Beam-column Joints Research Articles

Experimental investigation of EBROG and bore-epoxy anchorage methods used for interior RC beam-column joints strengthened with CFRP sheets

In severe earthquakes, the energy dissipation and ductility capacities of the structures depend on the performance of the beam-column joints where the load transfer is performed. Experiences in past earthquakes have shown that damage occurs in the beam-column joints that do not have sufficient strength and rigidity. In particular, the shear failure observed in deficient detailed joints has caused the collapse of many structures. Joints are effectively retrofitted with carbon fiber reinforced polymer (CFRP) sheets to increase the earthquake safety of the structures. However, the debonding problem experienced in CFRP sheets significantly affects the efficiency of the applied retrofit and the earthquake behavior of the member. In this study, the retrofit of reinforced concrete beam-column joints with deficient shear strength was carried out with CFRP sheets by using externally bonded reinforcement on grooves (EBROG) and bore-epoxy anchorage methods. These two retrofit methods were applied to effectively utilize the full capacity of CFRP sheets by delaying the debonding. Six ½ scaled reinforced concrete (RC) interior beam–column specimens without transverse reinforcement in the joint core were constructed. One reference and five retrofitted joints were subjected to displacement-controlled cyclic loading. The shear failures in the specimens were delayed until advanced displacement levels. The use of EBROG and bore-epoxy anchorage methods improved the yield load of the specimens by 32 % to 69.05 % compared to the reference specimen. Additionally, significant increases were observed in the initial stiffness, load-carrying, and energy dissipation capacities of the retrofitted specimens up to 68 %, 64 %, and 104 %, respectively. The ductility of the retrofitted specimens increased by approximately 7 % to 26 %. The EBROG and bore-epoxy anchorage methods proved to be highly successful in preventing the early debonding of CFRP sheets. In specimens strengthened with EBROG and bore-epoxy anchorage methods, the displacement values at which the FRP sheets began to debonding approximately doubled. It was concluded that EBROG and bore-epoxy anchorage methods were more effective than the externally bonded reinforcement (EBR) method in improving the overall structural performance of the joints.

Strengthening of reinforced concrete beam-column joints by means of fastened C-FRP ropes

The efficiency of using C-FRP ropes as external superficial reinforcement to strengthen beam-column connections in reinforced concrete structures with regard to seismic requirements is investigated experimentally. The method is an easy-to-apply, effective method for locally increasing the load-bearing capacity of beam-column connections in existing buildings. To strengthen the beam, external C-FRP ropes are placed in slots along each side of the beam at the top and bottom. The test results with test specimens on a scale of 1:1 in undamaged condition (JA0) and in strengthened condition after pre-damage (JA0b) are analysed and compared. From the comparative representation of the hysteresis reactions, it is concluded that the strengthened test specimens show an improved hysteresis reaction in all cases examined compared to the corresponding test specimens without strengthening. Comparisons of the damage index values and the equivalent viscous damping values obtained from the test results are also presented and commented on in order to enable objective and well-founded conclusions to be drawn. It can be concluded that the use of C-FRP ropes as external reinforcement is suitable as an efficient and easy-to-handle strengthening technique in all cases investigated.

Evaluation of various FRP strengthening configurations for RC beam-column joints

There are several methods for strengthening reinforced concrete joints. Due to the unique properties of FRP (Fiber Reinforced Polymer) composites, the use of FRP laminates is one of the most commonly used techniques. The high cost of preparing concrete surfaces and attaching FRP laminates is a restricting factor for its application in reinforced concrete joint retrofit. Therefore, determining proper configurations that reduce the needed FRP material, as well as the surface preparation required for attaching FRP is an important factor in decreasing the strengthening cost. The proper arrangements of FRP strips can improve their performance in the rehabilitation and retrofit of reinforced concrete joints. To determine the proper configuration of FRP strips, finite element modeling was employed. The connection specimens are modeled in ABAQUS general-purpose finite element software and are classified into 10 general groups. To improve the performance of FRP strip configuration, the determined arrangement is investigated for different thicknesses and different widths of the FRP strips, and their results are compared with those of the connection specimen strengthened with full FRP coverage. The analysis results indicated that the load-bearing capacity of the connection retrofitted by the combined configuration of X-shape and orthogonal strips of FRP is close to that of the specimen with full FRP coverage. In this suitable configuration, the required FRP strips are reduced by about 30%, which decreases the cost and construction works needed for concrete joint rehabilitation.

