• Computers and Concrete
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• 제8권4호
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• pp.445-463
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• 2011

In the design of reinforced concrete (RC) beams, apart from providing adequate strength, it is also necessary to provide a minimum deformability even for beams not located in seismic regions. In most RC design codes, this is achieved by restricting the maximum tension steel ratio or neutral axis depth. However, this empirical deemed-to-satisfy method, which was developed based on beams made of normal-strength concrete (NSC) and normal-strength steel (NSS), would not provide a consistent deformability to beams made of high-strength concrete (HSC) and/or high-strength steel (HSS). More critically, HSC beams would have much lower deformability than that provided previously to NSC beams. To ensure that a consistent deformability is provided to all RC beams, it is proposed herein to set an absolute minimum rotation capacity to all RC beams in the design. Based on this requirement, the respective maximum limits of tension steel ratio and neutral axis depth for different concrete and steel yield strengths are derived based on a formula developed by the authors. Finally for incorporation into design codes, simplified guidelines for designing RC beams having the proposed minimum deformability are developed.

• 한국추진공학회지
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• 제17권5호
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• pp.80-85
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• 2013

본 논문은 평균값과 Allowable 값 기준의 구조 안전율과 구조 신뢰도와 관계 비교를 통해 복합재 추진기관의 확률적 구조 설계 방법을 설명하였다. 일반적으로 복합재 압력용기의 평균 값 기준의 구조설계는 1.5 이상의 구조 안전율과 0.999 이상의 구조 신뢰도 값이 요구된다. 요구 압력 기준의 0.999의 구조 신뢰도를 만족하기 위해서 평균 값 기준의 구조설계는 섬유 강도의 변동률에 따라 다른 구조 안전율을 부여해야한다. 그러나 이미 섬유 강도 변동률이 고려된 Allowable 값을 이용할 때는 고정된 안전율이 부여된다. 이상의 해석 결과로 볼 때 섬유 강도는 복합재 압력용기 구조 설계에 가장 중요한 설계 변수이고, 우수한 성능의 복합재 추진기관을 개발하기 위해서는 섬유 강도의 변동률이 최소화되어야 함을 알 수 있었다.

• 근관절건강학회지
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• 제12권1호
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• pp.69-80
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• 2005

Purpose: The purpose of this study was to analyse the effects of Tai Chi on the muscle strength and flexibility. Method: 10 articles from Medline search of foreign journals(1981-2003) and 4 from Korean nursing journals (1981-2003) were surveyed. The research are analyzed according to research design, subjects, and dependent variables. Results: Research on Tai Chi Exercise increased rapidly in the 1990's. The experimental research design was more reported than the comparative design. The experimental design included; 21.4% one group pre-posttest design, 35.7% quasi-experimental design and 28.6% randomized design. Out of the subjects; 64.4% of papers were healthy older people, and 35.6% of papers were patients with osteoarthritis or rheumatoid arthritis. Style of Tai Chi was mostly used Yang or Sun form. Muscle strength was usually measured at lower extremity or grip strength. Classical Yang style or Long form was more effective to improve muscle strength. 75% of papers were significantly improvement in grip strength and 71.4% of papers in flexibility. Conclusion: To properly study the positive effects of Tai Chi exercise, it is suggested that meta analysis needs to be done to integrate the various results.

• 한국정밀공학회지
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• 제12권7호
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• pp.66-73
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• 1995

Rating systems of bevel gears(straight, spiral, and zerol bevel gears) which are commonly used as power transmission devices for non-papallel axes are developed on the personal computer, which analyze and/or evaluate the gear design and the service performance at the point of view of strength and durability. The typical considerations of the ratings are the bending strength, the surface durability, and the scoring resistance. The ratings are carried out using the reliable standards of AGMA & Gleason Works. Therefore, the system is built so that the variables or factors considered differently in those standards and the strength, dura- bility, and scoring partially in Gleason are appraised seperately by each method, and a series of the estimation processes is integrated into the system so as to compare each result. The developed rating systems can be used in the initial stage of gear design process, and also a better design can be performed by the evaluation of the initial design at the view point of gear strength and durability. Additionally, it is useful for the trouble-shooting of bevel gear system and to the purpose of introducing the methods for maintaining design strength in service, with appraising the gear strength after design or with appraising the influencing factor as a whole. Therefore, this rating systems can help the aim of design automation of bevel gears.

