• 한국지반공학회지:지반
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• 제11권4호
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• pp.99-110
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• 1995

본 연구에서는 정규압밀 건조 모래 지반내의 연직 강체 지반앵커에 대한 모형 인발실험을 실시해서 앵커 표면의 마찰각을 실측했다. 마찰각은 앵커 표면의 깊이 방향으로 설치된 다수의 2 방향 로드셀을 사용해서 측정된 수직응력, 전단응력으로 구했다. 실험은 평면변형률 앵커와 축대칭 앵커에 대해서 실시했는데 실험 분석 결과, 앵커표면의 최대마찰각은 평면변형률 압축시험에 의한 무신축방향의 면상의 응력경각의 최대치와 거의 일치한다는 것을 알았다. 이 결론은 모래의 강도 이방성과 구속압 의존성 등을 고려하여 얻은 것으로 앵커 표면 마찰각에 모래의 전단저항각을 적용해서 설계하면 위험측이 된다는 것도 알 수 있다.

• Steel and Composite Structures
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• 제39권3호
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• pp.337-352
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• 2021

The study presented experimental and numerical investigation on the seismic performance of steel reinforced concrete (SRC) L-shaped column- reinforced concrete (RC) beam joints. Various parameters described as steel configuration form, axial compressive ratio, loading angle, and the existence of slab were examined through 4 planar joints and 7 spatial joints. The characteristics of the load-displacement response included the bearing capacity, ductility, story drift ratio, energy-dissipating capacity, and stiffness degradation were analyzed. The results showed that shear failure and flexural failure in the beam tip were observed for planar joints and spatial joint, respectively. And RC joint with slab failed with the plastic hinge in the slab and bottom of the beam. The results indicated that hysteretic curves of spatial joints with solid-web steel were plumper than those with hollow-web specimens. The capacity of planar joints was higher than that of space joints, while the opposite was true for energy-dissipation capacity and ductility. The high compression ratio contributed to the increase in capacity and initial stiffness of the joint. The elastic and elastic-plastic story deformation capacity of L-shaped column frame joints satisfied the code requirement. A design formula of joint shear resistance based on the superposition theory and equilibrium plasticity truss model was proposed for engineering application.

• Structural Engineering and Mechanics
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• 제70권6호
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• pp.781-791
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• 2019

Earthquakes most often induce damage to structures, resulting in the degradation or deterioration of integrity. In this paper, based on the experimental study on 5 RC frames with different span length and different layout of buckling-restrained braces, the seismic damage evaluation law of RC frame with buckling-restrained braces was analyzed, and then the seismic damage for different specimens was calculated using different damage models to study the damage evolution. By analyzing and comparing the observation in test and the calculated results, it could be found that, damage evolution models including Gosain model, Hwang model as well as Ou model could better simulate the development of damage during cyclic loading. Therefore, these 3 models were utilized to analyze the development of damage to better demonstrate the evolution law for structures with different layout of braces and under different axial compression ratios. The results showed that from all layouts of braces studied, the eccentrically braced frame behaved better under larger deformation with the damage growing slowly. It could be deduced that the link beam benefited the seismic performance of structure and alleviated the damage by absorbing high values of energy.

• Steel and Composite Structures
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• 제21권2호
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• pp.267-287
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• 2016

The seismic performance of the ordinary steel reinforced concrete (SRC) columns has no significant improvement compared to the reinforced concrete (RC) columns mainly because I, H or core cross-shaped steel cannot provide sufficient confinement for core concrete. Two improved SRC columns by constructing with new-type shaped steel were put forward on this background, and they were named as enlarging cross-shaped steel and diagonal cross-shaped steel for short. The seismic behavior and carrying capacity of new-type SRC columns have been researched theoretically and experimentally, while the shear behavior remains unclear when the new-type columns are joined onto SRC beams. This paper presents an experimental study to investigate the shear capacity of new-type SRC joints. For this purpose, four new-type and one ordinary SRC joints under low reversed cyclic loading were tested, and the failure patterns, load-displacement hysteretic curves, joint shear deformation and steel strain were also observed. The ultimate shear force of joint specimens was calculated according to the beam-end counterforce, and effects of steel shape, load angel and structural measures on shear capacity of joints were analyzed. The test results indicate that: (1) the new-type SRC joints display shear failure pattern and has higher shear capacity than the ordinary one; (2) the oblique specimens have good bearing capacity if designed reasonably; and (3) the two proposed construction measures have little effect on the shear capacity of SRC joints embedded with diagonal cross-shaped steel. Based on the mechanism observed from the test, the formulas for calculating ultimate shear capacity considering the main factors (steel web, stirrup and axial compression ratio) were derived, and the calculated results agreed well with the experimental and simulated data.

