• Journal of the Korea Concrete Institute
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• v.24 no.4
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• pp.473-480
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• 2012

In order to develop an effecive seismic strengthening metghod for existing concrete structure, structural tests of aramid FRP reinforced RC columns are performed. The test variables were strengthening methods of aramid sheet and strip. The test results were evaluated by comparing strength and energy dissipation capacities of non-reinforced and reinforced specimens. The test result comparison showed that aramid sheet reinforcement on RC column was evaluated as the most efficient way to increase strength and energy dissipation capacity.

• Journal of the Earthquake Engineering Society of Korea
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• v.3 no.2
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• pp.97-106
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• 1999

In order to check the necessity of seismic reinforcement for a great number of existing structures effectively, it might be desirable to introduce the multi-step seismic evaluation system. This paper presents close relationships between shear-to-moment capacity ratio of a member and seismic performance of structures concerned through the failure mechanism investigation in the view of geological and structural characteristics. Based on it, the simple seismic performance evaluation method has been proposed and its effectiveness was verified by comparing with the damage condition of structures damaged under Hyogo-Ken Nambu Earthquake.

• Journal of the Korea Concrete Institute
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• v.20 no.6
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• pp.731-739
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• 2008

To evaluate the fiber orientation characteristics and estimate its effect on the flexural strength of steel fiber reinforced ultra high strength concrete with directions of concrete placing, we developed an image processing technique and carried out the flexural test to quantify the effect of fiber orientation characteristics on the flexural strength as well. The image processing technique developed in this study could evaluate quantitatively the fiber orientation property by the use of dispersion coefficient, the number of fibers in a unit area, and fiber orientation. It was also found that the fiber orientation characteristics were dependent on the direction of concrete placing. Fiber orientation characteristic was revealed to strongly affect the ultimate flexural strength, while hardly affecting the first cracking strength. Theoretical model for flexural strength was applied to compare with test results, which exhibited a good agreement.

• Proceedings of the Korea Concrete Institute Conference
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• 2009.05a
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• pp.519-520
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• 2009

The purpose of this research was to develop a very-early-strength dry-mix shotcrete without accelerator using a rapid-setting cement, to analyze the correlationship of test results among cube test, core test, pullout test and maturity

• Proceedings of the Korean Nuclear Society Conference
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• 1998.05b
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• pp.344-349
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• 1998

고리 1호기 원전의 원자로냉각재 배관의 파단전누설개념 적용성을 평가하기 위하여 일반적인 파단전누설 절차 및 기준을 검토하였다. 파단전누설 타당성을 검토하기 위하여는 한계하중방법 및 J-T 방법을 비교검토 하였다. 그리고 원자로냉각재 배관에 대해서는 탄소강일 경우와 스테인레스강에 대하여 분석하였고, 가압기 밀림관에 대해서는 열응력을 계산하였다. 그리고 원자로 냉각재 배관에 가상의 관통균열의 파괴안전성은 유한요소법을 이용한 탄소성파괴역학을 통하여 분석하였다. 분석결과 한계하중법과 J-T 방법 모두 스테인레스강과 탄소강재질에 대해 적용 가능한 것으로 나타났다.

• Journal of the korean Society of Automotive Engineers
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• v.15 no.4
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• pp.34-43
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• 1993

본 고에서는 피로해석을 통한 승용차 강도/내구기법에 대하여 개략적으로 언급하였다. 피로해석에 어려운 점은 수명예측방법이 이론적으로 완전히 정립된 것도 아니며 하중 및 재료특성 그리고 주변 사용환경등에 대한 불확실성으로 정량적인 평가가 힘들다는 것이다. 하지만 설계시간의 단축 및 효과적인 경량화 달성을 위해서는 보다 효율적이며 범용화된 피로해석 기법의 개발이 필요하며 해석과정의 자동화도 반드시 이루어져야 할 과제이다.

