End-plate Joints Research Articles

Flexibility and Durability in End Plate Joints: Insights from Advanced Modeling and Simulation

Flexibility and Durability in End Plate Joints: Insights from Advanced Modeling and Simulation

Experimental and numerical study on extended endplate beam-column joints after high temperature to resist progressive collapse

This paper presents experimental and numerical investigations on the collapse-resisting behavior of extended endplate beam-column joints after high temperatures. The failure patterns and structural responses of extended endplate (EP) joints after high temperature to resist progressive collapse were first described, and then the effects of fire temperature and temperature duration on their collapse resistance mechanisms were also analyzed in detail. The test results demonstrate that all specimens withdrew from work owing to the serious deformation of endplate bolt holes or the brittle fracture of high-strength bolts, resulting in the catenary mechanisms of EP joints not being adequately developed. Compared with previous studies, it is shown that the fire temperature exerts the most significant effects on the carrying capacities and deformability of EP joints, and the collapse resistance of corresponding assemblies is most sensitive to the fire temperature. However, the temperature durations have an insignificant influence on the development of flexural mechanism resistance, especially for those after 600 °C and 800 °C. Moreover, the corresponding refined FE models in consideration of the damage and fracture of ductile metals have been established to reproduce the structural response of specimens after high temperature. To improve the post-fire collapse-resisting performance of assemblies, both the lateral plate reinforcement and welding reinforcement methods were proposed and compared with the assistance of validated FE models. From a practical viewpoint, the reinforcement with lateral plates is determined as a superior technique for post-fire EP joints against progressive collapse.

Experimental and numerical investigations of seismic performance of stepped beam-column joints with different connection forms

The seismic resilience of prefabricated steel structures significantly depends on the design and construction of beam-column joints. To address the challenges related to the installation of prefabricated wall panels and overall system assembly, this study introduces a novel stepped beam-column joint. The effectiveness of different connection configurations on the seismic behavior of the joints was investigated. A series of cyclic tests were conducted on four joint specimens with different configurations, and their failure mechanisms, hysteretic curves, skeleton curves, stiffness degradation, load-bearing capacity, and energy dissipation capacity, were revealed. The experimental results showed that the stepped joint configuration offers favourable seismic performance, with notable asymmetry observed in the response patterns under positive and negative loading directions. Reducing the height of the stepped segment or the thickness of the end plate adversely affected the seismic performance, leading to early bolt failure. Consequently, a detailed finite element model of the stepped joint was developed and the model demonstrated satisfactory agreement with the experimental results. Furthermore, a parametric analysis focusing on variations in stepped segment's height was conducted, providing insights into optimization of the load-bearing capacity of the stepped joint. The difference in the performance between the stepped joints and traditional flush end plate joints is also highlighted.

Evolution characteristics and performance evaluation of extended end-plate joints with single and double side connections under cyclic loading

Experimental studies were conducted on four extended end-plate joints subjected to cyclic loading at the column top, investigating the evolving patterns of the joints' mechanical performance. The paper provides a detailed analysis and discussion of the test joints' failure modes, ductility, stiffness degradation, and energy dissipation capacity. The Mann-Kendall (M − K) trend analysis tool was applied to the mechanical response curves, identifying key performance evolution points (evolution initiation point P and overall yield point Q). The trends in bolt forces, deformations, and strains at critical joints were effectively validated, revealing the transition of the energy system from quantitative to qualitative changes and the component's failure process from stability to instability. Additionally, based on the experimental joints' hysteresis curves and energy dissipation capacity, a theoretical hysteresis model was established to predict the joint's hysteresis curve and cumulative dissipated energy accurately. According to EC3 requirements, joints were classified as partially rigid connections. The experimental results of the initial rotational stiffness and plastic moment were further used to evaluate the calculated values in existing standards EN 1993-1-8, ANSI/AISC 358-16, and GB 51017-2017. The results indicate that extended end-plate connections possess sufficient strength, joint rotational stiffness, ductility, and energy dissipation capacity, making them suitable for seismic moment frames.

