End-plate Moment Connections Research Articles

Experimental and numerical investigation of the bending behavior in nontraditional steel beam-to-beam tip connections

This study aimed to conduct combined experimental testing and numerical studies on the static performance of tip beam-to-beam flush endplate moment connections. The research parameters considered were bolt layout, diameters, and end plate thickness. Three specimens consisting of two IPE 300 beams connected to a beam of section HEA 300 using two end plates were designed and assembled with different bolt configurations. The grade of the steel elements was S235, while that of the bolts was 8.8. A monotonic load was applied to the specimen during testing, revealing failure modes such as fractures in bolts, end plate bending, and necking loosening of bolts. The study presented and discussed the moment rotation relationship, rotation capacity, and initial stiffness for the three specimens. A finite element (FE) model was constructed based on the moment-rotation curves of the tested connections, and the numerical and experimental results showed good agreement. An extensive parametric study was conducted to investigate the effect of different end plate thicknesses and bolts of various diameters and configurations on the connection's behavior. The study revealed that increasing the bolts' row number in tension rather than increasing the number of bolts in a row significantly affects the ultimate capacity and ductility of the connection. A thick end plate increases the connection's rotation capacity but decreases its ductility. The study also introduced a simple approach based on virtual work to predict the connections' bending stiffness using load and deflection results.

Four-Bolt Unstiffened End-Plate Moment Connections with 36-in.-Deep Beams for Intermediate Moment Frames

Previous testing has shown that four-bolt extended, unstiffened end-plate moment connections can be used with beams up to 24 in. deep and develop sufficiently ductile performance to satisfy seismic qualification. It is desirable to extend this depth limit to allow deeper beams for intermediate moment frames. Three moment connection specimens using built-up 36-in.-deep beams with a four-bolt extended, unstiffened end-plate moment connection were tested to determine if they satisfy the intermediate moment frame qualification criteria given in AISC 341-16 (2016a). The web of the specimens satisfied the moderately ductile section criteria for web slenderness, which is required for intermediate moment frames, but not highly ductile section criteria required for special moment frames.
 All three specimens passed qualification criteria for intermediate moment frames (IMFs) as given in AISC 341-16 by retaining at least 80% of the nominal plastic moment strength through 2% story drift. The observed failure modes included lateral torsional buckling of the specimen, flange local buckling, net section fracture of the beam flange, and failure of the beam flange-to-beam web fillet weld. The results of these tests support current moderately ductile limits associated with lateral bracing and cross-section slenderness, given that the associated specimens reached IMF qualification criteria but not special moment frame (SMF) criteria. It was concluded that four-bolt extended, unstiffened end-plate moment connections satisfy intermediate moment frame requirements with a beam depth of 36 in. and that a modification is needed for beam web to flange welds in built-up sections near the moment connection.

Strong column-weak beam relationship of 3D steel joints with tubular columns: Assessment, Validation and Design proposal

The study of moment connections in steel structures subjected to cyclic loads has been extensively studied, providing a great number of requirements, including the strong column-weak beam relationship, to guarantee a satisfactory cyclic performance. However, investigations on the cyclic performance of moment connections considering the bidirectional and axial load effects simultaneously with tubular columns are limited. This study aims to assess and validate the strong column-weak beam relationship of 3D steel moment connections using reduced order models. The simplified model (reduced order model) approach was employed to extend the range of beam and column elements sizes and reduce the experimental and computational costs. These models were calibrated from full-scale experimental studies. A great number of configurations with different beam and column sizes without loss of reliability and structural representativeness of the studied phenomenon were studied. A total of 13640 simplified models were developed. Results show a cyclic behavior controlled by the strong column-weak beam relationship to modify the joint's failure mechanism. The increasing of strong column-weak beam relationship and the biaxial effect caused degradation of the strength and stiffness as well as in dissipated energy. An optimal strong column-weak beam relationship was obtained for all joint configurations analyzed. Finally, a robust design procedure is proposed, ensuring the cyclic behavior of end-plate moment connection with built-up box column including biaxial effect and axial load. Therefore, the use of this type of moment connection can be used in special and intermediate moment frames designed according to Seismic provisions.

