Concrete Beam-column Joints Research Articles

Seismic performance of geopolymer concrete beam-column joints under reverse cyclic loading

All structural elements of the building are subjected to reverse cyclic loading during earthquakes, which causes large inelastic deformations in beam-column joints. Use of ductile concrete and presence of confinement in the joint region can reduce the seismic failure of beam-column joints. Cement industries produce a massive amount of greenhouse gases during its production and lead to global warming. Cement concrete is brittle in nature. It is necessary to reduce the production of cement for maintaining environmental sustainability. The present study investigates the behaviour of steel fibre reinforced geopolymer concrete beam-column joints under reverse cyclic loading. Steel fibres were added to GGBS-Dolomite geopolymer concrete to reduce its brittle nature. Enhanced strength properties were identified geopolymer concrete due to the presence of steel fibres. Parametric studies were conducted by finite element methods and observed similar load–deflection behaviour between GPC specimens (without ductile detailing) and cement concrete specimens in which ductile detailing provided as per IS 13920–2016, with reduced cost/strength ratio. Provision of ductile reinforcements creates congestion problem at the joints, which can be reduced by the use of geopolymer concrete made from GGBS and dolomite.

Simplified Plastic Hinge Model for Reinforced Concrete Beam–Column Joints with Eccentric Beams

In nonlinear analysis for performance-based design of reinforced concrete moment frames, a plastic hinge spring element is predominantly used in order to simply and accurately describe the inelastic behavior of beam–column joints, including strength degradation. Although current design codes and guidelines provide various beam–column joint models, the focus is on concentric beam–column joints. Therefore, more studies are required for eccentric beam–column joints, which are also common in practice. In the present study, to consider the effect of beam eccentricity on the behavior of beam–column joints, a simplified plastic hinge model was proposed using the effective joint width of current design codes. The proposed model was compared to the cyclic loading test results of beam–column joints with/without beam eccentricity. The comparison showed that the simplified plastic hinge model with the effective joint width of NZS 3101-2006 or Eurocode 8 is considered acceptable for design purpose.

Modelling and Validation of Seismic Performance for Corner and Interior Beam-column Joint Using HYSTERES Program

The validation between experimental and modelled hysteresis loops is a preliminary work in determining the dynamic behaviour of the beam-column joints under earthquake excitations using Ruaumoko 2D program. However, this paper only focuses on accurately modelling the hysteresis loops of corner and interior beam-column joint using the HYSTERES Program. The corner and interior beam-column joints were designed using Eurocode 8 and equipped with unbonded fuse-bars which acts as passive energy dissipators. The hysteresis loops were modelled based on the input parameters obtained from the experimental hysteresis loops. From the HYSTERES program, the Pampanin Reinforced Concrete Beam-Column Joint was chosen to represent the hysteretic behaviour (load versus displacement) for overall seismic behaviour of these joints. The lateral strength capacity, stiffness, ductility and equivalent viscous damping from experimental and modelled hysteresis loops were then compared, and the percentage difference from both hysteresis loops was calculated. Based on the outcomes, there are some parameters which have shown good agreement, and this proves the effectiveness of using HYSTERES program in modelling the hysteresis loops of the beam-column joints.

Seismic performance of precast concrete beam-column joint based on the bolt connection

This paper proposes a prefabricated concrete beam-column joint with the bolt connection. And the seismic performance of the proposed joint is investigated in depth. Specifically, the study includes the full-scale experiments and the finite element simulations. First, the full-scale experiments were conducted on the beam-column joints connected by grade 5.6 and grade 8.8 bolts, respectively, to study the impact of the bolt strength on the seismic performance of the proposed joint. Then the finite element simulations were made by the software Abaqus, based on which the results from the experiments and the simulations were compared. And the impacts of the bolt strength and the axial compression ratio on the seismic performance of the proposed joint were further studied based on the simulations. In more detail, for the bolt strength, the simulations show that the yield bearing capacity and the ultimate bearing capacity of the joints connected by the grade 8.8 bolts are higher by 8% and 18%, respectively, than those of the joint with the grade 5.6 bolts. In addition, the initial stiffness and energy consumption performance of the joint with the grade 8.8 bolts are slightly higher than those of the joint connected by the grade 5.6 bolts. Then for the axial compression ratio, we obtain from the simulation results that the bearing capacity of the joint with higher axial compression ratio decreases faster. And the joint with the higher axial compression ratio has relatively larger initial stiffness, but worse energy consumption performance. To summarize, the prefabricated joint with the bolt connection in this paper has an excellent performance in resisting seismic loading, good assembly efficiency and post-disaster repair rate, and can provide a reference for the development and application of a new type of prefabricated beam-column joint.

