• 대한토목학회논문집
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• 제30권1D호
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• pp.53-60
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• 2010

본 논문은 포장 공용성에 근거하여 연성포장체를 주된 대상으로 트럭의 하중제한을 하기 위한 방법을 평가하였다. 이러한 방법론의 적용을 위하여 연성포장에 대한 장기공용성은 VESYS 형태의 소성변형 모형과 Miner 이론을 적용한 피로균열을 각각 활용하여 예측하였다. 소성변형은 Alpha와 Gnu와 같은 소성변형 모형상수를, 그리고 피로균열은 $k_1$과 $k_2$를 피로균열 모형 상수를 각각 적용하였고 기존 국내문헌에서 활용 가능한 범위에서 연성포장에 대한 하중제한 평가를 위한 공용성 예측 및 민감도 분석에 필요한 자료를 적절하게 활용하였다. 이에 본 연구 결과에서는 공용성에 근거한 하중제한방법과 하중제한을 위한 간편한 제한하중법을 평가하여 제시하였다.

• Computers and Concrete
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• 제19권3호
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• pp.243-256
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• 2017

Epoxy-coated reinforcing bars are widely used to protect the corrosion of the reinforcing bars in the RC elements under their in-service environments and external loads. In most field surveys, it was reported that the corrosion resistance of the epoxy-coated reinforcing bars is typically better than the uncoated bars. However, from the experimental tests conducted in the labs, it was reported that, under the same loads, the RC elements with epoxy-coated reinforcing bars had wider cracks than the elements reinforced with the ordinary bars. Although this conclusion may be true considering the bond reduction of the reinforcing bar due to the epoxy coating, the maximum service loads used in the experimental research may be a main reason. To answer these two phenomena, service performance of 15 RC beam specimens with uncoated and epoxy-coated reinforcements under different fatigue loads was experimentally studied. Influences of different coating thicknesses of the reinforcing bars, the fatigue load range and load upper limit as well as fatigue load cycles on the mechanical performance of RC test specimens are discussed. It is concluded that, for the test specimens subjected to the comparatively lower load range and load upper limit, adverse effect on the service performance of test specimens with thicker epoxy-coated reinforcing bars is negligible. With the increments of the coating thickness and the in-service loading level, i.e., fatigue load range, load upper limit and fatigue cycles, the adverse factor resulting from the thicker coating becomes noticeable.

• 한국공작기계학회:학술대회논문집
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• 한국공작기계학회 2002년도 춘계학술대회 논문집
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• pp.125-133
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• 2002

In this study, it was investigated about endurance limit and fatigue behavior of load carrying fillet welded cruciform joints according to welding methods of SMAW, SAW, MIG and FCAW commonly using for welding structures in present. Endurance limit carried omit highly in the order of SMAW, MIG, SAW, FCAW and fatigue crack propagation ratio carried out lowly in the order of SMAW, MIG, FCAW, SAW. By these results, it is needed to use SMAW or MIG welding methods for welding structures with small welding capacity and SAW or FCAW methods for large welding structures after due consideration about economic gains and operation efficiency of welding. Fatigue crack propagation ratio is more effected by strength of welding materials than endurance limit of welding materials according to welding methods.

• 한국공작기계학회논문집
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• 제12권1호
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• pp.38-44
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• 2003

In this study, endurance limit and fatigue behavior of load carrying fillet welded cruciform joints depending on commonly used welding methods such as SMAW, SAW, MIG and FCAW are investigated. In respect of endurance limit SMAW specimen showes highest result, and then MIG, SAW, FCAW in descending order. However, SMAW specimen showes lowest crack growth rate and it followed by MIG, FCAW, SAW. By these results, it is needed to use SMAW or MIG welding methods for welding structures with small welding capacity and SAW or FCAW methods for large welding structures with respect to economic benefits and operation efficiency of welding. It was also shown fatigue crack growth rate was more influenced by the strenght of welding materials than the endurance limit of welding materials.

• 대한기계학회:학술대회논문집
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• 대한기계학회 2007년도 춘계학술대회A
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• pp.1813-1817
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• 2007

The present work presents plastic limit load solutions for piping branch junctions with local wall-thinning, based on detailed three-dimensional (3-D) and small strain FE limit analyses using elastic-perfectly plastic materials. Three types of loading are considered; internal pressure, in-plane bending on the branch pipe and in-plane bending on the run pipe. The wall-tinning located on variable area of the piping branch junction is considered. A wide range of piping branch junction and wall-thinning geometries are considered. Comparison of the proposed solutions with FE results shows good agreement

• 대한기계학회논문집
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• 제7권3호
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• pp.249-256
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• 1983

The study is concerned with the analysis of sheet metal for the prediction of limit drawing ratio and forming load. The direct redrawing process is analyzed by using an equilibrium approach and strain increment theory both for non-workhardening material and for workhardening material. Computations are carried out numerically for the workhardening case. Limit drawing ratios are predicted for some chosen variables. The forming loads are also computed with respect to punch travel. Then the predicted loads are compared with the experimental results. For ordinary lubricated conditions, the comparison shows reasonable agreement between the theory and experimental observation. It is also shown that limit drawing ration can be increased by using a greater die angle and proper lubrication significantly reduces the punch load. Finally numerical results show that material of greater R-value and strain-hardening exponent(n)is better for direst redrawing of sheet metal.

