Column Web Research Articles

Behavior of Extended Single-Plate Shear Connections Subjected to Combined Shear and Compression Forces Using Finite Element Analysis

Extended single-plate shear connections can be subjected to compression loads in addition to shear loads during extreme events like wind and earthquakes. However, the existing interaction equations found in the AISC Steel Construction Manual, in literature, and in design examples—which are being used in design for combined loading cases—have not been formally validated for use by experimental testing or finite element analysis. This research aims to study the behavior of these connections when subjected to combined loading of shear and compression force by performing a nonlinear finite element analysis in ABAQUS. The variables considered in the study are column web stiffness, connection configurations, and different bracing conditions of the beam. The results from these analyses were compared to the available interaction equations in the AISC Manual and in literature to assess their applicability under different conditions. Shear-compression interaction plots were generated from the results that show the shear strength decreases with an increase in compression force in the connection. The effect of the compression force on the shear strength depends on the column web’s rigidity and the bracing condition of the beam.

Numerical and experimental verification of column web in transverse compression

This paper focuses on the problem of steel members of open double symmetrical cross-sections in transverse compression. First, the problem is introduced with examples of its application in steel structures of buildings and followed by the overview of selected substantial literature resources and current design codes provisions. The essential part of the paper is a presentation of results of experimental tests and advanced numerical analysis of members subjected to selected cases of transverse compression. Where possible, the results are compared with resistances obtained using provisions in currently valid design codes for steel structures. The influence of selected parameters on the resistance in transverse compression is quantified within the evaluation with specific attention paid to plate buckling of the web. Based on data obtained from the experimental and numerical investigations, the most notable findings are summarized.

Experimental and numerical research on seismic behavior of end-plate connection beam-column joints considering concrete floor effect

With the aims to study the seismic performance of the end-plate connection (EPC) joint with concrete floor, four full-scale specimens with different configuration (two specimens in major direction, and the other in minor direction) of the pseudo-static cyclic loading tests were conducted. Based on the failure criteria, the mechanical behaviors and failure modes of the specimens were investigated, including major and minor connection directions. The hysteresis response, bearing capacity, stiffness evaluation, and energy dissipation of the specimens were evaluated, and with a average ductility coefficient value of all specimens is about γ = 4.0. Meanwhile, to analyze and verify the accuracy of experimental results, the nonlinear models of the specimens were performed in ABAQUS software. In addition, a series of parametric analysis were performed to study the influence of axial compression ratios, thickness ratios (the ratio(η1) of end-plate thickness to column flange thickness, and the ratio(η2), of end-plate thickness to column web thickness), and concrete compressive strength on the joint seismic performance. This parametric analysis result indicates that increasing the thickness ratio and concrete compressive strength reasonably can effectively improve the seismic behavior of the overall joint with the concrete floor, especially in minor direction joints.

Tensile behavior of novel column-to-column connection for modular steel construction using high-strength bolts

As an important aspect of the city upgrade plan, installing the elevators for existing multi-story residential buildings means a lot to the residents of the higher floors, especially for old people. To minimize the site disruption and overcome the space limitation of installation, the modular elevator shafts have been widely adopted. The external wall decoration panels are normally pre-installed on the elevator shaft frame elements in the workshop, which makes it difficult for the connection between upper and lower segments using the high-strength bolts due to very limited space for applying the pre-tension. A novel column-to-column connection is presented in this study, consisting of an end plate, web opening of column web and strengthening plate at each of the column end. The tensile behavior of the proposed connection is first investigated through an experiment. Subsequently, a detailed finite element model is built and verified using the test results, with which a parametric study is conducted with the main parameters considered. Finally, a simple analytical solution for predicting the design load of the proposed connection is developed employing the yield line theory. Comparisons with the finite element results indicate the high accuracy of the proposed solution. The presented connection is believed to be a good solution for the on-site connection between H-columns of highly assembled modular structures, not limited to the elevator shafts.

