Beam-column Connections Research Articles

Improvement effects of knee-bracing friction dampers on cyclic behavior of steel joints in antique buildings

To inherit the unique characteristics of historical timber architecture, the steel antique building (SAB) imitating ancient Chinese timber structures has been constructed using contemporary steel materials and fabrication techniques. These buildings typically exhibit premature yielding cracks and weak energy dissipation at the beam ends under seismic loads. To improve the seismic performance of SABs, two different types of friction dampers were deployed at the knee-bracing region around beam-column joints in SABs. First, cyclic loading tests on dampers indicate that both shear friction dampers and rotational friction dampers exhibit full hysteretic behavior, demonstrating an excellent and stable energy dissipation capacity. The friction coefficient of dampers with brass pads was theoretically calculated to be 0.35. Second, the quasi-static test showed that failure of steel joint specimens with knee-bracing dampers primarily occurred at replaceable angles in the beam-column connection region, which demonstrates that the repairability of steel joints in SABs can be greatly improved without overcomplicated labor. Adding knee-bracing dampers effectively postpones damage to the replaceable angles, which improves the strength, stiffness, and energy dissipation capacity of the steel joints significantly. The shear damper exhibits a more pronounced improvement in the overall structural seismic performance compared to the rotational damper with the same frictional sliding force. Moreover, numerical simulations showed that the strength of the proposed joints with knee-bracing friction dampers decreases with an increase in the axial compression ratio, while increasing the thickness of angles or the sliding force of dampers can effectively improve the seismic performance of the steel joints in SABs.

Post-tensioned steel beam-column connections with reduced length BFRP tendons

The seismic behavior of the traditional top and seat angle beam-column connection was experimentally evaluated using a half-scaled prefabricated exterior beam-column connection subassembly. Then, an ensemble of three post-tensioned beam-column connections using reduced length basalt fiber reinforced polymer (BFRP) tendons was tested with three different tendons' post-tension (PT) force levels of 15.9, 30, and 50% of the tendons' ultimate strength. Following that, another group of three additional subassemblies containing both reduced length BFRP tendons, as post-tensioning devices, and top and seat angles, as energy dissipation (ED) devices, was tested with the same three post-tension force levels used in the previously tested group. Finally, an analytical model was proposed to capture the moment-relative rotation response of the traditional top and seat angle and the connection combining both the top and seat angles and the BFRP tendons. The results showed that connections containing BFRP tendons only, with the lowest PT force level, provided the same envelope of the top and seat angle connection, and further enhancement could be achieved by increasing the PT force level. Also, the addition of the BFRP tendons to top and seat angle connection improved the connection strength, initial stiffness, post-yield stiffness, and reduced the residual drift. In addition, the proposed analytical model predicted the moment-relative response well, which ensures the reliability of the model in designing such connections.

Seismic Resilience of Concrete Moment Frames with Fibrous Rubberized Beam-Column Joints

ABSTRACT Ensuring resilience through rapid buildings recovery in seismic zones has been placed at the forefront of recent studies. However, studies that compare the relative resilience of buildings constructed with different materials are lacking. This paper focuses on a comparative resilience analysis of concrete moment frames where beam-column connections are made with varying types of concrete mixtures. The connections are made with normal strength concrete (NSC), rubberized concrete (RbC), steel fiber rubberized concrete (STFRC), synthetic fiber rubberized concrete (SYFRC), and high strength concrete (HSC). Nonlinear static pushover and incremental dynamic analysis (IDA) are utilized to understand system response and the level of damage sustained following an earthquake. Subsequently, seismic fragility functions are constructed for the five considered frame types. The frames are subjected to different seismic scenarios, and the corresponding losses, recovery time, and resilience are quantified. A comparison between the five frame types is carried out to examine the optimal concrete mixture to be used to reduce damage probabilities, total direct losses, and recovery time and subsequently enhance resilience. The results show that rubberized concrete strengthened with steel and synthetic fibers can reduce economic losses by up to 19% and increase building resilience by up to 37% compared with the frames constructed with normal strength concrete.