• 접착 및 계면
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• 제6권2호
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• pp.13-20
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• 2005

환경 친화적인 자연섬유 강화 고분자 복합재료의 계면 전단강도는 총체적인 기계적 물성을 조절하는데 매우 중요한 역할을 수행한다. Ramie와 Kenaf 섬유 강화 에폭시 복합재료의 계면 전단강도는 최종 물성을 위한 최적 조건을 찾아내기 위해 미세역학시험법과 비파괴 음향방출시험을 이용하여 평가했다. Ramie와 Kenaf 섬유의 동적 접촉각을 측정했고, 계면 접착에서 젖음성과 상호 관련시켜서 해석하였다. Ramie와 Kenaf 섬유의 기계적 물성은 단섬유 인장시험을 통해 조사했고, 통계학적으로 uni-와 bimodal Weibull 분포를 통해서 분석하였다. Ramie와 Kenaf 섬유에 대한 실제 신장율의 clamping 효과의 영향도 평가할 수 있었다. 두 가지의 다른 미세파괴 형상은 섬유다발과 단섬유 복합재료로부터 오는 축방향의 debonding과 섬유상의 fracture는 인장과 압축하중하에서 관찰할 수 있었다.

• 대한토목학회논문집
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• 제13권2호
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• pp.253-265
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• 1993

본 연구는 Lade에 의해서 제안된 비선형구성모델을 이용하여 지반거동을 해석하기 위한 수치해석 방법을 제시하고자 한것이다. 그 첫 시도로서 축대칭조건과 평면변형율조건의 비선형 경계치 문제를 해석하기 위하여 변위법을 이용한 유한요소 프로그램을 개발하였다. 모델의 매개변수를 결정하기 위한 시험과 모형기초지반의 시험재료는 백마강모래를 사용하였다. 그리고 실내시험 자료로 부터 비선형구성모델 의 매개변수를 결정할 때 컴퓨터 프로그램을 개발하여 사용하였다. 구성 모델의 정도를 검증하기 위하여 개발된 유한요소프로그램을 사용한 예측결과를 매개변수 결정에 사용된 실험 결과뿐만 아니라 결정에 사용되지 아니한 실험결과와도 비교하였다. 검증에 사용된 시험은 다음과 같다 ; (1) 등방압축팽창시험, (2) 구속압력을 달리한 배수삼축압축시험 (3) 모형기초지반의 재하시험, 이상의 시험과 수치해석결과를 비교하여 비선형구성모델과 유한요소해석프로그램의 정도를 확인하고 평면변형율조건에 있는 2차원모형기초지반의 거동 특성을 검토하였다.

• Steel and Composite Structures
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• 제47권2호
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• pp.269-287
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• 2023

The WGJ420 fire-resistant weathering (FRW) steel is developed and manufactured with standard yield strength of 420 MPa at room temperature, which is expected to significantly enhance the performance of steel structures with excellent fire and corrosion resistances, strong seismic capacity, high strength and ductility, good resilience and robustness. In this paper, the mechanical properties of FRW steel plates and buckling behavior of columns are investigated through tests at elevated temperatures. The stress-strain curves, mechanical properties of FRW steel such as modulus of elasticity, proof strength, tensile strength, as well as corresponding reduction factors are obtained and discussed. The recommended constitutive model based on the Ramberg-Osgood relationship, as well as the relevant formulas for mechanical properties are proposed, which provide fundamental mechanical parameters and references. A total of 12 FRW steel welded I-section columns with different slenderness ratios and buckling load ratios are tested under standard fire to understand the global buckling behavior in-depth. The influences of boundary conditions on the buckling failure modes as well as the critical temperatures are also investigated. In addition, the temperature distributions at different sections/locations of the columns are obtained. It is found that the buckling deformation curve can be divided into four stages: initial expansion stage, stable stage, compression stage and failure stage. The fire test results concluded that the residual buckling capacities of FRW steel columns are substantially higher than the conventional steel columns at elevated temperatures. Furthermore, the numerical results show good agreement with the fire test results in terms of the critical temperature and maximum axial elongation. Finally, the critical temperatures between the numerical results and various code/standard curves (GB 51249, Eurocode 3, AS 4100, BS 5950 and AISC) are compared and verified both in the buckling resistance domain and in the temperature domain. It is demonstrated that the FRW steel columns have sufficient safety redundancy for fire resistance when they are designed according to current codes or standards.

