• 대한건축학회논문집:구조계
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• 제36권2호
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• pp.127-136
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• 2020

Prism compressive strength is the most influential parameter to evaluate the seismic performance of non-structural concrete brick masonry walls, and is affected by the practice and workmanship of masonry workers. This study experimentally investigates the influence of workmanship on prism compressive strength throughout the compressive test with prism specimens constructed according to masonry workmanship. To do this, the workmanship is categorized into good, fair, and poor conditions which are statistically evaluated with thickness and indentation depth of bed-joints. Then, the effect of workmanship on the structural properties of masonry prisms is evaluated by investigating relations between properties such as their compressive strength, elastic modulus and numerical parameters such as thickness, filling of bed-joints. This study demonstrates that the indentation depth is more important parameter for structural properties of masonry prisms and masonry prisms with loss in bed-joint area less than of 7% can be in fair condition.

• 한국강구조학회 논문집
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• 제27권5호
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• pp.447-454
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• 2015

원형강관구조 접합부는 재료의 발전과 접합부의 복잡한 국부 거동 때문에 지속적인 연구되고 있다. 이 연구는 지강관에 압축력이 작용하는 원형강관 X-이음 트러스접합부의 주강관 소성화변형과 접합부 강도에 재료강도와 주강관벽세장비가 미치는 영향을 파악하는 것을 목적으로 한다. 이를 위하여 재료강도와 주강관벽세장비를 변수로 하여 다양한 원형강관 X-이음 트러스접합부에 대하여 범용 유한요소해석 프로그램인 ANSYS Mechanical APDL을 사용하여 정밀유한요소해석을 수행하였다. 해석결과를 토대로 현행 건축구조기준에서 제시하는 주강관소성화 한계상태의 접합부 설계강도를 검토하였다. 결론적으로 원형강관 X-이음 트러스접합부 설계에서 고려해야 할 사항을 제시하였다.

• Smart Structures and Systems
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• 제30권1호
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• pp.49-62
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• 2022

Experimental and discrete element methods were used to investigate the effects of triple joints lengths and triple joint angle on the failure behavior of rock mass under uniaxial compressive test. Concrete samples with dimension of 20 cm × 20 cm × 5 cm were prepared. Within the specimen, three imbedded joint were provided. The joint lengths were 2 cm, 4cm and 6 cm. In constant joint lengths, the angle between middle joint and other joints were 30°, 60°, 90°, 120° and 150°. Totally 15 different models were tested under compression test. The axial load rate on the model was 0.05 mm/min. Concurrent with experimental tests, the models containing triple joints, length and joint angle are similar to the experiments, were numerical by Particle flow code in two dimensions (PFC2D). Loading rate in numerical modelling was 0.05 mm/min. Tensile strength of material was 1 MPa. The results show that the failure behaviors of rock samples containing triple joints were governed by both of the angle and the length of the triple joints. The uniaxial compressive strengths (UCS) of the specimens were related to the fracture pattern and failure mechanism of the discontinuities. Furthermore, it was shown that the compressive behavior of discontinuities is related to the number of the induced tensile cracks which are increased by decreasing the joint length. Along with the damage failure of the samples, the acoustic emission (AE) activities are excited. There were only a few AE hits in the initial stage of loading, then AE hits rapidly grow before the applied stress reached its peak. In addition, every stress drop was accompanied by a large number of AE hits. Finally, the failure pattern and failure strength are similar in both methods i.e., the experimental testing and the numerical simulation methods.

• 한국콘크리트학회:학술대회논문집
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• 한국콘크리트학회 2005년도 추계 학술발표회 제17권2호
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• pp.271-274
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• 2005

Existing strut-and-tie model cannot be applied to analysis of slender beams without shear reinforcement because shear transfer mechanism is not formed. In the present study, a new strut-and-tie model with rigid joint was developed. Basically, concrete strut is modeled as a frame element which can transfer shear force (or moment) as well as axial force. Employing Rankine failure criterion, failure strength due to shear-tension and shear-compression developed in compressive concrete strut was defined. For verification, various test specimens were analyzed and the results were compared with tests. The proposed strut-and-tie model predicted shear strength and failure displacement with reasonable precision, addressing the design parameters such as shear reinforcement, concrete compressive strength, and shear span ratio.