Performance testing of roof beam–column connections for precast N-system

The precast N-system based on embedded-pin connections is used widely to construct large precast industrial halls in south-eastern Europe and further afield, including areas of high seismicity. To realistically assess the seismic performances, safety margins and limitations of the connections, experimental investigations are essential. Experimental results from laboratory tests on a large-scale prototype model of an original roof beam–column connection show its actual bearing capacity, damage propagation pattern and specific failure mode. The experimental study was then extended to a prototype model of an upgraded roof beam–column connection. To improve safety, the connection was upgraded with improved concrete confinement and stronger steel connecting pins. The experimental results show clearly that the method implemented to upgrade the pin-based connection provided very limited upgrading effects. To obtain much better and more reliable safety upgrading, an innovative and effective upgrading method had to be developed. The capability of the implemented refined nonlinear three-dimensional (3D) micro-modelling concept to realistically simulate the complex nonlinear response of the tested original and upgraded roof beam–column connections was demonstrated by an extensive analytical simulation study.

An investigation and design of novel moment-resisting beam-column connections for precast concrete construction

This study investigates the behavior of hybrid beam-column connections with numerous detailing methods to be incorporated into precast concrete moment-resisting frames under simulated reversed cyclic loading, and ultimately develops a design procedure. Seismic performance of moment-resisting precast concrete beam-column connections was investigated through simulated reversed cyclic load tests. In addition, nonlinear finite element analysis (FEA) of typical monolithic and precast concrete connections was carried out using a modified concrete damage plasticity model. Good agreement was achieved between experimental and numerical results, which indicates that the FEA model is capable of capturing failure modes of the investigated precast concrete connections. Simple detailing modifications resulted in major improvements in the performance of connections in terms of load-displacement curves, stiffness, and energy dissipation. Finally, a design procedure was developed for the investigated connections based on failure modes and investigated limit states.

Seismic performance analysis of sleeve beam-column nodes under different reinforcement conditions based on Abaqus

This study investigates the effect of different reinforcement designs on the seismic performance of RC columns with beam-column joints connected using grouted sleeves. Through finite element analysis using ABAQUS software, various reinforcement configurations were simulated and their seismic performance was evaluated. 3 reinforcement configurations were simulated and their seismic performance was evaluated through finite element analysis using ABAQUS software. The results showed that the use of grouted sleeve connections with additional installed reinforcement and composite hoop configurations were effective in improving the seismic performance of prefabricated columns with grouted sleeve beam-column connection nodes. The stiffness reduction and displacement ductility of the specimens were analyzed, and it was found that the longitudinal reinforcement diameter had a negligible effect on the stiffness reduction, while the use of composite hoops was more effective in improving the displacement ductility compared to parallel hoops. These findings help to understand the behavior of beam-column connections and provide a reference for the design of seismic-resistant structures and future research.

Importance of Web Reinforcement in Beam Column Joint Connections

The primary focus of this research is to determine the optimal stirrup configuration to prevent shear failure. This project aims to investigate the behavior of beam-column joint frames under concentrated loads. Specimens with dimensions of 700mm x 500mm and cross-sectional dimensions of 200mm x 100mm, using M30 Grade concrete, were prepared for this study. The specimen was tested in the linear, non-linear range and up to ultimate load limit for a concentrated load. The load responses are measured with LVDT & Data logger in this experimental work. The code of practice recommends (Bureau of Indian standards-13920-1993) the bond, shear, and ductility, reinforcement for shear and moment carrying capacity. This code aims to fulfill both bond and shear requirements. This paper provides a thorough review and offers recommendations on the design and detailing of beam-column joint connections. Analytical value of the load carrying capacity of the beam column joint was assessed using limit state method by eliminating the partial safety factors for the load and strength. The results were compared between experiments and analytical values and suggestions are presented in this paper.

Rigid-Plastic Model for Progressive Collapse Assessment of Composite Beam-Column Connection Subassembly under Internal Column Removal

Rigid-Plastic Model for Progressive Collapse Assessment of Composite Beam-Column Connection Subassembly under Internal Column Removal

Structural Behavior Analysis of the Beam-Column Connections of Existing Steel Structure Buildings based on Finite Element Modeling-Idea StatiCa

Structural Behavior Analysis of the Beam-Column Connections of Existing Steel Structure Buildings based on Finite Element Modeling-Idea StatiCa

Assessment of the impact of column-to-beam strength ratio on seismic response of RC beam-column connections

