• Proceedings of the Korea Concrete Institute Conference
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• 2000.04a
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• pp.539-544
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• 2000

The purpose of this study is to develop the mechanical anchorage, namely MAB-BOP (Mechanical Anchorage of 90$^{\circ}$ Hooked Bars with BOlt nad Plate) of the beam-column joint in precast concrete framed structures. Six specimens simulating typical interior beam-column joints were tested to investigate the mechanical characteristics of MAB-BOP. Of primary interest was the measurement of the slip of the anchored bar. Th load-slip curve obtained from this test were used to compare the mechanical performances of the different anchoring methods. Based on the test results, it was found that MAB-BOP showed sufficient anchoring strength capacity compared to 90$^{\circ}$ hooked bar method. So, MAB-BOP can be used as the anchoring methods of the reinforcing bars in PC beam-column joint.

• 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.

• Journal of the Earthquake Engineering Society of Korea
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• v.23 no.5
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• pp.249-259
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• 2019

To study the seismic resistance of the shear capacity of the RC beam-column joints of two-story and four-story RC buildings, sample buildings are designed with ordinary moment resisting frame. For the shear capacity of joints, the equations of FEMA 356 and NZ seismic assessment are selected and compared. For comparison, one group of buildings is designed only for gravity loads and the other group is designed for seismic and gravity loads. For 16 cases of the designed buildings, seismic performance point is evaluated through push-over analysis and the capacity of joint shear strength is checked. Not only for the gravity designed buildings but also for seismic designed buildings, the demand of joint shear is exceeding the capacity at exterior joints. However, for interior joint, the demand of joint shear exceeds the capacity only for one case. At exterior joints, the axial load stress ratio is lower than 0.21 for gravity designed buildings and 0.13 for seismic designed buildings.

• Earthquakes and Structures
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• v.20 no.4
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• pp.417-430
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• 2021

Due to functional requirements, SRC column-RC beam abnormal joints with characteristics of strong beam weak column, variable column section, unequal beam height and staggered height exist in the Steel reinforced concrete (SRC) frame-bent main building structure of thermal power plant (TPP). This paper presents the experimental results of these abnormal joints through cyclic loading tests on five specimens with scaling factor of 1/5. The staggered height and whether adding H-shaped steel in beam or not were changing parameters of specimens. The failure patterns, bearing capacity, energy dissipation and ductile performance were analyzed. In addition, the stress mechanism of the abnormal joint was discussed based on the diagonal strut model. The research results showed that the abnormal exterior joints occurred shear failure and column end hinge flexural failure; reducing beam height through adding H-shaped steel in the beam of abnormal exterior joint could improve the crack resistance and ductility; the abnormal interior joints with different staggered heights occurred column ends flexural failure; the joint with larger staggered height had the higher bearing capacity and stiffness, but lower ductility. The concrete compression strut mechanism is still applicable to the abnormal joints in TPP, but it is affected by the abnormal characteristics.

• Advances in concrete construction
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• v.9 no.3
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• pp.313-326
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• 2020

Glass fiber-reinforced polymer (GFRP) bars have been introduced as an effective alternative for the conventional steel reinforcement in concrete structures to mitigate the costly consequences of steel corrosion. However, despite the superior performance of these composite materials in terms of corrosion, the effect of replacing steel reinforcement with GFRP on the seismic performance of concrete structures is not fully covered yet. To address some of the key parameters in the seismic behavior of GFRP-reinforced concrete (RC) structures, two full-scale beam-column joints reinforced with GFRP bars and stirrups were constructed and tested under two phases of loading, each simulating a severe ground motion. The objective was to investigate the effect of damage due to earthquakes on the service and ultimate behavior of GFRP-RC moment-resisting frames. The main parameters under investigation were geometrical configuration (interior or exterior beam-column joint) and joint shear stress. The performance of the specimens was measured in terms of lateral load-drift response, energy dissipation, mode of failure and stress distribution. Moreover, the effect of concrete damage due to earthquake loading on the performance of beam-column joints under service loading was investigated and a modified damage index was proposed to quantify the magnitude of damage in GFRP-RC beam-column joints under dynamic loading. Test results indicated that the geometrical configuration significantly affects the level of concrete damage and energy dissipation. Moreover, the level of residual damage in GFRP-RC beam-column joints after undergoing lateral displacements was related to reinforcement ratio of the main beams.