Research on Seismic Performance of PC Beam-Column Joints Connected with Section Steel

Research on Seismic Performance of PC Beam-Column Joints Connected with Section Steel

Research on Seismic Performance of Beam-Column Joints with Reinforced Webs Connected with Fully Bolted Double-Angle Steel

Research on Seismic Performance of Beam-Column Joints with Reinforced Webs Connected with Fully Bolted Double-Angle Steel

Research on seismic performance of replaceable prefabricated RC beam-column joints

Based on the seismic design philosophy of recoverable functionality, this paper proposed a prefabricated concrete beam-column joint utilizing replaceable friction energy dissipation artificial plastic hinges (FAPH) as connecting devices. The connecting device comprised a pair of lugs and high-strength pins. This study analyzed the failure modes and hysteresis characteristics through cyclic loading tests performed on the precast beam-column joints. The results showed that the FAPH had a high peak capacity. However, the yield load was low, which reduced the energy-dissipation capacity of joints at the early stage. Therefore, lateral energy dissipation steel plates (EDPs) were added on both sides of the PAPH to improve bearing capacity. Then, utilizing ABAQUS finite element software, the mechanical behaviors of the optimized prefabricated joint such as the load-displacement curve, bearing capacity, ductility, and energy dissipation capacity were further analyzed. This paper also investigated the effect of the axial compression ratio, the friction coefficient, bolt preload, and connecting plate form of EDPs on the seismic capacity of the optimized joint. After optimization, the prefabricated joint exhibited a significant improvement in both yield capacity and cumulative energy dissipation, increasing by 47 % and 22 %, respectively. Additionally, there was a slight improvement in ductility. Increasing the axial compression ratio reduced the bearing capacity and ductility of prefabricated joints after the peak point. The specimen exhibited a significant increase in both peak capacity and cumulative energy dissipation as the friction coefficient increased. Additionally, the hysteresis curve of the joint became fuller with the increase in bolt preload. The connecting plates of EDPs mainly serve to transmit loads, and different forms of connecting plates had little effect on the bearing capacity and energy dissipation capacity of prefabricated joints.

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.

Application of BIM Technology in Structural Design of Prefabricated Building Based on Big Data Simulation Modeling Analysis

Aiming at the complex steel bar layout problem in prefabricated building, this research proposes a structural design method of prefabricated building based on big data simulation modeling building information modeling technology. It includes the reinforcement arrangement model based on agent path planning, the intelligent reinforcement arrangement of frame based on artificial potential field method and path optimization, and the modeling of Building information modeling. When analyzing the reinforcement arrangement effect of beam column joints in Prefabricated building, the calculation time of top corner joints is the shortest, 76.8 seconds, while that of middle layer joints is the longest, 141.7 seconds. In direction Y and direction X, differential evolution has the longest calculation time, 27s and 26.57s respectively, while particle swarm optimization algorithm has the shortest calculation time, 2.84s and 3.02s respectively. The algorithm designed through research is significantly superior to other algorithms in terms of computational time. In general, through building information modeling technology and big data simulation modeling, this study realized the collision free layout of rebar in beam column joints of prefabricated building. This improves the speed and efficiency of deepening design, and provides a new solution for structural design of prefabricated building.