Composite steel beam is commonly used element in multistory steel buildings today. The composite action between the concrete deck and the steel beam reduces both steel weight and deflection, accordingly, enhance floor economy and serviceability. Many earlier researches were carried out to optimize the design of the composite steel beams under both static loading and dynamic behavior. None of these

In many situations, it is necessary to have a beam web opening in the plastic hinge location. However, very limited studies investigated the behavior of reinforced concrete (RC) beam-column joints with nearby beam web openings. A previous study was conducted for investigating the behavior of beam-column joints with unreinforced nearby web opening. In this study, the effect of adding additional reinforcing around a nearby web opening on the seismic behavior of RC exterior Beam-Column joints is being investigated. Nine full-scale beam-column joints were tested, four joints had an unreinforced opening, while five joints had reinforced opening. The behavior of the beam-column joints is described in terms of maximum resisting load, deflection, energy dissipated, and stiffness degradation. The behavior was significantly affected by the nearby opening. The increase in opening width and the reduction in the distance between the opening and the column resulted in decreasing the strength and ductility of the RC beam-column joint. However, adding additional reinforcement improved the behavior. Thus, it is recommended to provide additional reinforcement all around the opening.

In many situations, it is necessary to have a beam web opening in the plastic hinge location. However, very limited studies investigated the behavior of reinforced concrete (RC) beam-column joints with nearby beam web openings. A previous study was conducted for investigating the behavior of beam-column joints with unreinforced nearby web opening. In this study, the effect of adding additional

the paper presents an efficient scheme for a Nonlinear PID (NPID) controller to improve the dynamic response of the Electric Vehicle (EV). The objective of the proposed controller is to track accurately the reference speed selected by the driver of the EV. A MATLAB/Simulink model is established and validated for the considered EV to study the system performance. The proposed NPID controller has been investigated by comparing it with the traditional PID controller. The optimal parameters of Both the NPID and PID controllers were obtained using the Harmony Search (HS) optimization technique based on a cost function. The desired rise time, settling time, steady-state error, and overshoot have been taken into account in the cost function. Two tests were performed, the first test was implemented at fixed reference speed while the second one was carried out at a staircase command of reference speed. The simulation results can be summarized as follows: in the first test, the NPID controller reaches the steady-state speed at 38.12 seconds while the PID controller stabilizes at 44.68 seconds. Moreover, the NPID controller has a 0.5% steady-state error however, the PID controller has a 4% steady-state error. Besides, the second test shows that the NPID controller can decrease the root mean square of error by 30.1% compared to the PID controller. Lastly, the proposed NPID controller can enhance EV performance significantly.

Quasi-static cyclic performance of RC exterior beam-column joint assemblages strengthened with geosynthetic materials

