• 한국방재학회:학술대회논문집
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• 2010.02a
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• pp.79.2-79.2
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• 2010

실제 교량 바닥판의 거동은 반복하중에 의한 피로누적 손상에 의해 발생되므로 성능분석을 위해서는 피로 실험결과를 통한 구조거동 분석이 이루어져야 할 것이다. 이에 본 논문에서는 현재 개발 중인 초간편 강합성 바닥판의 피로성능을 파악하기 위해 일점 재하 방식으로 반복 하중을 재하 하였다. 실험체의 거동을 파악하기 위해 변위계를 설치하여 변위를 측정하였고 이 실험의 결과로 신형식 바닥판인 초간편 강합성 바닥판의 피로 파괴 양상을 알 수 있었으며 피로 곡선을 얻을 수 있었다. 하지만 바닥판의 파괴요인 중 외부 환경적 요인과 실제 차량 하중 이동을 모사한 윤하중 재하 시 피로 성능에 대한 연구가 추가로 이루어져야 할 것으로 판단된다.

• Proceedings of the KSME Conference
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• 2005.11a
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• pp.142.2-142.2
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• 2005

• Journal of Korean Society of Steel Construction
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• v.16 no.6 s.73
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• pp.847-855
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• 2004

The criterion or specification on fatigue design has been generally based on fatigue strength curve derived by tests on specimens with varying thickness (10-30mm). Making the plate thicker, however, also decreases fatigue strength. It has been noted from the test results and the results of the analysis by fracture mechanics that the effect of thickness cannot be bypassed. From the several fatigue strength curves of specimen tests, modification of fatigue strength on plate thickness has been proposed. In this study, fatigue tests on SM520C-TMC were carried out, and the effects of thickness were evaluated. Finally, in consideration of the thickness, the modification of fatigue strength was derived. Comparing the results of this paper with those of previous studies, an outline of the behavior obtained is similar to previous ones, but the rate of decrease is smaller.

• Journal of Korean Society of Coastal and Ocean Engineers
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• v.21 no.2
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• pp.191-195
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• 2009

After developing the pre-crack to simulate a damaged reinforced concrete beam, fatigue test was conducted on the beam repaired by GFRP Bar and GSP embedded method. In the result of fatigue test, most residual displacement and crack of the experimental beams occurs in the early loading cycle and an increasing rate of these due to number of cycles were insignificant. Comparing with a non-repaired beam, a static strength of the repaired beam greatly increased, but fatigue strength decreased. In S-N curves, fatigue strength of the beam repaired by GFRP Bar and GSP was 58%, 52% of the static strength respectively.

• Journal of Korean Society of Steel Construction
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• v.15 no.2
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• pp.137-145
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• 2003

In this study, direct tensile fatigue tests of the PS bar were performed in terms of diameter, minimum stress level, and maximum stress level. In the static test, the stress - strain curve and ultimate streng th of the PS bar were determined. Results of the fatigue test indicate that the diameter of the PS bar was not influenced by fatigue life. Minimum stress also had quite an influence on the fatigue of the PS bar. Thus, the fatigue characteristic equation was proposed in terms of stress range and minimum stress through statistical process. Strains on specimen that loaded direct tension were measured in the fatigue test, with the secant modulus of elasticity calculated from measured strains. The strain development consisted of three different stages, i.e., rapid increases during the initial fatigue life, uniform increases during the middle stage, and rapid increases until failure. The secant modulus of elasticity decreased during the fatigue life with increasing strain. However, stress level seemed to have no influence on the secant modulus of elasticity.

• Journal of the Korean Society of Safety
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• v.15 no.1
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• pp.140-145
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• 2000

This paper was composed with fatigue test of the cruciform specimens, as load carrying and non-load carrying type. It also has performed computational analyses for geometric condition of the fillet welding bead. As test results, the effect of stress ratio in the specimen was insignificant. Stress ranges were varied with R=0.1~0.2. The fatigue cracks that were found in the load carrying type specimens and most specimens welded with contact were developed at the end of welds. The fatigue strength of specimen that have fractured in maternal plate was found about ${\Delta}\sigma_c$=63.5MPa. It's about 24% less than that of the non-load carrying type specimens having about ${\Delta}\sigma_c$=83.8MPa. A category of the Fatigue design specifications which provide for cruciform details was defined grade C as a stress of the maternal member. And then, the fatigue strength to be transformed into the maternal stress was found about 78.27 MPa, it tends to be less than that of allowable fatigue strength.