Analysis of Progressive Collapse Resistance in Precast Concrete Frame with a Novel Connection Method

The configuration of beam–column joints in precast concrete (PC) building structures varies widely, and different connection methods significantly affect the progressive collapse resistance of the structure. This study investigates the progressive collapse resistance of an innovative beam–column connection node frame. Finite element models of four-story, two-span space frame structures made of reinforced concrete (RC) and PC were developed using ANSYS 14.0/LS-DYNA R5.x software, employing nonlinear dynamic and static analysis to examine structural collapse behavior under bottom middle or corner column damage. Numerical results indicate that following the failure of the middle or corner column due to explosion loading, the vertical displacement and collapse rate of the PC structure with the novel connection method are less than those of the RC structure during collapse progression. Furthermore, upon removal of the middle or corner column, the residual load-carrying capacity of the PC structure with the innovative connection increased by 7% and 3.7%, respectively, compared to the RC structure. This suggests that PC structures with this type of connection demonstrate superior performance in resisting progressive collapse, offering valuable insights for future engineering applications.

Analytical and experimental investigation on performance of ENTA damper systems for RC moment frame under cyclic loading

An external ENTA damper system or steel frame seismic retrofit approach was investigated for historic reinforced concrete (RC) buildings. RC frame specimens were evaluated under cyclic lateral loading to confirm the external retrofit approach. The investigation involved an examination and comparison of hysteresis-based behaviors, such as strength, ductility, and energy dissipation, with the aim of gaining a deeper comprehension of the distinct impacts of external retrofit systems on seismic performance. The experimental findings indicate that the implementation of the external ENTA damper system and steel frame effectively enhanced the stiffness and durability of vulnerable RC moment frames, while maintaining their deformation capacity. The enhancement of the energy-dissipation capacity was achieved by the use of measures to prevent premature failure of the RC beam-column joints. On the basis of the experimental results, the failure mechanism of the RC frame was discussed, considering the shear connection behavior. In order to further validate the experimental results, analytical modeling of the undamaged specimens was carried out using the LS-DYNA program. The test strengths of the frame specimens were evaluated and compared to the anticipated values derived from a simple plastic mechanism.

Seismic fragility and resilience assessment of steel frame with replaceable T-stub connection components

Based on a rational design, steel beam-column joints with replaceable T-stub connection components (SBCJ-RTCCs) possess superior structural fuse performance and seismic resilience performance. To further evaluate the benefits of steel frames using RTCCs in terms of dynamic response, structural and non-structural components damage as well as seismic resilience, a 12-story steel frame equipped with RTCCs (SF-RTCCs) and a steel moment resisting frame (SMRF) were designed and established. On the basis of validating the simulation results with the experimental findings, the nonlinear dynamic analyses and incremental dynamic analysis (IDA) based seismic fragility analysis was performed. The results confirm that the introducing RTCCs into steel frames can significantly mitigate base shear and floor acceleration as well as produce a more uniform inter-story deformation and a more rational yielding mechanism. Meanwhile, the SF-RTCCs can obtain comparable collapse-resistant performance compared to SMRF, and both frames possess sufficient redundancy to resist structural collapse. Thanks to the lower floor acceleration responses, the SF-RTCCSs performs much better than SMRF in controlling non-structural components damage. After DBE excitations, the probabilities of RTCCs can be replaced by 1st class and 2nd class was 17.2 % and 84.9 %, respectively. After MCE excitations, RTCCs has about 29.3 % and 67.2 % probability that it can be replaced by 2nd class and 3rd class, respectively. Considering the lower economic losses, short repair time and fewer casualties, the rating of seismic resilience of SF-RTCCs was enhanced from one-star of SMRF to two-star.