The beam-column joints are the most critical and vulnerable part of the RC framed structures when subjected to earthquake load. The objective of the present study is to investigate the cyclic behaviour of seismic and non-seismic exterior reinforced concrete (RC) beam-column joints strengthened with innovative polymeric based geosynthetic materials. Two variants of geosynthetic material named geogrid and geotextile were used for strengthening the beam-column joints in the experimental program. In this strengthening protocol, two different types of strengthening patterns were used in which one was horizontal U-shaped pattern, and the other one was the diagonal cross (X-shaped) pattern. All the beam-column specimens were tested under the quasi-static cyclic loading with controlled amplitude to explore the cyclic performance on the parameters such as failure modes, hysteresis loops, load-deformation envelope curves, ductility, energy dissipation capacity, stiffness and strength degradation behaviour, pinching width ratio, damage index and joint distortion. The test results showed that the adopted strengthening schemes with geotextile and geogrid materials could successfully alter the failure of beam-column joints from shear to flexural and improved the ductile behaviour of the strengthened specimens. The load-carrying capacity and ductility-factor of the geosynthetic strengthened specimens significantly increased up to 48.4% and 37.8%, respectively when compared to the non-seismic control specimen, and it was highest in geogrid strengthened BCJs, especially in diagonal X-shape bonded specimen. The significant increment of energy dissipation capacity was also observed as 2.08 to 3.73 times for the strengthened specimens. Furthermore, the post-elastic performance and the joint shear strength of strengthened RC beam-column joints was also improved in comparison to the non-seismic control specimen. In addition, an analytical study was carried out to predict the shear strength contributions of externally bonded strengthening materials in the RC beam-column joint, which was compared with experimental findings. A good agreement was observed between the analytical and experimental results. Hence, the experimental and analytical study of the strengthened beam-column joints using geotextile and geogrid have confirmed that the appropriate bonding of these materials to the concrete can improve the seismic performance of the non-seismic exterior RC beam-column joints.

Seismic performance and shear bearing-capacity of truss SRC beam-column frame joints

The structural performance of a frame joint is particularly important, which can determine the safe state of the global structure. For this reason, the seismic performance of the truss steel reinforced concrete (SRC) beam-column frame joints is investigated by the experimental study and the nonlinear finite element modeling. The main design parameters include the section size of the web rods, the axial compression ratio and the section size of I-steel. The failure mechanism, load-displacement skeleton curve, the ductility and energy dissipation capacity, and shear deformation in the core zone of the truss SRC beam-column joints are studied. A formula is put forward to describe the shear bearing-capacity of the joints. The results indicate that the truss SRC beam-column frame joints generally have good seismic performance. The size of steel and web members have impact on the seismic performance of the truss SRC beam-column joints, and the axial compression ratio is an important factor that impacts the hysteresis behavior and energy dissipation. The proposed shear bearing-capacity formula can objectively reflect the performance of the joints.

Seismic performance of exterior reinforced concrete beam-column joint with corroded reinforcement

Corrosive environment adversely affects the durability of existing reinforced concrete (RC) structures as well as its performance under seismic loading. In this paper, the seismic behaviour of corroded reinforced concrete (RC) exterior joint was experimentally evaluated. Eight similar RC exterior joints with various corrosion level of reinforcements were tested under two levels of representative column axial force ratio. Lateral loading resisting, ductility, energy dissipation and stiffness of corroded specimens were examined and compared with uncorroded control specimens. Joint shear stress and the development length of beam longitudinal reinforcement were investigated and compared with available design code. In addition, the joint internal force flow of corroded joint was investigated analytically based on modified strut-and-tie model (STM). Experimental results indicate that corrosion of reinforcements have significant adverse effect on the strength and lateral drift capacity of the joints as well as other mechanical properties. Based on the STM model and parametric study, it is further found that the effect of corrosion level on joint stress level is more significant at higher axial force ratio. In addition, an axial force ratio above 0.2 is detrimental to the joint.

Improved shear strength model for exterior reinforced concrete beam-column joints using gene expression programming

Beam-column joints without transverse reinforcement can be considered as a weak link in reinforced concrete (RC) moment-resisting framed structural systems, particularly when subjected to seismic lateral loads. It is essential to fully understand the shear behavior of RC beam-column joints to avoid significant damage and eventual failure of RC structures in the case of joint panels excessively damaged. This study aims at developing a framework for systematic understanding of the shear behavior of RC beam-column joints where a novel joint shear strength model is presented. Totally, 56 test results on exterior RC beam-column joints without transverse reinforcement from various sources were used. The proposed model was generated by the utilization of the gene expression programming (GEP) approach. Thus, statistically, significant tests were applied for evaluating the different parameters influencing the shear strength of the joint, e.g., material features, design variables, and joint geometrical and detailing configurations. The proposed model was able to appropriately reflect the contribution of each variable of the beam-column joints involved in the GEP. The presented findings also include a comparison of the developed GEP-model with the existing analytical models, i.e., the conjectures of these available models were compared with the achieved results of this study. It is demonstrated that the presented GEP-model more accurately predicted the shear strength of RC beam-column joints than the existing models, having a much smaller coefficient of variation of 0.093 for the ratio between the predicted and experimentally determined shear strength values, compared to other models available in the literature.

