• Proceedings of the Korea Water Resources Association Conference
• /
• 2004.05b
• /
• pp.328-332
• /
• 2004

본 연구에서는 자연하천유역에 적합한 저류상수 산정공식을 개발하기 위하여 섬진강 유역에 대한 유역특성인자 및 강우특성인자를 분석하고, 이의 단계별 회귀분석으로부터 유역면적, 하도연장, 하도경사의 유역특성인자뿐만 아니라 강우특성인자인 유효강우강도를 설명변수로 갖는 저류상수 산정공식을 개발하였다. 그리고 개발된 공식의 적용성을 검토하고자 Clark의 단위도 모형에 기존의 경험공식 및 본 인구에서 개발된 공식을 이용하여 섬진강 유역의 실제 호우사상에 대한 유출수문곡선을 분석하여 관측수문곡선과 비교 검토한 겉과, 본 연구에서 개발된 공식에 의한 유출수문곡선이 관측치에 가장 적합하였다. 또한, 남한강의 지류인 섬강 유역에 대한 빈도별 설계강우량을 적용하여 저류상수 및 설계홍수량을 산정하고 기존에 분석된 저류상수 및 홍수량과 비교 검토한 결과 빈도별 유효강우강도의 변화를 고려한 저류상수의 적용 가능성 및 그 타당성을 확인할 수 있었다.

• Journal of the Korea Concrete Institute
• /
• v.22 no.4
• /
• pp.481-488
• /
• 2010

Since existing constitutive models developed for confined normal strength concrete overestimate ductility when they are applied to confined high strength concrete, these models cannot be directly applied to confined high strength concrete. In an effort to solve this problem, an accurate stress-strain relationship of the hihg strength concrete needs to be formulated by examining the confinement effects due to increase of the concrete strength. In this study, a constitutive model is developed to express the stress-strain relationship of confined high strength concrete by carrying out regression analysis of the main parameters affection strength and ductile behavior of reinforced high strength concrete columns. Twenty-five test specimens were chosen from the reported experimental studies in the literature. The experimental results of stress-strain relationships of show a good agreement with results of the stress-strain relationships of suggested high strength concrete, covering a strength range between 60 and 124 MPa.

• Journal of Korea Water Resources Association
• /
• v.36 no.2
• /
• pp.153-159
• /
• 2003

When available rainfall data is not sufficient, a rough tendency of I-D-F relationship appeared frequently. In fact, rainfall intensity on the curve shows abnormally higher value the longer rainfall duration is applied that gives rise to great confusion to apply a rainfall I-D-F relationships curve to a practical work, however, the research work will present a way to solve above mentioned problem by the use of the Box-Cox transformation formula for a given rainfall data. The study came to a conclusion that the Box-Cox transformation formula is satisfied to utilize in a practical work on the ground of analysis for rainfall data of Sancheong and Yeongcheon.

• Journal of Korea Water Resources Association
• /
• v.34 no.6
• /
• pp.577-586
• /
• 2001

This study proposes a theoretical methodology for deriving a rainfall intensity-duration- frequency (I-D-F) curve using a simple rectangular pulses Poisson process model. As the I-D-F curve derived by considering the model structure is dependent on the rainfall model parameters estimated using the observed first and second order statistics, it becomes less sensitive to the unusual rainfall events than that derided using the annual maxima rainfall series. This study has been applied to the rainfall data at Seoul and Inchon stations to check its applicability by comparing the two I-D-F carves from the model and the data. The results obtained are as followed. (1) As the duration becomes longer, the overlap probability increases significantly. However, its contribution to the rainfall intensity decreases a little. (2) When considering the overlap of each rainfall event, especially for large duration and return period, we could see obvious increases of rainfall intensity. This result is normal as the rainfall intensity is calculated by considering both the overlap probability and return period. Also, the overlap effect for Seoul station is fecund much higher than that for Inchon station, which is mainly due to the different overlap probabilities calculated using different rainfall model parameter sets. (3) As the rectangular pulses Poisson processes model used in this study cannot consider the clustering characteristics of rainfall, the derived I-D-F curves show less rainfall intensities than those from the annual maxima series. However, overall pattern of both I-D-F curves are found very similar, and the difference is believed to be overcome by use of a rainfall model with the clustering consideration.

• Tunnel and Underground Space
• /
• v.27 no.3
• /
• pp.121-131
• /
• 2017

We studied the time-dependent behaviors of rock and concrete materials by conducting the static and dynamic long-term strength tests. In particular, acoustic emission(AE) signals generated while the tests were analyzed and used for the long-term stability evaluation. In the static subcritical crack growth test, the long-term behavior and AE characteristics of Mode I and Mode II were investigated. In the dynamic long-term strength test, the fatigue limit and characteristics of generation of AE were analyzed through cyclic four points bending test. The graph of the cumulative AE hits versus time showed a shape similar to that of the creep curve with the first, second and third stages. The possibility for evaluating the static and dynamic long-term stability of rock and concrete is presented from the log - log relationship between the slope of the secondary stage of cumulative AE hits curve and the delayed failure time.