• Structural Engineering and Mechanics
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• 제18권4호
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• pp.389-410
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• 2004

In this study, theoretical and experimental results are presented which were obtained during an investigation of the influence of the $P-{\Delta}$ effect that was caused by the simultaneous changing of the axial load P of the column and the lateral displacement ${\Delta}$ in the external beam-column joints. The increase or decrease of ${\Delta}$ was simultaneous with the increase or decrease of the axial compression load P and caused an additional influence on the aseismic mechanical properties of the joint. A total of 12 reinforced concrete exterior beam-column subassemblies were examined. A new model, which predicts the beam-column joint ultimate shear strength, was used in order to predict the seismic behaviour of beam-column joints subjected to earthquake-type loading plus variable axial load and $P-{\Delta}$ effect. Test data and analytical research demonstrated that axial load changes and $P-{\Delta}$ effect during an earthquake cause significant deterioration in the earthquake-resistance of these structural elements. It was demonstrated that inclined bars in the joint region were effective for reducing the unfavourable impact of the $P-{\Delta}$ effect and axial load changes in these structural elements.

• Structural Engineering and Mechanics
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• 제47권6호
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• pp.741-756
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• 2013

Distributed-Steel Bar Reinforced Concrete (DSBRC) columns, a new and innovative construction technique for composite steel and concrete material which can alleviate the difficulty in the arrangement of the stirrup in the column, were studied experimentally and analytically in this paper. In addition, an ordinary steel Reinforced Concrete (SRC) column was also tested for comparison purpose. The specimens were subjected to quasi-static load reversals to model the earthquake effect. The experimental results including the hysteresis curve, resistance recession, skeleton curves and ductility ratio of columns were obtained, which showed well resistant-seismic behavior for DSBRC column. Meanwhile a numerical three-dimensional nonlinear finite-element (FE) analysis on its mechanical behavior was also carried out. The numerically analyzed results were then compared to the experimental results for validation. The parametric studies and investigation about the effects of several critical factors on the seismic behavior of the DSBRC column were also conducted, which include axial compression ratios, steel ratio, concrete strength and yield strength of steel bar.

• 한국공간구조학회논문집
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• 제21권3호
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• pp.35-42
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• 2021

An experimental study was carried out to evaluate the shear performance at the interface composed of structural laminates and concrete. The main variables are the number of CLT layers and the shape of the shear connector. The number of CLT layers consisted of 3 and 5 layers. A total of 6 test specimens for shear performance evaluation were prepared in the form of a shear connector, a direct screw type and a vertically embedded type. As a result of the experiment, similar behavior was shown in all specimens, regardless of the number of layers, including direct screw type (SC series) and vertically embedded type (VE series). The behavior at the joint surface was damaged due to the occurrence of initial shear cracks, expansion of shear groove cracks, and splaying at the interface after the maximum load.After the maximum load, the shear strength decreased gradually due to the effect of the shear connector. It can be seen that the shear strength of all specimens is determined by shear and compression stress failure of concrete at the interface of the notch joint.

