• Geomechanics and Engineering
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• 제13권3호
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• pp.431-446
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• 2017

Rock bridges in rock masses would increase the bearing capacity of Non-persistent discontinuities. In this paper the effect of ratio of rock bridge surface to joint surface, rock bridge shape and normal load on failure behaviour of intermittent rock joint were investigated. A total of 42 various models with dimensions of $15cm{\times}15cm{\times}15cm$ of plaster specimens were fabricated simulating the open joints possessing rock bridge. The introduced rock bridges have various continuities in shear surface. The area of the rock bridge was $45cm^2$ and $90cm^2$ out of the total fixed area of $225cm^2$ respectively. The fabricated specimens were subjected to shear tests under normal loads of 0.5 MPa, 2 MPa and 4 MPa in order to investigate the shear mechanism of rock bridge. The results indicated that the failure pattern and the failure mechanism were affected by two parameters; i.e., the ratio of joint surface to rock bridge surface and normal load. So that increasing in joint area in front of the rock bridge changes the shear failure mode to tensile failure mode. Also the tensile failure change to shear failure by increasing the normal load.

• Computational Structural Engineering : An International Journal
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• 제1권2호
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• pp.117-130
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• 2001

Investigations of low-rice unbounded reinforced concrete shear walls with or without openings are performed with comparison of analytical and experimental results. Theoretical analysis is based on nonlinear finite element algorithm, which incorporates concrete failure criterion and nonlinear constitutive relationships. Studios focus on the effects of height-to-length ratio of shear walls, opening ratio, horizontal and vertical reinforcement radios, and diagonal reinforcement. Analytical solutions conform well with experimental results. Equations for cracking, yielding and ultimate loads with corresponding lateral displacements are derived by regression using analytical results and experimental data. Also, failure modes of low-rise unbounded shear walls are theoretically investigated. An explanation of change in failure mode is ascertained by comparing analytical results and ACI code equations. Shear-flexural failure can be obtained with additional flexural reinforcement to increase a wall's capacity. This concept leads to a design method of reducing flexural reinforcement in low-rise bounded solid shear wall's. Avoidance of shear failure as well as less reinforcement congestion leer these walls is expected.

• Computers and Concrete
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• 제17권5호
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• pp.639-653
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• 2016

The present article discusses the effect of the ratio of bridge surface to total shear surface, number of bridge areas and normal stress on the failure behavior of the planar non-persistent open joints. Totally, 38 models were prepared using plaster and dimensions of $15cm{\times}15cm{\times}15cm$. The bridge area occupied $45cm^2$, $90cm^2$ and $135cm^2$ out of the shear surface. The number of rock bridges increase in fixed area. Two similar samples were prepared on every variation in the rock bridges and tested for direct shear strength under two high and low normal loads. The results indicated that the failure pattern and the failure mechanism is mostly influenced by the ratio of bridge surface to total shear surface and normal stress so that the tensile failure mode change to shear failure mode by increasing in the value of introduced parameters. Furthermore, the shear strength and shear stiffness are closely related to the ratio of bridge surface to total shear surface, number of bridge areas and normal stress.

• 한국콘크리트학회:학술대회논문집
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• 한국콘크리트학회 2000년도 봄 학술발표회 논문집
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• pp.533-538
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• 2000

In R.C. flat slab system, a brittle punching failure is a very fatal problem. But there is no generally well-defined answer to the problem and there are wide differences in current practical design codes. therefore, in this study, the factors affecting to punching failure mechanism have been studied to find out the punching shear behavior in R.C. flat slabs by comparing other investigations and practical design codes. Therefore, In this study, the factors affecting to punching failure mechanism have been studied to find out the punching shear behavior in R.C. flat slabs by comparing other investigations and practical design codes. The conclusions in this study are summarized as follows; 1) The factors affecting to punching shear are concrete strength ($f_\alpha$), ratio of column side length to slab depth (c/d), ratio of distance from column center to radial contraflexure (l/d), yield strength of steel ($f_y$), flexural reinforcement ratio ($\rho$) and size effects. 2) It is shown that th use of $\surd{f_{ck}}$in applying($f_\alpha$ to punching shear strength estimation may be more sensitive in high concrete strength. 3) The effects of l/d, ($f_y$, size are no clear in the punching failure mechanism, so in the future, it should be investigated with the effects of various composed load.

• 한국비블리아학회지
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• 제23권2호
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• pp.209-233
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• 2012

이 연구에서는 웹기반 온라인목록 이용자들의 전반적인 검색행태를 알아보기 위해, 7년 동안의 트랜잭션 로그를 분석하였다. 웹기반 온라인목록의 검색형태는 검색전략과 검색실패의 관점에서 조사하였다. 검색전략에서는 검색유형, 접근점, 연산자, 검색문의 길이, 단어 사용횟수, 웹기반 온라인목록 이용횟수, 시간대별 및 요일별 이용횟수를 분석하였다. 또한 검색실패는 검색실패율과 접근점별 검색실패율, 연산자별 검색실패율을 분석하였다. 이 연구결과는 향후 웹기반 온라인목록 시스템과 서비스 개선에 활용될 수 있을 것으로 기대된다.