• 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 Korea Concrete Institute
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• v.15 no.6
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• pp.894-901
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• 2003

The objective of this study is to clarify the seismic capacity and the characteristics in the hysteretic behavior of RC structures with non-seismic detailing. Interior and exterior beam-column subassemblages were selected from a ten-story RC building and six 1/3-scale specimens were constructed with three variables; (1) with and without slab, (2) with and without hoop bars in the joint region, (3) upward and downward direction of anchorage for the bottom bar in beams of exterior beam-column subassemblage. The test results have shown; (1) in case of interior beam-column subassemblage, there is no almost difference between nonseismic and seismic details in the strength and ductility capacity; (2) the Korean practice of anchorage (downward and 25 $d_{b}$ anchorage length) in the exterior joint caused the 10%∼20% reduction of strength and 27% reduction of ductility in comparison with the case of seismic details; and the existence of hoop bars in the joint region shows no effect in shear strain.

• Journal of the Korea Concrete Institute
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• v.24 no.6
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• pp.753-760
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• 2012

In this study, experimental research was carried out to evaluate and improve the constructability and seismic performance of high strength R/C interior beam-column joints regions, with or without the shear reinforcement, using high ductile fiber-reinforced mortar. Six specimens of retrofitted the beam-column joint regions using high ductile fiber-reinforced mortar are constructed and tested for their retrofit performances. Specimens designed by retrofitting the interior beam-column joint regions (IJNS series) of existing reinforced concrete building showed a stable mode of failure and an increase in load-carrying capacity due to the enhancement of crack dispersion by fiber bridging from using new high ductile materials for retrofitting. Specimens of IJNS series, designed by the retrofitting of high ductile fiber-reinforced mortar in beam-column joint regions increased its maximum load carrying capacity by 96~102.8% and its energy dissipation capacity by 0.99~1.11 folds when compared to standard specimen of SIJC with a displacement ductility of 5.

• Journal of the Korea Concrete Institute
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• v.25 no.2
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• pp.233-240
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• 2013

In this study, experimental research was carried out to evaluate and improve the seismic performance of high strength R/C interior beam-column joints regions using advanced reinforcing detailings and high ductile fiber-reinforced mortar. Five specimens of retrofitted the beam-column joint regions using advanced reinforcing detailings and high ductile fiber-reinforced mortar were constructed and tested for their retrofitring performances. Specimens designed by retrofitting the interior beam-column joint regions (IJIR series) of existing reinforced concrete building showed a stable mode of failure and an increase in load-carrying capacity. Specimens of IJIR series, designed by the retrofitting of advanced reinforcing detailings and high ductile fiber-reinforced mortar in reinforecd beam-column joint regions increased its maximum load carrying capacity by 114.2~123.5% and its energy dissipation capacity by 1.55~1.85 times in comparison with the standard specimen of SIJC with a displacement ductility of 5.

• Proceedings of the Korea Concrete Institute Conference
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• 2004.05a
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• pp.708-711
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• 2004

A typical structure was selected for a prototype and four 1:2.5 scaled models, representing the subassemblage including the interior column and the deep beam, were constructed. The transverse reinforcement was designed according to ACI procedure and the procedure proposed by Sheikh. In this study, the correlation between the experimental and analytical responses of the subassemblages subjected to the cyclic lateral displacement were evaluated through investigation of lateral load-lateral deformation, local deformation characteristics by using a nonlinear FEM analysis program RCAHEST.