• 한국도로학회논문집
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• 제10권4호
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• pp.269-279
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• 2008

본 연구는 프리스트레스트 콘크리트 포장(PSCP)의 횡방향 긴장 설계방안을 구축하기 위하여 수행되었다. 우선 PSCP에 횡방향 긴장을 가했을 경우에 긴장간격에 따른 슬래브의 응력분포를 분석하였다. 또한 환경하중과 차륜하중이 PSCP슬래브에 작용할 때 슬래브에 발생하는 인장응력의 분포도 분석하였다. 이러한 환경 및 차륜하중 등의 설계하중과 긴장응력을 결정하는 기준인 슬래브의 허용인장응력을 합리적으로 선정하는 방법에 대하여 논의하였으며 이러한 기준의 선정이 횡방향 긴장 설계에 미치는 영향을 분석하였다. 연구결과, 긴장간격이 커질수록 긴장응력의 손실을 가져오는 범위가 넓어지며 특히 Shoulder부분에서의 응력손실이 급격하게 증가하는 것을 알 수 있었다. 따라서 횡방향 긴장 설계는 설계하중에 대한 슬래브의 응력을 산출한 후 슬래브가 허용인장응력 이내의 응력을 받도록 평균긴장응력을 산출하여 긴장간격 및 긴장량을 결정하면 되지만, 이때 Shoulder, Wheel Pass, 중앙부 등 슬래브의 여러 다른 위치에서의 응력 또한 반드시 검토하여 적절한 긴장간격을 선정하여야 한다.

• 한국안전학회지
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• 제21권2호
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• pp.80-88
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• 2006

In the present study damage behavior of resilient sleepers on concrete ballasts is analyzed. Cracks of resilient sleepers in a railway track system are concentrated on inside of blocks to which the tie bars are connected. Finite element analysis is performed by dividing a block into the straight section and the curved section according to the load condition of the resilient sleeper, and limited the interpretation within the range of resilience. In addition, the value of stress obtained from the interpretation was compared with the allowable stress of concrete to determine the safety. According to the result of numerical analysis, compared with the stress before unequal settlement, the tensile stress of the inside of the block increased significantly after the settlement considering the entire block, and the tensile stress of this part exceeded the allowable stress of concrete, so was undesirable in terms of safety. In reality, the arrangement of tensile stiffeners inside blocks connected to tie bars is improper in the design of resilient sleepers, and when unequal settlement occurs, tensile stress increases on this part and consequently causes cracking damage. It is necessary to arrange wire meshes or tensile reinforcing bars in a structurally safe way to reinforce the inside of blocks on which cracks are concentrated.

• 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.

• Architectural research
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• 제9권1호
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• pp.31-37
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• 2007

This study presents the so-called Modified Allowable Stress Design (MASD) method for structural designs. The objective of this study is to qualitatively estimate uncertainties of tensile steel member's cross-sectional structural designs and find the optimal resulting design which can resist all uncertainty cases. The design parameters are assumed to be interval associated with lower and upper bounds and consequently interval methods are implemented to non-stochastically produce design results including the structural uncertainties. By seeking optimal uncertainty combinations among interval parameters, engineers can qualitatively describe uncertain design solutions which were not considered in conventional structural designs. Under the assumption that structures have basically uncertainties like displacement responses, the safety range of resulting designs is represented by lower and upper bounds depending on given tolerance error and structural parameters. As a numerical example uncertain cross-sectional areas of members that can resist applied loads are investigated and it demonstrates that the present design method is superior to conventional allowable stress designs (ASD) with respect to a reliably structural safety as well as an economical material.

• 한국기계연구소 소보
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• 통권17호
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• pp.75-82
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• 1987

Shrink-rings (Stress-rings) are used in the fabrication of powder compaction dies to increase the allowable compaction pressures for a given die material. Optimum Procedures are used to insure that the stress distributions in the die and stress-rings ultilize fully the strength available in each of the die elements. Two criteria for the optimum die design are used: Maximum shear stress limit for one-piece dies and zero tensile stress limit for combined dies. Examples for each case are presented in this paper.

