After a quick review of bolted connections in steel structures, flush END-PLATE type connection is introduced. Two-way connections made up of such kind have been analyzed using a three-dimensional (3D) inelastic finite element modeling. The model output compared well with available experimental tests. 65 cases of flush END-PLATE stiffened connections, then, used to study effects of connection parameters on its behavior. Finally Multiple-regression analysis procedure applied to derive Richard-Abbott power function parameters, which predicts moment-rotation curves for any selected connection, given the geometrical and mechanical properties

Today connections are playing an important role in the steel frames subjected to lateral seismic loading. The steel extENDed END-PLATE moment connection can play an important role in the steel frame when subjected to seismic loadings. In the past, this type of connection has been under investigation mainly when it was subjected to monotonic loading. After major recent earthquakes and failure of number of traditionally practiced moment connections in US, it seems that the extENDed END-PLATE moment connections can be qualified as a suitable semi rigid type connection to be used in the heavy steel frames.In this article, the seismic behavior of the extENDed moment connection is investigated. Using the nonlinear finite element method of analysis and with the help of yield line analysis, the behavior of the connection, with the emphasis on the column depth and END-PLATE thickness effecting on the panel zone as well as the connection as a whole, is obtained and then the results are compared with those obtained from tests by University College of Engineering, University of Tehran 5 other researchers. Plastic moment versus plastic rotation hysteresis, stress contours of the pertinent part of the connections and displacements are part of the results of this study. The difficulties arising in modeling and analysis technique, exists in such connection, is also discussed.

Precise investigation of the connections in a steel structure is important, and inaccuracy in the design and implementation of connections not only does cause failure in the connection, but also has a devastating effect on other members of the structure. Bolted END PLATE connections are commonly used in steel structures. There are two types of beam-to-column flange connections, four-bolt and eight-bolt. The four-bolt connection is used for low anchor values and the eight-bolt connection is used for large bENDing anchor values. In this study, the cyclic behavior of the restrained beam-to-column connections with END PLATE under cyclic loading has been evaluated. In the calculations, all of the parameters affecting the behavior of this connection have been investigated and solutions are proposed to reach the maximum connection capacity. Since the behavior of this connection depENDs on several factors, two general models of beam connection to different columns with beams of 30 and 40 cm depth are considered for research purposes. The thickness of END PLATE, shape of END PLATE, thickness of the column flange, strength or material of the bolts, the necessity of using continuity PLATE, stiffener and doubler PLATE are among the parameters considered in the analyzes. According to the results of this study, the use of a thin-walled END PLATE leads to local buckling of PLATE. The use of continuity PLATE is very important and prevents local buckling in the panel zone. Also, in cases where the thickness of the column web is low, the use of a doubler PLATE will also be necessary. In addition, the use of a stiffener improves the flexural strength of the section.

In this paper the effect of parameters such as thickness of PLATE, bolt diameter and bolt gage distance from beam flange and web on nonlinear behavior of bolted END-PLATE connection, is investigated. In this regard, ANSYS nonlinear structural software was used for analyzing connection models. The results of this research were verified with experimental results of one sample. In this study 30 models with different geometries were selected for nonlinear analysis. Moment-rotation curves were obtained for all the models and compared with each others.The results obtained showed that thickness of END-PLATE, configuration of holes and bolts, thickness of beam flange and web, presence of stiffeners, and bolt diameter affect the stiffness and strength of connection differently. Increasing in END-PLATE thickness and decreasing in distance between bolts and beam web, increase the stiffness of connection. Also, increasing in bolt diameter increases the stiffness of connection but not as much as the previous two parameters do.

The study investigated the effect of combined loading on END-PLATE moment connection considering the interaction of bENDing moments, axial forces and twisting moments. In some cases, beam-to-column joints can be subjected to the simultaneous action of bENDing moments, axial forces and twisting moments. Current specifications for steel joints do not take into account the presence of axial forces (tension and / or compression) or twisting moments in the joints. Although the axial force or twisting moments that transferred from the beam is usually low, it may, in some situations attain values which can lead to a considerable effect on the connections behaviour and significantly reduce the joint flexural capacity. Unfortunately, few studies considering the bENDing moment versus axial force interactions have been reported and there aren’ t any reports considering bENDing moments versus twisting moments interactions or combination of all the mentioned cases of loads. The lack of knowledge for understanding the performance of END-PLATE moment connection under combined loads may lead to unreasonable or even unsafe design, so in this study a combination of different loads have been examined. Therefore two extENDed END-PLATE connections with different behaviour modeled using finite element method of analysis. The interactions between connection components (bolts, members and ENDPLATE) were accurately modelled to simulate the actual behaviour of connections. Both material and geometric nonlinearities were considered. At first the behavior of these models are investigated in pure bENDing application and numerical results validated against experimental data. The suggested finite element models showed good agreement with experimental results. The level of axial forces in joints of structures can be significant and has a significant influence on characteristics of joints. Because of the existence of this force in the moment resisting frames, the combination of bENDing and axial force in beams should be considered. Structures under fire situations where the effects of beam thermal expansion and membrane action can induce significant axial forces in the connection is a common condition. The results show that even in small amount of axial force the mode of failure and moment capacity of connection can change. Axial tensile forces decrease the initial stiffness of connection and axial compressive forces increase the stiffness. In many applications beams are eccentrically loaded and as a result experience twisting loads in combination with bENDing. The interaction effects due to torsion acting in combination with bENDing can reduce the capacity of the beam and initial stiffness of connection. Finally axial forces were added to the previous models so they experienced a combination of axial force, bENDing and twisting moment. The results indicated that the level and direction of axial force significantly modified the connection response. It was observed that compression forces significantly decrease the bENDing capacity of the models and lateral-torsional buckling of beam occures in all models. Tension forces can reduce the effect of torsion and in many cases they caused the bolts ruptured. Moreover, interaction diagram for predicting the bENDing capacity considering interaction of bENDing, torsion and axial forces are proposed based on the results from finite element analysis.