Beam-column joints play an important role in the overall resistance of reinforced concrete frames during seismic events. The Earthquakes of Al Asnam on October 10, 1980, and Boumerdes on May 21, 2003 in Algeria, have highlighted the failure of beam-column joints as a cause of building collapse. 3D nonlinear finite element analysis with ANSYS software has been used in order to examine exterior RC beam-column joints under monotonic loading. The research has investigated the influence of the value of the column-to-beam strength ratio (CBSR) of these joints on shear strength and seismic performance of concrete structures by changing the height and longitudinal reinforcement of the beam while keeping column dimensions constant. It has been shown that the beam-column depth ratio and the beam longitudinal reinforcement ratio have a significant effect on the shear capacity and seismic behaviour of exterior beam-column joints. An appropriate value of the flexural strength ratio between the column and beam is crucial in order to establish a "strong column-weak beam" mechanism in reinforced concrete frames, because inadequate values can lead to premature failure or reduced shear capacity at the junction. The Algerian seismic code – RPA99/version2003 suggests a minimum value of column-to-beam strength ratio equal to 1.25 at joints for seismic design when building codes in other countries call for higher ratios. Nevertheless, this approach might not accurately represent the actual behaviour and could constrain the optimal performance of structures.

O efeito do grau de conexão viga-pilar na análise global de estruturas de concreto armado de múltiplos pavimentos

Abstract The effect of the semi-rigid connection between beams and columns on the global behavior of reinforced concrete (RC) structures was investigated. The relative rotations in the nodes of the spatial frames were determined using the analytical approach proposed by Alva and El Debs. The rotational restraint factor ( α r) was defined and applied in each node of the spatial frames. RC spatial frames with total heights of 21, 42, and 63 m were considered. It was found that the semi-rigid connection increases the lateral displacements, the 2nd order effects, and the γ z values. The lower the stiffness of the nodes, the lower the influence of α r on the global results. The total fixed beam-column connections can lead to an unrealistic behavior of the spatial frame and thus to global results.

Cyclic loading response of precast concrete beam-column connections with partially bonded draped prestressing tendon

An emulative precast concrete beam-column connection consists of prefabricated columns, T-shaped composite beams with partially bonded post-tensioned (PT) tendon, and cast-in-place (CIP) core region is proposed in this study. Experimental study was carried out to examine the hysteretic behavior of four full-scale beam-column connections under a high axial compression ratio (μ = 0.4). The specimens included a precast interior connection (PC1), a precast exterior connection (PC2), and two corresponding conventional CIP control specimens (RC1 and RC2). Performance assessment of the suggested connection was conducted by evaluating various factors, including failure mode, hysteresis curve, deformation, stiffness, and energy dissipation capacity. Test results revealed that all specimens fulfilled the design objective of strong column-weak beam with flexural failure showed at beams ends. In comparison to RC1, PC1 exhibited a 6.4 % increase in peak load-carrying capacity in the positive loading process and a 7.1 % decrease in the negative loading process. On the other hand, PC2 demonstrated approximately 11.9 % higher load-carrying capacity in the positive loading and a 2.0 % lower capacity in the negative loading when compared to RC2. The ductility coefficients of PC1 and PC2 was 3.39 and 2.64, respectively, which were slightly higher than that of RC1 and RC2 (3.01 and 2.43). All specimens exhibited good deformation restoring capacity and plump hysteretic loops, demonstrating satisfactory energy dissipation capacity. Overall, the proposed connection with partially bonded PT tendon showed comparable seismic performance with their CIP counterparts, indicated its promising potential for use in practical engineering applications.

Ductility of Precast Concrete Column Beams Using Dowels

Precast concrete structures are considered as monolithic structures, flexural reinforcement and beam column joint shear can be planned based on design capacity. This research is an experimental study. The objective is to assess the ductility of precast concrete column beams utilizing dowels. The test specimens comprise three configurations: monolithic beam column (BN), 2 post precast beam column (BG 1), and 4 post precast beam column (BG 2), with respective displacement values of 37.4 mm, 42.7 mm, and 47 mm. This research was carried out in the stages of calculating displacement ductility using displacement parameters, and curvature ductility using parameters of cross-sectional curvature or curvature values and load values due to cyclic loads. The research results show that the displacement ductility values for test specimens BN, BG 1 and BG 2 are 2.34, 2.21 and 2.06 respectively. The curvature ductility value for test specimens BN, BG 1 and BG 2 is more than the value required in ASCE 41-17, namely 0.01 in the LS condition and in the CP condition it is 0.015. Additionally, these values surpass the stipulated requirements. This leads to the conclusion that beam column connections, whether monolithic or precast, exhibit exceptional performance in withstanding earthquake loads under both moderate seismic conditions (moderate earthquakes) and severe seismic conditions (strong earthquakes)