ЭКСПЕРИМЕНТАЛЬНОЕ ИССЛЕДОВАНИЕ ЧЕТЫРЕХСТОРОННИХ УЗЛОВЫХ ПРИМЫКАНИЙ «БАЛКА – КОЛОННА», ВОСПРИНИМАЮЩИХ ДЕЙСТВИЕ ИЗГИБАЮЩЕГО МОМЕНТА В ДВУХ ПЛОСКОСТЯХ.

The paper considers the 4-way end-plate I-beams to the I-column connections. Сonsidered joints do not have additional members such as stiffeners and haunches. Numerical models of such «lightweight» end-plate connections are analyzed and the results of experimental studies are presented. It was found that the end-plates adjacent to the column wall have a reinforcing effect, the deformability and stiffness of the 4-way end-plate joints were evaluated, and the need to take into account the real stiffness of such joints in analysis of building frame was noted.

Experimental study on seismic performance of stainless steel full-scale frames: Global response

This paper presents an experimental study of the seismic performance of austenitic stainless steel full-scale frames using the pseudo-static test method. The bottom single-span, two-storey substructure of the designed prototype frame was chosen as the test frame. Two full-scale frames were tested, one with a bolt-welded joint and the other with an extended end-plate joint. This paper is the first of two accompanying papers to this experimental study and focuses on the specimen design, testing details and global response of the stainless steel frame under cyclic loading. The test results were utilized to analyse the global response of the frames, encompassing failure mode, bearing capacity, deformation capacity, energy dissipation capacity, the overstrength factor, ductility factor and seismic response modification factor. The experimental findings suggest that the stainless steel frames with two joint types demonstrate consistent ability to dissipate energy during cyclic loading. The structure also performs well in terms of deformation, with uniform inter-storey deformation and no soft-storey detected. The maximum storey drift ratio of the frame is 7%. Prior to reaching a storey drift ratio of 2%, the frames with both joint types exhibit similar cumulative plastic deformation, stiffness degradation, and cumulative energy dissipation.

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.

Strength Evaluation of Pipe‐Rack Connection Using Extended End Plate

AbstractPipe‐rack structure is generally designed as a steel structure, but size of each column and beam is small because vertical loads on the structure is relatively low. In addition, due to the surrounding environment, the end plate joint is mainly used as on‐site bolting rather than welding. In this paper, seismic performance evaluation of pipe‐rack structures was conducted for three types of extended type end plate connection using the panel zone reinforcement and end plate thickness as variables. Connection of the pipe‐rack structure which is commonly used is the type of panel zone yielding occurred before other members, and its ductility and energy dissipation capacity was calculated 24.2% and 19.5% higher than the type of reinforcing panel zone by plates. As a result of the test, it is judged that yielding of the panel zone in a steel structure such as a pipe‐rack structure can be beneficial in the seismic loads.

Structural property of stainless steel minor-axis joints of interior columns with box panel

With the component method, a design approach was derived for predicting the structural properties of stainless steel end-plate joints with box panel, where box panel was formed using the skin-plates welded between the column flanges along the minor-axis. Four end-plate minor-axis joints with box panel were tested under static and cyclic loading, involving beam-to-interior column joints made of austenitic and duplex stainless steels. The monotonic and hysteretic properties of the experimental joints were discussed, including the failure characteristics, experimental curves (F-Δ), and degradation and energy dissipation behaviour. Meanwhile, elaborate finite element (FE) models were developed for further analysis of the structural behaviour of the tested joints, and a parametric study was conducted afterwards. The proposed design approach provided reasonable estimations for the experimental and FE results of stainless steel minor-axis joints with box panel, demonstrating the applicability of this proposal.