Alternative Design of Menara 17 Structure in Surabaya with Castellated Steel Beam

Assigning structural material is one of critical step in designing, steel material often used because of it high ductility. Menara 17 is a 17 storey multipurpose building with reinforced concrete as an existing material structure. This research analyze Menara 17 alternative design with Special Moment Frame (SMF) steel structure to resist lateral load with high ductility and expected to withstand significant inelastic deformation. Castellated beam is used to increase it capacity to weight ratio and ease MEP installation through the opening. SNI and AISC is used for main design guide. From the analysis result, the alternative design has satisfy criteria of irregularity, P-delta effect, story drift, and Strong Column Weak Beam. Honeycomb castellated beam HCO 520.250.9.14 profile is used as main beam. King-cross column KC 800.400.16.30 profile is used as main column. Circular hollow section CHS 406,4.40 profile is used as diagonal bracing. Wide flange WF 200.200.8.12 profile is used as lateral bracing. Lateral bracing to beam is connected with shear connection. Beam to column is connected with endplate moment connection. Menara 17 design with steel structure is 59,17% less heavy than reinforced concrete structure.

Semirigid Bolted Endplate Moment Connections: Review and Experimental-Based Assessment of Available Predictive Models

Semirigid Bolted Endplate Moment Connections: Review and Experimental-Based Assessment of Available Predictive Models

Cyclic Response of Sloped Extended End-Plate Moment Connections

Bolted extended end-plate (BEEP) moment connections are extensively recommended in design standards to be used as a prequalified beam-to-column connection in steel portal frames and special moment frame buildings. These standards assume that in such a connection, the beam is perpendicular to the steel column or that the slope angle of the steel beam is very small. To expand the engineering applications of BEEP connections in large-slope angle buildings, in this study, three one-sided specimens at half scale with 0°, 15°, and 30° slope angles, respectively, were designed and tested under cyclic loading. All dimensions of these specimens were identical, except the slope angles of their steel beams. The experimental results showed that the maximum rotation angles of these sloped BEEP connections exceeded 0.05 rad, and they were remarkably larger than those of other types of sloped rigid-moment connections tested by Mashayekh and Uang. However, the force concentration that occurred in the flange at the heel location was similar to that observed by them, and it led to the development of brittle fractures. Particularly, with the increase in the slope angle, the force concentration tended to become more severe. Three strengthening schemes for reducing the force concentration and enhancing the deformation capacities of the sloped BEEP connections subjected to the extremely rare earthquake, i.e., less than 2% probability of exceedance in 50 years, were evaluated using the finite element approach. These were Scheme I: stiffening the rib in the acute-angle zone, Scheme II: employing a reduced beam section (RBS) connection, and Scheme III: forming a curved web cut in a non-RBS beam. The analytical results showed that the three schemes decreased the von Mises stress level in the acute-angle zone of the connection web. Scheme I enhanced the initial rotation stiffness, flexural strength, and deformation rotation capacity. For Scheme II, a RBS configuration was employed, which effectively improved the connection rotation capacity, whereas it decreased the flexural strength of the sloped BEEP connection. Scheme III without a reasonable design led to a degradation of the hysteretic performance, moderate rotation capacity, and low flexural strength. Therefore, Schemes I and II leading to much better seismic behavior than Scheme III are recommended.

Cyclic Behavior of Bolted Stiffened End-Plate Moment Connections for Different Bolt Pretensioning Levels: An Experimental Study

