• Earthquakes and Structures
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• 제22권3호
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• pp.231-243
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• 2022

Beam-column joints (BCJs) are recognized among the most crucial zones in reinforced concrete structures, as they are the critical elements subjected to a complex state of forces during a severe earthquake. Under such conditions, BCJs exhibit behaviors with impacts that extend to the whole structure and significantly influence its ductility and capability of dissipating energy. The focus of this paper is to investigate the effect of undamaged transverse beam (secondary beams) on the ductility of concrete BCJs reinforced with conventional steel and shape memory alloys bars using pushover analysis at tip of beam under different axial load levels at the column using a nonlinear finite element model in ABAQUS environment. A numerical model of a BCJ was constructed and the analysis outcomes were verified by comparing them to those obtained from previous experiments found in the literature. The comparison evidenced the capability of the calibrated model to predict the load capacity response of the joint. Results proved the ability of undamaged secondary beams to provide a noticeable improvement to the ductility of reinforced concrete joints, with a very negligible loss in load capacity. However, the effect of secondary beams can become less significant if the beams are damaged due to seismic effects. In addition, the axial load was found to significantly enhance the performance of BCJs, where the increase in axial load magnified the capacity of the joint. However, higher values of axial load resulted in greater initial stiffness of the BCJ.

• 한국콘크리트학회:학술대회논문집
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• 한국콘크리트학회 2004년도 춘계 학술발표회 제16권1호
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• pp.506-509
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• 2004

This paper proposes Headed bar as reinforcement of beam-column joint, and proves seismic performance and reduction of reinforcement congestion. In these case, the use of Headed bars have obvious advantages. The greatest benefit of using Headed bars is not only improved structural performance of beam-column joints, but also the ease of fabrication, construction, and placement. Three-dimensional finite element analysis model is compared with test program which was fulfilled by the proposed model with Headed bar. Also, the plastic hinge region is relocated to the center of the longitudinal beam length according to the strong column-weak beam design philosophy, so Headed bar is used as the joint reinforcement. Therefore, this paper presents results of a computer analysis of a practical solution for relocating potential beam plastic hinge regions by the placing of straight - Headed bar.

• Structural Engineering and Mechanics
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• 제5권5호
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• pp.625-634
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• 1997

Reinforced concrete (RC) interior beam-column joints with high-strength materials: concrete compressive strength of 100 MPa and the yield strength of longitudinal bars of 685 MPa, were analyzed using three-dimensional (3-D) nonlinear finite element method (FEM). Specimen OKJ3 of joint shear failure type was a plane interior joint, and Specimen 12 of beam flexural failure type was a 3-D interior joint with transverse beams. Though the analytical initial stiffness was higher than experimental one, the analytical results gave a good agreement with the test results on the maximum story shear forces, the failure mode.

• Structural Engineering and Mechanics
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• 제76권3호
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• pp.337-354
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• 2020

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.

• 토지주택연구
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• 제5권2호
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• pp.91-97
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• 2014

일반적으로 부분 PC 구조에서는 기둥, 보, 그리고 하프 PC 슬래브 등을 공장에서 제작하여 현장에서 조립한 후에 덧침 콘크리트의 타설에 의하여 일체화한다. 따라서 PC 부재가 연결되는 위치에서의 불연속면과 함께 PC 부재의 조립을 위한 걸침길이 확보와 같은 접합부 형상 등으로 인하여 접합부 보강을 위한 구조설계가 필요하다. 보-기둥 접합부에서 발생하는 PC 부재와 덧침 콘크리트 사이의 접합면에서 전단력 전달 성능은 접합부의 구조 성능에 큰 영향을 미치게 된다. 서로 다른 두 개의 부재가 만나는 면에서는 부재간의 미끄러짐(slip) 현상과 전단력이 발생되는데, 본 연구에서의 접합면 전단에 대해서는 실험을 수행하고 실험결과에 대해 ACI 기준 및 PCI 설계식을 활용하여 검토하였다. 보-기둥 접합부에 대한 접합면 전단 설계를 ACI 기준 또는 PCI 설계법에 따라 검토한다면, 구조성능을 확보할 수 있는 것으로 확인되었다. 또한 실험결과를 고찰하면 보-기둥 접합부에서 PC 보의 걸침길이를 30mm로 하여도 구조적인 문제는 없는 것으로 판단된다.

• Earthquakes and Structures
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• 제15권5호
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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.

