• Steel and Composite Structures
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• 제24권4호
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• pp.409-423
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• 2017

This paper presents an experimental study on damage evolution laws of solid-web steel reinforced concrete (SRC) T-shaped columns along the direction of the web under various loadings. Ten specimens with a scale ratio of 1/2 and a shear span ratio of 2.5 were designed and fabricated. The influences of various parameters, including the axial compression ratio, steel ratio, and loading mode, were examined. The mechanical performances including load-displacement curve and energy dissipation capacity under the monotonic and low cyclic loadings were analyzed. Compared with the monotonic loading, bearing capacity, ultimate deformation capacity, and energy dissipation capacity of the specimens decrease to some extent with the increase of the displacement amplitude and the number of loading cycle. The results show that the damage process of the SRC T-shaped column can be divided into five stages, namely non-damage, slight-damage, steadily-developing-damage, severe-damage and complete-damage. Finally, based on the Park-Ang model, a modified nonlinear damage model which combines the maximum deformation with hysteretic energy dissipation is proposed by taking into account the dynamic influence of the aforementioned parameters. The results show that the modified model in this paper is more accurate than Park-Ang model and can better describe the damage evolution of SRC T-shaped columns.

• 한국지반공학회:학술대회논문집
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• 한국지반공학회 2005년도 춘계 학술발표회 논문집
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• pp.320-327
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• 2005

Liquefaction characteristics of saturated sand under various dynamic loadings such as sinusoidal, wedge, increasing wedge and real earthquake loading are investigated focusing on the excess pore water pressure build up instead of liquefaction resistance strength in this paper. There are large differences between two types of earthquake loading - impact and vibration in liquefaction characteristics. The angle of phase change line of sinusoidal loading is very close to the vibration type, whereas the cumulative deviator stress and cumulative plastic strain are larger than two types of real earthquake loadings. On the other hand, the liquefaction characteristics of increasing wedge loadings are located in the range between vibration and impact earthquake loadings. It is concluded that the sinusoidal loading overestimates the resistance of soil under real earthquake loading. Based on results obtained, the increasing wedge loading can reflect the liquefaction behavior under real earthquake loadings more efficiently than sinusoidal loading based on equivalent uniform stress concept.

• 한국환경농학회지
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• 제27권1호
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• pp.10-17
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• 2008

The objective of this study was to estimate the pollutant loads from paddy fields by cultivation practices using a non-point-sources models. One of them is CREAMS-PADDY model that was developed considering the water balance and mass balance of paddy fields. The CREAMS-PADDY model was applied to provide basic data to reduce runoff loadings under various scenarios such as various water management control and various fertilizer condition. The model was verified against T-N, T-P and runoff flow data collected during cropping periods at 2000. The model results agreed well with the measured data in verification. The results showed that the model could be used for estimating the runoff loadings from irrigated paddy fields by cultivation practices was possible. Comparison of simulated the standard height and the sluice management of T-N and T-P runoff loadings from paddy fields were +32.4%, +10.3% in 10 mm below the standard height, -29.2%, -35.9% in 20 mm above the standard height, 52.6%, 59.0% in 40 mm above the standard height, respectively. Comparison of simulated the standard fertilizer and the fertilizer control of T-N and T-P runoff loadings from paddy fields were -1.3%, -21.7%in reduction of conventional fertilizer 30%, -1.0%, -12.5% in reduction of standard fertilizer 30%, respectively. Therefore, reducing nonpoint-sources nutrient loading by reducing fertilization may not work well in the range of normal paddy rice farming practices, and instead it could be achieved by reducing surface drainage outflow.

• International Journal of Concrete Structures and Materials
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• 제10권4호
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• pp.435-450
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• 2016

Experimental studies were conducted on 36 grouted splices to investigate their mechanical performance under four loading schemes: (1) incremental tensile loading, (2) repeated tensile loading, (3) cyclic loading at high stress, and (4) cyclic loading at large strain. Load-deformation responses of the grouted splices under cyclic loadings were featured with pinching effect and stiffness degradation compared to those responses under tensile loadings. The shape of the hysteresis loops of load-deformation curves was similar to that under incremental tensile loading. For the purpose of structural analysis, stress-strain relationships were presented for grouted splices under various loadings.