Bolted stiffened end-plate moment connections are one of the most usable connections used as a prequalified connection in special steel moment frames. According to the AISC design code, this connection can be considered one of the most important parts of moment resisting frames with enough bolt pretension levels. In this paper, using three full-scale bolted stiffened end-plate moment connections designed according to AISC, the effects of bolt pretension levels have been examined experimentally under SAC cyclic-loading protocol. Bolt pretension level has been defined as α coefficient to show pretensioning level in three specimens. The bolts of the first specimen are not pretensioned, called snug-tightened bolts, and are reference connections. The bolt pretension level of the second and third specimen is created in accordance with the AISC design code and more to Fu of bolts, called pretensioned and fully pretensioned, respectively. The bolt’s moment capacity, total energy absorption, initial rotational stiffness, and ductility of connection as well as stress and strain variation have been investigated. According to the results, increase in bolt pretension level would significantly improve the cyclic behavior of connections. Furthermore, an increase in bolt pretension led to the initiation of the inelastic deformation from a smaller rotation, and the ductility of the connection improved. In addition, the rate of growth in moment capacity and energy absorption in the pretensioned specimen was 8% and 9% compared with fully pretensioned, respectively. Note that the connection with bolt pretension level by design regulations in comparison with the reference connection can be considered as a connection of a special moment resisting frames where bolt pretension level higher than the value mentioned in the design code is better but not needed.

Artificial Neural Network–Based Predictive Tool for Modeling of Self-Centering Endplate Connections with SMA Bolts

Endplate moment connections with shape memory alloy (SMA) bolts provide self-centering for the seismic resilience of structures. Predicting the self-centering response of these new beam–column connections, which have not been codified yet, requires conducting experimental tests or detailed continuum finite-element simulations. Computationally efficient predictive tools are needed to facilitate the analysis, design, and assessment of self-centering connections and moment frames. In this paper, artificial neural networks (ANNs) are used to develop a MATLAB tool for predicting the moment-rotation backbone and self-centering response of extended endplate connections with SMA bolts. As the input for the neural networks, the predictive model development employs a design database of response parameters from 72 finite-element (FE) models and experimental tests of seven beam–column connection specimens. Neural networks are trained for seven response parameters, and the trained networks are used to develop a graphical user interface (GUI). The coefficient of determination for the trained ANNs is in the range of 0.92 to 0.99, indicating acceptable prediction accuracy. Furthermore, optimization studies using a multiobjective genetic algorithm are performed, seeking the minimization of material use (steel and SMA) and improved connection-response characteristics (i.e., stiffness, strength, and ductility). A phenomenological model of SMA connections is also developed in OpenSees. The use of the ANN-based predictive tool for accurate and efficient modeling of SMA-based connections and self-centering moment-resisting frames is illustrated. The computation time for predicting the moment-rotation response of a typical SMA connection is significantly reduced from seven hours in ANSYS to only three minutes in OpenSees while providing the same level of response prediction accuracy. Furthermore, the optimization results are confirmed by performing nonlinear pushover and response history analyses.

Cyclic Testing of Replaceable Steel Coupling Beams with Reduced Beam Sections and Moment End-Plate Connections

Cyclic Testing of Replaceable Steel Coupling Beams with Reduced Beam Sections and Moment End-Plate Connections

Finite element analysis of long bolted extended end plate moment connections in cold formed steel tubular sections

Finite element analysis of long bolted extended end plate moment connections in cold formed steel tubular sections

Finite element analysis of long bolted extended end plate moment connections in cold formed steel tubular sections

Finite element analysis of long bolted extended end plate moment connections in cold formed steel tubular sections

Bolt Pre-tension Effect on Performance of Bolted Extended End-plate Moment Connections under Cyclic Loading

The most important structural part of steel structures is the connections of the building frame. Tests conducted by the American Steel Institute have led to the introduction of prequalified connections, which is a good reference for designing connections in steel structures. In this paper, four bolted stiffened and unstiffened extended end-plate connections have been studied by numerical analysis with ABAQUS software. In this study, to examine the effect of bolt pre-tension rarely studied, a coefficient of pre-tension force, introduced based on the Iranian Steel Structures Design Regulations as well as the US Steel Design Regulations, has been considered. These connections have been modeled cyclically and in a displacement control manner. The cyclic behavior of the connections, dissipated energy, the resisting moment as well as the stress and strain distribution in the connection have been investigated. According to the results, by creating a pre-tension force in the bolts, the resisting moment of the connection would increase. The rate of growth of this resistance in the unstiffened connections was greater than that of the stiffened connections. The maximum increase in resistance was about 27% for the unstiffened connection and about 25% for the stiffened connection. The dissipated energy for the connections also increased with the increment of bolt pre-tension. The energy dissipation incremental rate was enhanced to a maximum of about 31% for the unstiffened connection and up to a maximum of about 24% for the stiffened connection.