Experimental investigation of the rotational characteristics of a novel hybrid laminated glass beam-column connection prototype

This article presents an experimental investigation of the rotational characteristics of a novel hybrid laminated glass beam-column connection prototype. The testing of small-scale prototype specimens is conducted to assess the effect of the main structural parameters such as glass pane thickness, interlayer and reinforcement properties on the rotational characteristics. To explore the possibility of using different lamination technologies for the realization of the joints, two different bonding technologies are considered separately: (a) autoclave and (b) UV-curing lamination. The specimens are subjected to a pair of self-equilibrated compressive forces up to failure in a custom-made setup. Digital image correlation (DIC) measurements together with strain gauges are used for tracking the kinematics of the main components. It was found that the prototype is able to develop a significant post-fracture and rotational capacity in a properly balanced combination of structural and material parameters. The results are presented in terms of moment-rotation (M - θ) curves, strains evolution in the steel and evolution of the crack patterns. Experimental observations suggest that depending on the choice of structural parameters three failure modes are possible: (a) crushing failure of the joint core, (b) plastic failure of the adjoining sections and (c) failure due to debonding of one of the bars in tension. It is concluded that one can achieve a desirable post-fracture and ultimate behaviour by properly balancing the structural and material parameters. Additionally, pull-out opening and tensile stresses in steel are measured at the interrupted section, revealing a transition in sectional behaviour from fully interrupted to a hybrid section over a certain transition length.

Research on Nonlinear Behavior of Local High-Performance Concrete Beam-Column Connections.

The seismic performance index of prefabricated structures is generally obtained via experimental analysis. However, in experimental research, it is impossible that every influencing factor can be taken into account. Therefore, the finite element analysis method can be used as a supplementary method for experimental research to carry out parametric analysis of joints. Based on this test, a hysteretic model of steel bars is developed on the ABAQUS platform; meanwhile, the model is used to simulate the seismic analysis of the proposed local reinforced joints. The hysteresis curve obtained via simulation exhibits a high degree of coincidence with the experimental results. Based on the validated model, a detailed parameter analysis of prefabricated local reinforced concrete frame joints is carried out. The analysis results illustrate that the axial pressure ratio at the top of the column has a minimal impact on the joint's performance. Decreasing the stirrup ratio within the core region, enlarging the diameter of the PC steel bar, and increasing the concrete strength that is poured in the keyway and the core region can raise the cumulative energy consumption of the joints, thereby reducing the damage degree of other units and improving the maximum bearing capability of the joints.

Fracture of beam-column connections with cope holes under large cyclic deformations

A relationship between cord rotation (θp) and the number of deformation cycles to fracture initiation (N) is developed for steel moment frame welded beam-column connections with different cope hole sizes. The selected ductile fracture model is calibrated using material monotonic test results. It is then verified using small coupons considering different test regimes. The model with 45 mm cope hole radius was then calibrated for a welded connection tested under a uniform test regime. Then, further analyses of the configuration were conducted with cope hole radii ranging from 15 mm to 55 mm subjected to different test regimes. The number of cycles before fracture varied by up to 2.44 times for the range of cope hole sizes considered for the largest end displacement. Fracture initiated at the inside edge of the cope hole. The strength decreased with an increasing cope hole size, and equations to describe this were developed as a function of the remaining section plastic modulus.

Seismic behavior and restoring force model of precast beam-column connections with locally reactive powder concrete

In this study, an innovative approach to enhance the seismic performance of prefabricated concrete frame beam-column joints, incorporating high-strength steel bars and reactive powder concrete (RPC), was developed. The research involved the construction of four prefabricated joints and one cast-in-place node, subjecting them to low-cycle reverse load tests. The findings indicate that the inclusion of high-strength steel bars in the node core area led to a notable increase in load-bearing capacity, ranging from 9.5 % to 9.7 %. Moreover, when RPC and high-strength steel bars were simultaneously used in the node core area, the load-bearing capacity improved even further, with an increase of 19.1 %–20.8 %. Additionally, RPC was found to enhance crack resistance in columns and beams, reducing the severity of node failures. Comparing specimens with different spacing of hoops in the core area, it was observed that RPC not only ensured the seismic performance of the nodes but also addressed the issue of excessive hoop density in the core area. Through experimental data, a restoring force model for prefabricated RPC/RC composite frame beam-column joints was established using theoretical analysis. This model exhibited strong agreement with experimental results and effectively depicted the stress distribution within the proposed joints at various stages.

