Extended Shear Tab Connections Research Articles

Demand and Supply of Rotational Ductility in Flexible Extended Shear Tab Connections

AbstractExtended shear tab connections have a long history in the steel construction industry as a practical solution to many framing problems, such as framing the supported member to the weak axis...

Full-scale testing of stiffened extended shear tab connections under combined axial and shear forces

Owing to the lack of a comprehensive published procedure for the design of stiffened extended shear tabs, practicing engineers usually follow design guides for unstiffened shear tabs. The results of recent laboratory experiments and numerical analyses have demonstrated that improvements to this approach are warranted. Furthermore, design methods for this connection type under combined axial and shear forces are not well established. To address these shortcomings, full-scale laboratory tests were carried out on the double-sided configuration of stiffened extended beam-to-girder shear tab connections with full depth shear plates. These experiments were complemented by a continuum finite element (CFE) study, with which the axial force demands along with other critical parameters that affect the connection behaviour were further examined. The experiments supported by the CFE findings indicated that the primary connection damage states are mainly associated with yielding and fracture of the shear plate due to the interaction of flexural, shear, and axial force. The study demonstrated that the direction and magnitude of the applied axial force significantly affected the shear and axial demands along the centerline of the interior bolt line. The current design practice for the double-sided configuration of the full-depth extended beam-to-girder shear tab was also evaluated; a significant underestimation was observed in the prediction of a connection’s ultimate resistance.

Behaviour of stiffened extended shear tab connections under gravity induced shear force

Stiffened extended shear tab connections (either in full-depth or partial-depth configurations) are widely used to connect simply supported beams to the web of supporting girders or columns. Full-scale laboratory tests of stiffened extended shear tab connections underscored the differences between their observed and expected design strength calculated according to current design specifications. In particular, the design procedure of such connections neglects the influence of the out-of-plane deformation of the supporting girder web on yielding and inelastic buckling of the shear plate. These are the main governing failure modes for the full-depth configurations of stiffened extended shear tabs, when placed on one side of a supporting girder or column. The research described in this paper aims to develop a better understanding of the load transfer mechanism and failure modes of extended beam-to-girder shear tab connections. The findings are based on finite element (FE) simulations validated with full-scale experiments on beam-to-girder shear tab connections. The influence of girder web flexibility on the behaviour of single-and double-sided shear tabs is assessed. The stiffened portion of the full-depth extended shear tabs yielded due to the interaction of horizontal shear and vertical axial force. Due to the flexibility of the girder web of the single-sided shear tab, its stiffened portion experienced much larger vertical axial force in comparison to that of the double-sided configuration.

03.36: Skewed extended shear tab connections: Behavior, analysis and parametric study

ABSTRACTThe objective of this study is to investigate the behavior of skewed extended shear tab connections with different support conditions: In which plate (shear tab) is welded to supporting member webs (flexible supports). And with the plate is welded to the supporting member flanges (rigid supports). The finite element analysis software ABAQUS was used to model different configurations for these connections. It was concluded that the connection orientation have significant effect on the connection torsional stability for the case with flexible supports. And there is a need to develop a unique design procedure for these connections. A parametric study was performed to develop a design procedure for skewed extended shear tab connections based on results obtained from finite element analysis for 300 models with different configurations. The variable parameters used for this study are: plate thickness, the a‐distance between the weld line and the bolt line, skewed angle, and number of bolts. These parameters were investigated in terms of the connection vertical displacement, plate twist along the bolt line, plate twist along the weld line, and the connection shear capacity. Modifications to the current connection lateral stability checks in the literature will also be addressed. The proposed design procedure on this study is specific procedure for the skewed extended shear tab connections. This procedure is compared with the current design procedure in the AISC Manual 14th edition.

Parametric Study and Design Procedure for Skewed Extended Shear-Tab Connections

Parametric Study and Design Procedure for Skewed Extended Shear-Tab Connections

Behavior of conventional and enhanced gravity connections subjected to column loss

Gravity frames in steel buildings use simple connections designed to support gravity loads primarily in shear. Under column loss scenarios, large axial loads several times the shear demand can develop at these connections. Recent work has shown that these connections may not be capable of resisting these loads. In this paper, gravity connections studied experimentally under column loss scenarios are presented. Ten specimens of five different connection types were initially tested, including all bolted double angles, welded-bolted double angles, conventional and extended shear tab connections. Because the capacity of these connections was significantly below the required demand given by the ASCE 7 extreme event load combination (1.2D+0.5L), two enhanced connections were developed and tested. These two connections consisted of a shear tab and a double angle connection, both reinforced with tension plates connecting the beam flanges to the column flanges. Of these two connections, the enhanced shear tab was capable of resisting the required demand.