Numerical assessment of an enhanced stiffened extended end-plate joint for composite frame structures

This paper presents the numerical assessment of a novel enhanced Bolted Stiffened Extended End-Plate (BSEEP) connection for steel frames with composite beams and H-shaped columns in the strong direction. Strain demand is a critical local response that directly controls rupture initiation, and it is more crucial in composite beams since the neutral axis shifts upwards due to the composite action. The proposed connection, called URBS-BSEEP, employs a reduced section in the beam upper flange to mitigate the strain demand problem and provide a stable and symmetric plastic hinge in the desired location. Nonlinear FEM is employed to study joint cyclic behavior. Eleven specimens are designed to compare the proposed connection with existing configurations and to investigate the effects of the slab isolation from the column, shear stud removal, reduced section geometry, and slab thickness. Hysteresis curves, ductilities, failure modes, strain profiles, and energy dissipation capacities are compared. The results indicate the superior performance of the connection compared to the conventional counterparts.

Numerical Study of the Robustness of Steel Frames with Bolted End-Plate Joints Subjected to Sudden and Gradual Internal Column Loss

The research project was carried out to estimate the robustness of flat steel-framed structures in a selected accidental situation. For this purpose, a multistage approach based on experimental tests and numerical analysis was performed. As the main objective of the work, a numerical dynamic analysis of the steel frames was performed under a sudden and gradual internal column loss scenario. FEA models were created in Abaqus software using solid and shell elements. Computer analyzes were carried out in a number of different cases, taking into account the size of the structure, the type of joints, and the method of removing the column from the structure. Detailed results on the axial forces and rotation of the joints under analysis are presented, and the robustness of the structures is estimated. In all cases of frames with flush end-plate joints, an insufficient level of robustness was observed and failures of the structures were obtained. In the cases of application of extended end-plate joints in frame analysis, the required level of robustness was reached in all cases and the stop of collapse was obtained. Finally, practical recommendations for designing robust joints and the whole frame structure are presented.

Variable-amplitude fatigue behavior of M30 high-strength bolts in end-plate connection joints

High-strength bolts are widely used in connection joints for steel structures. In this paper, the variable-amplitude fatigue behavior of M30 high-strength bolts in end-plate joints is studied. Variable-amplitude fatigue tests were carried out on 19 M30 high-strength bolts using an Amsler pulse fatigue tester. Four cyclic stress amplitude loading modes, including Low to High (L-H), High to Low (H-L), Low to High to Low (L-H-L), and High to Low to High (H-L-H), were applied to the test specimens. In addition, the variable-amplitude fatigue life of M30 high-strength bolts was studied using two forms of cumulative damage models. The stress - fatigue life (S-N) curve was plotted using the equivalent stress amplitude. The obtained S-N curve was compared with the existing bolt fatigue S-N curve and the current specifications. Finally, fatigue fracture was analyzed from macro and micro perspectives. It was found that for most specimens, fatigue fracture occurs at the first joint thread between the bolt and nut, while for a few bolts, fatigue fracture occurs at the joint between the bolt head and bolt. With a fatigue life of 2 million cycles as the threshold, the fatigue limit is 107.5 MPa, which is 2.67 times higher than that specified by ANSI/AISC 360 – 16. Additionally, the fatigue properties of high-strength bolts in end-plate connections are better than those in bolted sphere joints at higher stress levels. At low stress levels, the contact pressure formed by the extrusion of the end-plate reduces the fatigue life of the bolts. Furthermore, unlike the constant-amplitude fatigue fracture, the variable-amplitude fatigue fracture has an obvious load change boundary line.