• Journal of Korea Ship Safrty Technology Authority
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• s.29
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• pp.26-41
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• 2010

본 연구에서는 쌍동선 연결부의 횡강도와 관련하여 국내기준 및 국제표준, 선급 기준의 관련 내용을 조사하고 각 하중에 대한 계산식 및 관련 계수들에 영향을 미치는 외력 등을 비교 분석하며 샘플선박에 대한 구조계산 및 해석을 수행하여 국내에 적합한 쌍동선 연결부의 횡강도 구조안전성 평가기준을 제시하고 국제표준에 대한 대응방안을 마련하고자 한다.

• Journal of the Earthquake Engineering Society of Korea
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• v.14 no.2
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• pp.37-47
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• 2010

In order to attain enhanced seismic performance of RC bridges, premature shear failure prior to the achievement of target ductilities of the piers should be prevented. For this purpose, a reliable shear strength evaluation is required. The shear strength of an RC column subjected to a lateral force decreases with an increase in ductility. Many empirical equations for the shear strength have been proposed by many researchers. However, there are many discrepancies in the initial shear strength in the low ductility range, and in the decrease rate according to the ductility. In this study, a new empirical equation of shear strength considering the displacement ductility effect has been proposed, in which the initial shear strength equation proposed by the authors was revised on the basis of the investigation of many other researchers' test results. The resulting improvement in accuracy is confirmed by comparison with other empirical equations.

• Journal of the Korea Concrete Institute
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• v.15 no.4
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• pp.615-622
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• 2003

The purpose of this study is to propose the more reasonable equation of bond strength of grout-filled splice sleeve. To accomplish this objective, total 60 full-sized specimens were tested under monotonic loading. The experimental variables are compressive strength of mortar, embedment length and size of reinforcing bars. Following conclusions are obtained; 1) If the adequacy of existing equations which estimate the bond strength of grout-filled splice sleeve are investigated, they underestimate the bond strength of grout-filled splice sleeve by 8-18%. Also the existing equations have a tendency to underestimate with decrease in the embedment length of reinforcing bars. 2) From the test result of bond failure, the equation which estimates the confining pressure of grout-filled splice sleeve was proposed by making multiple regression analyses of which independent variables are embedment length of reinforcing bars and compressive strength of mortar. This equation predicted the measured bond capacity of this test more accurately than existing equations and eliminated the deviation according to the embedment length of reinforcing bars.

• Proceedings of the Materials Research Society of Korea Conference
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• 2010.05a
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• pp.39.1-39.1
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• 2010

겨울철 혹한지방에서의 차량운행 또는 여름철 혹서지방에서의 장시간 차량 운행시 차체를 구성하고 있는 강판에는 약 $-50^{\circ}C{\sim}150^{\circ}C$의 온도환경에 처하게 된다. 따라서 이러한 저온 고온 환경하에서 차체 충돌상품성 예측 및 충돌안전 설계를 위해 온도에 따른 차체 강판의 기계적 물성평가가 요구된다. 이를 위해 본 연구에서는 자동차용 충돌부재에 주로 쓰이는 HS440MPa, HS590MPa급 냉연 고장력 강판에 대해 $-60^{\circ}C{\sim}200^{\circ}C$의 온도범위로 저온 고온 인장시험을 수행 하였다. 각각의 인장시험 결과로부터 온도 별 항복강도, 인장강도, 연신율, 가공경화지수 등 기계적 물성 변화를 평가하였다. 저온 고온 인장시험은 ZWICK Z250 만능재료시험기를 사용하였고 KS5호 규격의 인장시편을 사용하였으며, 시편에 충분한 온도를 가하기 위하여 목표온도 도달 후 20분간 유지한 뒤 인장시험을 수행하였다. 인장시험결과 HS440MPa, HS590MPa급 두 강종 모두 온도가 낮아질수록 강도 및 연신율 등이 증가하였고, 온도가 증가할수록 강도 및 연신율 등 기계적 물성이 저하 되었다. 즉, 우리가 주로 평가해왔던 상온($25^{\circ}C$)에 비해 저온 고온 환경하에서는 강판의 기계적 물성 변화가 큰 것을 알 수 있다. 따라서 혹한 또는 혹서 지방 등 온도차이가 큰 운행환경하에서의 차체 강도 및 충돌안전성 확보를 위해 온도에 따른 강판의 정확한 물성평가가 필요하고 차체 설계시 온도에 따른 강도변화를 충분히 고려하여야 한다.