• 한국강구조학회 논문집
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• 제16권3호통권70호
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• pp.315-324
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• 2004

본 논문은 지관에 압축력을 받는 냉간성형 각형강관 T형 용접접합부의항복선 해석에 관한 연구이다. 기존 연구 중 냉간성형 정방형 각형강관 T형 용접 접합부만을 포함하는 실험결과와 Kato, Packer, Zhao, CIDECT 및 본 연구진들의 제안식을 비교하였다. 제안된 항복선 모델의 적용한계치를 제안하기 위하여, 항복선 해석에 기초하여 이전 논문에서 제안된 항복선모델을 재검토하였다. 제안된 항복선 모델은 냉간성형 각형강관 곡률부와 용접크기를 고려한다. 마지막으로, 실험상의 실체 파괴모드와 해석상의 비교결과를 참조하여, 항복선 해석의 적용범위를 ${\beta}^{\prime}{\leq}0.8$로 제안하였다. 여기서, ${\beta}^{\prime}=0.8$, ${\beta}^{\prime}=b_1^{\prime}/b_0^{\prime}$, $b_1{^{\prime}}=b_1+t_0$, $b_0{^{\prime}}=b_0-t_0$.

• 콘크리트학회논문집
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• 제26권1호
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• pp.35-46
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• 2014

중량 PC기둥의 양중부하를 저감하고 접합부 구조일체성을 개선하기 위하여, 두 가지 형태의 현장타설 콘크리트 채움 중공 PC기둥(HPC1, HPC2)을 개발하였다. 중공의 PC단면을 구현하기 위해, HPC1은 조립철근망이 설치된 선제작 PC패널 한 쌍을 활용하였으며, HPC2는 특별한 띠철근을 활용하였다. 심부콘크리트 타설시 측압을 측정하였으며, 내진성능을 평가하기 위하여 실물크기의 HPC1, HPC2 기둥과 비교용 RC 기둥에 대하여 일정축력하 주기횡하중실험을 수행하였다. 실험 결과 HPC 실험체는 초기강성, 최대강도, 변위연성도 등 구조성능면에서 RC 실험체와 유사한 거동을 보였으며, 다만 단면을 관통하는 내부띠철근이 없는 HPC2의 경우에는 주철근의 좌굴이 발생한 이후 에너지소산능력이 다소 떨어졌다. 하지만 세 실험체 모두 ACI 374에서 요구하는 에너지소산능력을 만족하였다.

• 한국도로학회논문집
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• 제8권1호
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• pp.139-152
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• 2006

Many experimental and numerical approaches have been developed to evaluate paving materials and to predict pavement response and distress. Micromechanical simulation modeling is a technology that can reduce the number of physical tests required in material formulation and design and that can provide more details, e.g., the internal stress and strain state, and energy evolution and dissipation in simulated specimens with realistic microstructural features. A clustered distinct element modeling (DEM) approach was implemented In the two-dimensional particle flow software package (PFC-2D) to study the complex behavior observed in asphalt mixture fracturing. The relationship between continuous and discontinuous material properties was defined based on the potential energy approach. The theoretical relationship was validated with the uniform axial compression and cantilever beam model using two-dimensional plane strain and plane stress models. A bilinear cohesive displacement-softening model was implemented as an intrinsic interface and applied for both homogeneous and heterogeneous fracture modeling in order to simulate behavior in the fracture process zone and to simulate crack propagation. A disk-shaped compact tension test (DC(T)) with heterogeneous microstructure was simulated and compared with the experimental fracture test results to study Mode I fracture. The realistic arbitrary crack propagation including crack deflection, microcracking, crack face sliding, crack branching, and crack tip blunting could be represented in the fracture models. This micromechanical modeling approach represents the early developmental stages towards a 'virtual asphalt laboratory,' where simulations of laboratory tests and eventually field response and distress predictions can be made to enhance our understanding of pavement distress mechanisms, such its thermal fracture, reflective cracking, and fatigue crack growth.