• Earthquakes and Structures
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• v.15 no.5
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• pp.499-511
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• 2018

This paper aims to investigate the seismic performance of the prestressed steel strips retrofitted RC beam-column joints. Two series of joint specimens were conducted under compression load and reversed cyclic loading through quasi-static tests. Based on the test results, the seismic behavior of the strengthened joints specimens in terms of the failure modes, hysteresis response, bearing capacity, ductility, stiffness degradation, energy dissipation performance and damage level were focused. Moreover, the effects of the amount of the prestressed steel strips and the axial compression ratio on seismic performance of retrofitted specimens were analyzed. It was shown that the prestressed steel strips retrofitting method could significantly improve the seismic behavior of the RC joint because of the large confinement provided by prestressed steel strips in beam-column joints. The decrease of the spacing and the increase of the layer number of the prestressed steel strips could result in a better seismic performance of the retrofitted joint specimens. Moreover, increasing the axial compression ration could enhance the peak load, stiffness and the energy performance of the joint specimens. Furthermore, by comparison with the specimens reinforced with CFRP sheets, the specimens reinforced with prestressed steel strips was slightly better in seismic performance and cost-saving in material and labor. Therefore, this prestressed steel strips retrofitting method is quite helpful to enhance the seismic behavior of the RC beam-column joints with reducing the cost and engineering time.

• Journal of the Korea Concrete Institute
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• v.12 no.2
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• pp.53-62
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• 2000

Under severe lateral loads, ductile moments-resisting reinforced concrete frames will be subjected to large loads and displacements. Thus, large deformation and shear stree are occurred at the beam-column joints which are the most critical region in ductile moments-resisting system. The purpose of this study was to investigate the shear strength of beam-column connection using high strength concrete. Four subassemblies were designed 2/3 scale of read structures and tested. The obtained results are as follows. 1) The transverse beams increase the shear resistance and ductility of joint, 2) The slab was contributed to increase of the flexural capacity of the beam, but was not contributed to increase the joint ductility under cyclic loads. 3) The shear stress factors. given by the ACI code would be modified in evaluating the shear strength of beam-column joints of frame which were constructed with high-strength concrete.

• Computers and Concrete
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• v.31 no.5
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• pp.419-432
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• 2023

Beam-column joints are a critical component of reinforced concrete frame structures. They are responsible for transferring forces between adjoining beams and columns while limiting story drifts and maintaining structural integrity. During severe loading, beam-column joints deform significantly, affecting, and sometimes governing, the overall response of frame structures. While most failure modes for beam and column elements are commonly considered in plastic-hinge-based global frame analyses, the beam-column joint failure modes, such as concrete shear and reinforcement bond slip, are frequently omitted. One reason for this is the dearth of published guidance on what type of hinges to use, how to derive the joint hinge properties, and where to place these hinges. Many beam-column joint models are available in literature but their adoption by practicing structural engineers has been limited due to their complex nature and lack of practical application tools. The objective of this study is to provide a comparative review of the available beam-column joint models and present a practical joint modeling approach for integration into commonly used global frame analysis software. The presented modeling approach uses rotational spring models and is capable of modeling both interior and exterior joints with or without transverse reinforcement. A spreadsheet tool is also developed to execute the mathematical calculations and derive the shear stress-strain and moment-rotation curves ready for inputting into the global frame analysis. The application of the approach is presented by modeling a beam column joint specimen which was tested experimentally. Important modeling considerations are also presented to assist practitioners in properly modeling beam-column joints in frame analyses.

• Proceedings of the Korea Concrete Institute Conference
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• 2006.05a
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• pp.106-109
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• 2006

It has been shown that many reinforced concrete(RC) structures designed without seismic details have experienced brittle shear failures in the beam-column joint area and may result in large permanent deformations and structural collapse. In this study, experimental investigations for RC beam-column joints strengthened with the carbon fiber-reinforced polymer(CFRP) under cyclic loadings were presented. The use of CFRP in the joint was varied to determine the effective way of improving the structural performances of RC joints. Ten RC beam-column joints were designed and tested with cyclic loadings. The experimental results showed that the use of CFRP in RC joints would be very effective solutions to improve the seismic performances of the non-seismic RC joints. All of the non-seismic design specimens strengthened with CFRP sheets showed the significant increase of strength and ductility.

• Structural Engineering and Mechanics
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• v.21 no.4
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• pp.393-406
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• 2005

Cyclic loading tests were carried out on six half-scale reinforced concrete beam-column subassemblages designed to the current Chinese Seismic Design Code for Buildings. The deformation behavior and restoring force characteristics of the subassemblages were studied. Emphasis was directed on their seismic behavior and deformation components. Based on test data and a simplified analysis model of the global and local deformation, the contribution of the deformation components due to beam flexure, column flexure, joint shear, and slippage of longitudinal reinforcement in the joint to the global deformation of subassemblages at different displacement amplitudes of cyclic loading was investigated.