Seismic Performance of Wall-Type Concrete-Filled Steel Tubular Column to H-Beam Connections with Internal Diaphragms

This study introduces a new internal diaphragm joint to connect steel beams with wall-type concrete-filled steel tubular (WCFST) columns. This study combines experimental research with numerical simulations for analysis. Firstly, one full-scale test specimen was designed and subjected to cyclic loading. The obtained failure mode and hysteresis curves illustrate that the joint specimens exhibit ample energy dissipation capacities. Subsequently, a reliable FE model was obtained based on experimental verification, and parametric analysis was conducted. The findings indicate that axial compression ratios critically affect the load-carrying capacity and displacement at failure, with a 2% reduction in capacity for each 0.1 increment in the ratio. The thicknesses of the column web and flange in the joint area are recommended to be 0.85 to 1.2 times and 1 to 1.2 times the beam flange thickness, respectively. The length of the internal diaphragm is advised to be between 0.2 and 0.3 times the width of the cross-section. Overall, these results significantly enrich our understanding of WCFST systems and will inform future design and construction best practices.

Large displacement model for the nonlinear behaviour of the face plate component

This paper deals with the face plate component in steel joints and addresses the full characterization of the nonlinear behaviour of the face plate component. An equivalent beam strip model is proposed that tackles the connection of a beam to the column web of open I-sections in a minor axis joint or the face of tubular columns, covering endplate or fin plate joint typologies. Closed-form analytical solutions are obtained for the elastic large displacement and the elastic-plastic large displacement behaviour of the equivalent beam strip. Criteria for the establishment of the design resistance using the continuous strength method are also proposed. It was concluded that the model is easy to apply, was validated against a large parametric study using finite element beam models, leads to accurate solutions and demonstrates the need to consider membrane effects in design.

An Investigation on the Seismic Behavior of the End-Plate Connection between a Steel Beam and the Weak-Axis of an H-Shaped Column Using a U-Shaped Connector

The seismic behavior of the end-plate connections between a steel beam and the weak axis of the H-shaped steel column using a U-shaped connector was investigated using numerical analysis. Finite element (FE) models were established using ABAQUS 6.14 software, and the applicability of the modeling approach was verified by comparing the numerical results with the relevant experimental results. This parametric study of the joint was carried out to analyze the effects of the thickness of the U-shaped connectors, the thickness of the end-plates, the axial compression ratio of the columns, and the linear stiffness ratio of the beam to the column. The results show that the U-shaped connector set in the weak axis of the H-shaped column can form a box-shaped panel zone with the column flange and web. The volume of the panel zone and its resistance to shear deformation are increased through this connection. Finally, the recommended reasonable ranges for the thickness of the U-shaped connector, the thickness of the end-plates, the axial compression ratio of the columns, and the linear stiffness ratio of the beam to the column are proposed in this paper.

Improving a Conventional Connection of Beam-to-Weak Axis of H-shaped Column to Modify Load Path in Panel Zone

This study aims to propose an improvement to the conventional connection of beam-to-weak axis of H-shaped columns with in-plane load paths and to compare the improved connection with the conventional one. The conventional connection detail consists of continuity plates and face plates, while the improved connection detail, in addition to the previous components, has a plate perpendicular to the column web (middle panel zone) acting as a panel zone. A numerical study using ABAQUS was conducted, and the study results showed that the most appropriate value for the middle panel zone thickness is equal to the column flange thickness, and it should be designed for 30% of the force demand induced by the beam bending moments. Furthermore, the study findings indicated that the proposed connection resulted in an average of 59.5% decrease in the force demands induced to the panel zone in comparison with the conventional connection. In addition, it was observed that the force demand on the face plate experienced the most decrease due to reducing the out-of-plane performance of the face plate in the improved connection models. Moreover, the results showed that the improved connection models experienced lower levels of von Mises stress, approximately 35.7% less than the conventional connection models.

Welded beam-to-column steel joints: Assessment of European design rules

Properly validated high-quality Finite Element (FE) models with experimental tests permit an accurate description of the load-deformation path and stress state of steel joints and are nowadays accepted as “experimental results”. Changes to the design of welded joints in Eurocode 3 are currently proposed that affect the resistance and stiffness of the components associated with the column web panel. This paper presents an assessment of the design formulations included in the current Eurocode 3, part 1–8, and its forthcoming update in terms of stiffness and moment resistance, compared against a large parametric study of strong-axis beam-column welded joints for open sections carried out using validated sophisticated FE models. The results show that both the old and new Eurocode formulations provide a large scatter and no big differences between both methods. Additionally, the presence of axial force in the column shows a clear increase in the ratio between design resistance vs numerical resistance that, particularly in the case of transversally stiffened joints, may be unconservative.