• Journal of Korean Society of Steel Construction
• /
• v.30 no.1
• /
• pp.1-12
• /
• 2018

A curved member should resist bending and torsional moments simultaneously even though the primary load is usually supposed to be gravitational load. The torsional moment causes complicate stress state and also can result in early yielding of material to reduce member strength. According to analysis results, the strength of a curved member that has 45 degrees of subtended angle could decrease more than 50% compare to straight girder. Nevertheless, there have been very few of researches related with ultimate strength of curved girders. In this study, various kinds of stiffness about bending, pure torsion and warping were considered with a number of models in order to verify the main factor that affects ultimate behavior of curved girder. Lateral and rotational displacement of curved member were introduced as lateral-torsional-vertical behavior and bending-torsional moment interaction curve was derived. Finally, a strength equation for ultimate moment of horizontally curved steel I-girders subjected to equal end moments based on the interaction curves. The equation could take account of the effect of curvature, unbraced length and sectional properties.

• Proceedings of the KSMRM Conference
• /
• 2003.10a
• /
• pp.21-21
• /
• 2003

목적： 악성뇌종양 주변부위의 역동자기공명영상에서의 시간신호강도곡선 양상으로 종양의 성장 양상이나 예후를 판단할 수 있는지를 알고자 한다. 대상 및 방법： Anaplastic oligodendroglioma 3예, Anaplastic astrocytoma 1예, Glioblastoma multiforme 1예, Malignant ependymoma 2예, Medulloblastorna 1예로서, 총 8예의 종양절제전, 혹은 후의 잔류 종양을 대상으로 하였다. Routine MRI에 추가하여 종양부위에서 Turbo spin echo T1 강조 역동자기공명영상을 하였으며, Gd-DTPA 0.1 mmol/kg를 급속 주사 한 후, TR/TE, 350/15, slice thickness 6 mm, slice number 3, NEX 2회, scan time은 15 초로 하여 5 분 동안 20회 영상을 얻었다. 가시적으로 조영증강이 없는 종양의 주변부위나 수술경계부위에 관심영역을 그려서 시간신호강도곡선을 얻었으며, 첫 회 조영제 통과시의 peak 이후에 신호가 감소하는 경우를 Normal pattern으로, peak 이후에 신호가 계속 유지되거나 증가하는 경우를 Tumor pattern으로 하였으며, Normal pattern과 Tumor pattern을 보인 예들을 구분하여 종양의 재성장 상태와 환자의 생존 기간을 비교 관찰하였다.

• Computational Structural Engineering
• /
• v.11 no.4
• /
• pp.253-265
• /
• 1998

본 논문에서는 연계논문에서 제시한 비대칭 박벽단면을 갖는 곡선보 및 직선보 이론을 토대로, 곡선보 요소 및 직선보 요소를 개발하고 이를 이용한 유한요소 정식화 과정을 제시한다. 유한요소 정식화 과정에서는 요소의 변위장을 도심에 대하여 정의한 후, 요소 변위벡터에 관한 3차의 Hermitian 다항식을 형상함수로 사용하고 가우스 적분을 행함으로써 탄성 강도행렬 및 기하학적 강도행렬을 산정하였다. 얻어진 강도행렬을 이용하여 고유치 문제를 계산함으로써 좌굴하중을 계산하였으며 다양한 해석 예제를 통하여 다른 연구자들의 해석 결과와 비교 검토함으로써 본 연구의 타당성과 우수성을 입증하고자 한다.

• Magazine of the Korea Concrete Institute
• /
• v.9 no.6
• /
• pp.165-174
• /
• 1997

고강도 및 보통강도 콘크리트의 압축파괴 거동에 영향을 미치는 요소들 (재료의 강도, 시편의 세장비, 전단구속, 실험장치의 강성, 피드백 신호)에 관한 연구가 수행되었다. 피드백 신호로 자동 조절되는 유압 실험기계항에서 원주변형 피드백 신호를 사용하여 연화곡선을 구했다. 재하장치로부터의 단부 전단 구속을 줄이면 제한된 영역 안에서 재하방향 균형이 형성되고, 또한 연화곡선의 경사가 급해지고 파괴에너지도 작아진다. 이때 길이가 큰 시편에서 파괴에너지가 커지는 것은 안장과는 달리 단순균열이 형성되는 것이 아니고 , 파괴가 용적을 가진다는 것을 의미한다. 압축응력하의 국부 파괴는 재료특성이 아니므로, 단부 전단구속이 없더라도 재료적 특성으로서의 응력-변형도 곡선은 정하기 어렵다.

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