Analysis of the bearing resistance of the modified bolted end-plate joints of thin-walled profiles used in modular construction

Analysis of the bearing resistance of the modified bolted end-plate joints of thin-walled profiles used in modular construction

Seismic pre-qualification tests of EC8-compliant external extended stiffened end-plate beam-to-column joints

An experimental and numerical campaign was carried out to validate the design procedure and prequalify extended stiffened end-plate (ESEP) joints for ductile seismic resistant moment-resisting frames in the framework of Eurocodes. In fact, the tested ESEP joints have been designed with the aim of guaranteeing ductile and dissipative seismic response in accordance with the principles of the hierarchy of resistances to enforce plastic deformations in ductile components of the joints. Two alternative types of dissipation mechanisms are promoted, namely either (i) plastic deformations solely in the connected beam using full strength joints or (ii) plastic deformations in both the beam and the connection using equal strength joints. The adopted design criteria and technological details are described and discussed. The results of experimental tests confirmed the expected yielding mechanisms of the joints, which satisfied the acceptance criteria for both North American and European prequalification. Finite element simulations of ESEP joints have been validated against the experimental results and have been used to investigate the local response of the joints, thus highlighting the influence of both geometrical and mechanical parameters.

Pseudo-static test on stainless steel frame with high-strength bolted extended endplate joint

Many studies have been conducted on stainless steel materials, components and joints; however, experimental research on the seismic response of stainless steel structures is rare. This study reports pseudo-static loading tests on S2205 duplex stainless steel and Q355B carbon steel frames with high-strength bolted extended endplate beam-to-column joints. The two frames have the same geometric configuration and equivalent elastic limits (approximately 350 MPa). The detailed test processes and failure modes are presented. The Q355B carbon steel frame failed with extensive plastic deformation at the end of the beam, whereas the S2205 duplex stainless steel failed from fracture of the weld between the beam flange and endplate. The test results were analyzed at the global level (lateral load capacity, energy dissipation, etc.), beam-column joints (hysteresis curves), and yielding sequence. Owing to the considerable strain-hardening of stainless steel, the S2205 stainless steel frame had a higher loading capacity, whereas the Q355B carbon steel frame had a higher ductility and energy dissipation capacity.

Cyclic performance of fully assembled joints between H-Beam and CFST shear wall

The steel pipe of the concrete bundle shear wall is a new structural system suitable for steel structures. This study presents experimental findings of six fully assembled end-plate joints of H-beam based on high-strength bolts and one fully assembled side-plate joint of the concrete-filled steel tubes (CFST) shear wall. Two fully assembled joints of H-beam were proposed for the concrete bundle shear wall. Seven joints were subjected to low-cycle reciprocating tests in this testing program. The experimental parameters included the thickness of the end plate for H beam, the thickness of the end plate on wall, and the anchorage length of the bolts in the concrete, among which, the side-plate joints effectuated the rigid connection of unsupported frames in EC3 classification. Moreover, two fully assembled joints proposed in this study could effectuate the rigid connection of supported frames in EC3 classification. The strengthened end-plate joints significantly exceeded the rigid connection stiffness limit. The test results also indicated that the stiffness of the end-plate joint primarily depended on the thickness of the end plate for H beam and end plate on wall, while the side-plate joint mainly dissipated energy through the slip of bolts, which had excellent ductility and energy dissipation capacity, and thereby exhibiting the characteristics of low yielding load capacity and high ductility.

Genetic algorithm model of PEC column-steel plate shear wall with flush end-plate joints based on component method

The partially encased concrete (PEC) column-steel beam frame steel plate shear wall (SPSW) structure of semi-rigid joint has good cooperative working performance and seismic performance. In this paper, based on the EC3 component model, considering the contribution of the new concrete components in the PEC column to the initial rotational stiffness of the joint domain, the component model of the flush end-plate PEC column joint was established. A 1/3-scale two-story single-span flush end-plate PEC column-steel beam frame SPSW structure was tested under quasi-static cyclic loading. The OpenSees model of this structure was established, which was validated by test results. Parametric analysis of the additional damping ratio for semi-rigid joints was conducted using OpenSees. The suggested value of additional damping ratios for semi-rigid joints was given. Finally, based on Matlab and OpenSees, the model was input in the form of tool command language (TCL), an optimal arrangement model of flush end-plate PEC column joints with the genetic algorithm (GA) as the main procedure was designed. The effects of different arrangement schemes of semi-rigid joints on the seismic response of PEC column-steel beam frame SPSW structures were analyzed. The results show that the seismic performance of the flush end-plate PEC column-steel beam frame SPSW structures is reliable. The results of the finite element (FE) are in good agreement with the test results, which indicates that the established OpenSees model is effective. The contribution of the new concrete components to the initial rotational stiffness of the middle joints, top and bottom joints is 45.02% and 49.68%, respectively. The optimal arrangement scheme of semi-rigid joints can be efficiently computed by the proposed GA model.