A novel analytical formulation for the stiffness of the component column web panel in shear with additional plates in bolted steel joints.

Given that the stiffness of joints has an important influence on the global behavior of steel structures, considerable efforts have been made to develop methods to characterize their behavior. In the component method, that is adopted by Eurocode 3, one of the most relevant components is the column web panel in shear; however, this component has never been the subject of research when additional plates are welded between the column flanges to attach the secondary beams to the minor axis of the column. This paper proposes a stiffness formulation for the component column web panel in shear with additional plates, taking into account the stiffening contribution of these additional plates. To archive this, four experimental tests of beam-to-column joints were carried out, a finite element model was calibrated with the experimental data by comparing moment-rotation and moment-deformation curves, a parametric study of sixty different configurations was performed with the calibrated finite element models to obtain the stiffness of the component column web panel in shear and the initial stiffness of the joint. Then, the proposed stiffness formulation for the component was validated with the results of the parametric study, obtaining a very good agreement. Finally, a compilation of the stiffness formulation of all the components of the joint type extended end plate with additional plates was made and validated, when comparing this analytical stiffness with the initial stiffness of the joints of the parametric study, satisfactory concordance was found.

NEW INSIGHTS INTO THE WEB PANEL COMPONENT

AbstractThe column web panel is a fundamental component of beam‐column joints. This component has been thoroughly studied and codified in the past. In this paper, new insight on its behaviour is obtained using a large amount of high‐quality Finite Element (FE) models, covering a wide range of panel slenderness and aspect ratios. The study shows that the existing models in part 1‐8 of the current and forthcoming Eurocode 3 present a wide scatter in terms of resistance and stiffness, being unconservative in some specific cases.

Test on seismic behaviors of stainless steel bolted extended end-plate beam-column joints

This study conducted tests on the seismic behavior of austenitic stainless steel bolted extended end-plate beam-column joints, which have been few reported. Considering the influence of material type, end-plate thickness, bolt diameter, panel zone thickness, and loading scheme, 11 stainless steel joints and two carbon steel joints were designed and tested. Material properties, joint failure modes, moment-rotation curves, bolt load distributions, and joint component yield sequences were reported in detail. Experimental research showed that the beam-column joints in austenitic stainless steel experienced four failure modes, i.e. plastic hinge at the beam end, fracture failure of weld between the beam flange and end-plate, bolt rupture failure, and composite failure. All the tested joints had good seismic behavior, with rotation capacity greater than 0.03 rad. The influence of joint configurations on the seismic behavior were analyzed. The results indicated that the end-plate thickness, end-plate stiffener, and bolt diameter had a substantial impact on the joint seismic behavior, while the thickness of column web in panel zone, material properties, and loading scheme had a comparatively small effect. The initial rotational stiffness and moment resistance(yield moment) of joint obtained from the experiment were compared with the predictions of the EN1993-1-8, Design Guide 16, and JGJ 82-2011. Comparisons indicated that the EN1993-1-8 overestimated the initial rotational stiffness; Both the EN1993-1-8 and JGJ 82-2011 underestimated the moment resistance, while the predictions from the Design Guide 16 were significantly higher than the moment resistance and closer to the ultimate moment.

Cyclic behavior of dual-steel beam-to-column welded flange-bolted web connections

Cyclic loading tests on dual-steel beam-to-column welded flange-bolted web connections were conducted to quantify their moment resistance, plastic deformation and energy dissipation capacities. The test program consisted of five one-sided connection specimens, where Q355 grade beams and Q690 grade columns were used, to study the effects of beam-to-column welded flange connection details and panel zone shear strength on the connection seismic performance. Two types of welded connection details were considered; one was the traditional complete-joint-penetration (CJP) welded connections by use of backing bars, and the other type was those with the bottom backing bar further reinforced by a fillet weld. Three column web thicknesses were designed to arrive at strong, intermediate and weak panel zones, respectively. It was found that the CJP weld with the backing bar reinforced only under the bottom beam flange produced satisfactory performance and accommodated plastic rotations larger than 0.03 rad, while a maximum plastic rotation of 0.04 rad could be developed in the high-strength steel panel zone before fracture occurred. These results evidenced that those dual-steel connections could still sustain high seismic deformation demands.