Behavior of skewed extended shear tab connections part II: Connection to supporting flange

It has been proven that the torsional behavior of the extended shear tab connections is affected by the connection orientation due to the additional torsional moment when the plate is welded to the supporting member web (flexible support) in Part I of this study. However, these connections may act differently when the plate is welded to the flange of the supporting member (rigid support). The goal of this study is to check the adequacy of this finding for skewed extended shear tab connections when the plate is welded to the supporting member flange (rigid support). The finite element software ABAQUS ABAQUS (2013a) [1] was used to simulate and study the behavior of orthogonal extended shear tab connections studied experimentally by Metzger (2006). The Finite Element Analysis (FEA) of these connections captured the same failure modes as the experiments. Moreover, additional failure modes were observed by the FEA such as shear yield of the plate, bolt shear, plate twist, and local buckling of the supporting member. After validating the models, the shear tab and supported beam in the orthogonal configurations were oriented at different angles to check the effect of the connection orientation on the behavior of these connections. It was observed that the supporting member contributes in resisting the additional torsional moment at the elastic level. However, this contribution significantly reduces with the increase of the connection shear force and becomes neglected at the plastic level. Additionally, the effect of the connection orientation on the torsional and bending behavior of these connections overall is insignificant. Thus, the modifications on the design procedure for the skewed extended shear tab connections with flexible support in Part I do not apply to these connections.

Behavior of skewed extended shear tab connections part I: Connection to supporting web

The objective of this study is to investigate the behavior of skewed extended shear tab connections in which plate (shear tab) is welded to supporting member webs (flexible supports). To achieve the study goals, Finite Element Analysis (FEA) for orthogonal configurations of extended shear tab connections were performed using the finite element software, ABAQUS. To validate the finite element models, the FEA results were compared with experimental results obtained from experimental investigation by Sherman and Ghorbanpoor [19]. Then, finite element models for skewed connections at different angles were created, analyzed and investigated. It was observed that skewed and orthogonal configurations have the same failure modes, however, the shear tab's twist increases with increased connection orientation due to additional torsional moment transferred from the supported beam to supporting member. Additionally, it was observed that the connection's vertical displacement slightly decreases as connection orientation increases. Relationships between the shear tab twist and skewed angle as well as and the shear tab vertical displacement and the skewed angle were investigated. It was observed that plate twist-skewed angle relationship can be represented using a linear equation. This equation can be used to relate the shear tab twist of skewed and orthogonal connections. Finally, the shear tab's torsional strength equation in the American Institute of Steel Construction (AISC) manual 14th edition [4] was modified to consider the additional torsional moment added to the shear tab due to the connection orientation.

Investigation of Structural Steel Webs for Punching Shear

Shear tab connections or simple connections are widely used in structural steel structures. There are several limit states associated with these connections such bolt shear, bolt bearing, block shear, shear yielding and shear rupture. A modified version of the shear tab has been developed during the last decade, which is extended shear tab connections. In developing design provisions for the extended shear tab connections, experimental work showed that there are additional limit states other than those mentioned above that limit the capacity of the extended shear connection. Extended shear tab connections could be used to frame beam-to-column or beam-to-girder. In the case where a beam is framed into girder, a new limit state develops in the web of the supporting girder. This limit state is punching shear of the supporting girder web which is due to a higher moment. The higher moment in extended shear tab connections is due to the larger moment arm (eccentricity) from the bolt line, the location of the shear force, to the support, which is in this case the girder's web. This study investigates the supporting girder web using experimental work, finite element analysis, and yield line theory. This paper shows the result of this investigation and proposes an evaluation of the web capacity equation which should be used when calculating the beam-to-girder connection capacity.

