thus, first this damper and its CONNECTION is simulated. After validation of results, the effect of various dimensional parameters including radius slot, of damper on the performance of damper and its CONNECTION was investigated. Then various forms of this damper simulated and their effect on the performance of damper and the steel BEAM-to-COLUMN CONNECTION is studied. Moment-rotation, Hysteresis curves and plastic strains for each size of radius slot and different shapes extracted from the analysis were compared. Furthermore base shear force for steel frames with and without slit dampers in term of energy absorption and deformation are compared together. Findings indicated seismic behavior fitted to such dampers. The results indicate that the slit damper shows a proper function in absorbing energy. Recommendation for appropriate size and shape of slit steel dampers proposed.

In the design process of a moment resisting frame (MRF), the principle of weak–BEAM and strong–COLUMN should been considered because of the occurrence of plastic hinge in the BEAMs. This mechanism is caused because the frame is capable of dissipating significant energy and remaining stable in the inelastic region. Stability is defined as the ability of the frame to maintain its elastic level of resistance throughout the entire inelastic range of response. Using this principle, plastic hinges can be developed in the BEAMs adjacent to the CONNECTIONs and usually very close to the COLUMN face. This mechanism allows the cracks to be caused by the plastic hinging. The cracks can also propagate into the CONNECTION core region, and initiate a brittle failure mechanism. Furthermore, the mechanism has not been established in many existing MRFs - designed based on the previous codes. Hence, the methods have been proposed and developed in order to relocate the plastic hinges away from the COLUMN face. Fiber Reinforced Polymer (FRP) has been used as a strengthening solution of BEAM–COLUMN CONNECTIONs and successfully reported for retrofitting existing structures. In fact, the web–bonded FRP retrofitting system can control the mechanism of plastic hinge and provide the strong–COLUMN weak–BEAM concept. Due to many advantages, such as high strength, low weight, endurance and convenience, Carbon Fiber–Reinforced Polimers (CFRPs) have been used in strengthening concrete structures. However, the strength and stiffness of CFRP are severely reduced at elevated temperatures, which will affect the strengthening effect seriously. In this study, six schemes are proposed for strengthening concrete BEAM–COLUMN CONNECTIONs using CFRP and the seismic performance of strengthened CONNECTIONs is investigated. In order to achieve this purpose, seven downscaled RC exterior joint of a typical ordinary MRF are chosen, and modeling this strengthened CONNECTION is implemented in a general finite element program, ABAQUS software. In the finite element model of strengthened concrete BEAM–COLUMN CONNECTION, the concrete is modeled using the damaged plastic model. The sheets of CFRP are also considered as the elastic and orthotropic model. These schemes of strengthened concrete BEAM–COLUMN CONNECTIONs are tested under moderately monotonic/cyclic loads. In order to verify the finite element model of the CONNECTION, the analysis results of this model is compared with the experimental investigation on the external BEAM–COLUMN CONNECTION repaired using CFRP. The results demonstrate the verification of the finite element model. Selection of the best scheme of strengthened concrete BEAM–COLUMN CONNECTION using CFRP is based on the improvement of the seismic performance of CONNECTION such as the load–carrying capacity, the energy absorption, the initial stiffness and changing failure mechanism of CONNECTION. The nonlinear results show that the proper layout of CFRP sheets can increase the load–carrying capacity, the energy absorption and the initial stiffness of CONNECTIONs. Furthermore, the proposed schemes of strengthened concrete BEAM–COLUMN CONNECTION cause the failure to relocate from the COLUMN face and locate in BEAM. Therefore, the best proposed scheme of strengthened concrete BEAM–COLUMN CONNECTION using CFRP can be recommended and utilized in the practical projects of concrete structures.

In order to solve the problem of access to inside of hollow COLUMNs for tightening bolts and achieving a suitable CONNECTION both in terms of rigidity and stiffness and in terms of the proper behavior, various solutions have been suggested by researchers. One of these solutions is steel BEAM to hollow COLUMN CONNECTION by an angle and blind bolts. This CONNECTION can be made in different types with different number of blind bolts. CONNECTION with flange angle and blind bolts have showed proper and semi-rigid behaviour. In this research, the effect of changing various parameters on the behavior of steel BEAM-hollow COLUMN CONNECTION with angle and blind bolts was investigated under monotonic loading. The nonlinear finite elements method and Abaqus software was considered and solid three-dimensional elements as continuum elements was supplied in CONNECTION models. The behavior of CONNECTION was studied by changing various parameters such as BEAM height, COLUMN thickness, length of angle leg and number of blind bolts. The results show that increasing height of the BEAM, thickness of the COLUMN and length of angle leg raises the CONNECTION’ s rigidity. Also, increasing the above mentioned parameters leads a simple CONNECTION toward semi-rigid CONNECTION. Also, by studying the models, the rigidity degree of most models except a few of them, which is less than 20%, is between 20% and 90%. Considering the rigidity degree, studied models behaved as semi-rigid CONNECTIONs.

The present study focuses on the performance of a 0.6 scale new moment resisting precast concrete BEAM-COLUMN CONNECTION subjected to cyclic loading by conducting experiments. The precast CONNECTION considered for this study was a BEAM-COLUMN CONNECTION where BEAM is connected to COLUMN with inverted E corbel. The experimental results of the precast specimens have been compared with that of the reference monolithic CONNECTION. The performance of the precast CONNECTIONs in terms of the ultimate load carrying capacity, load-displacement hysteresis behaviour, energy dissipation capacity, equivalent viscous damping ratio and ductility factor were compared with that of the monolithic BEAM-COLUMN CONNECTION.