• Steel and Composite Structures
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• 제33권1호
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• pp.93-109
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• 2019

In the present study, vibration analysis of double bonded micro sandwich cylindrical shells with saturated porous core and carbon/boron nitride nanotubes (CNT/BNNT) reinforced composite face sheets under multi-physical loadings based on Cooper-Naghdi theory is investigated. The material properties of the micro structure are assumed to be temperature dependent, and each of the micro-tubes is placed on the Pasternak elastic foundations, and mechanical, moisture, thermal, electrical, and magnetic forces are effective on the structural behavior. The distributions of porous materials in three distributions such as non-linear non-symmetric, nonlinear-symmetric, and uniform are considered. The relationship including electro-magneto-hydro-thermo-mechanical loadings based on modified couple stress theory is obtained and moreover the governing equations of motion using the energy method and the Hamilton's principle are derived. Also, Navier's type solution is also used to solve the governing equations of motion. The effects of various parameters such as material length scale parameter, temperature change, various distributions of nanotube, volume fraction of nanotubes, porosity and Skempton coefficients, and geometric parameters on the natural frequency of double bonded micro sandwich cylindrical shells are investigated. Increasing the porosity and the Skempton coefficients of the core in micro sandwich cylindrical shell lead to increase the natural frequency of the structure. Cylindrical shells and porous materials in the industry of filters and separators, heat exchangers and coolers are widely used and are generally accepted today.

• Computers and Concrete
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• 제32권5호
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• pp.499-511
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• 2023

Anchor channels are commonly used for façade, tunnel, and structural connections. These connections encounter various types of loadings during their service life, including high rate or impact loading. For anchor channels that are placed close and parallel to an edge and loaded in shear perpendicular to and towards the edge, the failure is often governed by concrete edge breakout. This study investigates the transverse shear behavior of the anchor channels under quasi-static and high rate loadings using a numerical approach (3D finite element analysis) utilizing a rate-sensitive microplane model for concrete as constitutive law. Following the validation of the numerical model against a test performed under quasi-static loading, the rate-sensitive static, and rate-sensitive dynamic analyses are performed for various displacement loading rates varying from moderately high to impact. The increment in resistance due to the high loading rate is evaluated using the dynamic increase factor (DIF). Furthermore, it is shown that the failure mode of the anchor channel changes from global concrete edge failure to local concrete crushing due to the activation of structural inertia at high displacement loading rates. The research outcomes could be valuable for application in various types of connection systems where a high rate of loading is expected.

• 대한공간정보학회지
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• 제1권1호
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• pp.171-180
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• 1993

도시하수와 관련된 비점원 오염에 대한 관심은 더 나은 수질계획을 위한 새로운 도구의 발전을 이끌어 왔다. 이 논문은 도시의 수질연구를 위해 지리정보체계가 어떻게 응용되는지를 보여준다. 지리정보체계는 비점원 오염 모형화를 위한 토지이용자료를 관리하기 위해 이용되고, 또한 여러 가지 형태의 지리적 집합체내에서 오염물질을 평가하는데 이용된다. 경험적인 수질모형은 토지이용에 근본을 둔 오염물질 축적을 평가하기 위해 이용된다. 토지이용범위는 최근 사진의 판독을 통해서 구범위를 갱신함으로써 결정된다. 이러한 토지이용범위는 각각의 토지이용 다각형에 대한 오염물질 축적을 기록하는데 이용된다. 도시하수 유역과 소하수 유역의 범위를 결정하기 위해 하수지도를 수치화 시키고 해석한다. 하수구 소유역층에서 오염물질 축적을 중첩시킴으로써 주요하수의 출구에 대한 오염 축적물이 계산된다. 축적 정보를 기본으로 과다 오염 축적물의 임계지역이 어디에 위치하고 있으며, 오염 축적물을 통제하기 위한 최선의 관리기법의 효율성이 평가된다.