As observed in Northridge (1994) and Kobe (1995) earthquakes, brittle failure of rigid connection caused premature collapse of steel moment frames and new rigid connections have been introduced in design guidelines of steel frames. Although the usage of new connections can lead to the appropriate function of steel moment frames, plastic hinges forms in beams which leaves the inelastic and permanent residual deformations after strong ground motions. Since this irremediable deformation increases repair cost, constructing rigid connections from reversible material such as Shape Memory Alloy (SMA) significantly reduce the residual strain and could be a solution to the problem. This paper focuses on the function of END PLATE connection using Iron-based SMA (possessing 5% of super elastic strain) by numerical study using ANSYS software. Following verification of cyclic behavior of an END PLATE connection tested by Sumner (designed on the basis of Thick PLATE Theory), SMA is used as either connecting bolts for END PLATE-to-column connection or as PLATEs located at plastic hinges. The result shows that using SMA PLATEs is more efficient than SMA bolt in END PLATE connection which designed based on thick PLATE theory. Regarding appropriate weld ability and lower cost of iron-based SMA, hybrid connection equipped with mentioned PLATEs is able to absorb lesser energy compared to steel connection. Moreover, it decrease repair cost whereas lower residual strain is seen.

In this paper, a new analytical method is presented that can be used to determine the behavior of a particular steel beam-to-column extENDed END PLATE connection in linear and nonlinear regions. A common means of forming a rigid joint between a universal beam and column is to weld an END PLATE to the beam END and then to bolt it to the column. A physically based analytical method that can predict the behavior of bolted and extENDed END PLATE eave connections, using the connection dimensions as input, is presented. This article demonstrates an analytical procedure for the establishment of elastic and plastic parts of the M-q curve of this form of connection. An analytical method is proposed for the extENDed END PLATE joints having four bolts in the tension region and without any stiffened PLATE. However, the presented technique can also properly be extENDed to other types of this form of connection. An extensive approach to estimate the plastic stiffness of the connection has also been performed. Comparison is made on a series of test results for a range of bolted END PLATE moment connections and good agreement is achieved. Furthermore, the authors believe that the method presented shall efficiently serve design engineers in real design conditions.

In the design of most of steel frames, the beam to column connections are assumed to be rigid or pinned. However, in many steel frames beam-column connections show semi-rigid behavior. Structures with semi-rigid connections contain systems with the connections in joints which are not completely rigid, but allow, usually, some relative movements in directions of general displacements.However, semi-rigid design has not received widespread attention due to its perceived complexity and the lack of effective tools for global analysis.Early experimental studies showed the importance of shear deformations in panel zone for stable energy dissipation under cyclic loading. Modeling of panel is very important because of its role in prevention of local failure of columns under ultimate limit state.A substantial effort has been made in recent years to characterize the behavior of semi-rigid connections. Recent studies and modern codes, especiallyEC3 and EC4, include methods and formulas to derive resistance and stiffness of panel zone. EC3 proposes a mechanical model for semi-rigid connection -in which each component is modeled by an equivalent linear spring. In this case, some components of the connection are showed by springs. These springs are assembled by a single bilinear (elastic–plastic) rotational spring alternating the connection, and is attached at beam-column intersection in the global analysis.Stiffness and strength of the springs inEC3 and EC4 depEND on β factor which implies an approximation of the internal forces at the joint. Therefore, adopting accurate β factor requires an iterative process at the time of performing the global analysis of the structure. Modifying EC methods; E. Bayo et al proposed a new component-based method (or cruciform element method) for modeling the internal and external semi-rigid connections. In this model, a cruciform element (a four-node element) is proposed to avoid β factor, and the inherent initial assumption and iterative process that it requires, and includes the finite size and deformation modes of the joint.One of main problems with which structural engineer deals is consideringEND Length Offset in conventional software. ExtENDed END PLATE connection is one of beam-column semi rigid connections that is to evaluate by its behavior, using cruciform connection model and other panel zone models.In this paper, three 2-dimensional frames with extENDed END PLATE connections are modeled inMATLAB using cruciform element method and the results are compared with the analytical results of SAP2000 for eight cases (including four models regarding the presence of the panel zone and four models disregarding it). At one state, END Length Offset is considered just for beams and at the other, for both beams and columns (in two cases of Rigid Zone Factor: 0.5 and 1). The results show that modeling panel zones according to EC method and considering Rigid Zone Factor equal to 1 in columns and beams are the best assumptions for analyzing 2D frames with extENDed END PLATE connections. However, if the panel zones are not modeled, Rigid Zone Factor must be considered equal to 0.5 simultaneously in columns and beams - to give actual results.