Performance of extended end-plate bolted connections subjected to static and blast-like loads

In this study, numerical models were developed to predict the behavior of steel extended end-plate moment connections subjected to static and blast-like loading. Two types of extended end-plate connections were considered, stiffened, and unstiffened, with pretensioned bolts. The models were verified by comparing the results with published experimental data. The models were used to compute the moment-rotation curves for the connection under static loading, and then under different blast durations. The pressure impulse diagram and the energy dissipation for the connection under dynamic loading were determined. The failure modes were examined, and the numerical results were compared with the simplified models presented in codes and standards. Improvement in the performance of the connection by adding one or two stiffeners was demonstrated. For the configuration studied, introducing a stiffener increased plastic dissipation energy for blast loading by 45% compared to the unstiffened connection, whereas under static loading, the plastic energy dissipation for stiffened connection, SC2, was higher than the unstiffened connection by 30%. A conservative estimate for the dynamic increase factor (DIF) was found to be 1.2 for steel yield stress and 1.05 for bolt failure.

Extended end-plate connections for replaceable shear links

Extended end-plate moment connections are used in a number of applications including the beam-to-column connections in seismic moment resisting frames (MRFs) and replaceable link-to-frame connections in eccentrically braced frames (EBFs). While the extended end-plate connections have been extensively studied for MRF applications, little is known about their performance in EBFs. The loading conditions and the acceptance criterion are different for these connections when they are used in MRFs or in EBFs. This paper presents an experimental and numerical study undertaken to investigate the performance of extended unstiffened and stiffened end-plate connections used in replaceable shear links. Pursuant to this goal, 10 nearly full-scale EBF tests were conducted where the thickness, width and stiffening of the end-plate were considered as the variables. The results showed that end-plates designed according to the AISC guidelines or Eurocode provisions show acceptable performance in terms of the target link rotation angle. Due to strain hardening effects, thinner plates than the ones suggested by the codes were also found to show satisfactory performance. Finite element simulations were conducted to investigate the bending strains for different plate thicknesses and to study the levels of axial forces developed in the links. Modifications to the AISC design guidelines have been proposed to determine the plastic resistance of end-plated connections more accurately.

Strength of extended stiffened end-plate bolted joints: Experimental and numerical analysis

The analysis of behaviour of extended one-sided stiffened bolted end-plate moment connection is revisited here. On the basis of experimental tests, the behaviour of beam-to-column joint with and without stiffener is investigated. The stress distribution and deformation characteristics were determined and discussed with corresponding results of finite element analysis of joint behaviour. Furthermore, the extensive finite element simulations were carried out and the obtained results are discussed in this paper. The main analyzed parameters are the geometrical characteristics of the plates added to the beam-to-column joint. Their influence on joint resistance and stiffness is observed including the possibility of material cost optimization. Overall, the comparison of used approaches confirms their conjoint importance except for the postulation where the stiffener is assumed to behave as a strut in the joint. Also, there are some practical recommendations in design which can be used by engineers.

The plastic and the ultimate resistance of four-bolt extended end-plate connections