• Nuclear Engineering and Technology
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• 제52권7호
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• pp.1486-1494
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• 2020

To evaluate transport-induced cladding embrittlement after interim-dry storage, ring compression tests were carried out at room temperature(RT) and 135 ℃. The ring compression test specimens were prepared by simulating the interim-dry storage conditions that include four peak cladding temperatures of 250, 300, 350 and 400 ℃, two tensile hoop stresses of 80 and 100 MPa, two hydrogen contents of 250 and 500 wt.ppm-H and a cooling rate of 0.3 ℃/min. Radial hydride fractions of the ring specimens vary depending on those interim-dry storage conditions. The RT compression tests generated lower offset strains than the 135 ℃ ones. In addition, the RT and 135 ℃ compression tests indicate that a higher peak cladding temperature, a higher tensile hoop stress and the lower hydrogen content generated a lower offset strain. Based on the embrittlement criterion of 2.0% offset strain, an allowable peak temperature during the interim-dry storage may be proposed to be less than 350 ℃ under the tensile hoop stress of 80 MPa at the terminal cool-down temperature of 135 ℃.

• Nuclear Engineering and Technology
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• 제49권8호
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• pp.1740-1747
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• 2017

To investigate allowable peak cladding temperature and hoop stress for maintenance of cladding integrity during interim-dry storage and subsequent transport, zirconium alloy cladding tubes were hydrogen-charged to generate 250 ppm and 500 ppm hydrogen contents, simulating spent nuclear fuel degradation. The hydrogen-charged specimens were heated to four peak temperatures of $250^{\circ}C$, $300^{\circ}C$, $350^{\circ}C$, and $400^{\circ}C$, and then cooled to room temperature at cooling rates of $0.3^{\circ}C/min$ under three tensile hoop stresses of 80 MPa, 100 MPa, and 120 MPa. The cool-down specimens showed that high peak heat-up temperature led to lower hydrogen content and that larger tensile hoop stress generated larger radial hydride fraction and consequently lower plastic elongation. Based on these out-of-pile cladding tube test results only, it may be said that peak cladding temperature should be limited to a level < $250^{\circ}C$, regardless of the cladding hoop stress, to ensure cladding integrity during interim-dry storage and subsequent transport.

• 한국강구조학회 논문집
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• 제28권4호
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• pp.263-270
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• 2016

해안 및 해양 환경에 노출되어 내부식성이 필수적인 항만 및 해양 구조물용 내식성강 STKM500 강재가 최근 국내의 독자적인 기술로 개발되어 KS D 3300에 신규 등록되었다. 개발된 강재는 일반 구조용 강재에 비해 부식속도가 현저하게 느리고, 지금까지 대표적으로 사용되었던 STK400 및 STK490와 A690 강재보다 경제적이고 고강도여서 미래 수요를 대체할 수 있을 것으로 기대된다. 본 연구에서는 STKM500 강재를 이용한 인장실험을 통해 고강도강의 강도를 측정한 후, 2m, 6m, 12m로 제작된 강관에 대한 좌굴실험을 수행하여 허용압축응력을 산정하였다. 특별히 12m 시험체의 경우, 추가 유한요소해석을 수행하여 결과를 보완하였고, STK500 강관에 대한 축방향 허용 압축응력곡선을 제안하였다.

• Structural Engineering and Mechanics
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• 제82권6호
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• pp.757-770
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• 2022

For the design of flexural and shear crack control for reinforced concrete (RC) beams related to serviceability and reparability ensuring, eight simply-supported normal-strength reinforced concrete (NSRC) beam specimens are tested and the existing high-strength reinforced concrete (HSRC) experimental data are included in the investigation of this work. According to the investigation results of flexural and shear cracks, this works modifies the existing design formulas to determine the spacing of the tensile reinforcement for the flexural crack control of a HSRC/NSRC beam design. Additionally, for a specified shear crack width of 0.4 mm, the allowable stresses of the shear reinforcement are also identified. For the serviceability and reparability ensuring of HSRC/NSRC beams, this works proposes the relationship curves between the maximum flexural width and allowable stress of the tensile reinforcement, and the relationship curves between the shear crack width and allowable shear force that can be used to do the crack width control directly.

• 한국공간구조학회논문집
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• 제16권1호
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• pp.35-42
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• 2016

Until recently, almost all ETFE film structures that have been erected is the cushion type because there are problems at lower allowable strength under elastic range and viscosity behaviour such as creep and relaxation of ETFE films under long-term stresses. But the number of tension type structures is currently increasing. This paper proposes the stretch fabrication of ETFE film to verify the applicability of ETFE films to tensile membrane structures. First of all, to investigate the possibility of application on tensile membrane structures, the stretch fabrication test is carried out, and it is verified that it is possible to increase the yield strength of the film membrane structures. After simulating the experiment also carries out an analytical investigation, and the effectiveness of the elasto-plastic analysis considering the viscous behavior of the film is investigated. Finally, post-aging tension measurement is conducted at the experimental facilities, and the viscosity behavior resulting from relaxation is investigated with respect to tensile membrane structures.