Finite Element Analysis of Prefabricated Semi-Rigid Concrete Beam–Column Joint with Steel Connections

This paper introduces a novel type of prefabricated semi-rigid concrete beam–column joint, aiming to examine its load-carrying capacity and seismic performance in comparison with a traditional cast-in-place joint. This study utilized the ABAQUS 2020 software to establish finite element models for both types of joints and conducted finite element analysis under low circumferential reciprocating displacement loads. When comparing the energy dissipation capacity, ductility, ultimate load-carrying capacity, stress mechanism, and damage mode, a comprehensive evaluation of the two types of joints was performed. Furthermore, this study investigated the impacts of various factors such as the axial compression ratio, concrete strength, reinforcement strength, and connector strength on the ultimate load-carrying capacity, ductility, and energy dissipation performance of the joints. Based on the findings, the newly combined joint exhibited a substantial 31.7% increase in its ultimate load-carrying capacity, along with a notable 7.23% enhancement in ductility and an improved energy dissipation capacity when compared with the cast-in-place joint. As a result, it can be concluded that the seismic performance of the new joint surpasses that of cast-in-place joints. Additionally, this study examined the impact of modifying relevant parameters on the seismic performance of the new prefabricated semi-rigid concrete beam–column joint.

Optimization and experimental study on seismic performance of precast dry-wet hybrid beam-column joint with local prestressing

In order to improve the seismic performance, a novel dry-wet hybrid beam-column joint was optimized based on the findings of the preliminary experiment. Four full-scale prefabricated specimens were tested under cyclic loading to further investigate their seismic behavior and explore the various factors, including the connection methods for beam top longitudinal reinforcement in the joint core, magnitude of prestressing force, forms of hoop reinforcement at beam ends, and types of grouting material used in corrugated steel ducts. The results indicate that the new joint failed in the flexural mode, and its experimental bearing capacity value was consistent with the theoretical value, indicating a good safety margin. Additionally, it exhibited remarkable ultimate deformation capacity and displacement ductility coefficient exceeding 3, comparable to cast-in-place structures. The performance indicators of post-tensioned (PT) bar specimens were similar to those of cast-in-place structures and superior to PT rod specimens. The energy dissipation of PT rod specimens accounted for approximately 80 % to 90 % of that of the PT bar specimen. The viscous damping ratios of specimens with PT bars and PT rods were approximately 20 % and 15 %, respectively. Two methods of connecting beam top longitudinal bars by grouting or couplers, accompanied by a local unbonded treatment, could both fulfill anchorage requirements. However, the later one resulted in loosening of steel bars within the connector during late loading stages. The anchoring performance of prestressed grouting material could satisfy the anchoring requirements of PT bars, but still failed to meet the slippage resistance requirements of PT rods. Increasing the prestressing force can enhance the initial stiffness, significantly reduce yield displacement, and improve ductility coefficient, while having minimal impact on strength and energy dissipation. The open composite stirrups at beam ends do not significantly impact overall performance of the joint. The optimal details for the novel joint involves a combination of high-strength PT bars, grouting in corrugated ducts with local debonding treatment, and open composite stirrups at beam ends.

Experimental study and design methodology of sacrificial-energy dissipation beam-column joint

To enable secondary energy-dissipation components to actively attract and dissipate seismic energy, a new type of sacrificial-energy dissipation beam-column joint (SEDJ) was proposed. This study validates the performance of the proposed SEDJ through full-scale quasi-static loading tests. The rotation angle of the proposed SEDJ at the beam end, corresponding to the peak strength Fu, can be controlled within 1/250 - 1/50. In addition, the beam and column components remain elastic, thereby achieving the seismic performance objectives of "no damage, sacrificial-energy dissipation, and no collapse under service-level (SLE), design-basis (DBE), and maximum-considered (MCE) earthquakes", respectively. This study enhances the design of the SEDJ by adopting a built-in sleeve connection scheme to significantly reduce the free-stroke displacement, and a double-coupling block scheme to solve the issue of stress concentration in friction plates that leads to cracking. Furthermore, the efficiency of the installation and disassembly of friction plates is improved, thus enabling the rapid replacement of bolts and friction plates after strong earthquakes. Finally, a practical engineering design methodology is proposed that decouples the bending moments of the sacrificial MR and energy-dissipation MS stages, this methodology activates the sacrificial mechanism under DBEs or MCEs to protect primary beam and column components, and will provide potential insights for the development and application of innovative structural components based on the sacrificial mechanism design philosophy.

