• 한국콘크리트학회:학술대회논문집
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• 한국콘크리트학회 1997년도 가을 학술발표회 논문집
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• pp.679-684
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• 1997

In this study, compressive strengths of reinforced concrete compression members rehabilitated with C.F.L. were analyzed from the test. Test parameters are spacing, spliced length, and section area of rehabilitation material. Displacement, failure load were measured during test. The failure mode and ultimate load were analyzed from these measured data. Test result shows that closer spacing of C.F.L. is more effective. strengthening with 1-ply C.F.L. is more effective than that of specimen with 2-ply C.F.L. The compressive capacity of specimen spliced ($\pi$.D)/2 shows almost similar strength to that of non-spliced specimen. The ultimate load carrying capacity of specimen strengthened with C.F.L. is increased to 1.11~1.68 times of that of non-rehabilitation specimen.

• 한국전산구조공학회:학술대회논문집
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• 한국전산구조공학회 2001년도 봄 학술발표회 논문집
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• pp.291-298
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• 2001

When the compression members have the variable cross sections along their member axes, the determination of the elastic critical loads by classical methods becomes impossible and if possible involves complicated calculation only to obtain the approximate values of critical load. In this paper the elastic critical load coefficients of the tapered members with simply supported ends were determined by finite element method. And then the results were represented by simple algebraic equations of two parameters, a( =taper parameter) and m ( = sectional property parameter). One the basis of algebraic equations, the equivalent moment of inertia concept originally proposed by Bleich for a spesific case, are extended to the general cases.

• 한국전산구조공학회:학술대회논문집
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• 한국전산구조공학회 1999년도 가을 학술발표회 논문집
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• pp.421-428
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• 1999

The elastic critical load of a slender compression member plays an important role when the proper design of that member is required. For the tapered compression members, however, there are cases when the conventional neutral equililbrium or energy method can't be applied to the determination of critical loads of those members. In this paper, finite element method is applied to the approximate determination of the symmetrically tapered bars. Here in this paper, the bars are assumed to take sinusoidally changing shapes along their axes. The parameters considered in this study are taper parameter, $\alpha$ and the sectional property parameter, m. The computed results by finite element method are represented in the forms of algebraic equations. Regression technique is employed to determine the coefficients of algebraic equations. The critical loads estimated by the proposed algebraic equations coincide fairly well with those of finite element method.

• Computers and Concrete
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• 제29권 5호
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• pp.285-301
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• 2022

This study aims at developing a torsional strength model based on a nonlinear analysis method presented in the previous studies. To this end, flexural neutral axis depth of a reinforced concrete section and effective thickness of an idealized thin-walled tube were formulated based on reasonable approximations. In addition, various sectional force components, such as shear, flexure, axial compression, and torsional moment, were considered in estimating torsional strength by addressing a simple and linear strain profile. Existing test results were collected from literature for verifications by comparing with those estimated from the proposed model. On this basis, it can be confirmed that the proposed model can evaluate the torsional strength of RC members subjected to combined loads with a good level of accuracy, and it also well captured inter-related mechanisms between shear, bending moment, axial compression, and torsion.

• 한국강구조학회 논문집
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• 제22권6호
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• pp.609-616
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• 2010

이 논문은 600MPa급 고강도강이 원형강관 건축구조용으로 이용될 때 중심압축재의 좌굴강도에 관하여 수치해석적으로 조사한 것이다. 600MPa급 고강도강의 소재인장시험 결과로부터 중심압축재의 좌굴강도를 산정하였으며, 좌굴강도 산정에는 Beam-Column이론에 근거한 방법과 Tangent Modulus 이론에 의한 양자의 방법을 이용하였다. 그리고 소성흐름이 없는 인장시험의 응력-변형도 관계를 비례한도의 크기와 비례한도에서 항복점에 이르는 접선계수의 기울기로 근사시키고 좌굴강도 미치는 영향인자를 조사하였다. 600MPa급 고강도강에 적용되는 현재의 건축기준은 압축재의 경우 항복강도 Fy값을 480Mpa 까지 상향조정하여도 무리가 없다고 사료된다.