• 한국구조물진단유지관리공학회 논문집
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• 제18권6호
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• pp.72-81
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• 2014

이 논문은 고강도 콘크리트를 사용한 철근콘크리트 외부 보-기둥 접합부의 실험결과를 보고한 것이다. 실험체의 주요 실험변수는 접합부 파괴모드, 콘크리트 압축강도, 철근의 정착 방법이다. 모든 실험체는 ACI 352R-02 기준에 바탕을 두어 J파괴와 BJ파괴가 되도록 계획하였다. 주철근은 90도 표준갈고리로 하거나 확대머리철근으로 하였다. 실험결과는 콘크리트 압축강도에 제한되는 현행 ACI 설계 기준식이 고강도 콘크리트를 사용한 보-기둥 접합부의 강도를 다소 과소평가하고 있음을 보여준다. 또한 확대머리철근을 가진 J파괴형 보-기둥 접합부의 강도는 표준갈고리를 가진 접합부보다 약 10% 이상 높게 평가되었다.

• Structural Engineering and Mechanics
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• 제63권5호
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• pp.617-628
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• 2017

In order to study the failure mode and seismic behavior of the interior-joint in steel traditional-style buildings, a single beam-column joint and a double beam-column joint were produced according to the relevant building criterion of ancient architectural buildings and the engineering instances, and the dynamic horizontal loading test was conducted by controlling the displacement of the column top and the peak acceleration of the actuator. The failure process of the specimens was observed, the bearing capacity, ductility, energy dissipation capacity, strength and stiffness degradation of the specimens were analyzed by the load-displacement hysteresis curve and backbone curve. The results show that the beam end plastic hinge area deformed obviously during the loading process, and tearing fracture of the base metal at top and bottom flange of beam occurred. The hysteresis curves of the specimens are both spindle-shaped and plump. The ultimate loads of the single beam-column joint and double beam-column joint are 48.65 kN and 70.60 kN respectively, and the equivalent viscous damping coefficients are more than 0.2 when destroyed, which shows the two specimens have great energy dissipation capacity. In addition, the stiffness, bearing capacity and energy dissipation capacity of the double beam-column joint are significantly better than that of the single beam-column joint. The ductility coefficients of the single beam-column joint and double beam-column joint are 1.81 and 1.92, respectively. The cracks grow fast when subjected to dynamic loading, and the strength and stiffness degradation is also degenerated quickly.

• 한국콘크리트학회:학술대회논문집
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• 한국콘크리트학회 1995년도 봄 학술발표회 논문집
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• pp.339-344
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• 1995

In the design of ductile moment-resisting frames (DMRFs) following the strong column-weak beam dsign philosophy, it is desirable that the joint and column remain essentially elastic in order to insure proper energy dissipation and lateral stability of the structure. The joint has been identified as the "weak link" in DMRFs because any stiffness or strength deterioration in this region can lead to substantial drifts and the possibility of collapse due to P-delta effects. Moreover, the engineer is faced with the difficult task of detailing an element whose size is determined by the framing members, but which must resist a set of loads very different from those used in the design of the beams and columns. Four 2/3-scale beam-column-slab joint assemblies were designed according to existing code requirements of ACI 318-89, representing interior joints of DMRFs with reinforced high strength concrete. The influence on aseismic behavior of beam-column joints due to monolithic slab, has been investigated.estigated.

• 한국구조물진단유지관리공학회 논문집
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• 제10권6호
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• pp.197-204
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• 2006

최근 시공의 합리화와 경제성의 목적으로 한 다양한 연구가 진행되고 있다. 철근 콘크리트 기둥과 철골 보로 이루어진 RCS 구조의 개발에 대한 연구 역시 활발해지고 있다. RCS 구조 보-기둥 접합부 패널존의 저항기구는 내부패널에서 외부패널로 응력이 전달될 때 직교보의 영향을 받지만, 기존연구에는 직교보의 영향을 고려하지 않고 있다. 본 연구에서는 웨브, 플랜지, 직교보의 두께, FBP의 유뮤등 다양한 변수들을 가지는 5개의 철근콘크리트 기둥과 철골보로 이루어진 보-기둥 내부접합부 실험체의 실험을 통해 직교보들의 영향과 구조적 성능을 조사하고자 한다. 이러한 실험결과들로부터, 보-기둥 접합부의 직교보가 전단내력과 구조성능을 향상시키는데 효과적이라는 것을 알 수 있다.