• 한국해양공학회지
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• 제35권2호
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• pp.131-140
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• 2021

The paper deals with comparative study of various surrogate models based approximate optimization in the structural design of the passive type deck support frame under design load conditions. The passive type deck support frame was devised to facilitate both transportation and installation of 20,000 ton class topside. Structural analysis was performed using the finite element method to evaluate the strength performance of the passive type deck support frame in its initial design stage. In the structural analysis, the strength performances were evaluated for various design load conditions. The optimum design problem based on surrogate model was formulated such that thickness sizing variables of main structure members were determined by minimizing the weight of the passive type deck support frame subject to the strength performance constraints. The surrogate models used in the approximate optimization were response surface method, Kriging model, and Chebyshev orthogonal polynomials. In the context of numerical performances, the solution results from approximate optimization were compared to actual non-approximate optimization. The response surface method among the surrogate models used in the approximate optimization showed the most appropriate optimum design results for the structure design of the passive type deck support frame.

• 한국콘크리트학회:학술대회논문집
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• 한국콘크리트학회 1998년도 가을 학술발표논문집(II)
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• pp.571-576
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• 1998

This paper is a part of a research plan aimed at the verification of basic design rules of high-strength concrete columns. A total of 19 slender column specimens were tested to measure secondary moment and stiffness of eccentrically loaded reinforced concrete tied columns. Main variables included in this test program were concrete compressive strength, steel amount, eccentricity, and slenderness ratio. The concrete compressive strength varied from 356kg/$\textrm{cm}^2$ to 951kg/$\textrm{cm}^2$, the longitudinal steel ratios were between 1.13% and 5.51%, and slenderness ratios were 40 and 61. Calculated moment magnification factors and column stiffness based on design codes are higher than the test results for high axial load under small eccentricity, for higher slenderness ratio, for lower longitudinal steel ratio, and for high-strength concrete. The moment magnification method of the current design codes may provide a very conservative design for high-strength concrete slender column.

• 한국전산구조공학회:학술대회논문집
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• 한국전산구조공학회 2005년도 춘계 학술발표회 논문집
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• pp.592-600
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• 2005

Ship have cutout inner bottom and girder and floor etc. Ship's structure is used much, and structure strength must be situated, but establish new concept when high stress interacts sometimes fatally the area. There is no big problem usually by aim of weight reduction, a person and change of freight, piping etc.. Because cutout's existence grow up in this place, and elastic buckling strength by load causes large effect in ultimate strength. Therefore, stiffened perforated plate considering buckling strength and ultimate strength is one of important design criteria which must examine when decide structural concept at initial design. Therefore, md, reasonable buckling strength about stiffened perforated plate need to ultimate strength limited design . Calculated ultimate strength varied several web height and cutout's dimension, and thickness in this investigated data. Used program(ANSYS) applied F.E.A code based on finite element method

• 한국전산구조공학회:학술대회논문집
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• 한국전산구조공학회 2007년도 정기 학술대회 논문집
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• pp.315-320
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• 2007

An effective reinforcement method for steel tubular joints having a large chord diameter is the use of internal ring stiffeners. This paper presents the results of a numerical study on the static strength of internally ring-stiffened tubular X- and T-joints subjected to brace axial compression loading. Nonlinear finite element analyses are used to compute the joint strength. The influence of geometrical parameters has been studied and the maximum reinforcement effect of a ring stiffener has been evaluated. A strength ratio is defined. by the ratio of ring-stiffened joint strength to unstiffened joint strength, and an equation for this strength ratio is derived by regression analysis. Design optimization for ring stiffener of tubular joints is carried out using metropolis genetic algorithm.

• 한국콘크리트학회:학술대회논문집
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• 한국콘크리트학회 1996년도 가을 학술발표회 논문집
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• pp.232-238
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• 1996

In this paper, the properties of high-strength concrete are described with respect to materials and mix conditions(water-cement ratio, chemical admixture, replacement of fly ash). As primary purposes of this study, the optimum mix design method of high-strength concrete to decrease unit cement contents is investigated, and the properties of fresh and hardened concretes are tested in terms of slump, air content and compressive strength. As results of this study, workability and strength development of the high-strength concrete depend on the water-cement ratio, replacement ratio of fly ash and dosage of the chemical admixture. The conditions which are proposed optimum mix design of the high-strength concrete show W/C 37%, S/A 42~45% and unit cement content 470~480kg/$\textrm{m}^3$. Based on the results, the applicability of high-strength concrete in site is clearly proved.

• 한국콘크리트학회:학술대회논문집
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• 한국콘크리트학회 2003년도 봄 학술발표회 논문집
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• pp.83-88
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• 2003

In this paper, the medium strength self-compacting concrete with simple mix design method was manufactured and investigated about the properties of flowability and strength. Two types of binders like as fly-ash and RP(rock powder) were contained to the SCC in order to obtain the target medium strength of 270-350kgf/$cm^2$. The experimental tests about slump-flow, reaching time to the slump-flow of 50cm, V-funnel and U-box were carried out in accordance with the specified by the Japanese Society of Civil Engineering(JSCE). The mechanical properties such as compressive strength, splitting tensile strength and static modulus of elasticity were checked with the requirements specified by KS.