Study on seismic performance of tapered castellated steel member portal frame

Low-cycle reciprocating loading test is applied to a tapered castellated steel member portal frame to study its seismic performance. Moreover, 52 finite element models are utilized to analyze the effects of the opening ratio of the beam web, the opening ratio of the column web, and the taper ratio of the beam on the failure mode, hysteresis curves, ductility, and energy-dissipating capacity of tapered castellated steel member portal frame. The results show that tapered castellated steel member portal frame can realize the failure mode of the plastic hinge at the beam end. The ductility coefficient of the specimen is between 4.78 and 5.49, and the maximum equivalent viscous damping coefficient is 0.146, indicating that the structure offers good ductility and energy-dissipating capacity. When the opening ratio of the castellated beam web is 60–70%, and the taper ratio of the castellated beam is less than 1.4, the structure exhibits good seismic performance. As castellated beams and columns have different stiffness values due to different web opening ratios, this study proposes an equivalent beam–column linear stiffness ratio to satisfy the seismic performance design requirement of “strong columns and weak beams” for tapered castellated steel member portal frame. A method is also devised to calculate the equivalent stiffness of tapered castellated members. Comparing the predictions of this method with experimental results reveals that its maximum error is 7.66%, indicating its high precision. It is recommended that the equivalent beam–column linear stiffness ratio of tapered castellated beam–column portal frames should be higher than 2.735. On this basis, an opening ratio of the castellated column web ranging from 50% to 70% has a negligible effect on the seismic performance of the structure.

Finite Element Analysis and Parametric Study of Panel Zones in H-Shaped Steel Beam–Column Joints

This paper investigates the mechanical properties of a traditional welded rigid joint with a weakened panel zone under seismic load. The created finite element model is calibrated by the high-strength steel joint test, carried out by the team in the early stage, and the effectiveness of the finite element method was verified. The finite element software ABAQUS is used to investigate the influence of different joint web thicknesses on the mechanical properties of middle column joints under a low-cyclic-loading test. Supported by a validated numerical model, the ductility, energy dissipation, and other properties of different thicknesses of panel zone column webs are carefully analyzed. The results indicate that the thickness of the web plate in the panel zone significantly affects the location of the joint plastic hinge. The ultimate loading capacity of the joints increased significantly with an increase in the thickness of the webs in the panel zones. Compared with the joint with a weakened panel zone, the hysteresis curve of the strengthened joint is fuller; meanwhile, it cannot alleviate the stress concentration at the weld holes of the web. When the thickness of the joint domain web is too weak, excessive deformation in the joint domain will lead to a decrease in the bearing capacity of the joint, causing damage. The stiffness degradation coefficient of the web-thickened specimen was found to be dominated and controlled by the stiffness of the beam; however, with an increase in the thickness of the web, the stiffness degradation coefficient remained basically unchanged. Finally, a recommendation for weakened beam–column interior joints based on the steel frame panel zone is made, which will lay a foundation for the simulation and analysis of the seismic performance of this structure.

Experimental investigation of steel beam-to-column end-plate joints under static and impact loading

Events like blasts, vehicle impacts, gas explosions, or terrorist attacks can induce dynamic structural responses. Traditional design practices focus on structures' static or quasi-static behavior, neglecting dynamic effects. However, the response of structural members and joints under dynamic loading can differ significantly from that under static loading. For instance, the mechanical properties of steel, such as yield strength and tensile strength, exhibit variations depending on the strain rate. Experimental impact load tests of members and connections are needed to validate FEM models, but a very limited number of such tests have been presented in the literature. This article presents experimental static and impact tests of double-sided extended steel bolted end-plate joints. The tests were carried out on three identical steel specimens of a beam-to-column system, with static tests on one specimen and impact tests on two other specimens. A free-falling concrete-steel package was used as the impact load, with varying values of its weight and the height of the fall. The structural responses of the joints and selected components were measured using advanced measuring equipment for experimental static and dynamic tests. In both static and impact tests, significant deformation of the connection elements, especially the column and end-plate, was observed. Moreover, local buckling appeared in the compression zone of the column web as well as fracture of the end plate below the lower flange of the beam. Based on the results of the deformation measurements, the actual strain rate and dynamic increase factor (DIF) were obtained.