• Proceedings of the Korea Concrete Institute Conference
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• 2006.11a
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• pp.105-108
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• 2006

Current ACI and AIJ guidelines only address the importance of the concrete strength and geometry of the joint. There are no significant attention paid to other variables. In addition, the current design code doesn't predict the ductility of the beam-column assemblies. The former researcher proposed the analytical model to predict the shear strength of the joint panel as well as the ductility of the beam-column assemblies in year 2004. In this study, the experiments to investigate shear behavior of reinforced concrete beam-column joints and to verify proposed model were carried out, based on the experimental results. As the formal researcher proposed, the factor K (K=0.5), the ductility of BJ-failure was predicted reasonably when the transverse reinforcement ratio exceeded 0.0186. However, the proposed equation showed a large discrepancies in the ductility estimating when transverse reinforcement ratio was below 0.0186.

• Structural Engineering and Mechanics
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• v.71 no.4
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• pp.341-350
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• 2019

Exterior beam-column joint is typically the weakest link in a limited-ductile reinforced concrete (RC) frame structure. The use of diagonal haunch element has been considered as a desirable seismic retrofit option for reducing the seismic demand at the joint. Previous research globally has focused on implementing double haunches, while the use of single haunch element as a less-invasive and more architecturally favorable retrofit option has not been investigated. In this paper, the key formulations and a design procedure for the single haunch system for retrofitting RC exterior beam-column joint are developed. An application of the proposed design procedure is then illustrated through a case study.

• Earthquakes and Structures
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• v.9 no.1
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• pp.233-256
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• 2015

This paper presents an experimental study to assess the effectiveness of using ferrocement to strengthen deficient beam-column joints. Ferrocement is proposed to protect the joint region through replacing concrete cover. Six exterior beam-column joints, including two control specimens and four strengthened specimens, are prepared and tested under constant axial load and quasi-static cyclic loading. Two levels of axial load on column (0.2fc'Ag and 0.4fc'Ag) and two types of skeletal reinforcements in ferrocement (grid reinforcements and diagonal reinforcements) are considered as test variables. Experimental results have indicated that ferrocement as a composite material can enhance the seismic performance of deficient beam-column joints in terms of peak horizontal load, energy dissipation, stiffness and joint shear strength. Shear distortions within the joints are significantly reduced for the strengthened specimens. High axial load (0.4fc'Ag) has a detrimental effect on peak horizontal load for both control and ferrocement-strengthened specimens. Specimens strengthened by ferrocement with two types of skeletal reinforcements perform similarly. Finally, a method is proposed to predict shear strength of beam-column joints strengthened by ferrocement.

• Structural Engineering and Mechanics
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• v.30 no.6
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• pp.733-761
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• 2008

The failure of reinforced concrete structures in recent earthquakes caused concern about the performance of beam column joints. Confinement of joint is one of the ways to improve the performance of beam column joints during earthquakes. This paper describes an experimental study of exterior beam-column joints with two non-conventional reinforcement arrangements. One exterior beam-column joint of a six story building in seismic zone III of India was designed for earthquake loading. The transverse reinforcement of the joint assemblages were detailed as per IS 13920:1993 and IS 456:2000 respectively. The proposed nonconventional reinforcement was provided in the form of diagonal reinforcement on the faces of the joint, as a replacement of stirrups in the joint region for joints detailed as per IS 13920 and as additional reinforcement for joints detailed as per IS 456. These newly proposed detailing have the basic advantage of reducing the reinforcement congestion at the joint region. In order to study and compare the performance of joint with different detailing, four types of one-third scale specimens were cast (two numbers in each type). The main objective of the present study is to investigate the effectiveness of the proposed reinforcement detailing. All the specimens were tested under reverse cyclic loading, with appropriate axial load. From the test results, it was found that the beam-column joint having confining reinforcement as per IS: 456 with nonconventional detailing performed well. Test results indicate that the non-conventionally detailed specimens, Type 2 and Type 4 have an improvement in average ductility of 16% and 119% than their conventionally detailed counter parts (Type1 and Type 3). Further, the joint shear capacity of the Type 2 and Type 4 specimens are improved by 8.4% and 15.6% than the corresponding specimens of Type 1 and Type 3 respectively. The present study proposes a closed form expression to compute the yield and ultimate load of the system. This is accomplished using the theory of statics and the failure pattern observed during testing. Good correlation is found between the theoretical and experimental results.

• Architectural research
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• v.20 no.2
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• pp.53-64
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• 2018

A nonlinear analytical model has been proposed for two-span two-story reinforced concrete frames with relaxed section details. The analytical model is composed of beam, column, and beam-column joint elements. The goal of this study is to develop a simple and light nonlinear model for two-dimensional reinforced concrete frames since research in earthquake engineering is usually involved in a large number of nonlinear dynamic analyses. Therefore, all the nonlinear behaviors are modeled to be concentrated on flexural plastic hinges at the end of beams and columns, and the center of beam-column joints. The envelope curve and hysteretic rule of the nonlinear model for each element are determined based on experimental results, not theoretical approach. The simple and light proposed model can simulate the experimental results well enough for nonlinear analyses in earthquake engineering. Consequently, the proposed model will make it easy to developing a nonlinear model of the entire frame and help to save time to operate nonlinear analyses.