Mechanical properties of prestressed tendon-planted glulam beam-column connections under cyclic loading

Traditional glulam beam-column connections have the disadvantages of low bearing capacity, low stiffness, low ductility and poor energy dissipation ability. This paper proposed a new prestressed tendon-planted connection for glulam beam-column joints. Six groups of the connections were tested under reversed cyclic loading. The effects of the number and prestressed value of steel bars, tendon reinforcement ratio and tendon anchorage length on the performance of the connection were analyzed. The results indicated that the proposed connection showed ductile failure, involving the splitting failure of the beam and the bearing failure around the planting holes. The proposed configuration improves the ultimate bearing capacity, initial stiffness and energy dissipation performance, and slows down the stiffness degradation of the glulam beam-column connections. The number of steel bars and prestressed value have a positive effect on the initial stiffness of the joint, whilst the tendon reinforcement ratio has a significant positive influence on the bearing capacity of the joint. The bearing capacity of the joint no longer increases with the increase of the tendon anchorage length, when the anchorage length is 12.5 times greater than the tendon diameter. The prediction formula for the flexural capacity of the new joint is proposed, whilst the moment-rotation characteristics of the connection are also assessed.

Experimental and simulation study on seismic performance of the new beam-column transfer joint as the embedded part of the basement roof

A new beam-column transfer joint is proposed, which consists of an upper column with a concrete-filled steel tube column (CFST), a lower column with a variable-diameter steel-concrete column (SRC), and a reinforced concrete beam. The new transfer joint is mainly set on the roof of the basement of a high-rise building structure. Compared with traditional transfer joints, it reduces the amount of steel used, increases the use space of the basement, and improves the seismic performance of the structure. New transfer joint and traditional joint were tested under cyclic loading to investigate response of the proposed joint. The main performance indicators studied are hysteretic response, energy dissipation, ductility, and stiffness degradation. Research results show that the energy consumption and carrying capacity of the new transfer joint are higher than those of the traditional joint. The correctness of the finite element analysis was verified through the test results, and a parametric analysis was carried out on this basis. It was found that the diameter reduction position of the steel tube and the length of the corbels of the lower column have little impact on the seismic performance of the new transfer joint. The thickness of the steel tube has a greater impact on the seismic performance of the new transfer joints. The peak bearing capacity is increased by about 17 %. Finally, according to the formula given by the specification, the embedding effect of the new transfer joint and the traditional joints are compared. The effect of the new transfer joints is better than that of the traditional one, which can provide a reference for future basement design of high-rise building structures.

Hysteresis Behavior of RC Beam–Column Joints of Existing Substandard RC Structures Subjected to Seismic Loading–Experimental and Analytical Investigation

Four exterior reinforced concrete beam–column joint subassemblages with poor reinforcement details and low-quality materials were constructed and subjected to cyclic lateral deformations under constant axial loading of the columns. The longitudinal rebars at the top of the beams were well-anchored in the joint region with a 90° hook and transversely welded to prevent premature slippage. The same was true for the longitudinal rebars at the bottom of the beam of the first specimen. Contrarily, the anchorage of the rebars at the bottom of the beam of the other three subassemblages was straight and of insufficient length. One of these specimens (the second) also had deficient lap splices of the column reinforcement, while the other three specimens had continuous column rebars. The third and the fourth subassemblage were designed with different joint aspect ratio and beam shear span/depth ratio values. The overall seismic performance of the specimens was evaluated and compared. The failure mode of the subassemblages was accurately predicted by the proposed analytical model. It was clearly demonstrated that the anchorage of the rebars, the length of the lap splices, the joint aspect ratio and the shear span/depth of the beam ratio value crucially affect the cyclic response of beam–column joints and, hence, may cause a severe detrimental impact to the overall structural integrity.