Finite element analysis and hysteretic model of self-centering steel connection with dual energy dissipation mechanism

In the traditional steel beam-column connection, the beam flanges were welded to the column face, while the beam web was bolted to the column face by shear tab. During seismic events, this connection often suffers from brittle failure. This paper presents a novel self-centering steel connection with dual energy dissipation mechanism. The connection utilizes the sliding of friction elements and the plastic deformation of T-stub at different stages to dissipate energy. As a result, the proposed connection not only enhances energy dissipation capacity but also increases the safety redundancy of the structure. The main focus of this study is to investigate the structural behavior of this new type of connection by refined finite element analysis models. These models are constructed using ANSYS and validated against experimental results. Furthermore, parametric analysis is conducted to investigate the influence of various factors on the seismic performance of the connection. These factors include the initial post-tensioning force of prestressed steel strands, the shape form of T-stub flange, the flange thickness of T-stub, the coefficient of friction between friction plates and web of T-stub, and the pre-tension force of high-strength bolts. The results demonstrate that increasing the initial post-tensioning force of the steel strands reduces the residual deformation and enhances the self-centering ability of the connection, and the dual energy dissipation behavior is more obvious. Meanwhile, the occurrence of both sliding and plastic deformation of T-stub is postponed. The influence of the thickness of the T-stub flange is minimal during the friction-based energy dissipation stage but significant during the energy dissipation stage of the plastic deformation of T-stub. Moreover, increasing either the coefficient of friction between friction plates and T-stub webs or the initial post-tensioning force of high-strength bolts significantly improves the bending strength of the connection and reduces residual deformation. Meanwhile, these factors mostly affect the friction sliding stage to delay the starting point of sliding, but their influence on the plastic deformation is minimal. Finally, a theoretical hysteretic model is proposed based on the dual energy dissipation mechanism. The model is compared and analyzed against experimental results, demonstrating good agreement. This provides theoretical foundation for the design of similar structural connection.

Experimental and numerical research on the lateral behaviour of glued timber frame structures with and without X-type diagonal bracing

The advanced processing technology of glued wood can provide strong support for the construction and application of the modern timber structures. The modern timber structure can meet the requirements of low-carbon development goals and natural living standards, but there still exist some technical difficulties to research, such as seismic performance and design code problems. Hence, this paper presents the lateral behaviour of glued timber frame structures with and without X-type diagonal bracing by experimental and numerical research methods based on these problems. Two single-layer single-span bare glued-laminated timber (GLT) frame specimens and two GLT frames infilled with X-type diagonal bracing specimens with a 1:1.5 scale were designed to investigate the lateral behaviours under the cyclic loading tests. Three types of beam-column joint connectors (the exposed type with infilled steel plate, the coated type with infilled steel plate and the extended coated type with infilled steel plate) were designed to guarantee the effective connection between components. The failure mode, hysteretic characteristics, lateral load-bearing capacity, stiffness degradation, deformation and the lateral load resistance cooperative working mechanism between X-type diagonal bracing and GLT frame of specimens were analyzed. The test results present that the lateral behaviour of the GLT frame is significantly improved after being infilled with the X-shaped diagonal bracing, and the yield lateral load-bearing capacity and the elastic stiffness of the coated type beam-column joint connection in the GLT frame were 1.876 and 1.36 times than that of the specimen with exposed type beam-column joint connection, respectively. The beam-column joint of the bare GLT frame specimen is failure before the column-base joint. The diagonal bracing joints of the GLT frame specimen infilled with the X-shaped bracing were failures first, and then the beam-column and the column-base joints of the GLT frame were damaged. For the specimen infilled with the X-type diagonal bracing, the lateral resistance load was borne by the GLT frame and diagonal bracing, in which the percentage of the lateral load borne by the diagonal brace gradually decreases, while the percentage of the lateral load borne by the GLT frame gradually increases. In addition, the load-deformation relationships of the specimen joints were derived. Based on these relationships, the numerical analysis of the specimen was carried out to study the influences of GLT frame span-depth ratio, the slenderness ratio of GLT diagonal bracing and the wall thickness of steel tube diagonal bracing on the lateral resistance of this structural system.

Analysis of steel beam column connection under cyclic loading with reduced web opening type fuses

Analysis of steel beam column connection under cyclic loading with reduced web opening type fuses