• 한국농공학회논문집
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• 제51권5호
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• pp.87-94
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• 2009

The objectives of this paper were to estimate cell based pollutant loadings for total maximum daily load (TMDL) programs and to evaluate the applicability of the agricultural nonpoint source (AGNPS) model for an intensive agricultural watershed in Korea. The model was calibrated and validated at a watershed of 384.8 ha of drainage area using the observed data from 1996 through 2000 in terms of runoff, suspended solid, total nitrogen, and total phosphorus on a hourly basis. Analysis of spatial variations of pollutant loadings for rainfall frequencies of various intensities and durations were conducted. In addition, the validated model was applied to estimated the TMDL removal efficiency for best management practices (BMPs) scenarios which were selected by taking into account the pollutant characteristics of the study watershed. The model can help to understand the problems and to find solutions through landuse changes and BMPs. Thus, the method used for this study was able to identify TMDL quantitatively as well as qualitatively for various sources pollution that are spatially dispersed. Also it provides an assessment of the impact of BMPs on the water bodies studied, allowing the TMDL programs to be complemented more effectively.

• 한국산학기술학회논문지
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• 제12권3호
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• pp.1465-1472
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• 2011

평택호의 수질개선 대책을 수립하기 위하여 호수 내 수질조사를 2회 수행하였으며, 상류 유역의 부하량 삭감에 따른 호소 내 수질개선 효과를 파악하기 위하여 WASP/EUTRO5 모형을 사용하여 시뮬레이션 하였다. 현재의 부하량이 장래에도 지속이 되는 경우에는 호소 내 수질이 상류 유역의 개발에 따른 오염부하량의 증가로 수질이 더욱 더 악화되는 것으로 나타났다. 이에 본 연구에서는 다양한 부하량 삭감 대책을 수립하여 장래의 수질을 예측하였으며, 대안 6가 다른 대안에 비하여 호소의 수질농도를 낮추는 데 크게 기여하는 것으로 나타났다. 그러나, 대안 6의 경우에도 2016년에 호소 내 COD 농도가 9.74 mg/L로 호소수질환경기준 약간 나쁨(4등급, COD 8 mg/L 이하)에도 미치지 못하는 것으로 나타났으며, 2021년에도 유사한 경향을 나타내었다. 대안 6에 부하량을 추가로 삭감하여도 호소의 수질개선 효과는 미미하며 경제적인 측면에서도 적합하지 않은 것으로 나타났다.

• 한국농공학회논문집
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• 제54권6호
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• pp.29-37
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• 2012

This study was carried out to runoff characteristics in an upland livestock manure compost. Irrigation, runoff and water quality data in the upland were analyzed periodically from May to November in 2011. The observed amount of rainfall, irrigation, runoff for the experimental upland during the investigation period were 1,299.7 mm, 32.0 mm, and 340.7 mm, respectively. The concentrations of T-N in compost and non-compost upland during study period were ranged from 2.09 mg/L to 6.66 mg/L and from 1.99 mg/L to 6.01 mg/L, respectively. which was generally higher than the quality standard of agricultural water (1.0 mg/L). The concentrations of T-P in compost and non-compost upland during study period were ranged from 0.069 mg/L to 0.525 mg/L and from 0.018 mg/L to 0.152 mg/L, respectively. The runoff pollutants loadings of T-N and T-P in compost upland were 10.05 kg/ha and 0.56 kg/ha, respectively. The runoff pollutants loadings of T-N and T-P in non-compost upland were 9.09 kg/ha and 0.26 kg/ha, respectively. The runoff pollutants loadings in T-N and T-P from this study were much lower values than the pollutant loadings of T-N and T-P from the upland published by the others studies. Runoff pollution loadings due to the upland field in order to identify the characteristics of various crops, farming methods and a variety of targets taking into account regional characteristics by conducting continuous monitoring runoff load estimate will be required.