Seismic behavior of high-performance steel (HPS) weakened beam-column joints: Experimental tests and numerical analysis

This paper experimentally and numerically investigates the seismic behavior of high-performance steel (HPS) weakened beam-column joints. Three different geometrical configurations of weakened joints were designed, and experimental tests were conducted under cyclically varying lateral load. The test results revealed that the connection type had a significant influence on the seismic behavior of the joints. The specimen JD-2 exhibited excellent ductility and energy dissipation capacity. Moreover, the seismic behavior of specimen JD-3 was significantly improved due to the existence of transition plates, and its energy dissipation efficiency was 1.25 times that of the prototype specimen JD-1. Additionally, the relationship between the development of damage and the various mechanical response of each joint was discussed based on the model proposed by Krawinkler and Zohrei. Detailed finite element (FE) model were then developed and validated. The benchmarked models were utilized to evaluate the seismic behavior of HPS joints, including stiffness and strength degradation, energy dissipation, ductility coefficient, and damage evolution. Based on the experimental tests and FE analysis, a new trilinear hysteretic model considering damage development was proposed, which was in good agreement with the test results. It is indicated that the simplified model can effectively capture the seismic behavior of HPS weakened beam-column joints under cyclic loading conditions.

Behavioural Study of Beam-Column Joint for Seismic Loading

Abstract: The seismic performance of Reinforced Concrete (RC) structures is a critical aspect of structural engineering, particularly in regions prone to seismic activity. This project presents a detailed study focusing on the behaviour of joints in RC structures following seismic events, utilizing the powerful computational tool ETABS. The primary objectives include understanding the response of joints under seismic loading, assessing their vulnerability, and proposing strategies for enhancing their seismic resilience. The study employs ETABS, a widely used software package for structural analysis and design, to simulate seismic actions on RC structures. Various types of joints, including beam-column joints and slab-column connections, are meticulously analysed under different seismic intensities and structural configurations. Through comprehensive analysis, the project aims to identify critical failure modes, such as shear failure, flexural failure, and joint sliding, and evaluate their impact on overall structural performance. Findings from this study contribute to the advancement of seismic design and retrofitting practices, offering insights into effective strategies for enhancing the seismic resistance of RC structures. The outcomes are valuable for engineers, researchers, and practitioners involved in earthquake engineering, providing essential knowledge for designing resilient structures capable of withstanding seismic hazards. This project underscores the importance of understanding joint behaviours in RC structures subjected to seismic loading, offering practical implications for improving structural safety and mitigating the impact of earthquakes on the built environment.

Seismic performance evaluation of precast post-tensioned high-performance concrete frame beam-column joint under cyclic loading

Precast concrete structures have developed rapidly because they meet the requirements of green and low-carbon social development. In this paper, a precast post-tensioned high-performance concrete frame beam-column joint was proposed, and the low-cycle reversed load test was performed on the four proposed joints. The main differences between the four joints are the different prestress values applied by the joints and whether the beam-column joint is provided with L-shaped steel. The seismic performance indexes such as hysteresis curve, stiffness degradation, deformation capacity, energy dissipation capacity and residual deformation of each node were obtained through experiments. By comparing various seismic performance indicators, it could be found that the use of high-performance concrete could effectively avoid the phenomenon of local crushing of concrete due to excessive prestressing. At the same time, it was found that the setting of L-shaped steel plate at the beam-column junction could effectively avoid the early damage at the beam-column junction. On the basis of the test, the three-line restoring force model of the joint was established by the method of experimental regression analysis. The model could better reflect the stress situation of each stage of the joint. Based on the experimental and theoretical analysis, the finite element analysis model of the joint was established, and the model calculation results were in good agreement with the experimental results.