• Journal of the Korea institute for structural maintenance and inspection
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• v.9 no.1
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• pp.127-135
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• 2005

Recently, as the concrete structures are becoming bigger, higher, longer and more special, high strength concrete is demanded. But the fracture behavior of high strength concrete is shown more brittle than that of the normal strength concrete. Therefore, in order to improve the brittle fracture behavior and crack propagation resistance, ACI Committee363 has been recommend the use of fiber reinforced concrete which showed superior property against the crack propagation resistance. On the other hand, bridges, concrete pavements and railroads etc. have been exposed to the repetition loading at least several million times during the service life. Therefore, fatigue load is dominantly most of all, but it is very difficult to estimate the suitable fatigue strength calculated by fatigue load. In this research, in order to examine the fatigue behavior of hybrid fiber reinforced high strength concrete, the static and fatigue tests were carried out. And from these results, it was estimated the fatigue strength of hybrid fiber reinforced high strength concrete.

• Journal of Advanced Marine Engineering and Technology
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• v.7 no.2
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• pp.36-49
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• 1983

최근 높은 경제성과 용접성의 우수성에 의한 마찰 용접의 응용에 있어서 내열.내식 재료가 개스터어빈, 기관, 핵 발전기등의 기계 부품 생산 공업에 널리 이용되고 있다. 따라서 이종내열 합금강의 마찰 용접된 부품을 이용함에 있어서 내식.내마모 및 용접성 뿐만 아니라 고온 피로 강도와 크리이프 강도 등의 복합 특성에 관한 연구가 요구되고 있다. 본 연구에서는 마르텐사이트계 실크롬 내열강과 오오스테나이트계 닉켈크롬 스테인레스강의 이종 내식.내열 합금강의 최적 용접조건하에서 마찰 용접된 후의 시효 열처리가 용접재의 700 .deg.C 고온 회전 굽힘 피로강도 특성에 미치는 영향에 관하여 실험과 강도해석에 의해 조사되었고 용접후의 용체화 처리와 시효 열처리법에 의한 내열강 마찰 용접강도 개선법을 개발코저한 것이다.

• Journal of the Korean Society of Hazard Mitigation
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• v.4 no.4 s.15
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• pp.1-6
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• 2004

Fatigue tests were carried out for butt welded joints with SM520-TMC steel plate with thickness between 20mm and 80mm. The test results were analysed statistically and the effect of plate thickness on the fatigue strength investigated. The fatigue strengths based on nominal stress range satisfy the requirement of the standards. Due to misalignment of the specimens, the measured stresses are higher than the nominal stresses especially for 20mm thick plates. If fatigue strengths are evaluated based on the measured stresses, then the fatigue strengths are greater than those based on nominal stresses. The results show that the thickness effect is similar to the formula proposed by Gurney.

• Computational Structural Engineering
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• v.10 no.3
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• pp.7-14
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• 1997

본 고에서는 설계자가 초기 설계시 적용할 수 있는 간이피로해석방법에 대하여 기술하였으며, 특히 선체의 각 구조상세에 대하여 산정된 응력집중계수를 이용하여 피로수명을 쉽게 평가할 수 있는 집중응력방법을 정립하였다. 이 집중응력방법을 사용하면 모든 구조상세에 대하여 한개의 S-N 선도를 적용하게 되므로 일관성 있는 피로상도해석을 수행할 수 있다. 또한 피로수명에 큰 영향을 미치는 파랑하중은 설계조건에 주어진 선급규칙에 따라 계산되어진다. 선체구조의 피로강도평가 기술은 계측, 실험, 해석 및 경험을 포함하는 광범위하고 포괄적이면서 정밀함을 요구하는 종합기술이지만 여기에는 많은 불확실성이 내포되어 있다. 따라서 이를 구명하고 모든 선체구조에 적용할 수 있는 신뢰성 있는 피로강도 평가기술을 개발하기 위하여는 실선계측을 통한 피로하중규명 선체구조에 적용할 수 있는 피로강도 Data base개발, 균열진전해석 등 많은 과제에 대한 집중적인 연구가 계속 수행되어야 한다.