Analytical Examination of Reinforced Concrete with Hybrid Fibres Exterior Beam Column Joint

This research paper pacts with the analytical examination of synthetic fibres (Polypropylene and Recycled polyethylene terephthalate RPET) and steel fibres in reinforced exterior beam column joint by using ANSYS. Based on IS 10262-2009, M40 grade of concrete was prepared along by volume fractions up to 0.5% of synthetic and steel fibre. 9 number of exterior beam column joint with various proportions of hybrid fibre incorporated reinforced concrete specimens were tested by means of monotonic loading. Their experimental results exhibited that reinforced concrete exterior beam column joint specimens with hybrid fibre specimens achieved superior performance along with high ductility, high strength and less crack patterns. The main aim of this research paper was based on the experimental input, analytical examination by ANSYS was carried out and related with the experimental results found. The comparison showed that both the experimental and numerical results similar.

Main factors determining the shear behavior of interior RC beam-column joints

Reinforced concrete beam-column (RCBC) joints of laterally loaded unbraced frames are sometimes controlled by their shear behavior. This behavior relies on multiple and interdependent complex mechanisms. There are already several studies on the influence of some parameters on the shear strength of reinforced concrete joints. However, there are no studies methodically tackling all the most relevant parameters and quantifying their influence on the overall joint behavior, not just on its shear strength. Hence, considering the prohibitive cost of a comprehensive parametric experimental investigation, a nonlinear finite element analysis (NLFEA) was undertaken to identify the key factors affecting the shear behavior of such joints and quantify their influence. The paper presents and discusses the models employed in this NLFEA and the procedure used to deduce the joint behavior from the NLFEA results. Three alternative, or complementary, quantities related to shear are considered when comparing results, namely, the maximum shear stress supported by the joint, the secant shear stiffness at maximum shear stress and the secant shear stiffness in service conditions. Depending on which of these is considered, the lower or higher the relevance of each of the six parameters investigated: transverse reinforcement in the joint, intermediate longitudinal bars and diagonal bars in the column, concrete strength, column axial load and confining elements in transverse direction.

A Review on Reinforced Concrete Beam Column Joint: Role, Modeling and Recent Details

Reinforced concrete frames are commonly used systems in buildings. The philosophy behind the proper design for this type of frames is to provide them with sufficient ductility. The structural ductility of a frame is mainly determined by the ductility of its components, i.e., the beams, columns, and joints forming this frame. Beam-column joint role in a building is to connect its components together and enable these components to reach their ultimate resistance. Its stiffness, strength, and ductility are key characteristics needed to guarantee efficient building behaviour under the action of different loads. Previous research attributed some building’s damage to inadequate reinforcement details of its joints. Deficiency in joints performance is related to inadequate codes guidelines or to bad construction practice. This paper reviewed the provisions of three different codes (ACI 318-08, Eurocode 8, and ECP-203) concerning the proper design and detailing of different joints. This review study aims to introduce a wider overview on the assessment of joints performance in buildings under different loading scenarios. This data base will enable practicing engineers to identify the joint key parameters with providing different analytical procedures. This study investigates joints in different configurations. These include planner joints, joints with transverse beams, and the common joint situation with the presence of both transverse beams and slab. This survey includes experimental and analytical representation of the previous mentioned joints. Different retrofitting schemes are presented as well for every considered joint. This review allows to identify the evolution of joints capacity in function of reinforcement detailing, level of axial stresses, and loading history. The analysis shows that a decrease in joint resistance can be recovered by using i) haunches brackets, ii) FRP, or iii) post tension metal strip.