Failure evolution analysis of end-plate connection joint based on structural stressing state theory

Based on the structural stressing state theory, the structural behavior of four extended end-plate joints under cyclic loading was analyzed to visualize their operational performance and failure evolution. The experimental strain data are modeled as generalized strain energy density (GSED) to characterize the structural stressing state and the corresponding characteristic parameters, and the Mann-Kendall (M − K) criterion is coined to determine the critical loads (P and Q) of the Mj−Ej curves of the joints and derive the starting point of structural continuity damage. Then, the trend of the joint stressing state curves before and after the critical load is reflected by analyzing the parameters of the working state of the joint (hysteresis performance, strain distribution mode at key measurement points, bending and shear deformation development, bolt force and prying force). Finally, the sample point expansion (SPE) method is introduced to effectively extend the joint experimental data, visualize the change process of strain/stress field, and reveal the mechanical response mechanism and evolutionary degradation law behind it in depth. The results of the study provide a new perspective for conducting nodal analysis and a reference for failure analysis of end-plate connection structures.

Static performance of non-through one-side bolted end-plate joint for floor-by-floor assembled steel structures

The static performance of non-through end-plate joint with one-side bolts for floor-by-floor assembled steel structures was investigated by means of tests and finite element simulations. A total of six monotonic static loading tests were carried out on the column-end and beam-end joints individually. The stiffness, strength characteristics and failure mechanism were obtained. A partial numerical model of the thread-fixed one-side bolted connection was established. It was proposed that the corresponding mechanical properties could be simplified to a trilinear load–displacement relationship and applied to the overall joint models. The tests and numerical simulations of the specimens were compared and analyzed. The results showed that the failure mode of the column-end joints was the tearing of the bottom welds after the yielding of cross web, while the failure modes of the beam-end joints were the failure of the threads or bolts. The influences of the thickness of cross web and flange of the column-connection, the thickness of beam end plate and the depth of threads on the failure modes and mechanical properties were studied with the test and finite element models. According to the force mechanism of the column-end and beam-end joints, the bearing capacity calculation formulae of the non-through one-side bolted end-plate joint were proposed finally.

Experimental and numerical investigations of bolted assembled joints to concrete encased CFST columns with different connection details

Concrete encased CFST (CECFST) composite components have prominent advantages over traditional CFST components such as better durability, high stiffness and strength, etc. However, the encased concrete outside caused certain difficulty in connecting to the steel beam. In this paper, two types of bolted assembled joints between CECFST column and steel beam were proposed and tested under cyclic loads, in which the end plate and cover plate joints were included. Typical failure modes of the joints were analyzed and characterized. In comparison, the CECFST column in end plate joints exhibited more severe failure and higher strength than that in cover plate joints. Seismic performance including hysteretic curves and energy dissipation were also discussed. In addition, numerical modelling of the joint was established considering the complicated material models and interactions in the joint core, of which the accuracy was validated against the test results. Further, parametric analyses were performed on the cover plate joints with CECFST columns through the numerical approach. It demonstrated that the axial ratio, thickness and strength of cover plate, diameter of bolt, strength and thickness of steel tube significantly affected the stiffness and strength of the joint. The experimental and numerical results revealed that the proposed two types of joints with CECFST column performed relatively favorable seismic behavior and could be employed in engineering practice.