• 대한기계학회논문집A
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• 제29권12권
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• pp.1605-1614
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• 2005

For the last four decades, tension test of notched bars has been performed to investigate the effect of stress triaxiality on ductile fracture. To quantify the effect of the notch radius on stress triaxiality, the Bridgman equation is typically used. However, recent works based on detailed finite element analysis have shown that the Bridgman equation is not correct, possibly due to his assumption that strain is constant in the necked ligament. Up to present, no systematic work has been performed on fully plastic stress fields for notched bars in tension. This paper presents fully plastic results for tension of notched bars and plates in plane strain, via finite element limit analysis. The notch radius is systematically varied, covering both un-cracked and cracked cases. Comparison of plastic limit loads with existing solutions shows that existing solutions are accurate for notched plates, but not for notched bars. Accordingly new limit load solutions are given for notched bars. Variations of stress triaxiality with the notch radius and depth are also given, which again indicates that the Bridgman solution for notched bars is not correct and inaccuracy depends on the notch radius and depth.

• 한국구조물진단유지관리공학회 논문집
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• 제16권1호
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• pp.99-109
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• 2012

이 연구에서는 변형률계를 사용하여 변위를 추정하는 이론식을 제안 및 검증하고 하중 작용점과 크기를 추정하여 강재보의 건전도 평가 시스템을 개발하고자 하였다. 실험결과 160kN(항복하중의 56%)가력시 최대처짐 점에서 변형률계를 사용하여 얻는 처짐과 변위계의 측정처짐과의 오차율이 2%이내로 나타났으며 하중작용점 및 크기의 추정도 오차율1% 이내로 나타났다. 이를 통해 변형률계로 강재보의 변위 및 하중을 계측 할 수 있으며 나아가 변위계와 하중계의 생략으로 경제적인 센서설계를 할 수 있다. Lab VIEW로 구현된 건전도 평가 프로그램은 측정된 데이터가 일정 범위(강도 한계상태, 사용성 한계상태, 항복변형률)를 넘어설 때 단계별 경고를 발생하였고 변형률계 만으로 사용성한계상태와 강도한계상태를 동시에 모니터링 할 수 있었다.

• Geomechanics and Engineering
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• 제15권3호
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• pp.879-888
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• 2018

Probability-based design codes have been developed to sufficiently confirm the safety level of structures. One of the most acceptable probability-based approaches is Load Resistance Factor Design (LRFD), which measures the safety level of the structures in terms of the reliability index. The main contribution of this paper is to calibrate the load and resistance factors of the design code for tunnels. The load and resistance factors are calculated using the available statistical models and probability-based procedures. The major steps include selection of representative structures, consideration of the limit state functions, calculation of reliability for the selected structures, selection of the target reliability index and calculation of load factors and resistance factors. The load and resistance models are reviewed. Statistical models of resistance (load carrying capacity) are summarized for strength limit state in bending, shear and compression. The reliability indices are calculated for several segments of a selected circular tunnel designed according to the tunnel manual report (Tunnel Manual). The novelty of this paper is the selection of the target reliability. In doing so, the uniform spectrum of reliability indices is proposed based on the probability paper. The final recommendation is proposed based on the closeness to the target reliability index.

• 한국해안·해양공학회논문집
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• 제33권6호
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• pp.293-297
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• 2021

소파블록 피복제 제체의 한계상태설계법 개발을 위해 하중저항계수 보정을 수행하였다. 실제 시공된 소파블록 피복제 제체의 설계자료를 분석하여 신뢰성해석을 수행하였으며 목표신뢰성지수에 따른 부분안전계수와 하중, 저항계수를 차례로 산정하였다. 최적화기법을 통해 한계상태설계법 개발을 위한 하중계수와 저항계수를 도출하였다. 최종 하중저항계수를 이용하여 방파제를 재설계하였으며 목표수준의 신뢰성지수를 상회하는지 검증하였다. 해외기준의 하중저항계수와 본 연구에서 구한 하중저항계수를 비교하였다.