Experimental study on seismic behavior of cover-plate connections between steel beams and high strength steel box columns

As one of the beam-to-column fully restrained connections that could shift the plastic hinges of the beam away from the face of the column, cover-plate reinforced connections are expected to be a practical choice for high strength steel frame seismic applications. Five cover-plate reinforced and one unreinforced welded flange-bolted web connection specimens combined with Q355 steel I-shaped beams and Q460 or Q690 steel box columns were designed according to Chinese codes and tested under cyclic loads at full scale. Failure modes, including local buckling of the beam, complete joint penetration (CJP) weld fracture, and column web fracture, were reported. The strength, stiffness, deformation, and energy dissipation features were analyzed. The four cover-plate connections met the AISC requirements for special moment frames (SMF) with maximum story drift angles greater than 0.06 rad and exhibited satisfactory seismic behavior. According to the test results, a limit on the ratio of the diaphragm plate to column plate thickness should be considered when the electroslag welding (ESW) process is used in high strength box columns. The strong panel zone designed with a panel zone resistance ratio (γpz) greater than 1.20 was recommended for box columns with steel strength no less than 690 MPa. Additionally, other design implications of the results were discussed.

Column web component under out‐of‐plane loading: experimental and numerical studies

AbstractCharacterization of the column web under out‐of‐plane tension or compression (CWOP) is required for the application of the component method to the design of joints in which a beam is directly attached to a column web (open sections) or face (hollow sections). This component, however, is neither covered by the current version of the Eurocode EN 1993‐1‐8 (2005), nor its ongoing revision. While several researchers have worked on characterizing the column faces, primarily in welded tubular section connections, only a few studied the component in open sections. A set of experimental campaigns are currently underway at the University of Coimbra to characterize the resistance and stiffness of connections bolted to the webs of hot‐rolled and welded columns. The current paper highlights the experimental results of two tests and calibration of their numerical models.

Experimental comparison between threaded‐bars and single‐bolts end plate asymmetrical steel joints

AbstractEnd plate beam‐column bolted joints are widely used in the field of steel structures. The usual configuration consists of individual bolts that join the end plate of the beam with the column flange. Usually, the use of stiffeners is needed in this type of joints, in order to reinforce the tension and compression zones of the column web, and to avoid local buckling problems.This configuration, applied to asymmetric connections, gives rise to the appearance of shear stresses in the column web, even with symmetric loading conditions on both sides of the connection.The method proposed in this work to improve the behavior of end plate asymmetrical steel joints, without using welded stiffeners (which significantly increases the cost of the joint), consists in using threaded bars as joining elements, instead of single bolts. Threaded bars have several purposes: to create the joint itself, to reinforce the tension and compression zones, and to reduce the shear stresses in the column web panel.In the present work, two end plate steel joints made up of an HEA200 column, and IPE200 and IPE300 beams have been tested. One of them with threaded bars with double nuts (internal and external) in the traction and compression zones, and the other one with single bolts.Symmetrical forces have been applied at the ends of the beams, subjecting the joints to symmetrical bending moments on both sides of the connection. The tests have been instrumented through the use of load cells, displacement sensors and inclinometers. The results show an important increase in the stiffness and the resistance of the joint with threaded bars, compared with the single bolts joint.This work will serve as the basis for the calibration of the corresponding finite element models, and the subsequent parametric study of this type of joints.

Hysteretic behaviour of welded connections with highly inelastic panel zones

AbstractThe current practice in capacity‐designed steel moment resisting frames (MRFs) worldwide allows for limited shear yielding in the column web panel zone. As such, inelastic deformations concentrate near the beam ends, thereby leading to flexural strength deterioration due to local buckling often at modest lateral drift demands. Experiments on post‐Northridge welded connections suggest that prior to a story drift angle of 5% rad, panel zone kinking does not induce fracture for panel zone shear distortions of up to 10γy. Within such a context, this paper presents an alternative design of a welded moment connection with highly inelastic panel zones. The connection features simplified weld details including a customised beveled backing bar that can be kept in place after the completion of the complete joint penetration welds at the beam flange‐to‐column flange joint. Full scale experiments suggest that the hysteretic response of the connection remains stable up until a story drift angle of 8% rad. The specimen did not exhibit visible structural damage prior to story drift angles of 4% rad, which are characteristic to a maximum considered earthquake. Modest local buckling occurred near the beam ends only after a story drift angle of 5% rad, which is a typical drift threshold in current collapse assessment methodologies. This paper summarises the primary findings of the experimental program for one of the test specimens.