• 한국구조물진단유지관리공학회 논문집
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• 제24권6호
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• pp.59-66
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• 2020

축소모형 팔각형 기둥 실험체 2개를 제작하여 일정한 축력 하에서 반복 횡하중을 가력하는 실험을 수행하였다. 실험체는 중실단면과 중공단면이고 모든 실험체의 횡방향 나선철근 체적비는 0.00206의 값을 갖는다. 실험체들은 휨-전단 파괴거동을 보였다. 본 논문에서는 실험결과에 따른 파괴거동과 내진성능을 분석하였다. 실험결과, 중공 실험체는 초기강성, 초기 균열양상, 에너지 소산능력 등의 구조성능이 중실 실험체와 유사한 거동을 보였으나, 중공 실험체의 경우에는 3% 변위비 이후에 횡력, 극한변위, 에너지소산능력이 현저하게 감소되었다.

• 수산해양기술연구
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• 제33권4호
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• pp.346-351
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• 1997

The pin bearing strength is one of the most important design parameters for mechanical joints composed of fiber reinforced composites. Thus the effect of the edge distance and the width of specimen on the pin-bearing strength of unidirectional CFRP composites were experimentally investigated in this paper. As results, the failure modes and the pin bearing strength of mechanical joints turned out to depend on the edge distance and also the width of specimen. The failure of specimen with low ratio of width to hole diameter was caused by the net tension from the hole boundary, on the other hand, the failure of specimen with low ratio of edge distance to hole diameter was caused by the shear-out. The bearing strength in case of the failure by shear-out was quite lower than that in case of failure by net tension.

• 한국임상약학회지
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• 제24권2호
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• pp.115-125
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• 2014

Purpose: The purpose of the present study was to assess the incidence of the potentially inappropriate medication (PIM) use in Korean elderly patients with heart failure, and to evaluate factors that influence PIM use. Method: Korean National Health Insurance claims database between January 2009 and December 2009 was used. Using 2012 updated Beers criteria, PIM use in heart failure patients aged 65 years or older was examined. Result: The incidence of PIM use in elderly heart failure patients was higher than in overall elderly patients. Among the 12,759 elderly patients with heart failure, 46.2% of study subjects were prescribed PIM(s) at least once. The number of PIM per 10 medications that patients received per patient was 1.53. The most commonly used PIMs in elderly heart failure patients were benzodiazepines (30.9%), non-steroidal anti-inflammatory drugs (NSAIDs) including COX-2 inhibitors (16.3%), digoxin (9.9%), and spironolactone (9.0%). Women (odds ratio, 1.20; 95% CI, 1.17-1.24), medical aid (odds ratio, 1.11; 95% CI, 1.08-1.13), and long-term facilities (odds ratio, 2.69; 95% CI, 2.44-2.96) were revealed to be important factors associated with PIM use. In addition, patient's age also seems to influence PIM use. Conclusion: Elderly heart failure patients are at a greater risk for adverse drug events attributed by inappropriate medication use. Efforts to increase awareness of PIM use in elderly heart failure patients are needed. In addition, various comprehensive strategies and policies to identify and prevent PIM use should be established nationwide.

• Composites Research
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• 제16권3호
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• pp.18-24
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• 2003

샌드위치 구조물들은 적은 무게의 첨가로 높은 강성(stiffness)을 요구하는 조선업에 널리 사용되어져 왔다. 국부하중 조건 하에서 샌드위치 구조물에 대한 디자인 변수들을 고려하는 것은 중요시되어졌다. 이 연구는 샌드위치 보의 강도에 대한 core층의 밀도, core층의 두께 그리고 face층의 두께 비율의 영향을 기술하였다. 이차원 탄성이론에 바탕을 둔 파손 하중은 AS4/3501-6 facing과 polyurethane foam core 샌드위치 보의 3점 굴곡 실험 결과와 잘 일치 하였다. 또한 그러한 파손 하중들은 face층의 비율의 변화와 함께 비교되었다. 파괴 mode들의 교차점으로 결정되어진 최적조건은 강도(strength)와 강성(stiffness)에 대한 샌드위치 빔의 최적 core 밀도의 값이 결정되었다. 추가적으로 강도에 대한 최적조건과 그렇지 못한 샌드위치 보에 대한 face 두께 비율 효과가 하중 길이에 따라 비교되었으며, 강도와 강성이 core/face무게 비율과 항께 검토하였다.

• Steel and Composite Structures
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• 제43권2호
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• pp.139-152
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• 2022

Steel-reinforced concrete (SRC) L-shaped column is the vertical load-bearing member with high spatial adaptability. The seismic behavior of SRC L-shaped column is complex because of their irregular cross sections. In this study, the hysteretic performance of six steel truss reinforced concrete L-shaped columns specimens under the combined loading of compression, bending, shear, and torsion was tested. There were two parameters, i.e., the moment ratio of torsion to bending (γ) and the aspect ratio (column length-to-depth ratio (φ)). The failure process, torsion-displacement hysteresis curves, and bending-displacement hysteresis curves of specimens were obtained, and the failure patterns, hysteresis curves, rigidity degradation, ductility, and energy dissipation were analyzed. The experimental research indicates that the failure mode of the specimen changes from bending failure to bending-shear failure and finally bending-torsion failure with the increase of γ. The torsion-displacement hysteresis curves were pinched in the middle, formed a slip platform, and the phenomenon of "load drop" occurred after the peak load. The bending-displacement hysteresis curves were plump, which shows that the bending capacity of the specimen is better than torsion capacity. The results show that the steel truss reinforced concrete L-shaped columns have good collapse resistance, and the ultimate interstory drift ratio more than that of the Chinese Code of Seismic Design of Building (GB50011-2014), which is sufficient. The average value of displacement ductility coefficient is larger than rotation angle ductility coefficient, indicating that the specimen has a better bending deformation resistance. The specimen that has a more regular section with a small φ has better potential to bear bending moment and torsion evenly and consume more energy under a combined action.