• 한국구조물진단유지관리공학회 논문집
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• 제4권4호
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• pp.171-180
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• 2000

This study aims to present a more reasonable control value than the exiting one by comparing and analyzing control values and field instrumentation values of the whole excavation depth of the four case sites using geometric averaging as a statistical method. The range of the study is confined to three things: (1) the axial force of the braced excavation walls among a variety of items prescribed in the control values by stress deformation of walls and adjacent structures; (2) by approximation of the allowable and design value; (3) and by safety factor. As a res it is desirable to revise "(Long term allowable stress + Short term allowable stress)/2 ~ Short term allowable stress," presented in the present control values by stress deformation of walls and adjacent structures, to "(Long term allowable stress + Short term allowable stress)/5 ~ (Short term allowable stress)/3." The result also shows that since there is a difference of about 3.5%, it is not necessary to revise 70, 90, and 100 percent of LEVEL I, II, and III, prescribed in the control values by the allowable and design value approximation. In addition, modifying the control value by the safety factor, now 1.07, is unnecessary, although it varies little difference from the present value.

• 한국가구학회지
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• 제23권2호
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• pp.214-221
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• 2012

Sustainable energy consumption and increasing $CO_2$ emissions stimulate Eco-friendly industry. Wood has positive various properties as alternative energy such as solar, wind and water. Wood provide lumber, pallet, paper, pulp and fuel through production process. Even Korea republic has 63.7% of forest rates, weather condition makes low forestry production capacity. For utilization of domestic small diameter log needs study mechanical properties. In this study, various properties tested on domestic Japanese Larch small diameter lumbers and make mechanical properties table for allowable stress calculation. Result of compressive test, allowable compressive stress is 13 MPa. Allowable bending stress is 12 MPa.

• Journal of the Korean Wood Science and Technology
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• 제43권1호
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• pp.25-35
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• 2015

본 연구에서는 국산 침엽수재의 육안 등급구분과 허용응력설정에 관한 국내의 학술논문을 정리하였다. 국립산림과학원 고시(KFRI 1995-27, KFRI 2000-39, KFRI 2007-3, KFRI 2009-1)를 활용하여 국산 낙엽송재의 육안 등급 구분한 연구를 비교한 결과 등급구분 비율이 연구자마다 상이했다. 보다 신뢰할 수 있는 등급구분 분류를 위해서 공증된 목재이용 기관에서 숙련된 연구자에 의한 등급구분을 시행하여야 할 것으로 사료된다. 허용응력설정에 관한 연구를 고찰한 결과, 연구자 마다 허용응력산출 방법이 ASTM D 245, KS F 2152, JAS 1990으로 모두 상이했다. 이는 침엽수 구조용재(KS F 3020)에서 기준허용응력을 제시하고 있지만 허용응력을 산출하는 명확한 방법이 제시되어 있지 않기 때문인 것으로 나타났다. 따라서 공식적인 허용응력 결정방법이 제정되어야 할 것으로 사료된다.

• 한국정밀공학회:학술대회논문집
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• 한국정밀공학회 1997년도 춘계학술대회 논문집
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• pp.475-480
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• 1997

It is common to assum identical allowable safety factors in static strength, defined by mean stress and in fatigue, defined by stress amplitude. Under the load with asymmetrical cycles the safety factor is not the same. In this paper, with the consideration of unequal allowable safety factors a general method for estimating fatigue reliability of a machine element under a combined state of stress is derived based on the theory proposed by Prof. Kececioglu and normal distribution. The calculation of fatigue reliability for limited life is discussed with example.

• Journal of the Korean Wood Science and Technology
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• 제41권5호
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• pp.432-439
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• 2013

The aim of this study was to investigate the processes for evaluating the allowable bending stress. The confidence levels and the size-adjustment in standards were reviewed with experimental data. The results show that, (1) KS F 2152 was more strict than others overseas standards due to the higher confidence level. The 5% NTL of bending strengths by a method in KS F 2152 were lower than the overseas standards and more specimens were required for evaluating the structural properties according to KS F 2152. (2) Due to the absence of size-adjustment method in domestic standards, the specified size and the exponential parameters on the size-adjustment equation were reviewed by size factors. The specified size (width: 286 mm, length: 6096 mm), and the exponential parameters (w: 0.29, l: 0.14) will be suitable for developing the allowable bending stress in domestic standard. (3) The size adjusted allowable bending stresses of No. 2 grade Korean pine were lower than the allowable stresses tabulated in KBC even though less strict method (75% confidence level) to calculate 5% value was used. The allowable stresses tabulated in KBC are needed to be reviewed by continuous experimental data.