• Steel and Composite Structures
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• 제18권5호
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• pp.1259-1277
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• 2015

The present study is focused on the behavior and design of perforated steel storage rack columns under axial compression. These columns may exhibit different types of behavior and levels of strength owing to their peculiar features including their complex cross-section forms and perforations along the member. In the present codes of practice, the design of these columns is carried out using analytical formulas which are supported by experimental tests described in the relevant code document. Recently proposed analytical approaches are used to estimate the load carrying capacity of axially compressed steel storage rack columns. Experimental and numerical studies were carried out to verify the proposed approaches. The experimental study includes compression tests done on members of different lengths, but of the same cross-section. A comparison between the analytical and the experimental results is presented to identify the accuracy of the recently proposed analytical approaches. The proposed approach includes modifications in the Direct Strength Method to include the effects of perforations (the so-called reduced thickness approach). CUFSM and CUTWP software programs are used to calculate the elastic buckling parameters of the studied members. Results from experimental and analytical studies compared very well. This indicates the validity of the recently proposed approaches for predicting the ultimate strength of steel storage rack columns.

• Structural Engineering and Mechanics
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• 제84권4호
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• pp.517-530
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• 2022

In re-assessing the Jacket-type fixed steel structures, the current standards often allow the simplicity of corrosion sections using local buckling or equivalent section approach to applying empirical formulae of frame stress and resistance analyses. However, those approaches can lead to significant errors for non-uniform corroded frames in a specific area, including force distribution, stress, and allowable strength of the tubular section, compared to the actual cases. This paper investigates a suitable approach to determine the actual stress on non-uniform corroded tubular frames under compression through the non-linear ABAQUS model by considering the effect of large deformation on the frame axis and the frame section. There are 3 scenarios of interest. In the 1st and 2nd scenarios with simple corrosion cases, the stress ratios using the numerical model and theoretical formulae correspond to the calculation of allowable strength reduction ratios in standards. However, scenario 3, which describes non-uniform corroded sections based on survey data, provides considerable differences in results. Therefore, it proves the reliable and effective results when using this method to analyze the resistance of the actual corroded section in the Jacket platforms.

• Steel and Composite Structures
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• 제1권1호
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• pp.97-110
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• 2001

Architectural steel structures with visible tension and compression members are becoming more prevalent as a popular form of construction that reflects the nature of the resistance to the applied loads. These members require the use of structural steel pins at their ends to ensure either axial tension or axial compression in the members. Structural pins have been used as a means of connection for centuries and it would appear that their behaviour is relatively well understood. However, the rules for the design of pins vary quite considerably from code to code and this has caused some confusion amongst consulting structural engineers operating internationally. To provide some insight into this problem, a comprehensive testing program has been carried to examine the influence of parameters such as pin diameter, material properties of the pin, thickness of the loading plates, material properties of the loading plates and the distance of the pin to the edge of the loading plates. The modes of failure have been carefully examined. Based on this study, modifications to current design procedures are proposed that properly take into account the different possible modes of failure.

• 콘크리트학회논문집
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• 제13권4호
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• pp.379-388
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• 2001

콘크리트를 위한 기존의 미소면 모델은 2차원 부재에 대한 해석에서도 3차원의 구형 미소면을 사용하고 있으며, 또한 인장-압축 상태의 철근콘크리트의 인장균열 후 거동을 정확히 나타낼 수 없다. 본 연구에서는 이러한 기존 모델의 미비점을 보완하기 위하여 철근콘크리트 면 부재의 해석에 적합한 새로운 미소면 모델을 개발하였다. 이 미소면 모델은 기존의 구형 미소면 대신에 원판형 미소면을 사용한다. 따라서 이 모델은 보다 적은 수의 미소면과 2차원의 응력을 사용하므로 수치계산에서 효과적이다. 또한, 이 모델에서는 인장-압축상태의 철근콘크리트의 압축거동을 나타낼 수 있도록 변형률한계의 개념이 도입되었다. 이 미소면 모델은 유한요소해석에 적용되었으며, 기존의 실험과의 비교를 통하여 이 모델의 유효성이 검증되었다.

• 한국응급구조학회지
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• 제25권3호
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• pp.81-92
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• 2021

Purpose: The aim of the study is to measure the quality of cardiopulmonary resuscitation (CPR) and the fatigue of rescuers wearing PPE (Level D) during a CPR session and to ultimately provide suggestions of safety standards for rescuers. Methods: 36 subjects were enrolled in the study. The subjects were divided randomly into three groups of two-members, three-members, and four-members. Each group performed CPR for 30 minutes. Blood lactate concentration, heart rate, rating of perceived exertion, chest compression depth and rate were measured before experiment and after each cycle. Results: There was a difference in the blood lactate concentration during CPR cycle by member of shifts (p=.014). The blood lactate concentration increased during CPR (p=.000). Subjective fatigue was a significant difference of chest compression in cycles 3, 4, and 5 for the member of shifts during CPR (p=.049, p=.009, p=.015). Depth and rate of chest compression were not different for the member of shifts during CPR. Conclusion: It is necessary to establish standards for the member of shifts during CPR, to reduce the fatigue of rescuers.