• 한국강구조학회 논문집
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• 제30권2호
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• pp.115-126
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• 2018

고강도 강재의 높은 항복비와 같은 특이한 물성에 대한 우려 등의 이유로 국내외 대표적인 강구조 설계기준에서는 강관구조에 고강도 강재를 적용하는 것을 금지하거나 제한하고 있다. 대부분의 설계기준에서는 강관의 항복강도가 355 또는 360MPa을 초과하는 경우 제시된 설계강도식을 사용할 수 없거나 강도저감계수를 통해 설계강도를 낮추어야 한다. 반면 이러한 제한사항에 대한 역학적 근거는 명료하지 않다. 또한 최근 저자들에 의해 수행된 X형 원형강관접합부에 대한 실험연구는 고강도강에 대한 규제가 과도하게 보수적일 수도 있다는 점을 지적한 바 있다. 본 연구에서는 고강도강 X형 원형강관접합부의 지관 압축 하에서의 거동을 더 자세히 분석하기 위해 실험에 이은 수치해석 변수연구를 수행하였다. 일반 강재부터 매우 항복강도가 높은 고강도 강재까지 넓은 범위의 강종을 고려하였다. 본 수치해석 연구에서도 현행의 고강도강 페널티가 매우 보수적이며 완화될 여지가 있음을 확인할 수 있었다. 또한 주관 축응력 하에서의 고강도강 접합부의 거동을 분석한 결과 현행 기준식이 고강도강 접합부의 주관 축응력에 의한 강도 감소 효과를 보수적으로 예측함을 확인하였다. 일반적으로 주관 축응력이 작용할 때 고강도강 접합부는 일반강 접합부에 비해 접합부 강도를 더 잘 유지하였다. 더불어 현행 기준식의 형태가 실제 접합부 거동을 정확히 표현하는 데에 한계가 있으며 개선될 여지가 있음을 지적하였다.

• 한국강구조학회 논문집
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• 제29권1호
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• pp.81-88
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• 2017

확장단부판 접합부는 강구조물의 보-기둥 접합부 혹은 변단면 부재로 구성된 PEB 구조시스템에 적용되는 접합부의 한 형태이다. 확장단부판 접합부는 접합부를 구성하는 단부판의 두께, 고장력볼트의 게이지 거리, 고장력볼트 축부의 직경, 고장력볼트의 개수 등의 영향으로 상이한 거동특성을 나타낸다. 확장단부판 접합부는 미국 및 유럽 등지에서는 다양한 형태로 강구조물의 기둥-보 접합부에 적용되고 있으나 우리나라에서는 널리 적용되고 있지 않다. 이러한 이유로는 확장단부판 접합부에 대한 설계강도식 제안, 접합부상세 제안, 내진성능 평가, 제작 및 시공지침서 개발 등이 적절히 이루어지지 못하고 있기 때문이다. 따라서 이 연구는 비보강 확장단부판 접합부의 국내 적용을 위한 기초자료를 제공하기 위하여 진행하였다. 이를 위하여 두께 12mm의 비보강 확장단부판에 대한 비선형 유한요소해석 및 실험을 수행하였다.

• Composites Research
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• 제27권6호
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• pp.213-218
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• 2014

본 논문에서는 특성길이 및 특성 곡선 방법을 굽힘 하중 상태의 복합재 기계적 체결부에 적용하여 강도를 예측하는 연구를 수행하였다. 선행 연구들이 특성길이 및 특성 곡선 방법을 인장과 압축 하중에만 적용한 것과 달리 본 연구에서는 굽힘 하중에 적용하고 그 가능성을 확인했다. 체결부 파손 해석을 위해 ABAQUS를 사용하여 핀과 모재의 접촉 및 마찰을 고려한 비선형 해석을 수행하였다. 해석결과를 이용하여 얻은 특성 곡선상에서 Tsai-Wu 이론을 적용하여 파손 및 파단 양상을 예측하였다. 또한 복합재 시편에 굽힘 하중을 가해 파손하중을 알아보는 실험을 통해 검증한 결과 해석으로 얻은 복합재 체결부의 파손하중이 실험 결과와 매우 잘 일치함을 확인하였다. 결론적으로 특성길이 및 특성 곡선 방법이 굽힘 하중 상태의 복합재 기계적 체결부의 강도를 비교적 잘 예측할 수 있다는 것을 알 수 있었다.