• Journal of the Computational Structural Engineering Institute of Korea
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• v.24 no.2
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• pp.201-210
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• 2011

This paper presents a nonlinear finite element analysis procedure for the seismic performance assessment of deep beam-and-interior column joints. A computer program, named RCAHEST(Reinforced Concrete Analysis in Higher Evaluation System Technology), for the analysis of reinforced concrete structures was used. Horizontal cyclic load tests were conducted to estimate the strength, ductility, and behavioral characteristics of deep beam-and-interior column joints. Experimental parameters are axial forces and amount of transverse reinforcement. The proposed numerical method for the seismic performance assessment of deep beam-and-interior column joints is verified by comparison of its results with reliable experimental results.

• Structural Engineering and Mechanics
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• v.86 no.3
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• pp.417-430
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• 2023

As the key part in the reinforced concrete column-steel beam (RCS) frame, the beam-column joints are usually subjected the axial force, shear force and bending moment under seismic actions. With the aim to study the seismic behavior of RCS joints with and without RC slab, the quasi-static cyclic tests results, including hysteretic curves, slab crack development, failure mode, strain distributions, etc. were discussed in detail. It is shown that the composite action between steel beam and RC slab can significantly enhance the initial stiffness and loading capacity, but lead to a changing of the failure mode from beam flexural failure to the joint shear failure. Based on the analysis of shear failure mechanism, the calculation formula accounting for the influence of RC slab was proposed to estimate shear strength of RCS joint. In addition, the finite element model (FEM) was developed by ABAQUS and a series of parametric analysis model with RC slab was conducted to investigate the influence of the face plates thickness, slab reinforcement diameter, beam web strength and inner concrete strength on the shear strength of joints. Finally, the proposed formula in this paper is verified by the experiment and FEM parametric analysis results.

• Computers and Concrete
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• v.18 no.6
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• pp.1083-1096
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• 2016

Beam-column joints are recognized as the weak points of reinforcement concrete frames. The ductility of reinforced concrete (RC) frames during severe earthquakes can be measured through the dissipation of large energy in beam-column joint. Retrofitting and rehabilitating structures through proper methods, such as carbon fiber reinforced polymer (CFRP), are required to prevent casualties that result from the collapse of earthquake-damaged structures. The main challenge of this issue is identifying the effect of CFRP on the occurrence of failure in the joint of a cross section with normal ductility. The present study evaluates the retrofitting method for a normal ductile beam-column joint using CFRP under monotonic and cyclic loads. Thus, the finite element model of a cross section with normal ductility and made of RC is developed, and CFRP is used to retrofit the joints. This study considers three beam-column joints: one with partial CFRP wrapping, one with full CFRP wrapping, and one with normal ductility. The two cases with partial and full CFRP wrapping in the beam-column joints are used to determine the effect of retrofitting with CFRP wrapping sheets on the behavior of the beam-column joint confined by such sheets. All the models are subjected to monotonic and cyclic loading. The final capacity and hysteretic results of the dynamic analysis are investigated. A comparison of the dissipation energy graphs of the three connections shows significant enhancement in the models with partial and full CFRP wrapping. An analysis of the load-displacement curves indicates that the stiffness of the specimens is enhanced by CFRP sheets. However, the models with both partial and full CFRP wrapping exhibited no considerable improvement in terms of energy dissipation and stiffness.

• Journal of the Earthquake Engineering Society of Korea
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• v.10 no.5 s.51
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• pp.25-33
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• 2006

This paper provides a method to predict the ductile capacity of reinforced concrete beam-column joints that fail in shear after the plastic hinges occur at both ends of the adjacent beams. After the plastic hinges occur at both ends of the beams, the longitudinal axial strain at the center of the beam section in the plastic hinge region abruptly increases because the neutral axis continues to move upward toward the extreme compressive fiber and the residual strain of the longitudinal bars continues to increase with each cycle of inelastic loading. An increase in the axial strain of the beam section after flexural yielding widens the cracks in the beam-column joints, thus leading to an decrease of the shear strength of the beam-column joints. The proposed method takes into account shear strength deterioration in the beam-column joints. In order to verify the shear strength and the corresponding ductility of the proposed method, test results of 52 RC beam-column assembles were compared. Comparisons between the observed and calculated shear strengths and their corresponding ductilities of the tested assembles, showed reasonable agreement.

• Proceedings of the Korea Concrete Institute Conference
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• 2003.05a
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• pp.397-402
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• 2003

This paper presents strut-and-tie models for predicting shear strength of RC interior beam-column joints considering the plastic hinge rotation of adjacent beams. On seismic design of frame system, it is controlled beams to occur plastic hinges and to be ductile so as to dissipate earthquake energy efficiently. The plastic hinge deformation of beams is used as analysis parameter in terms of strain of beam tensile bars at column face. The shear strengths of beam-column joints are evaluated by combining direct strut mechanism with truss mechanism. It is assumed that the max force transferred by direct strut mechanism is based on the strength of cracked concrete element, and that by truss mechanism is based on bond capacity.