Application of ultra-high performance fiber reinforced concrete for retrofitting the damaged exterior reinforced concrete beam-column joints

In the present research work, the effectiveness and the efficiency of a retrofitting approach using a layer of ultra-high performance fiber reinforced concrete (UHPFRC) jacket for damaged substandard exterior beam-column joints (BCJs) is experimentally investigated. The main objective of this study is to rehabilitate the already damaged BCJs to meet the serviceability requirements without compromising safety. According to the proposed strengthening technique, a chipped surface, lightly brushed with a dry condition was selected for making a successful bond between normal concrete substrate surface (NCSS) and UHPFRC. Then a fresh UHPFRC jacket with a thickness of 30 mm was cast around the damaged specimens. The entire test matrix was comprised of three 1/3 scale damaged exterior BCJs with a different column axial load (CAL). These specimens were repaired with UHPFRC and retested under monotonic loading. Based on the experimental results, repaired specimens showed an excellent performance in terms of their load-displacement response, maximum strength, displacement ductility, initial stiffness, secant stiffness and energy dissipation capacity when compared with the corresponding values registered when these specimens were tested in their virgin state. This rehabilitative intervention not only restored the strength, stiffness, ductility and energy dissipation capacity of severely damaged specimens but also improved their performance.

Seismic performance of reinforced concrete interior beam-column joints with novel reinforcement detail

Horizontal stirrups are normally required in reinforced concrete (RC) beam-column joints (BCJs) for resisting shear forces in seismic design. For RC moment-resisting frames subjected to a high lateral load, a large number of stirrups are needed in joint cores. This may cause reinforcement congestion, leading to construction difficulty and insufficient concrete compaction, which can result in poor seismic performance. In this study, a novel reinforcement detail in the form of unbonded diagonal bars mechanically anchored at beam ends is proposed for RC interior BCJs. The detail alleviates the reinforcement congestion through partially replacing horizontal stirrups, and improves the seismic performance of BCJs by plastic hinge relocation and input shear force reduction mechanisms. Four 2/3-scale RC interior BCJ specimens were prepared and tested under quasi-static cyclic load, including one specimen designed with the current code and three specimens adopting the proposed reinforcement detail. Test results show that the proposed reinforcement detail is able to relocate the plastic hinges away from beam-joint interfaces as well as improve the loading capacity, energy dissipation capacity, stiffness, and bonding condition of beam reinforcements within the cores of BCJs. The combined use of stirrups and the proposed reinforcement detail significantly enhances the cracking resistance and reduces joint distortion, while additional amount of stirrups results in a marginal improvement. Moreover, an analytical model considering plastic hinge relocation and input joint shear force reduction is proposed for BCJs with the novel reinforcement detail. The model can adequately predict the failure mode and loading capacity of BCJ specimens.

Upgrading of precast RC beam-column joints using innovative FRP/steel hybrid technique for progressive collapse prevention

This study aims at investigating the efficacy of using an innovative hybrid strengthening technique composed of near-surface mounted (NSM) steel rebars along with fiber reinforced polymer (FRP) sheets to prevent (or diminish) the risk of progressive collapse in precast reinforced concrete (RC) beam-column joints. The study details tests involving one control specimen that is a half-scale single-story precast RC beam-column assembly having two bays. One monolithic test specimen with continuous longitudinal beam rebars was employed for comparison. The third specimen was similar to the control one, but it was retrofitted using FRP sheets combined with NSM steel rebars within the beam-column joint zone. The base of the center column was released, and a dynamic load was applied in the vertical direction on this column for simulating the column-removal scenario of progressive collapse. The proposed strengthening technique was efficient at enhancing the peak load and dissipated energy of the upgraded specimen by about 16.9 and 12.4 times, respectively, of control precast specimen. Three dimensional (3D) finite element (FE) models that consider rate-dependent material nonlinearity and bond behavior at FRP-to-concrete interface were also devised to predict the behavior of test specimens. Good agreement was obtained between the experimental and FE results with prediction errors ranging from 0% to 4%, 1% to 17%, and 3% to 10% for peak load, center column displacement at peak load, and dissipated energy at ultimate state. The validated FE models were employed for parametric studies of practical interest for investigating the impact of different strengthening parameters on the behavior of test specimen under the middle column-loss scenario.