Widely used design guidelines and specifications provide methods to calculate plastic resistance of end-plates considering yield line mechanisms. Experiments reported to date showed that the ultimate resistance of end-plates can be considerably larger than its plastic resistance due to strain hardening. Using the ultimate strength in design can be a viable and cost-effective option; however, limited studies exist on quantifying the ultimate strength. In this paper, a database of four-bolt extended end-plate moment connections was developed. The capacities of these connections were calculated using AISC Design Guidelines and EN1993-1-8. The results showed that the plastic resistances of connections are on average 29% greater than the capacities calculated using the AISC Design Guidelines. On the other hand, the test-to-predicted ratios were found to have an average of 1.08 for EN1993-1-8. The ratios of the ultimate resistance to the calculated plastic resistance are 2.07 and 1.73 for AISC and European approaches, respectively. A numerical study was undertaken to propose modified design expressions for the plastic resistance which are compatible with AISC Guidelines. Furthermore, the ultimate resistance of end-plates was quantified. Stiffened and unstiffened T-stub models were analyzed using the finite element method. Expressions based on yield line mechanisms were developed to calculate the plastic and ultimate resistance. The evaluations showed that the averages of the test-to-predicted ratios are 1.06 and 1.17 for the plastic and ultimate resistance respectively when the proposed expressions are used.

얇은 절곡단면을 사용한 콘크리트 충전형 합성부재를 위한 관통볼트 단부강판모멘트접합부의 거동

얇은 절곡단면을 사용한 콘크리트 충전형 합성부재를 위한 관통볼트 단부강판모멘트접합부의 거동

Cyclic Performance of End-Plate Biaxial Moment Connection with HSS Columns

This paper presents a numerical study on the seismic performance of end-plate moment connection between I-beam to HSS (hollow structural section) column stiffened by outer diaphragms (EP-HSS). In previous experimental research, this moment connection showed a satisfactory performance according to requirements established in Seismic provisions. However, one type of joint was studied and bidirectional and axial loads were not considered. In this since, several configurations representative of 2D interior joints and 3D interior and exterior joints in a steel building were modeled and subjected to unidirectional or bidirectional cyclic displacements according to protocol in seismic provisions. Firstly, a similar joint configuration was calibrated from experimental data, obtaining an acceptable adjustment. The assessment of seismic performance was based on hysteretic curves, failure mechanisms, stiffness, dissipated energy, and equivalent damping. The results obtained showed a ductile failure modes for 2D and 3D joint configurations with EP-HSS moment connection. The axial load has no significant effect on the moment connection. However, it affects the column strength due to the increase of the stresses in the column wall. Compared with 2D joints, 3D joints reached higher deformations even when a similar number of beams is used. The external diaphragms to the column panel zone provided rigidity in the joints and no degradation of slope for each loop in load/reload segment for elastic loop; therefore, curves without pinching were observed. All inelastic deformation is concentrated mainly in the beams. A moment resistance above 80% of the capacity of the beam at a drift of 4% is achieved in all joints. From the results reached, the use of EP-HSS moment connection with hollow structural section columns is a reliable alternative in seismic zones when steel moment frames are employed.

Bidirectional Response of Weak-Axis End-plate Moment Connections: Numerical Approach

Brittle failure mechanisms can affect the seismic performance of structures composed of intersecting moment resisting frames, if the biaxial effects are not considered. In this research, the bidirectional cyclic response of H-columns with weak-axis moment connections was studied using numerical models. Several configurations of joints with bidirectional effects and variable axial loads were studied using the finite element method (FEM) in ANSYS v17.2 software. The results obtained showed a ductile behavior when cyclic loads are applied. No evidence of brittle failure mechanisms in the studied joint configurations was observed, in line with the design philosophy established in current seismic provisions. However, beams connected to the column minor axis reached a partially restrained behavior. Joints with four beams connected to the column exhibited a partially restrained behavior for all axial load levels. An equivalent force displacement method was used to compare the hysteretic response of 2D and 3D joints, obtaining higher deformations in 3D joints with respect to 2D joints with a similar number of connected beams. Consequently, design procedures are not capable of capturing the 3D deformation phenomenon.

Closure to “An Unstiffened Eight-Bolt Extended End-Plate Moment Connection for Special and Intermediate Moment Frames” by Machel L. Morrison, Doug Q. Schweizer, Shahriar Quayyum, and Tasnim Hassan

Closure to “An Unstiffened Eight-Bolt Extended End-Plate Moment Connection for Special and Intermediate Moment Frames” by Machel L. Morrison, Doug Q. Schweizer, Shahriar Quayyum, and Tasnim Hassan