• Steel and Composite Structures
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• 제7권4호
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• pp.303-320
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• 2007

The objective of this study is to clarify the structural features of members consisting of connection, as a series of the previous study on the CFT column-to-beam tensile connection with combined cross diaphragm. This connection has the merits that the stress is distributed evenly on the beam flange and the diaphragm and the stress concentration is reduced, by improving the stress transfer route and restraining abrupt deformation of diaphragm. The finite element analysis was performed to find out the stress transfer through sleeve which is an important member of the connection with combined cross diaphragm. The length and thickness of sleeve were used as variables for the analysis. As the analysis results, the length and thickness of sleeve didn't influence on the capacity of the connection and played a role of a medium to transfer the stress from the diaphragm to the filled concrete. It is proposed that the appropriate length of sleeve be the same value as the diameter of sleeve and the appropriate ratio of sleeve diameter to sleeve thickness be 20. Two equations for evaluation of the load-carrying capacity of the connection were also proposed through the modification of the evaluation equation suggested in the previous study.

• 대한건축학회논문집:구조계
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• 제34권4호
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• pp.35-42
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• 2018

This study evaluated the fire resisting capacity and post-fire serviceability of the concrete beams retrofitted by near surface mounted method(NSM) using GFRP plates. Main parameters in the test are grout materials and fire exposure. For the test, two types of grout materials between concrete substrate and GFRP plate were used; flame resisting epoxy and filling mortar. Four RC beam specimens were made and two of them were exposed to fire according to real scale fire curve proposed KS F 2257. After the fire exposure test, flexural test were performed to investigate the flexural performance of concrete beams including strength and deformation. From the test results, it was found that the beam retrofitted by NSM-GFRP presented higher flexural strength than that of the beam without retrofit, which indicates NSM-GFRP retrofit technologies is effective to maintain flexural strength even after fire exposure. In addition, the specimens grouted by epoxy showed good performance in strength but bad performance in ductility.

• Computers and Concrete
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• 제30권1호
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• pp.43-74
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• 2022

Machine learning technique is recently opening new opportunities to identify the complex shear transfer mechanisms of reinforced concrete (RC) beam members. This study employed 1224 shear test specimens to train decision tree-based machine learning (ML) programs, by which strong correlations between shear capacity of RC beams and key input parameters were affirmed. In addition, shear contributions of concrete and shear reinforcement (the so-called V_c and V_s) were identified by establishing three independent ML models trained under different strategies with various combinations of datasets. Detailed parametric studies were then conducted by utilizing the well-trained ML models. It appeared that the presence of shear reinforcement can make the predicted shear contribution from concrete in RC beams larger than the pure shear contribution of concrete due to the intervention effect between shear reinforcement and concrete. On the other hand, the size effect also brought a significant impact on the shear contribution of concrete (V_c), whereas, the addition of shear reinforcements can effectively mitigate the size effect. It was also found that concrete tends to be the primary source of shear resistance when shear span-depth ratio a/d<1.0 while shear reinforcements become the primary source of shear resistance when a/d>2.0.

• Computers and Concrete
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• 제10권5호
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• pp.489-505
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• 2012

This paper presents a simplified grid beam model for simulating the nonlinear response of reinforced concrete flat-plate structures. The beam elements are defined with nonlinear behavior for bending moment and torsion. The flexural stiffness and torsional strength of the beam elements are defined based on experimental data to implicitly account for slab two-way bending effects. A failure criterion that considers the interaction between the punching strength and slab flexural behavior is incorporated in the model. The effects of bond-slip of slab reinforcement on connection stiffness are examined. The proposed grid beam model is validated by simulating large-scale tests of slab-column connections subjected to concentric gravity loading and unbalanced moment. This study also determines the critical parameters for a hysteretic model used to simulate flat-plates subjected to cyclic lateral loading.

• Earthquakes and Structures
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• 제7권5호
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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.

• 한국공간구조학회논문집
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• 제24권1호
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• pp.65-72
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• 2024

This paper aims to advance our understanding of extensible beams with multiple cracks by presenting a crack energy and motion equation, and mathematically justifying the energy functions of axial and bending deformations caused by cracks. Utilizing an extended form of Hamilton's principle, we derive a normalized governing equation for the motion of the extensible beam, taking into account crack energy. To achieve a closed-form solution of the beam equation, we employ a simple approach that incorporates the crack's patching condition into the eigenvalue problem associated with the linear part of the governing equation. This methodology not only yields a valuable eigenmode function but also significantly enhances our understanding of the dynamics of cracked extensible beams. Furthermore, we derive a governing equation that is an ordinary differential equation concerning time, based on orthogonal eigenmodes. This research lays the foundation for further studies, including experimental validations, applications, and the study of damage estimation and detection in the presence of cracks.