• 한국농공학회지
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• 제17권4호
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• pp.3921-3930
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• 1975

This research was carried out to investigate several mechanical characteristics of pre-stressed steel beams. The configuration of specimens used for this study were as follows; a cover plate having permissible fiber stress of 4,000 kg/$\textrm{cm}^2$ was welded at bottom having the allowable bending stress 2500 kg/$\textrm{cm}^2$ steel beam, the section ratios of pre-stressed steel beam and cover plate were 0.5 and 0.6. Adopted pre-stresses were 0%, 50%, and 100% of an allowable fiber stress of a steel beam. The results obtained from the study may be summarized as follows; 1. The elastic range of a beam was increased by the application of pre-stress to the beam, which leads to a lighter section. 2. The permissible moment capacity of a pre-stressed steel beam was greated than that of a steel beam without pre-stressing. 3. The equivalent allowable stress induced by adopting the different section ratio of pre-stressed beam to cover plate were figured out 4. The optimum value of section ratio of beam and cover plate was 0.3 to 0.4 in case of a 1.5m span composite beam, a combination of an allowable stress 2,500kg/$\textrm{cm}^2$ steel beam and a permissible fiber stress 4,000 kg/$\textrm{cm}^2$ steel cover plate, was used. 5. The magnitude of the pre-stress was desirable to be same as the allowable stress of a steel beam. 6. It was concluded that if the construction techniques in the field are developed and improved, the practicing of pre-stress to the steel structure has a promising future.

• 제어로봇시스템학회:학술대회논문집
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• 제어로봇시스템학회 1988년도 한국자동제어학술회의논문집(국내학술편); 한국전력공사연수원, 서울; 21-22 Oct. 1988
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• pp.556-561
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• 1988

Shrink-rings (Stress-rings) are used in the fabrication of dies for cold forming and powder compaction processes to increase the allowable pressures for a given die material. Optimum procedures are to minimize a die thickness under the conditions that the stress distributions in the die and stress-rings utilize fully the strength available in each of the die elements. This paper proposes a new approach, where the maximum allowable shrinking pressures are calculated on shrinkage plans in the radial direction and the fractional shrinking pressures below the maximum allowable pressures are used as the design values. Two criteria for the optimal die design are used: Maximum shear stress limit for one-piece dies and zero tensile stress limit for combined dies. A computer program, DIECOM, is developed for illustrating the computer-aided design procedures. Finally, examples for each case are presented in this paper.

• 한국구조물진단유지관리공학회 논문집
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• 제16권4호
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• pp.9-17
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• 2012

선행연구에서는 강도이론을 바탕으로 영향인자들을 반영한 해석단면에 대해 허용압축응력($Kf_{ci}$)을 해석하였고, 해석결과를 바탕으로 허용압축응력산정식을 제안하였다. 이전 연구에 대한 일련의 연구로서, 본 연구에서는 서로 다른 편심비(e/h)를 갖는 프리텐션 보 부재에 대한 프리스트레스 도입 실험을 수행하였다. 실험결과를 토대로 제안식을 검증한 결과 낮은 e/h를 갖는 프리텐션 부재의 경우, ACI318-08 및 EC2-02의 설계기준이 $Kf_{ci}$를 비안전측으로 결정하고 있음을 확인하였다. 또한 높은 e/h를 갖는 프리텐션 부재의 경우 현행의 설계기준은 $Kf_{ci}$를 과도하게 안전측으로 제안하고 있다. 이에 비해 제안식은 e/h에 따른 $Kf_{ci}$를 합리적으로 평가하는 것으로 나타났다.

• 한국산업융합학회 논문집
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• 제9권4호
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• pp.269-276
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• 2006

Strength Design method for involute spur gears is developed. The developed gear strength design system can design the optimized gear that minimize the number of pinion teeth with face tooth. Method of optimization is matrix form which is developed from this study. Design variables are transmitted power, gear volume, gear ratio, allowable contact stress and allowable bending stress, etc. Gear design method developed this study can be apply to the gears of plants, machine tools, automobiles.

• 한국안전학회지
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• 제22권1호
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• pp.13-18
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• 2007

Structural integrity assessment of thin-walled pipes and pipe items has become one of the major issues in the nuclear power plant. ASME Section XI Code Case N-597-2 provides a criterion for acceptance of the pipes. But the code case has several limitations for application and sometimes gives too conservative or non-conservative results. So it is necessary to understand fully the technical bases of the code case. In the code case N-597, the allowable local thicknesses of thinned straight pipes are given for three different cases. Because of the different technical base, each case gives different thickness values and sometimes gives contradictory values. In this paper attempts were made in order to propose a unified rule for the allowable local thickness and in order to remove or relax the restrictions on the application of the code case. For this purpose elastic stress analyses were made using the finite element method and the stress results were examined. Based on the obtained bending stress results, a very simple procedure was proposed to obtain the consistent allowable local thickness for the thinned straight pipes.