Experimental Research on Seismic Behavior of High Strength Bar Concrete Beam-Column Joints Reinforced by Steel Fiber

Experimental Research on Seismic Behavior of High Strength Bar Concrete Beam-Column Joints Reinforced by Steel Fiber

Cyclic behaviors of reinforced concrete beam-column joints with debonded reinforcements and beam failure: experiment and analysis

It was experimentally validated that partially debonded high-strength longitudinal reinforcement can provide strong self-centering capacity to minimize residual deformation, and greatly mitigate seismic damage of column. To continuously investigate the influence of partially debonded longitudinal rebars (PDLR) of column and beam on seismic behaviors of beam-column joint assembly, three interior and three exterior joint specimens were fabricated to subject to cyclic lateral loading. It was showed experimentally that joint specimens with PDLRs in both beams and columns had slighter seismic damages, smaller stiffness and energy dissipating ratios, better ductility compared with joint specimens without PDLRs in the beams. Furthermore, the lateral load of joint specimens without PDLRs in the beams decreased from lateral drift of about 4.0%–5.0% due to much crushing and spalling of concrete in the compressive zones of the beams. Whereas, joint specimens with PDLRs in the beams had continuously increased lateral load until lateral drift up of 10.0%. An analytical approach was derived to evaluate the lateral behavior of beam-column joint assembly which can considering joint deformation and steel bond slip. The proposed approach can reasonably predict the lateral behaviors of joint specimens with or without PDLRs. Analytical results indicate that approximately 70% of total deformation of joint specimens with PDLRs in both beams and columns is contributed by slippage deformation of the beams, whereas, that contribution ratio of the other joint assembly specimens is only 30%.

Evaluation of a Macro Lump Plasticity Model for Reinforced Concrete Beam-Column Joint under Cyclic Loading

Lateral deformations of reinforced concrete (RC) frames under extreme seismic excitation are highly affected by the stiffness of their beam-column joints. Numerous models have been proposed to simulate the responses of RC beam-column joint under cyclic loading. Development of RC beam-column joint model based on macro modeling using spring elements becomes more popular because of its considerably simple application for seismic performance evaluation purposes. In this study, a simple modification to previously developed macro-spring element-based model for RC beam-column joint is done and is used to simulate the behavior of seven external and five internal RC joints under cyclic loading in SAP2000. The model consists of several spring elements to define column, beam, joint, and bond-slip responses according to its individual moment-rotation relationships. Overall, the analysis results show that the modified model can simulate well the cyclic behavior of RC beam-column joints when are compared to previously available experimental results

Investigation of dynamic bond-slip behaviour of reinforcing bars in concrete

Under dynamic loading conditions, the bond between reinforcing bars and concrete significantly affects the structural behaviour of reinforced concrete beam-column joints. Nonetheless, limited data are available with regard to the dynamic bond-slip relationship of steel reinforcement. This paper describes the dynamic bond-slip behaviour of steel rebars in concrete. In the experimental programme, a total of 63 specimens, with different compressive strengths of the surrounding concrete and embedment lengths of reinforcement, were tested under pull-out loads. The loading rate ranged from 0.1 mm/s to 100 mm/s. Besides the tension force and the measured slip, the strain profile of reinforcement was also monitored by using strain gauges mounted to the reinforcement along its longitudinal ribs, and the corresponding bond stress was calculated based on force equilibrium. Comparisons were made between static and dynamic bond stresses to shed light on the influence of loading rate on bond stress distribution. Moreover, an analytical method was developed based on test data, and the analytical stress-slip relationship, strain and bond stress distributions were obtained by using the method. The analytical results are in reasonably good agreement with the experimental data, suggesting that the model can be used to predict the bond-slip behaviour of reinforcing bars subjected to different loading rates.