• Structural Engineering and Mechanics
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• 제38권4호
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• pp.459-477
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• 2011

Due to the low elastic modulus of FRP, concrete members reinforced with FRP rebars show greater deflections than members reinforced with steel rebars. Deflection is one of the important factors to consider the serviceability of horizontal members. In this study flexural test of AFRP reinforced concrete beams was performed considering reinforcement ratio and compressive strength as parameters. The test results indicated that flexural capacity and stiffness increase in proportion to the reinforcement ratio. The test results were compared with existing proposed equations for the effective moment of inertia including ACI 440. The most of the proposed equations were found to over-estimate the effective moment of inertia while the equation proposed by Bischoff and Scanlon (2007) most accurately predicted the values obtained through actual testing.

• Structural Monitoring and Maintenance
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• 제1권2호
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• pp.159-171
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• 2014

Real-time near and far-field monitoring of concrete structural components gives enough information on the time and condition at which damage occurs, thereby facilitating damage detection while in the same time evaluate the cause of the damage. This paper experimentally investigates an integrated monitoring technique for near and far-field damage detection in concrete structures based on simultaneous use of electromechanical admittance technique in combination with guided wave propagation. The proposed sensing system does not measure the electromechanical admittance itself but detect time variations in output voltages of the response signal obtained across the electrodes of piezoelectric transducers bonded on surfaces of concrete structures. The damage identification is based on the spectral estimation MUSIC algorithm. Experimental results show the efficiency and performance of the proposed measuring technique.

• 한국강구조학회 논문집
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• 제25권6호
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• pp.601-612
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• 2013

본 연구에서는 중간 지진 영역대에서 사용 가능한 TSC 합성보-PSRC 합성기둥 접합부의 내진 상세를 개발하였다. 시공성 향상을 위하여 TSC보의 상하부 플랜지는 조인트를 관통시키지 않고, 웨브만 조인트를 관통하였다. 이에 따라 접합부 공칭강도 평가시 상하부 플랜지의 인장력은 고려하지 않았다. 두 개의 내부 접합부와 한 개의 외부 접합부에 대하여 반복가력 실험을 통하여 내진성능을 검증하였다. 내부 접합부의 실험 변수는 보 춤으로 슬래브 두께를 포함하여 600mm, 700mm이다. 실험결과, 실험체는 KBC 2009로 예측한 접합부의 하중재하능력은 실험결과와 잘 일치하였으며, 변형능력과 에너지 소산에 있어서 중간모멘트 골조 요구조건을 만족하는 우수한 성능을 보여주었다. 3%~4% 층간변위비 이후 보 웨브 강판의 좌굴 및 파단으로 인하여 실험체의 하중 재하능력이 감소하였다. ASCE 합성접합부 설계기준을 수정하여 TSC보-PSRC기둥 접합부의 전단강도를 평가하였다.

• 콘크리트학회논문집
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• 제18권5호
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• pp.603-610
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• 2006

철근콘크리트 구조물의 외부 비부착 보강방식은 다른 보강기법과 비교하여 설치가 빠르며 간단하다는 장점을 가진다. 고장력 인장봉을 사용한 보강방식은 강판 또는 탄소섬유쉬트 부착공법과는 달리 설치를 위한 콘크리트 표면가공이 필요치 않고 환경적인 조건에 영향을 받지 않는다. 본 연구를 통해 개발된 보강방식은 정착핀 또는 정착판을 통하여 보의 단부에서 고장력 인장봉과 RC보를 연결하는 보강방식이다. 여기에 편심기를 통하여 외부보강 강봉이 RC보의 곡률에 대응하도록 하였다. 본 논문에서는 보강된 RC보에 관한 총 10개의 실험체 제작하여 실험을 실시하였다. 실험의 주요 변수는 보강재료의 직경, 강봉 보강의 깊이와 개수이다. 본 논문에서는 본 연구를 통하여 개발된 보강공법으로 보강된 RC보의 구조적 거동을 기술하였으며, 보강된 RC보의 실험 결과를 무보강 실험체와 비교하였다. 실험결과 제안된 보강방법은 무보강 실험체와 비교하여 매우 우수한 강도 증진효과를 나타내었고 편심장치의 사용은 효율성을 향상시켰다. 또한, 두개의 편심기를 사용한 실험체는 1개의 편심장치를 사용한 실험체에 비해 모멘트 성능이 우수하였고, 외부보강 강봉은 보의 휨강도 뿐만 아니라 전단강도를 향상시키는 결과도 가져왔다.