• Advances in concrete construction
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• v.3 no.3
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• pp.237-250
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• 2015

Beam-column joints are highly vulnerable locations which are to be designed for high ductility in order to take care of unexpected lateral forces such as wind and earthquake. Previous investigations reveal that the addition of steel fibres to concrete improves its ductility significantly. Also, due to presence of slab the strength and ductility of the beam increases considerably and ignoring the effect of slab can lead to underestimation of beam capacity and defiance of strong column weak beam concept. The influence of addition of steel fibres on the strength and behaviour of steel fibre reinforced high performance concrete (SFRHPC) interior beam-column-slab joints was investigated experimentally. The specimens were subjected to reverse cyclic loading. The variable considered was the volume fraction of crimped steel fibres i.e., 0%, 0.5% and 1.0%. The results show that the addition of steel fibres improves the first crack load, strength, ductility, energy absorption capacity and initial stiffness of the beam.

• Earthquakes and Structures
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• v.7 no.5
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• pp.705-718
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• 2014

This paper presents an analytical model for determining the transverse reinforcement required for reinforced concrete exterior beam-column joints subjected to reversed cyclic loading. Although the joint aspect ratio can affect joint shear strength, current design codes do not consider its effects in calculating joint shear strength and the necessary amount of transverse reinforcement. This study re-evaluated previous exterior beam-column joint tests collected from 11 references and showed that the joint shear strength decreases as the joint aspect ratio increases. An analytical model was developed, to quantify the transverse reinforcement required to secure safe load flows in exterior beam-column joints. Comparisons with a database of exterior beam-column joint tests from published literature validated the model. The required sectional ratios of horizontal transverse reinforcement calculated by the proposed model were compared with those specified in ACI 352R-02. More transverse reinforcement is required as the joint aspect ratio increases, or as the ratio of vertical reinforcement decreases; however, ACI 352R-02 specifies a constant transverse reinforcement, regardless of the joint aspect ratio. This reevaluation of test data and the results of the analytical model demonstrate a need for new criteria that take the effects of joint aspect ratio into account in exterior joint design.

• Computers and Concrete
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• v.15 no.5
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• pp.807-831
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• 2015

In the previous analytical studies on 2D reinforced concrete (RC) beam-column joints, the modified compression field theory (MCFT) and the strut-and-tie method (STM) are usually employed. In this paper, the limitations of these analytical models for RC joint applications are reviewed. Essentially for predictions of RC joint shear behaviour, the MCFT is not applicable, while the STM can only predict the ultimate shear strength. To eliminate these limitations, an improved STM is derived and applied to some commonly encountered 2D joints, viz., interior and exterior joints, subjected to monotonic loading. Compared with the other STMs, the most attracting novelty of the proposed improved STM is that all critical stages of the shear stress-strain relationships for RC joints can be predicted, which cover the stages characterized by concrete cracking, transverse reinforcement yielding and concrete strut crushing. For validation and demonstration of superiority, the shear stress-strain relationships of interior and exterior RC beam-column joints from published experimental studies are employed and compared with the predictions by the proposed improved STM and other widely-used analytical models, such as the MCFT and STM.

• Steel and Composite Structures
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• v.29 no.6
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• pp.717-734
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• 2018

This paper presents the flexural performance of steel beam-to-column joints composed of hollow structural section beams and columns. A finite element (FE) model was developed incorporating geometrical and material nonlinearities to evaluate the behaviour of joints subjected to bending moments. The numerical outcomes were validated with experimental results and compared with EN1993-1-8. The demountability of the structure was discussed based on the tested specimen. A parametric analysis was carried out to investigate the effects of steel yield strength, end-plate thickness, beam thickness, column wall thickness, bolt diameter, number of bolts and location. Consequently, an analytical model was derived based on the component method to predict the moment-rotation relationships for the sub-assemblies with extended end-plates. The accuracy of the proposed model was calibrated by the experimental and numerical results. It is found that the FE model is fairly reliable to predict the initial stiffness and moment capacity of the joints, while EN1993-1-8 overestimates the initial stiffness extensively. The beam-to-column joints are shown to be demountable and reusable with a moment up to 53% of the ultimate moment capacity. The end-plate thickness and column wall thickness have a significant influence on the joint behaviour, and the layout of double bolt-rows in tension is recommended for joints with extended end-plates. The derived analytical model is capable of predicting the moment-rotation relationship of the structure.

• Earthquakes and Structures
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• v.7 no.5
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• pp.861-875
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• 2014

This paper studies the response of seismic behavior of reinforced concrete exterior beam-column joints under reversal loading with different anchorages and joint core details. The joint core was detailed without much confinement (group-I) and/or with proposed X-cross bars in the core (group-II). The beam longitudinal reinforcement's anchorages were designed as per ACI 352 (headed bars), ACI 318 (conventional $90^{\circ}$ bent hooks) and IS 456 ($90^{\circ}$ bent hooks with extended tails). The nonlinear finite element analysis response of the beam-column joints was studied, along with initial and progressive cracks up to failure. The experimental and analytical results were compared and presented in this paper to make more scientific conclusions.