Numerical study of unstiffened extended shear tab connections

This paper presents the results of a numerical study on the behavior and strength of unstiffened extended shear tab connections using finite element modeling. The model was verified with the experimental results reported in the literature. The parameters studied included the web slenderness ratio of supporting member, distance between the center bolt line and weld line, plate thickness, number of bolts, double-row of bolts, and beam lateral restraint. Results were analyzed to determine the effects of these parameters on the behavior and bolt shear strength and also used to assess the effectiveness of the AISC manual 2011 design procedure. It shows that the AISC design procedure for bolt shear fracture was overly conservative for extended shear tab connections with number of bolts less than 6 in a single row configuration. For connections with 6 bolts or higher or double-row bolts, the AISC design procedure provided reasonably good estimate. When the AISC design procedure was used but in combination with the finite element determined effective eccentricity, the estimate on bolt shear strength was markedly improved, especially for connections with less than 6 bolts in a single row configuration.

The Analyses of Extended Shear Tab Steel Connections Part II: Stiffened Connections

The objective of this paper is similar to the companion paper published in the same issue of the Engineering Journal, to develop a viable, comprehensive 3-D finite element model capable of predicting the nonlinear behavior of shear tab connections, except this paper addresses in detail the analyses and failure prediction of the stiffened shear tab connection versus the unstiffened connections discussed in Part I. Correlation between the results of the computational finite element method and the experimental investigation is established and verified. Past experimental investigations have shown that the unstiffened shear tab connections are prone to twisting failure and low load-carrying capacity. Therefore, the use of stiffened shear tab connections is a viable design approach to overcome these problems. This paper compares various predicted failure modes from a finite element analysis with those observed in a recent experimental study performed by Sherman and Ghorbanpoor. In this paper, three, six, and eight-bolt stiffened extended shear tab connections are analyzed and compared. In addition, five FE models of 2-bolt and deep connections are analyzed in the plastic range to predict their failure modes. These models are two-bolt beam-to-column, 10-bolt beam-to-girder connection, 10-bolt beam-to-column connection, 12-bolt beam-to-girder connection, and 12-bolt beam-to-column connection.The three- and the five-bolt connections failed primarily in shear yielding, bearing failure of the holes around bolts, and in bolt shear. Secondary failure was observed in the form of girder web mechanism and shear tab twist. The eight-bolt connection failed primarily in bolt shear and bearing of holes around bolts. The failure modes predicted by the FE analysis were in agreement with those from the experimental investigation. The locations of high plastic strain, bearing failure of holes, plate twisting mechanism, and the web deterioration were identical in the FE model and the experimental observations. The FE model generated in this analysis proved to be accurate in predicting the failure mechanism of the extended shear tab connections.

The Analyses of Extended Shear Tab Steel Connections Part I: The Unstiffened Connections

The objective of this paper is to develop a viable, comprehensive 3-D finite element model capable of predicting the nonlinear behavior of unstiffened extended shear tab connections building on the experimental investigations of Sherman and Ghorbanpoor. In order to overcome the limitations and the extensive and expensive demands required by the experimental investigation, the development of a computational model to validate and expand on the experimental results is merited and presents a powerful tool in examining the actual structural behavior. It presents the opportunity for the analyst and the designer to investigate full field results output for all the structural members. The model allows the examination of a wide range of connection types, configurations, materials, and loadings. The paper also identifies and presents important relevant parameters that are crucial in making the finite element (FE) analysis possible. The FE model is intended to validate the existing experimental results and to predict the behavior of deeper connections without the need for further expensive experiments. This model presents a viable modeling procedure to effectively account for contact behavior, bolt tensioning and nonlinearity. Analysis of surfaces in contact requires special numerical techniques due to the inherent nonlinearity. Parameters such as coefficient of friction, bolt pre-tensioning, and surface stiffness must be considered to achieve proper contact between the surfaces. In this paper two 3-D FE models, having 3-bolt and 5-bolt unstiffened extended shear tab connections are constructed. The 3-bolt connection failed primarily in column web mechanism failure mode with bolt shear and twist of the shear tab as secondary failure modes. However, the 5-bolt connection failed primarily in twisting of the shear tab, while column web mechanism and bolt shear were the secondary failure modes. The web mechanism failure mode is due to the punching of the shear tab into the web of the column, resulting in high plastic strains and permanent deformation in the web.